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Salt: More confirmation bias for your preferred narrative

Judging by the recent press reports, the latest Cochrane review reveals that everything we’ve been told about eating salt, and cardiovascular disease, is wrong:

The New York Times: Nostrums: Cutting Salt Has Little Effect on Heart Risk

The Daily Mail: Cutting back on salt ‘does not make you healthier’ (despite nanny state warnings)

Scientific American: It’s Time to End the War on Salt

Sometimes it’s possible to completely miss this point. And that’s what’s happened here.

When it comes to health, it’s the hard outcomes we care about. We pay attention to measures like high blood pressure (hypertension) because of the relationship between hypertension and events like heart attacks and strokes. The higher the blood pressure, the greater the risk of these events. The relationship between the two is well established. So when it comes to preventive health, we want to lower blood pressure to reduce the risk of subsequent effects. Weight loss, diet, and exercise are usually prescribed (though often insufficient) to reduce blood pressure. For many, drug treatment is still required.

There is reasonable population-level data linking higher levels of salt consumption with higher blood pressure. From a population perspective, interventions that dramatically lower salt intake result in lower blood pressure. Not everyone responds in the same way — many people with normal blood pressure can regularly consume a high salt load without any apparent change in blood pressure. But not everyone, and not forever. Salt sensitivity seems to increase with age and is more pronounced in some ethnic groups, as well as in those with salt-sensitive conditions such as kidney disease. And chronic high levels of salt consumption may be associated with the subsequent emergence of hypertension. There may be additional effects, unrelated to blood pressure, too. However, the causality between salt consumption, and all of these negative effects, is less clear.

So does reducing dietary salt reduce cardiovascular events? That’s the key question. To definitively answer the question, we’d randomize patients to high- and low-sodium diets, force them to follow these diets for years or decades, and monitor consumption, blood pressure, and cardiovascular events. We’d also want to explore the factors that seem to make some more sensitive to the effects of salt than others. To ensure we could see a difference (if it exists), we’d need a large sample size — hundreds or thousands of people, ideally. See any problems with the feasibility? Like any dietary intervention trial, this type of study would be exceptionally difficult to do — forcing dietary changes is very difficult, and cannot be done in a blinded manner. Even randomization is unlikely to be effective in ensuring there’s adherence — established dietary habits don’t lend themselves to long-term change easily. So we must look to lower-quality evidence — inferences from observational studies that have tracked consumption, or indicators like blood pressure and salt consumption in the short-term. And there are fair criticisms of the data. Some see relationships, and others dismiss them.

When it comes to clinical practice guidelines, low salt diets are the mainstays of pretty much every set of guidelines on the management of high blood pressure. The evidence supporting the relationship with hard outcomes is robust, but not rock-solid. We don’t have causal data, but we do have considerable epidemiologic evidence to suggest that reducing dietary salt consumption is likely to offer net benefits in the management of hypertension.

And that’s where the recommendations to cut salt come from. The vast majority of the salt we eat (75%) is from processed foods. Restaurants are a large source, too. Few foods in their original state are naturally high in salt, and in general, we don’t add that much at the table. Interestingly, when foods are reduced in sodium, we don’t tend to add the same amount back at the table. So public health initiatives have concentrated on a few strategies: education on how to reduce your own salt consumption, and putting pressure on packaged food manufacturers to reduce the amount of sodium that they use in their products. But reducing salt may hurt sales: if we’re accustomed to eating salty foods, low-salt foods taste unpalatable. Just last week Campbell Soup Company announced that it’s raising the salt content in its products in an attempt to boost sagging sales.

So do dietary intervention strategies work? That’s what a recent Cochrane review attempted to answer. But you wouldn’t know it, based on the headlines above. Scientific American described the paper as:

This week a meta-analysis of seven studies involving a total of 6,250 subjects in the American Journal of Hypertension found no strong evidence that cutting salt intake reduces the risk for heart attacks, strokes or death in people with normal or high blood pressure.

The Daily Mail?

Eating less salt will not prevent heart attacks, strokes or early death, according to a major study.
Its findings contradict all recommendations by the Government and medical profession urging the public to reduce the amount of salt they consume.

Neither statement accurately describe the findings. Rod Taylor and colleagues set out to do a meta-analysis of dietary intervention studies. They analyzed only studies that measured the effects of dietary interventions that restricted salt consumption, or where the intervention was advice to reduce salt consumption. This was an update of a prior analysis.

Seven studies made up this meta-analysis, including 6,489 patients in total. Three studies looked at those with normal blood pressure, two included patients with high blood pressure, and one was a mixed population, including patients with heart failure. The overall effect? Interventions had small effects on sodium consumption, which led to small effects on blood pressure. There was insufficient information to analyze the effects on cardiovascular disease endpoints.

The authors go on to make the following point, which was ignored in the media coverage:

Our findings are consistent with the belief that salt reduction is beneficial in normotensive and hypertensive people. However, the methods of achieving salt reduction in the trials included in our review, and other systematic reviews, were relatively modest in their impact on sodium excretion and on blood pressure levels, generally required considerable efforts to implement and would not be expected to have major impacts on the burden of CVD.

The authors did not conclude that reducing salt consumption is ineffective. They concluded that interventions such as dietary advice, do not result in substantial reductions in consumption. As expected, blood pressure didn’t change much as a consequence. This finding should not be a surprise. Given the vast majority of salt is consumed via processed foods, it should come as no surprise that dietary approaches are modestly effective at reducing consumption.

Despite the modest and equivocal results, the authors seem to have lost the narrative on their own research findings:

Professor Rod Taylor, the lead researcher of the review, is ‘completely dismayed’ at the headlines that distort the message of his research published today. Having spoken to BBC Scotland, and to CASH, he clarified that the review looked at studies where people were advised to reduce salt intake compared to those who were not and found no differences, this is not because reduced salt doesn’t have an effect but because it’s hard to reduce salt intake for a long time. He stated that people should continue to strive to reduce their salt intake to reduce their blood pressure, but that dietary advice alone is not enough, calling for further government and industry action.

Conclusion

The true finding from the Cochrane review is that dietary interventions to reduce salt intake are largely ineffective at reducing salt consumption. Salt’s impact on cardiovascular events is less clear than its effects on blood pressure. And the long-term benefits of population-level interventions to reduce dietary salt consumption are not yet well established. Until the data are more clear, you can find the data to support whatever narrative you believe. If you want to demonize salt and ignore other factors that contribute to poor cardiovascular outcomes, you can do that. And if you believe that interventions to reduce salt consumption are misguided and unwarranted, and symptomatic of an overreaching nanny state, then you can find data to support that position, too.

My personal take is that most of us will ultimately end up with salt-sensitive conditions. Odds are good we’ll be hypertensive, too. Gradually reducing our chronic salt consumption would seem to be a conservative approach — not by focusing strictly on the salt, but by working to reduce the consumption of salty, processed foods, and substituting healthier, more nutritious choices instead. But I won’t worry when I finish an entire bag of chips — I’ll consider it in the context of an overall strategy: a diet that minimizes processed foods, maintaining an appropriate weight, and getting regular physical exercise.

Reference
ResearchBlogging.org
Taylor RS, Ashton KE, Moxham T, Hooper L, & Ebrahim S (2011). Reduced dietary salt for the prevention of cardiovascular disease. Cochrane database of systematic reviews (Online), 7 PMID: 21735439

Posted in: Science and Medicine

Leave a Comment (60) ↓

60 thoughts on “Salt: More confirmation bias for your preferred narrative

  1. Rick says:

    Thank you for brining this up. I read Scientific American “It’s Time to End the War on Salt” and was surprised to say the least. However, I think the point that is ended up is that everyone’s bodies respond differently, and as you point out depending on age, race, probably gender, you can respond differently to salt than the next person.

    Also, as you pointed out that quality studies just aren’t out there.

  2. Angora Rabbit says:

    Scott, terrific post. How much do you think is confirmation bias and how much is media spin to manufacture controversy? Because, sadly, it is controversy rather than fact that seems to sell news.

    And adding to this is oversimplification and ignoring that hypertension is multifactoral. If I could expand on your post, sodium is a significant element, but data also implicate high chloride intake (which accompanies the sodium), low potassium intake (high in unprocessed foods and removed by processing), low calcium intake, and unsurprisingly, obesity and lack of exercise. A landmark study on this is the DASH Diet (Dietary Approaches to Stop Hypertension) and related studies therein (PMID: 20101007 for a recent study) (Sorry; I’ve no idea how to insert a hot link into a blog).

    As Scott points out, dietary intervention can be useful for those with sodium-sensitive hypertension. For other folks, their hypertension is genetic and diet-independent. For example, my family has the hyperactive ACE variant. When my lean (and healthy-eating) brother developed hypertension at 35yr, the diuretics and sodium intake of course had no influence on his BP. But that ACE inhibitor was a wizard.

  3. BenE says:

    “But I won’t worry when I finish an entire bag of chips.”

    Since this is a myth busting kinda site, I want to mention that chips don’t have that high of a salt content anyways. They taste salty because the salt is on the surface. Food where salt is diluted in water are much worst in general. Water hides the taste of salt. If you are trying to avoid salt, soups and sauces are your enemy. Not chips.

    Consider:

    28g (about half a bag) of Lays classic has 170mg of sodium

    12 oz of Gatorade (normal size is 20 oz) has 200mg. (It doesn’t even taste salty!)

    A cup of milk has about 120mg.

    one cup (about half a can) Of Campbell’s Healthy Request® Vegetable Soup has 410mg of sodium. That’s 820mg for the whole can!

    http://www.fritolay.com/our-snacks/lays-classic-potato-chips.html
    http://www.campbellwellness.com/product-collection.aspx?brandCatID=834&brandID=1&productID=120603&catID=617
    http://www.annecollins.com/sodium_diet/sodium-milk.htm
    http://caloriecount.about.com/calories-gatorade-energy-drink-i88302

  4. woertink says:

    How does water intake effect the damage from salt intake? Is this a concentration effect or total dose effect?

  5. Dile E. Tante says:

    Thanks for this analysis which is personally relevant to me as one who has hypertension.

    When I finally decided to try controlling my salt consumption (after years of reasonable nagging by my physician), I found that, while it took some time and effort to get accustomed to reading food labels, I had no difficulty finding products at the ordinary grocery store where I normally shop that allowed me to reduce my salt consumption to the level recommended by the American Heart Association (1,500 mg/day).

    In fact, eventually I was using off-the-self products that had so little salt that I could once again ADD salt, if I wanted to. A couple examples – fresh meat has far less sodium than processed lunch meat, and there are salt free potato and corn chips.

    It’s unfortunate if Campbells is adding more salt to their products. They should just indicate that the product has reduced salt content and advise people that they can easily add more salt if they want it. So, for example, with salt-free potato chips, it’s my choice how much salt I add, if any.

  6. ccbowers says:

    To emphasize the point better we should consistent in our use of the term: sodium. This may seem trivial to some but when “salt” is used the general public may think of the salt shaker or salty tasting foods. Often high sodium foods don’t taste salty because they have other more dominant characteristics like very sweet or otherwise bland taste (in absence of salt.). That’s why Campbells is increasing the sodium content, and because their soups havelittle flavor to begin with.

  7. rork says:

    “if we’re accustomed to eating salty foods, low-salt foods taste unpalatable”
    I have the reverse problem. Restaurants and food processors try to please the median taste in the U.S. I guess, so much of it tastes horrible. It’s a competition to see who can use the most salt, sugar, and vinegar, and often all three. When I reject some food for that reason other people are often questioning – cause for them, it’s hard to taste. (They are sometimes unable to detect sugar and various acids except at huge concentrations.) They have been well trained. So I think they can be trained the other way too, but it’s probably hard.

    PS: I disputed a sports health person about recommending sodium in sports drinks recently, sighting tribes from New Guinea, Africa, and N and S America that used none, that docs are trying to get us to consume less, and James Neel’s assertion that very low sodium was probably the norm for most of human evolution (but “natural” does not imply good, I know). Since my actual medical knowledge on the subject was nil, I could use an education.

  8. LovleAnjel says:

    Thanks for the post! Many people in my family have hypertension/high blood pressure, so it’s good to have this to show them during the inevitable conversations.

    I’m a table-salt fiend, but I cook mostly from scratch, so I feel better about it now.

  9. Geoff says:

    This is a very fair assessment of the data. It’s generally pretty weak, and thus doesn’t really favor either direction.

    Here’s the thing: without a unifying theory of biology, this data just represents confirmation bias. But with a unifying theory of biology, namely evolution, we have a much better picture of what is going on, and the data very clearly favors maintaining the null hypothesis.

    In the case of salt, it is very well established that in the latter phase of our evolution, namely becoming homo sapiens while isolated in South Africa, we ate A LOT of seafood, particularly shellfish that we collected from the beach at low tide. The physical evidence for this, including cook sites, is pretty strong. It stands to reason then, that since seafood in general and shellfish in particular have a very high amount of salt in them, that we probably ate a lot of salt. We also have a taste bud for the taste of salt, which is suggestive of the fact that actively seeking out sources of salt afforded us a selection advantage. As such, it is improbable to suggest that salt is unhealthy at least up until the point of high level of seafood consumption, and any such suggestion requires a high burden of proof to overturn the null hypothesis. This study does not represent that level of evidence.

    Just my two cents.

  10. Geoff says:

    One more point to add. I am talking tabula rasa, in healthy individuals. This does not mean that in an unhealthy individual, salt tolerance may be a problem. Still, I think that the majority of the data that suggests that maybe salt is problematic is as a result of confounding processed foods with salt. There are a number of other problems with processed foods, including wheat, excess linoleic acid, fructose and hyper-rewarding properties.

  11. Harriet Hall says:

    @Geoff,

    Your hypothesis illustrates the problem with evolutionary arguments. You picked seafood eaters for an example; you could have picked people who lived inland and ate food without salt. I would argue that the majority of our ancestors had no access to seafood. You have not presented data, you have presented speculation.

  12. Geoff says:

    @Harriet

    Your response illustrates your lack of knowledge about homo sapien evolution. There is very good evidence of a major bottleneck (possibly as small as 20,000 individuals) leading to the evolution of homo sapiens, and that we all came from one relatively small area in South Africa that was located on the sea. There is some debate about this, but it is mostly around the discussion of modern homo sapiens interbreeding with archaic homo sapiens, the understanding of modern homo sapiens coming from Sub-Saharan Africa is pretty widely accepted as far as I know.

    I understand your point. We don’t know everything, and in most areas the evidence is tenuous at best. However, there are certain areas where it is not. The consumption of seafood in the caves of modern South Africa is another.

  13. Harriet Hall says:

    @Geoff,

    Is there any reason why conditions at that bottleneck would determine our relationship with salt rather than conditions earlier or later in our evolutionary history? What if we evolved to eat less salt and the bottleneck was not enough to change our earlier evolved propensities? It’s all speculation.

  14. Geoff how about recent evolution? Check this.

    “Genome researchers at the University of Chicago have identified more than 700 regions in human DNA where apparently strong selection has occurred, driving the spread of genes linked to a broad range of characteristics.

    “These are very recent events—within the past ten thousand years,” said Jonathan Pritchard, a geneticist whose laboratory team conducted the study.

    The results suggest that humans in different regions have continued to adapt in numerous ways to both environmental changes and cultural innovations.”

    http://news.nationalgeographic.com/news/2006/03/0308_060308_evolution.html

  15. Ken Hamer says:

    Suddenly, I feel like a poster child.

    There’s an old saw in nautical lore that the best bilge pump on a sinking ship is a scared crew member with a bucket.

    On September 14 last year I saw my family doctor for the usual 6 month blood presure check and prescription refill. Only this time she wanted me to also check my weight, which I had not done in several years. Both my weight and BP were scary high. And when I say “scary” I mean they scared me into drastic action.

    My BP was on the order of 150/100, and my weight was 167.5kg. To Americans, that might not look so bad, but it translates into about 368lbs. As a result of that shock, I made serious and immediate changes in my diet. Mostly, I checked nutrition labels and restaurant nutrition guides (where they were available — if they were not available I no longer patronized that restaurant.)

    My focus was to reduce sodium, fat, and calories, in that order of priority. In a few days, I *thought* I saw an improvement in my BP, but wasn’t sure. But after 2 weeks there was clear improvement in my BP. A few months later my prescription was reduced from 10mg to 5mg (Norvasc) per day. And at my last checkup a few weeks ago, my BP was 120/70. If this keeps up, I may soon be taken off the medication.

    As for my weight, I set a goal of losing 1lb / week. I haven’t quite attained my goal, but I have been averaging about 0.85 lbs per week over the past 9 months or so, having lost a total of about 15.4kg, or about 34 lbs, during that time.

    I don’t doubt that losing weight has accounted for some of the improvement in my BP. But improvement in the first two weeks was significant (150/100 to about 135/90) while my weight loss was probably less than 1kg/1lbs.

    BTW, I still consume a lot of processed and restaurant foods. I’m just a lot more careful on the sodium (and calories and fat.) So at least in my anecdotal case, it appears the sodium content was more a factor than the “processed-ness” of the food.

  16. matt79 says:

    What would be the selective pressure for sodium tolerance when most of the proposed negative consequences are chronic diseases which affect individuals far past their reproductive years?

  17. rwk says:

    @Dr Hall

    I was hoping that you’d comment on the article itself which is
    critical of the Cochrane review

  18. CC says:

    I’m with rork – I rarely use salt and I rarely eat much in the way of processed foods, so lots of “normal” stuff tastes salty to me. I still enjoy the occasional restaurant meal, but it frequently does strange things to my digestive system, and if I eat out too often (meaning more than 3 times in a week, which I only ever get close to on a work trip) I start to feel a little sick at the thought of another restaurant meal.

    I realized a short while ago that I had no salt in the pantry at all, and hadn’t for several months. I still haven’t bought any, because nothing has made me think “I need salt”.

    And sugar! Once while travelling in the US I bought what appeared at first glance to be a “healthy” breakfast cereal, from a hippie health food grocery store. I didn’t read the ingredients list until later – I think 6 of the first 10 ingredients were various forms of sugar. (The other 4 were the whole grains which were advertised on the front panel.) I gagged my way through the first bowl then went and found something else to have for breakfast. It was way too sweet for me.

    On another conversation, and pure speculation on my part here, but wouldn’t the presence of a salt-tasting ability and the perception of that as a “good” flavour imply that we were very short on salt in our diet when that evolved, and therefore needed to seek it out specifically to remain healthy?

  19. KB says:

    rork:

    It is my understanding that sports drinks are meant to be consumed after heavy exercise: exercise that causes a lot of sweating. Sweat contains salt. If you become dehydrated by sweating and replace your volume with plain, salt-free water (also known as “free water”), you could find yourself with a serious electrolyte imbalance, the kind that causes heart arrhythmias and brain swelling. You lost salt through sweat, and then diluted the salt you have left with the free water you drank, and you did this very quickly. (It’s not just the overall low level of salt that matters, but also the speed with which the change happens.) The salt in sports drinks is meant to prevent this short-term danger. You’re adding salt to an already salt-depleted state, so you’re not worried about the effect of salt intake on blood pressure. It’s most important for football players and marathon runners in the middle of summer, while someone walking a half-mile on their air-conditioned gym’s treadmill can probably stick to plain water and be OK. I don’t know exactly how much sweating you should do before switching over. :) There are plenty of people who live and work in warm climates without sports drinks, but there are also plenty of people who have gotten in trouble with drinking plain water to replace losses from sweat.

    (This is also a problem in severe diarrhea. If you drink only water while losing salt and water in profuse diarrhea, you can get electrolyte imbalances. This is why pedialyte has salt.)

    Of course, because sports drinks taste good, people like to drink them while they’re not exercising/sweating. : ) They’re not really in danger of brain swelling then, and water would probably be better. I personally don’t think I ever work out hard enough to need sports drinks, so I usually stick to water.

  20. Harriet Hall says:

    @rwk,
    I don’t understand what you are asking. As Scott said, the Cochrane review did not draw any firm conclusions, so readers can keep their previous biases.

  21. JPZ says:

    @everyone

    An excellent review of salt flavor and preference is here: http://www.ncbi.nlm.nih.gov/books/NBK50958/

    Bottom line, it is not clear why we like excess salt.

    @CC

    I hear you. Sandwich meat is just unpleasantly salty to me, but I can still handle chips (nice with a beer at a party, not so great by themselves). The new salt technology on Lay’s potato chips is really a step in the right direction.

  22. Lytrigian says:

    @Geoff: Citing the possible (or even probable) dietary habits of H. sapiens back when the average lifespan was less than 20 years isn’t helpful when considering strategies that may help individuals live well past their 8th decade.

    We likely have a taste for salt for the same reason we have a taste for sugar and fat: it’s a necessary nutrient that can be hard to come by in lean times or when far from easy-to-exploit sources like the sea. Just because we really, really like it doesn’t mean we should have a lot of it now that it’s plentiful.

    In any event, you misunderstand the report if you think it shows evidence is weak. The evidence is actually pretty solid. Please read more carefully.

    My own anecdata is that I’ve become noticeably more sensitive to salt as I’ve gotten older, resulting in marked bloating and a general feeling of malaise if I get even a little too much. I wonder how much it contributes to the problem that people don’t pay attention to their own bodies? (Or, perhaps, they eat so much salt that they never notice the difference.)

    Yes, you can take it too far in the other direction. Once, while staying with my father at my grandparents’ house — it was summer break from college and I was working in the area — there was an evening when he nearly passed out for no apparent reason and I had to drive him to the emergency room. The only thing they could find that was a little suspect was that the blood work showed his sodium levels to be too low. Sure enough, he was eating mainly the food my grandmother prepared, which was tailored to my grandfather’s very low sodium diet. The doctor “prescribed” an anchovy pizza.

  23. JPZ says:

    @Lyt

    If the preference for salt confered no evolutionary advantage, why would we retain salt taste receptors (although I accept that there are vestigial genes and that the addiction hypothesis has weight)? Why do salt depleted individuals have a higher sensitivity to salt (see previous reference I listed)? Cats lost the sweet receptor somewhere along the way in evolution, and it did not make them extinct. Tribes with no previous contact with civilization seem to do fine without external salt sources (still trying to find that reference I read, so take my comment with a grain of…). So, what I am saying is that this salt preference really has not been worked out no matter how simple the action potential mechanism of the salt taste receptor may seem.

  24. Nescio says:

    This story is an excellent example of how a journalist reading a press release about a research paper can completely misinterpret what it means. It happens far too often, perhaps because newspaper science correspondents these days are not as well educated in science as they used to be. I am not surprised by the Daily Mail, whose health reporting has become something of a running joke among sceptics. But I am surprised and disappointed by Scientific American.

    It’s as if someone looked at a program to help obese people to lose weight, but found that they didn’t lose very much weight, and showed little improvement in their health. The correct conclusion would not be that obesity is not a risk to health. As Scott wrote, the press coverage of this story completely misses the point. No wonder so many people refuse to believe any scientific research, particularly in the area of nutrition.

  25. Geoff says:

    @Harriet

    The bottleneck would suggest that if there was ever a harmful effect of dietary salt, that trait would have been selected against, leaving the survivors, whom every human on the planet is descended from, adapted to process salt in very high quantities. This is not sufficient to prove anything, but it is sufficient to form a null hypothesis, and the cursory evidence against salt is certainly not sufficient to overturn the null.

    I have seen the first hand effects of salt intake myself. When I was in congestive heart failure prior to my transplant, I was told to go on a low sodium diet, and if I ate too much salt I would see the water pooling in my ankles. But blood pressure was not my issue.

    From the research I have seen, the increase in blood pressure due to salt is somewhere on the order of 3 points, and it is temporary. I have not seen any evidence, nor even any plausible mechanism, that suggests that salt intake might be detrimental long term in healthy individuals.

    Also, isn’t there some relationship between dietary carbohydrate and salt retention? Correct me if I’m wrong, but it has for a while now been my understanding that without carbohydrate in the diet, sodium does not retain excess water, which as I understand it is how blood pressure gets raised in the short term by salt intake.

    @Lytrigian

    The average lifespan of H. Sapien has never been 20 years. Check your facts on that. Humans are a “K” species on the r-K continuum, meaning that we need to survive into old age in order to pass on knowledge to our kin for survival. While the life expectancy was in the 35-45 range, this factors in something like a 20% infant and young child mortality rate. People who survived past the age of 15 had a life expectancy on the order of 60 or so years. And life expectancy is an average. On the long tail, humans have been living into their 80s, 90s and 100s for tens if not hundreds of thousands of years.

    Keep in mind that the life expectancy of humans dropped when we started farming, and didn’t really surpass that of our hunter gatherer ancestry until ~150 years ago. It wasn’t over 50 until after the invention of penicillin.

    @All

    Putting salt, sugar and fat in the same category is ridiculous. While we have a hard wired taste for all of these things, one of these things is not like the other.

    The amount of fructose in the natural environment is VERY small. With the exception of short periods of time when fruit is in season in certain parts of the world, it is unlikely that it made up a large proportion of our calories, certainly no where near the amount that it makes up today. Salt and animal fat, by contrast, are available in very large amounts in the natural environment, and mostly together.

    This matters because based on what we know about physiology, in my opinion it is likely that there is an upper limit to the amount of fructose that the liver can process at one time, and quantities beyond that may be mildly toxic. From whole food sources like fruit, it is impossible to exceed this level, but in our modern world with processed sugar, it is not. In fact, if one chugs a 12oz can of coca cola, he will exceed this threshold, and the excess fructose will be immediately stored as fat. If this happens too often, non-alcoholic fatty liver disease is the result. Even still, in my opinion the amount of pure sucrose intake required to create this situation is very high.

    As an alternative hypothesis, there is some evidence for the idea that it is fructose and PUFA taken together that is problematic, whereas fructose by itself may be harmless up into reasonably high quantities. I choose to err on the side of caution when it comes fructose consumption, and stick to relatively small quantities when I do consume it.

    Conspiracy theory alert:
    One of these days you will figure out that the AHA, FDA and NIH are all in the pocket of drug companies and industrial agriculture companies, and as such their health recommendations are totally unreliable. This started with the McGovern commission, and our country has never looked back. We now have a huge uphill battle where things that were never probable and never proven have become the medical consensus, and now the burden of proof has somehow been shifted to the scientific minded, rational people to PROVE A NEGATIVE; e.g. somehow demonstrate that saturated fat is not bad; which, for those of you keeping score, is a logical impossibility.

    Wheat, soy, to a lesser extent other grains and legumes, and vegetable oil; these are the problem foods. Saturated fat, cholesterol, animal proteins; these are the foods that are molecularly IDENTICAL to those that make up your body.

    When you lose weight, you are metabolizing saturated and monounsaturated animal fats, as well as a small proportion of your muscles. Once these fatty acids and amino acids are released from the muscles/adipose into the bloodstream, they are indistinguishable from those that come from eggs or a fatty steak doused with butter.

  26. Harriet Hall says:

    @Geoff,
    “The bottleneck would suggest that if there was ever a harmful effect of dietary salt, that trait would have been selected against,”

    Another example of the pitfalls inherent in evolutionary thinking. Evolution is not that simple. Some traits are not selected against because of “spandrels” and chance factors. Harmful traits like G6PD
    deficiency and beta thalassemia were not selected against because they also offered some protection from malaria. And a bad gene can be linked on a chromosome with a good gene and be perpetuated when the good gene is selected for.

  27. rhanneman says:

    Back to the original Rod Taylor study, whether or not it’s the strongest study in the world, and despite the fact that it tracks mostly observational studies, it still examines one of the two questions: Do people who actually ingest less salt have better or worse outcomes? We spend millions of dollars and have invested 30+ years in promoting this intervention and now find no evidence that it works. In fact, the two studies Taylor includes which are randomized trials (of congestive heart failure patients — a group that has for generations been advised to take low salt diets) found that those randomized to consume their normal salt diets lived longer and were re-hospitalized less. Still, the federal government chants its low-salt mantra and refuses to fund a prospective health outcomes study. They say it would take too long, but the truth is that the study would have been completed and its results available by now if it had been done when recommended.

    The second question is unexamined by Dr. Taylor et al and ignored in the comments so far, namely: is it even POSSIBLE to achieve a population reduction in salt intake. Studies by Willett, McCarron, Geerling, Staessen and others show salt intake levels unchanged over many decades (probably longer if studied), suggesting that, as Dr. Geerling’s research indicates, salt appetite is physiologically determined and not a matter of dietary choices at all.

  28. Geoff says:

    @Harriet

    From Shermer’s “The Believing Brain:”

    “Between technical and popular science writing, there is what I call integrative science [emphasis his], a process that blends data, theory and narrative. Without all three of these metaphorical legs, the seat upon which the enterprise of science rests will collapse. Attempts to determine which of the three legs has the greatest value is on a par with debating whether [pi] or r^2 is the most important factor in computing the area of a circle.”

    I understand your point and I agree. However, calling these “pitfalls” rather than “limitations” is unfair. Just because these limitations exist does not discount evolutionary reasoning as a tool in our tool box.

    I would argue that epidemiology is much less reliable, but that doesn’t stop people from using it, nor should it. We just need to be aware of the limitations, and make sure that we have an understanding of the “theory” (evolution) and “story” (the final stage of our evolution involved a lot of shellfish consumption, and as such, salt, so it is unlikely that salt would be harmful in comparable quantities) to bring it back the above Shermer quote.

    You mentioned that Shermer is a friend of yours, and as far as I know he’s also a very outspoken “skeptic.” Throughout the book, he consistently refers back to evolutionary reasoning to create a plausible story for why we make errors of patternicity, why we make errors of agenticity, why we experience a “sensed presence,” etc. Yet in the comments in the review of the book on this site, how many times did you criticize his use of evolutionary reasoning? Reasoning about behavior is MUCH more tenuous than reasoning about nutrition, for which we have a lot of hard evidence, including isotope studies, cook sites, comparative anatomy, fossils with tool markings, remnants of ancient tools, etc.

  29. Harriet Hall says:

    @Geoff,

    I see nothing wrong with trying to think of possible evolutionary explanations. But proving that your stories are true and basing modern dietary prescriptions on those stories is another matter entirely. In Shermer’s case, we know that humans make those errors today regardless of how they evolved, and we can try to overcome them: evolutionary explanations are fun to think about, but they don’t change our behavior. In the case of salt, we must rely on scientific studies about the health implications today, not speculations about human evolutionary history. Evolutionary stories based on what we “did” eat can’t tell us what we “should” eat today.

  30. Nescio says:

    Geoff,

    From the research I have seen, the increase in blood pressure due to salt is somewhere on the order of 3 points, and it is temporary. I have not seen any evidence, nor even any plausible mechanism, that suggests that salt intake might be detrimental long term in healthy individuals.

    Then I don’t think you have looked very hard. If people consume a high salt diet day after day this leads to constantly high blood pressure, and high blood pressure is strongly linked to cardiovascular disease. Salt has other detrimental effects as well. You might take a look at this recent review study. Here are the key messages of that study:

    - A dietary sodium chloride intake of more than 6 g per day is associated with increased blood pressure and thus cardiovascular risk.

    - Excessive dietary sodium chloride intake is not only associated with raised blood pressure and resultant organ damage but is also a risk factor independently of blood pressure.

    - Restricting the daily salt intake to 5–6 g in the general population is associated with an average reduction in blood pressure and a lowered incidence of hypertension and a lower cardiovascular risk.

    - Lowering the daily amount of salt ingested in food in the general population is possible only by means of reducing the sodium chloride content of processed foods.

    As for the mechanisms, there is a huge amount of research available into this if you look on PubMed. For example this study which looks at the kidneys and the aldosterone/mineralocorticoid receptor system in salt-sensitive hypertension.

    One of these days you will figure out that the AHA, FDA and NIH are all in the pocket of drug companies and industrial agriculture companies, and as such their health recommendations are totally unreliable. This started with the McGovern commission, and our country has never looked back.

    It seems you haven’t noticed that there are other countries in the world that do scientific research, like Germany which was the source of the first study I link to above, and Japan which is the source of the second, and that their health recommendations are generally similar to those in the USA. It is ridiculous to suggest that there is a global conspiracy to persuade people to restrict salt consumption. What would be the purpose and how could it be kept quiet?

    now the burden of proof has somehow been shifted to the scientific minded, rational people to PROVE A NEGATIVE; e.g. somehow demonstrate that saturated fat is not bad; which, for those of you keeping score, is a logical impossibility.

    Are you suggesting that the entire international scientific community is composed of unscientific, irrational people? Having spent many years in that community I can assure you that is not the case, the most intelligent and thoughtful people I have met have been part of the scientific community, and none of them would allow any government or business to dictate their research findings. I am constantly amazed at how the painstaking work of thousands of scientists over many decades can be so casually dismissed by people who clearly have little grasp of the facts.

  31. Scott says:

    Phrased a bit differently, evolutionary explanations can be explanatory, but are rarely predictive.

  32. Nikola says:

    Thank you for an excellent write-up, Scott.
    I’m not one to pull punches when it comes to media critique, but I have to blame this “misunderstanding” on the research team.

    Their ‘plain language summary’ clearly states:

    “Cutting down on the amount of salt has no clear benefits in terms of likelihood of dying or experiencing cardiovascular disease”

    Nothing even hinting at interventions or dietary advice. English isn’t my first language, but I would say that’s not simply poorly worded, but wrong.

  33. Geoff says:

    @Harriet

    We need evolutionary stories to make sense of the experiments we observe, again because “nothing in biology makes sense except in light of evolution.” We cannot take one without the other.

    If you show me a clinical trial in which grain intake, vegetable oil intake, sleep and blood vitamin d levels are controlled for (where the only source of vitamin d is whole food sources and the sun), and in that trial the experimental group still gets high blood pressure, even in a good animal model, I will take the risks of salt intake seriously. But until then, the burden of proof is still on those trying to overturn the null. And again, the null is not the medical consensus, the null is that which is predicted by our fundamental theory of biology.

    The title of this article says “more confirmation bias for your preferred narrative.” That means that you can use the data to support either view point, i.e. it is not definitive, i.e. the medical consensus, which states that salt intake causes high blood pressure, is not based on science. So if you take a completely agnostic approach to the literature from the onset, even without the evolutionary reasoning, you HAVE TO state the null as “salt intake has no effect on health,” and the burden of proof is still on the salt-phobes, not on me. That’s how statistics works, that’s how science works. I use the evolutionary story as support, because this does happen to be a situation in which I feel it is relevant, but the argument stands on its own without it.

    I know you don’t think that evolutionary stories about what we did eat can tell us what we should eat today, but this is something that you are wrong about. I look forward to the day when this is proven beyond a reasonable doubt.

    @Nescio

    Your link is epidemiology. Did they control for wheat intake? Other grains? Separate out white rice? Fructose? Linoleic acid? Sleep? Sun exposure corrected for skin tone? Whole foods vs. processed foods? If they didn’t correct for all of these factors, then they didn’t prove anything. Not that epidemiology can ever prove anything, but if they didn’t include all of these factors, then it’s not even worth a look because of our understanding of homo sapien evolution.

    I am not suggesting that the entire scientific community is unscientific, although I do think that a large portion of it is. I am suggesting that the entire medical community is unscientific, and I think that’s the basic premise of SBM in the first place. The whole point of SBM is to affect change in the medical community to make it more scientific.

    “I am constantly amazed at how the painstaking work of thousands of scientists over many decades can be so casually dismissed by people who clearly have little grasp of the facts.”
    I am constantly amazed that even in this day and age, people like you still think that scientists who live and die on grants have their best interest at heart. Do you even read this blog? Almost every post is about one scientist or another either fudging/cherry picking data or jumping to conclusions not supported by the facts.

  34. Scott says:

    That’s just it, though. You can’t make such confident predictions from pure evolutionary arguments in any but very rare cases. Certainly nothing that is so confident as to become the null hypothesis.

  35. Geoff says:

    @Scott

    First of all, yes you can. I can also make such predictions about chronic sun exposure, adequate sleep, acute vs chronic stress, dating dynamics, etc. If the model can predict outcomes correctly, then it should be considered. For example, the sun exposure thing is another huge myth. People think that it’s total sun hours, but there is absolutely no evidence that tanning without burning has any detrimental health effects. Also, melanomas tend to occur in areas that are rarely exposed to the sun, and seem to be highly correlated with one single acute exposure without any subsequent exposure. Read more about that stuff in Dr. Holick’s “The Vitamin D Solution,” but the point I am making is that the fact that we evolved spending most if not all of our daylight hours out in the sun without sunscreen in the summer predicts that chronic sun exposure on a proper diet while getting proper sleep is probably not bad for you (unless you have VERY pale skin). It requires an extremely high burden of proof to overturn this hypothesis. This burden of proof has absolutely NOT been met in the literature. On the other hand, a LACK of sun exposure is very highly correlated with other types of cancer. Which is more dangerous? Well, I think you know my opinion on the matter.

    Second of all, it doesn’t matter, because even without an evolutionary basis, the null hypothesis is still that salt does not cause long term problems, and this still has not been overturned.

  36. Nescio says:

    Geoff,

    Your link is epidemiology.

    No it is not. It is a review of several studies, some are epidemiological studies, some are prospective intervention studies. There is a broad agreement between these studies on the effect of salt consumption and of reduction in salt consumption. Why would there be any difference between the intervention groups and non-intervention groups for any of the factors you mention? That is the purpose of randomization in studies, to eliminate such confounding factors.

    I am suggesting that the entire medical community is unscientific, and I think that’s the basic premise of SBM in the first place. The whole point of SBM is to affect change in the medical community to make it more scientific.

    The entire medical community is unscientific? I don’t think many of the contributors here would agree with you, because that’s ridiculous. If that was true the whole of modern medicine would be unscientific, and that is clearly not true. There is work to be done making it more scientific, and that is what I understand this blog to be about. Anyway, it is not the medical community (if by that you mean clinicians) that has come to the conclusion that high salt consumption is an important risk factor for cardiovascular disease. It is the scientific community.

    Do you even read this blog? Almost every post is about one scientist or another either fudging/cherry picking data or jumping to conclusions not supported by the facts.

    Yes I do read this blog, and I think you misrepresent it. In any case, the hypothesis that consuming too much salt leads to cardiovascular disease and that reducing salt consumption reduces the risk of cardiovascular disease is not based on the work of one maverick scientist “fudging/cherry picking data or jumping to conclusions not supported by the facts”, it is based on a large body of evidence from thousands of scientists all over the world. I think you need more than a half-baked theory about Paleolithic people eating a lot of shellfish to refute that body of evidence.

  37. Harriet Hall says:

    @Geoff,

    “chronic sun exposure on a proper diet while getting proper sleep is probably not bad for you”

    You can question melanoma, but you can’t question skin damage. Just look at both sides of the shirt line on any elderly farmer’s neck. Sun exposure markedly increases wrinkles. But I bet you can think of some evolutionary explanation to show that wrinkles are good for us. :-)

  38. Harriet Hall says:

    @ Geoff,

    Fruitarians argue that we evolved to eat fruit. Evolutionary arguments could support either salt eating or salt avoidance, a raw meat diet, only eating food that we gathered or hunted ourselves, etc. Even the best evolutionary explanation could be telling us what actually happened in our evolutionary history or could be telling us a false or distorted story. You have thought of a plausible explanation but there may be another more plausible explanation that you have not thought of. Scott is right that you can’t make confident predictions from pure evolutionary arguments in any but very rare cases.

    One could even argue (I hope you don’t!) that we should eschew lifesaving medical interventions because they interfere with the survival of the fittest principle. Evolutionary arguments may inform, but they can’t dictate. Usually they can’t be tested for accuracy.

  39. pmoran says:

    Geoff:
    So if you take a completely agnostic approach to the literature from the onset, even without the evolutionary reasoning, you HAVE TO state the null as “salt intake has no effect on health,” and the burden of proof is still on the salt-phobes, not on me. That’s how statistics works, that’s how science works.

    Ultimately, yes. Always, where nothing less than near-absolute truth will do.

    But this is applied medical science, which often has to make do with less certainty. Medical advice often reflects “this is what the balance of evidence suggests for the present practical purpose.”

    So if there is evidence that salt restriction reduces blood pressure (there is) and that hypertension is a major factors in certain morbitities (it is), then it is prudent to advise limiting salt intake.

    Note that people’s lives and brains are at stake so there is also a precautionary aspect to that advice. This is why chiropractors should not be manipulating necks willy-nilly even if they believe that the risk of stroke is not fully “proved”.

  40. Geoff says:

    @Harriet

    You’ve mentioned this thing about fruititarians before. I’m sorry but taking the position that we evolved to eat only fruit is the logical equivalent of saying that homeopathy works, same level of evidence. It is not an equally valid statement given the facts. I feel like we’ve been pretty civil with each other in this comment thread, but for you to suggest that it is equally plausible that we evolved to eat meat or we evolved to eat only fruit is just complete and utter BULLSHIT. I will not let you get away with that reasoning, just like SBM doesn’t let the homeopaths get away with their pseudoscience, and for the same reason.

    There is also very good evidence of cooking food for hundreds of thousands of years if not more. There were definitely periods of time in which we had very high salt intake, so while I would say that the evidence of this is weaker, it is still pretty plausible.

    To the question of sun causing skin damage, I’m not going to argue the point much more, but in my opinion the damage that the sun does to the skin is more about the inflammatory conditions in the body than it is about the actual sun exposure. What I am saying is that if someone eats paleo-ish and gets over eight hours of sleep a night in a pitch black room, once he builds up a base tan in a sensible way, the sun no longer affects significant oxidative stress on the body. There is a little bit, but because the the inflammatory conditions of the body are low, the body can deal with these issues without causing problems. I would predict that the aging effect of sunlight goes to miniscule levels, and the health benefits of the sun far outweigh any risks.

    @pmoran

    I haven’t seen any intervention trials that show that to my satisfaction, please link to one or more relevant trials to I can take a look.

    I can give you a number of possible explanations as to why reducing salt intake could improve blood pressure in an intervention trial that are not actually about the amount of salt:

    1) Salt represents a rewarding quality of food, so reducing salt intake reduces the reward value of the food, reducing the fatmass setpoint, When they reduce the salt intake, does weight go down? Does salt intake reduce blood pressure independent of weight loss? Independent of calories?
    2) Salt, as a preservative, is in high amounts in processed foods. processed food is designed to be hyperrewarding, so reducing processed food intake should also reduce the fatmass. Was processed food controlled for?
    3) Wheat, vegetable oil, soy, fructose, corn, beans, were these all controlled for?

    I wish that I had a few millions of dollars lying around to fund studies, because I can in fact all but guarantee that if we go head to head, diet to diet, I can design a diet inordinately high in salt (~8g a day or more) that is more effective at reducing blood pressure than an AHA/food plate or whatever diet that is extremely low in salt.

    1. Harriet Hall says:

      @ Geoff,
      “for you to suggest that it is equally plausible that we evolved to eat meat or we evolved to eat only fruit is just complete and utter BULLSHIT.”

      Thank you for lowering the tone of the discussion and for misinterpreting my words. I was certainly not suggesting that we evolved to eat fruit! I was trying to point out that when people start making up evolutionary “just so” stories they can come up with a variety of stories. Some are obviously more plausible than others, but there is no way to prove that even the most plausible explanation is the correct one. It’s still only speculation. You keep managing to sidestep this crucial point.

      “I can in fact all but guarantee that if we go head to head, diet to diet, I can design a diet inordinately high in salt (~8g a day or more) that is more effective at reducing blood pressure than an AHA/food plate or whatever diet that is extremely low in salt.”

      Since you started it, I call bullshit on that statement. Those are the words of a true believer, not of a scientist. Perhaps you don’t understand how foolish such a statement looks to science-based thinkers. A true believer wants to use science to prove he is right; a scientist wants to do science to find out whether his hypothesis is correct. A scientist asks questions; you are trying to impose your preconceived answers.

  41. Nescio says:

    Geoff,

    Are seriously suggesting that UV exposure is not a risk factor for melanoma? That is seriously crazy. I suggest you take a look at some accurate information about melanoma instead of believing Dr Holick who was interviewed on ‘Coast to Coast’ (a major red flag for quackery in itself) and claimed that the dinosaurs became extinct because of vitamin D deficiency (link to MP3).

    Maybe (but only maybe) the importance of vitamin D has been underestimated by conventional medicine, but it has certainly been massively overhyped by CAM proponents.

  42. Nescio says:

    I’m not sure why that first link failed. It should have linked to this page: http://www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/dermatology/cutaneous-malignant-melanoma/

    Oh for a preview function on SBM!

  43. Geoff says:

    @Harriet

    I am convinced, not a true believer. I trust the judgement of my mind, and am convinced enough to wager a significant portion of my net worth, maybe upward of 90%, on the outcome of that particular experiment. Just like last night when I was playing pot limit omaha and I shoved all in with the made nut straight and nut flush draw, even though it was possible for the guy I was heads up in the pot against to have the made nut straight and nut flush draw as well as be drawing to a full house. There were only three four-card hands in the deck that could possibly be ahead of me, so my confidence interval about wining the hand gave me the odds to make that kind of a wager. Same goes here.

    If the experiment happened and it turned out that I was wrong, I would reevaluate my stance, but at this juncture, I am convinced enough; based on the evidence that I have seen with my own two eyes; of that outcome to risk it, just as the first person to test a parachute was confident enough in the science of terminal velocity to risk his life.

  44. Harriet Hall says:

    @Geoff

    “I trust the judgement of my mind.”

    You are wrong to trust that. We know from long experience that the mind’s judgment is not reliable: that’s why we need science. Apparently you have not learned that lesson or perhaps you imagine that you are somehow exempt. You may well be right, but you could very well be wrong. It is premature to be convinced without adequate evidence.

  45. Nikola says:

    @Geoff

    What you “see with your own two eyes” is anecdotal experience.
    And anecdotes do not scientific evidence make.

  46. Geoff says:

    @Nikola

    That was metaphorical. It includes reading an article, for example.

  47. Rob Tarzwell says:

    Pot Limit Omaha is relevant, uhh, *how* exactly?

  48. Nikola says:

    Pot Limit Omaha is relevant, uhh, *how* exactly?

    I think he means that his powers of inference are more reliable than what he sees as weak evidence to the contrary.
    As Harriet said, it’s possible he turns out to be “right”, just not very probable.

  49. JPZ says:

    @Nescio

    We had Holick speak to our group about vitamin D because we were concerned about cases of rickets arising in developed economies. His advice was “Wait 15 minutes, then apply sunscreen.” He likes flashy animation on his slides and bold language, but that advice struck me as prudent when you consider vitamin D metabolism and the probable minimal increase in melanoma risk from 15 minutes exposure each time.

    @Geoff and Harriett Hall

    A high intake of fruits and vegetables is unquestionably healthy. We evolved to eat meat as evidenced by vitamin B12 deficiency. In this era of modern science, we can overcome that need with synthetic or microbial B12. In some respects, we can now be healthier and make scientifically-supported, healthier diet choices than evolution allowed us to do before.

  50. Geoff says:

    @Rob

    It was an illustration of the concept of a high confidence interval, as a direct contrast to the concept of a “true believer.” It’s possible that I’m wrong, and it’s always a possibility that I’m open to, but my confidence interval is high enough that I’d be willing to stake nearly all of my money on it.

    @JPZ

    There is no question that there are people for whom fruit is problematic in high quantities. I am in agreement that for healthy individuals, fruit is not an issue, but for people with a fatty liver, or glucose tolerance issues, this is not the case.

    In general, I find the idea of “magical plant foods” to be highly implausible, i.e. it is unlikely that any individual plant food is an essential part of our diet. In my opinion, a large proportion of the correlation in the literature of fruits and vegetables with health is due to already healthy people making what they perceive as “healthy” food choices. Other than that, fruits and vegetables are healthy because they displace calories from grains and snacks, and they have relatively low reward values, so they help bring the fat mass setpoint back to normal.

    While I agree that we can be healthier now on average than in the past due to a lack of natural predators and the use of antibiotics, in my opinion it is naive to suggest that it is possible to achieve health beyond the long tail of our hunter gatherer ancestors through “proper nutrition.” Our digestive tract and metabolism evolved with the specific intent of processing a set of foods, and it is unlikely that foods outside of this subset would be healthier, though very likely that they would be less healthy. That would be akin to putting rubbing alcohol or jet fuel into a mustang and expecting it to run more efficiently than it does on high octane gasoline.

  51. Harriet Hall says:

    @Geoff,

    “a high confidence interval”

    You are misusing a statistical term to denote your personal opinion based on inadequate evidence and speculation.

    “Our digestive tract and metabolism evolved with the specific intent of processing a set of foods, and it is unlikely that foods outside of this subset would be healthier, though very likely that they would be less healthy.”

    Unwarranted assumption. We evolved to survive with the foods that were available, but that could have prepared us to survive even better with other foods. And as food sources multiply, we evolve to adapt to the changes. And someone who is arguing on the basis of evolution should know better than to say something evolved “with intent.”

  52. JPZ says:

    @Geoff

    You are partially right on fatty liver and, unfortunately, incorrect on glucose tolerance (http://www.ncbi.nlm.nih.gov/pubmed/12806219). I did not mention the so called “super foods,” I don’t believe the hype, and please don’t use them as a “straw man” to support your argument. Your opinion about fruits and vegetables functioning by displacing other less healthy foods (caloric density) is a bit misleading and overlooks components like fiber, potassium, magnesium, ALA et al. and useful contributions to glycemic load. Fruit and vegetable interventions have shown specific health benefits (http://www.who.int/dietphysicalactivity/publications/f&v_cvd_diabetes.pdf).

    “Our digestive tract and metabolism evolved with the specific intent of processing a set of foods, and it is unlikely that foods outside of this subset would be healthier, though very likely that they would be less healthy.”

    Provide citations please. I do not believe this has any basis in fact.

    My point was that we now have scientific evidence that allows us to make food choices that facilitate our living healthier and longer. Evolutionary selection not only makes meat conditionally essential to our survival (vitamin B12), but it also gave us a taste and satiety system making us prone to obesity in our economically privileged situation. Why these came to be is speculation and opinion based on partial evidence. Evolutionary arguments must be taken with a grain of salt and can be tailored to say anything.

  53. Chris says:

    I was thinking the following was going to be off-topic, but reviewing the article by Mr. Gavura realized it is on topic.

    I recently made pizza dough at home. I thought it was because I was still sleep deprived from attending TAM, but the normally well behaved dough was a nightmare. The dough rose too fast, and it was difficult to roll out (I kept having to add more flour).

    After making three personal pizzas and three “cheese bread” pizzas it was remarked that the dough was bland. I had totally forgotten to add the salt. The salt regulates the yeast growth and moisture.

    Growing up with a stepmother who had genetic high blood pressure we often found ways to avoid salt more than other families (say what you will, but her family used to regularly die a horrible painful death in their 40s until early diuretic medication became available, then they lived well into their 80s). The main cook, my father, took it as a challenge to figure out ways to create flavor with less salt. When I got married I continued this, and had to physically resort to pulling the salt shaker from my husband admonishing to taste before shaking.

    I cannot make pasta in water that is as salty as the sea, which is what it recommended on cooking shows. It is against my nature, and no one in my house has complained. I did once go to a pasta cooking demonstration at my local high-end cookware shop, only to find it inedible due to the amount of salt! What we perceive as salty or not may be what we are used to.

    Even still, when the Campbell Soup company put out low-sodium cream of mushroom soup I found it bland. I also found the lack of mushrooms disappointing. My solution was to slice mushroom, put them in a pan with a sprig of rosemary, cover them with a bit of white wine and cook them down. Those gave me both the flavor and texture kick that made the soup much better.

    Yes, there are some cases where salt should be limited. And it is very necessary in yeast breads. But there are the matter of what you get used to, and sometimes there are creative ways to get flavor.

  54. eurogene says:

    Interesting and not uncommon misreadings of Cochrane reviews. However in fairness to the misreporting by the press (but NOT SciAM!) whoever wrote the Cochrane “Plain Language Summary” headline is the first culprit:

    Cutting down on the amount of salt has no clear benefits in terms of likelihood of dying or experiencing cardiovascular disease

    Apart from all the other issues discussed it did show that “encouragement to reduce salt intake did lead to a reduction in salt eaten and a small reduction in blood pressure after more than six months”

    OK that is not a cure – but a small reduction in 6 months in a risk factor for diseases that develop over 20-30 years is i think a clear benefit. Just DO NOT expect short trials to show a clear benefit in “likelihood of dying or experiencing cardiovascular disease”

    the plain language summary is easy to understand, pity it is plain wrong

  55. margaretrc says:

    The way I see it, the evidence is not strong enough to warrant advising everyone to limit salt consumption, as the USDA does in its 2010 Dietary Guidelines (though everyone would do well to limit consumption of processed foods!). We need some salt and everyone’s individual needs vary depending on activity levels, etc. Individuals who demonstrate a clear salt sensitivity would be a different case to be treated as appropriate under the guidance of his/her physician.
    @Ken Hammer, You might want to consider switching to a low or restricted carbohydrate, high fat diet to address your BP and weight issues. There are at least 14 RCTs (good ones–many others that aren’t so good) that demonstrate superior success for weight loss on restricted carbohydrate diets: http://www.dietdoctor.com/low-carb-winning-14-%E2%80%93-0 The same studies also show more improvement in cardiovascular markers for the low carbohydrate, high fat diet compared to low fat, high carbohydrate. Restricting carbohydrates–without restricting fat or calories (the latter will restrict themselves naturally when you eat LCHF) allows you to lose weight without feeling hunger, which will ultimately doom any low calorie, low fat diet to failure and all your previous problems will return, with a vengeance. In addition, and this is Biochemistry, restricting carbohydrates lowers blood insulin levels, which in turn signal the kidneys to not retain water and that should address any BP issues that remain fairly quickly, although it seems you’ve already corrected that. (Elevated insulin levels direct the kidneys to hold onto water. When the insulin levels fall, this direction ends and water is flushed out naturally. It’s true that, on a LCHF diet, the initial weight loss includes water weight.) In fact, on a low carbohydrate, high fat, moderate protein diet, it is advised to up sodium intake–at least at the beginning–to compensate for that lost via the kidneys due to the drop in insulin levels. http://www.proteinpower.com/drmike/saturated-fat/tips-tricks-for-starting-or-restarting-low-carb-pt-ii/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+drmikenutritionblog+%28The+Blog+of+Michael+R.+Eades%2C+M.D.%29 Unlike a low fat, high carbohydrate diet, the LCHF diet is fairly easy to maintain because it doesn’t ask the body to live with conditions that go against it’s nature. And anyone who’s tempted to call proponents of LCHF quacks, please check the science first. Both the links above are to sites maintained by medical doctors who have done extensive research into the science behind both LCHF and LFHC and found the latter wanting, and there are many more like them. I am not saying LCHF is for everyone. People who haven’t messed up their metabolism from years of eating the low fat, low cholesterol, high carb diet recommended by our USDA (without the science to back it up) (and all the sugar and starch laden processed foods and beverages put out by industry in response) can perhaps exercise moderation in all things and maintain weight (or even lose weight if they only have a moderate amount to lose), as evidenced by myriad cultures outside the US who eat a wide variety of traditional cuisines, yet have a much better health profile than exists here in the US. (And those who switch(ed) to our guidelines suffer(ed) the same consequences!) Is this off topic? Perhaps, but I don’t think so, as it is quite possible that the recommendations to eat an (unnaturally) low fat, high carb, grain based diet (full of those same processed foods and beverages mentioned above) have contributed to any problems we do have with salt. Cultures that eat traditional diets–Mediterranean, French, Thai, Inuit, for example–do not have the same issues and don’t require/recommend limits to salt intake. It happens naturally from eating natural, whole foods that we were meant to consume.

  56. CarolynS says:

    I find the tone of much of this discussion a little discouraging and not science-based. Basically the implication is that we already know the answer but this is based on a kind of peculiar reasoning. If we have data that A causes (or is associated with) B and that B is associated with C, therefore if we change A, C will change, and we don’t need any actual evidence as to the effects on C of changing A. It almost seems that various people here take the null findings as evidence that salt restriction will work! The logic is something like”well,it’s obvious that salt restriction is beneficial but we can’t show it beause it’s too hard to demonstrate, therefore let’s just assume it’s beneficial.” Isn’t this kind of the opposite of science-based? It seems that the press in fact fairly correctly reported the written conclusion of the authors. Although the interventions didn’t work to change salt intake very much if at all, perhaps that in itself should tell us something about the possible effects of trying to intervene.

  57. margaretrc says:

    @CarolynS, Well said.
    @Scott Gavura, “From a population perspective, interventions that dramatically lower salt intake result in lower blood pressure.” Really? How much? Can you link to some studies that prove that? Not that population studies are all that reliable. “we do have considerable epidemiologic evidence to suggest that reducing dietary salt consumption is likely to offer net benefits in the management of hypertension.” Again, really? Again, where are the studies? And epidemiological evidence is just as suspect as population studies–too many confounding variables. It is epidemiological evidence that led to the (extremely misguided) war on saturated fat, a war that has had a plethora of unintended consequences–epidemiological evidence that a) was fudged and b) has not held up to the scrutiny of RCTs. So you’ll pardon me if I retain my skepticism as to the positive effects of a reduction in salt intake for the vast majority of the population that is not salt sensitive–myself included. And I am 64 years old and my blood pressure is great. My husband is 70 and his blood pressure is right where it was 30 and 40 years ago and great. My husband loves salt and sprinkles liberally on everything except ham. Anecdotal, for sure, but definitely black swans for the “salt sensitivity seems to increase with age” hypothesis. Here’s another take on the same Scientific American article: http://www.fathead-movie.com/index.php/2011/08/01/another-a-salt-on-science/ If a person truly is sensitive to salt and lowering salt intake produces marked improvement in blood pressure, it stands to reason that that person should lower salt intake. But perhaps there is something else causing both the salt sensitivity and the high blood pressure and it might be wise to investigate that. For the rest of us, forget it.

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