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Red Meat: Is It Hazardous to Health?

Red meat consumption has been linked to diabetes, cardiovascular disease, and several types of cancer (breast, colorectal, stomach, bladder, prostate, and lymphoma). There are plausible mechanisms: meat is a source of carcinogens, iron that may increase oxidative damage, and saturated fat. But correlation and plausibility are not enough to establish causation. Is red meat really dangerous? If so, how great is the risk? A couple of recent studies have tried to shed light on these questions, but they have raised more questions than they have answered.

A Systematic Review and Meta-Analysis

A new study in Circulation, “Red and Processed Meat Consumption and Risk of Incident Coronary Heart Disease, Stroke, and Diabetes Mellitus. A Systematic Review and Meta-Analysis,” by Micha, Wallace and Mozaffarian, is a systematic review of the literature. It analyzed 17 prospective cohort studies and 3 case-control studies, with a total of 1.2 million subjects. As far as I can judge, it appears to be a well-done systematic review with excellent methodology and multiple precautions. They even looked for things like publication bias (which they did not find).

They found that the consumption of processed meats, but not red meats, is associated with a higher incidence of coronary heart disease and diabetes. (Processed meats include bacon, sausage, ham, hot dogs, salami, luncheon meat and other cured meats.) The increased risk per 50 gram serving of processed meats per day was 42% for heart disease and 19% for diabetes. Unprocessed red meats were not associated with CHD and were associated with a nonsignificant trend towards higher risk of diabetes. They found no association with stroke, but this was based only on 3 studies.

They commented that

“…each of these individual studies has potential limitations, and our findings should be interpreted in that context. On the other hand, this represents the most complete worldwide evidence to date of the potential effects of red and processed meat consumption on incidence of CHD, stroke, and diabetes mellitus.”

A Large Study of Meat and Mortality

A 2009 study in the Archives of Internal Medicine, “Meat intake and mortality: a prospective study of over half a million people,” by Sinha et al., was more comprehensive in that it looked at many different conditions like cancer and cardiovascular disease, and it measured various causes of mortality as well as all-cause mortality.

The half a million subjects were 51-70 years old and were from various geographic locations in the US. They filled out a questionnaire that asked about their usual consumption of foods and drinks and portion sizes over the previous twelve months. Their diets were classified as high, medium or low risk meat diets based on the amount of red meat and white meat adjusted for energy, and they were split into two groups using median consumption as cutpoints. The study was prospective: it assessed diet first and then followed subjects for 10 years and recorded deaths and causes of death.

It concluded that red and processed meat intakes were associated with modest increases in total mortality, cancer mortality and CVD mortality.

In general, those in the highest quintile of red meat intake tended to consume a slightly lower amount of white meat, but a higher amount of processed meat than those in the lowest quintile. Subjects who consumed more red meat tended to be married, more likely to be of non-Hispanic white ethnicity, more likely to be a current smoker, have a higher body mass index, and a higher daily intake of energy, total fat and saturated fat; whereas they tended to have a lower education level, were less physically active and consumed less fruits, vegetables, fiber and vitamin supplements.

They found an increased risk associated with accidental deaths with higher consumption of red meat in men but not in women. It’s hard to know how to interpret that. They found an inverse association for white meat intake: it appeared protective against total mortality, but there was a small increase in risk for CVD mortality in men.

The overall hazard ratios for men ranged from 1.06 to 1.31 for red meat (increasing steadily by quintile of meat intake), .90 to.92 for white meat, and 1.01 to 1.16 for processed meats. The effect of red meat was greater than the effect of processed meats, which was opposite to the findings of the review in Circulation.

They tried to correct for confounders. In the process, they found an increased risk with white meat consumption among never-smokers and commented that the reason was not readily apparent. I suspect that the reason was that if you look at a large enough number of subgroups you can always find an occasional chance correlation that is meaningless.

Their data also showed that increased red meat consumption was correlated to smoking, lack of exercise, higher total calorie intake, higher body weight, higher total fat and saturated fat intake, lower intake of fruits, vegetables and fiber, and lower use of vitamin supplements. Could it be this constellation of factors, rather than red meat itself, that leads to higher mortality?

They estimated that

For overall mortality … 11% of deaths in men and 16% of deaths in women could be prevented if people decreased their red meat consumption to the level of intake in the first quintile.

I don’t think this can be determined from the data. They haven’t reliably ruled out all possible confounding factors and they don’t have any direct evidence that taking people with a high red meat intake and reducing their intake improves their longevity.

What about Vegetarians?

A recent study comparing vegetarians to non-vegetarians found that

…in comparison with regular meat eaters, mortality from ischemic heart disease was 20% lower in occasional meat eaters, 34% lower in people who ate fish but not meat, 34% lower in lactoovovegetarians, and 26% lower in vegans. There were no significant differences between vegetarians and nonvegetarians in mortality from cerebrovascular disease, stomach cancer, colorectal cancer, lung cancer, breast cancer, prostate cancer, or all other causes combined.

Meta-analysis of several prospective studies showed no significant differences in the mortality caused by colorectal, stomach, lung, prostate or breast cancers and stroke between vegetarians and “health-conscious” nonvegetarians.

In vegetarians, a decrease of ischemic heart disease mortality was observed probably due to lower total serum cholesterol levels, lower prevalence of obesity and higher consumption of antioxidants. Very probably, an ample consumption of fruits and vegetables and not the exclusion of meat make vegetarians healthful.

Conclusion

Epidemiologic studies based on self-reporting and recall are not the most reliable form of evidence. What are we to make of all the confusing data? The evidence is far from conclusive, but it suggests that it would be wise to limit our consumption of red meat. The evidence is not strong enough to support recommendations that we give up red meat entirely or become vegetarians.

Aristotle said “Moderation in all things.” Mom said “Eat your vegetables.” They were both right.

Posted in: Cancer, Nutrition

Leave a Comment (38) ↓

38 thoughts on “Red Meat: Is It Hazardous to Health?

  1. Ken Hamer says:

    Moderation is right… in both directions.

    I recall many years watching a local news station doing a piece on healthy eating. They featured a woman who had for lunch every day two slices of brown bread with four slices of cucumber between them. (I hesitate to call that a “sandwich.”) This “vegetarian” meal was called an excellent choice by the dietician at the centre of the news piece.

    But I couldn’t help but think if I was forced to eat that every day cancer, CVD, diabetes, and the rest would pale in comparison to the risk of death by suicide.

  2. Ken Hamer says:

    Oh yeah, and seen on a poster in my office complex:

    “Vegetables are what food eats.”

  3. rmgw says:

    Before this discussion takes off, can we please keep the distinction between eating as a vegan, which is part of a whole ethical stance towards sentient life, and food fads/attempts to live forever etc?
    If refraining from eating animal products of all sorts is good for human health, whizzo. The American Dietetic Association has pronounced on vegan diets to the effect that, properly planned, as any diet has to be, vegan eating is appropriate from cradle to grave, however soon or late the latter is reached. So we can discard all the hype about tweaking our diet for an extra five minutes or whatever is claimed and concentrate on the ethics of the situation.
    The fact that there exists legislation in favour of animal welfare in almost every country in the world points to the fact that humans believe they have ethical obligations to other species: veganism takes this to what many – including myself, in case you hadn’t guessed – think to be a logical conclusion. The debate on details of the omnivore diet is another issue altogether.

  4. “Epidemiologic studies based on self-reporting and recall are not the most reliable form of evidence.”

    That’s putting it kindly. Self-report can generate interesting findings, such as that Americans’ broccoli consumption is six times US sales.

  5. BillyJoe says:

    Talking about moderation:

    A local dermatologist had for a long time been notorious for insisting that his patients use sunscreen 365 days of the year. He, himself, used to be observed donning hat and gloves everytime he left the clinic.
    One day he did a quick about face…and fractured his ankle.

  6. Alison – LOL – how did we manage to hide all that broccoli under our plate?

  7. Keith Logan says:

    The health industry I have found is very fond of extremes; especially in terms of Nutrition. As stated in the article it is best that things are taken in “moderation” but often this is too vague a plee for the general population.

    As I have seen in the short time I have been studying Nutrition the consensus of my lecturers suggst that we are currently in a high protien low carb section of the diet cycle (western society seems to be cycling between high carb/low protien and high protien/low carb). So as a result people tend to over consume red meat, or other sources of protien.

  8. Keith Logan says:

    The health industry I have found is very fond of extremes; especially in terms of Nutrition. As stated in the article it is best that things are taken in “moderation” but often this is too vague a plee for the general population.

    As I have seen in the short time I have been studying Nutrition the consensus of my lecturers suggst that we are currently in a high protien low carb section of the diet cycle (western society seems to be cycling between high carb/low protien and high protien/low carb). So as a result people tend to over consume red meat, or other sources of protien.

  9. windriven says:

    “The increased risk per 50 gram serving of processed meats per day was 42% for heart disease and 19% for diabetes.”

    This from a meta-analysis! I would love to read the authors’ discussion of the statistical legerdemain used to produce this breathtakingly precise result. I’ll never be able to look a strip of bacon in the face again!

    As Mark Twain noted: Facts are stubborn, but statistics are more pliable.

  10. passionlessDrone says:

    Hi Harriet Hall –

    Thank you for posting this. Very nicely done.

    - pD

  11. Bovine Love says:

    Very interesting article. As an aside, I always find the phrasing “… deaths … could have been prevented.” to be quite odd. Postponed, perhaps, but I doubt it could be prevented.

  12. I’ve heard that before regarding processed meat vs fresh meat. I’m curious, is there any information about what may be problematic in processed meats. Is it the high fat content, high salt, sodium nitrate, something else in the processing, or a cocktail of some or all?

  13. qetzal says:

    Apropos Alison’s comment, I wonder how much is known about the (un)reliability of self-reporting. Are there methods that are ‘proven’ to sufficiently minimize bias? Are some kinds of self-reporting more reliable than others? (E.g., maybe you can’t trust people’s recall of total broccoli consumption, but their recall of consumption frequency or consumption relative to other foods might be more reliable.)

    Seems to me this would be a hard thing to study. You need a way to compare recall to actual consumption, but measuring actual consumption could also alter people’s recall behavior.

    I hope there is at least some research to show how far to trust recall. Otherwise, I’m not sure how we can believe anything these studies find.

  14. Ash says:

    qetzal – I don’t think there are any perfect ways to evaluate food consumption (at least not for people living their normal lives and not in a controlled setting). You can ask people to record what they’re eating throughout the day, possibly even measuring it, but this has its own biases – people may not eat normally if they’re forced to write down what they’re eating, and there could also be issues with people under-reporting the “bad” stuff they’re eating out of embarrassment (not to mention it’s harder to collect this sort of data since it requires active participation by the subjects). You can also monitor food purchased from stores or grown/imported, but this doesn’t tell you how much is wasted vs. eaten or give any information about individual dietary patterns.

  15. qetzal,

    Quite a lot is known about the unreliability of self-reporting.

    Discussion of validity of food and nutrient intake collection methods (generally) here:
    http://ije.oxfordjournals.org/cgi/content/full/32/6/1062
    [T]he food frequency questionnaire (FFQ) was found to have very low validity for both total energy and protein intake measurements: attenuation factors were found to be close to 0.1 in both cases.”

    Because any method of evaluating food intake has inherent problems, understanding consumption typically needs to be triangulated in several ways.

    The method here was a 124-item food frequency questionnaire that was mailed to 3.5M retired people between the ages of 50 and 71, and replied to adequately by 0.55M people. “The FFQ collected information on the usual consumption of foods and drinks and portion sizes over the last twelve months.” The advantage of a food frequency questionnaire is that it’s simple to administer; disadvantage is that it’s unreliable.

    To cross-check the results of the FFQ, “The validity of the FFQ was estimated using two 24-hour recalls,14 and the estimated energy adjusted correlations ranged from 0.36 to 0.76 for various nutrients, and attenuation factors ranged from 0.24 to 0.68.”

    A 24-hour recall is ideally done by interview. Someone sits down with you and asks when you ate or drank for the first time yesterday, and what it was, and works from there. They don’t ask what you had for breakfast, because that’s a leading question: not everyone has breakfast. And if you ate or drank for the first time at 17h30 yesterday, and it was a six-pack of beer, that’s fine. The interviewer does not propose a list of 123 other things you might have consumed yesterday that would make you look better, but goes on to ask if you consumed anything else or whether that was it. An advantage of a 24-hour recall is that, done properly, it gives you a pretty good idea of what someone actually ate; disadvantages are that it’s only one day, and that day may be atypical; people forget things; and no matter how skilful you are, people are likely to lie.

    It’s possible but unlikely that their two “24-hour recalls” were phone interviews with each of the 550k people who answered the questionnaire. It’s more likely that they asked people to use the FFQ to check off the foods they ate on two different days. (The cited reference that explains the methodology for cross-checking isn’t one I could locate online, even in the abstract.) This is likely to lead to overestimating food variety and underestimating portions.

    A 24-hour recall is superior to a 12-month FFQ, but for the purposes of the study they need to use the 12-month FFQ. The correlations between the FFQ and the two 24-hour recalls were between 0.36 and 0.76.

    Another method of collecting food intake information is a 7-day weighed food intake diary, in which you carry a scale around with you and weigh everything you eat. An advantage is that the recorded food is known very accurately. Disadvantages are that it’s difficult; people know they are being observed and may make choices that make them look good during the observation period; people may choose food that’s easy to weigh and not record food that’s difficult to weigh.

    Yet another method is to look at grocery receipts for a time period. Advantage is that you see what people really buy. Disadvantages are for multi-person households (who’s getting the milk: the baby? the teenage boy? the latte addict who eats meals there but doesn’t sleep there? is it shared?) and that waste is not recorded. (What — you never throw out food?)

    A related method is inspecting the cupboards. Unreliable in that people might have cans that they’ve never opened in years and shouldn’t count as part of the diet; same issues of multi-person household as above; and doesn’t include food eaten outside the house. Still, it’s a good quick-and-dirty starting point if you want to know whether anyone in the household is likely to be eating well.

    To get around the problem of what is actually being eaten as opposed to being bought and stored or allowed to go bad, there is garbage inspection. Works well for people who eat all packaged food, and you can see what got thrown out. However we’re back to the multi-person household problem and the eating-away-from-home problem and it doesn’t work for people who prepare their own food.

    *** *** ***

    Question: can someone explain attenuation factors? Both articles I reference in this comment refer to them, but I don’t know what they are.

  16. Well, that’s good news. No more guilt for me. Surprising that vegans aren’t much better off than the rest of us. Also surprising that colorectal cancer wasn’t affected greatly by meat consumption

  17. passionlessDrone says:

    Hello friends –

    It occurs to me to wonder if some of the problems with self reporting confounds could be addressed by animal studies, where someone gets to choose which foods animals get and we don’t have to worry about the fuzzy nature of people relaying their habits.

    This might be very time consuming, expensive, and ultimately a negative finding, which might make it problematic to perform, but I was still curious if anyone had any thoughts on this.

    - pD

  18. rork says:

    Attenuation: I did not read the articles, nor am expert on diets, but attenuation in my areas refer to the actual differences in subjects being larger (or more rarely, smaller) than the estimated differences, often particularly for the largest values. Like when instruments or chemistry “saturates”. Perhaps heaviest meat eaters under-report their actual grams/day, so the risk increase per gram/day would be off. I could be off too.

    @rmgw: Some people avoid the flesh of some animals (like cow, pig, chicken), not primarily because of the ethics about that animal’s treatment, but because of the environmental sins resulting from it’s having been raised. I do not feel for cows, I hate them. It’s about Diet for a Small Planet.

    I have trouble filling out diet questionnaires, since deer is not a separate category, so I count it as red meat, even though I don’t think the fat content competes with cow.

  19. BobbyG says:

    As I wrote in my essay about my late daughter:

    ___

    “A Healing Burger

    Or, the “healing pizza/chocolate shake/fries”? One day not long ago, after we’d visited with a pleasant, seemingly intelligent woman of recent acquaintance who had also endured a long struggle with cancer and was committed to a “holistic healing” regimen, I ribbed Sissy that we ought cruise down Sunset for lunch, specifically to order some “healing burgers,” — my facetious reaction to having been cut off mid-sentence the prior evening after uttering the phrase “fruit juice” in the course of responding to a query concerning Sissy’s daily diet. “Oh, no! No fruit juice!” “No sugar!” “No fat!” “No meat!”
    The magical quality that “holistic” evangelists impute to various vitamins, herbs, and certain foods (the latter for both good and ill), frequently shouts down the more circumspect and common-sense notion of an adequate and balanced diet. In my mind I parry their personal anecdotes with the equally anecdotal evidence of the long and mostly healthy lives of the large extended family comprising my in-laws. Most of these rural northern Alabama farmers manage somehow to live into their 90′s despite life-long daily breakfast doses of sausage and eggs with biscuits and gravy– along the rest of the typical meat-laden, putatively carcinogenic and arteriosclerotic farm fare that would make a brown rice zealot shrink in horror.

    Most of these dietary-herbal and related recuperative obsessions ring resonant with the “bargaining” stage of Elizabeth Kubler-Ross’s dying process model. Please, Lord, I’ll change my indulgent, unhealthy ways, please– just spare my life! See, I’m doing my herbal/ carrot juice/ seaweed/ colonic/ aromatic/ crystalite/ meditative/ mega-vitamin/ macrobiotic/ psycho-spritual penance; please, please spare my life!…”
    ___

    http://www.bgladd.com/1in3

  20. Robin says:

    Very probably, an ample consumption of fruits and vegetables and not the exclusion of meat make vegetarians healthful.

    Did the meta-analysis take note of what foods the vegetarians were eating? I don’t have access to the full study. They compared vegetarians to “health conscious” meat eaters but they didn’t say if the vegetarians were health conscious. There are more than a few grilled-cheese-sandwich vegetarians; you can eat potato chips and oreos all day still satisfy the criteria of non-meat eater.

    @ Ken Hamer:

    All vegetarian food isn’t bland and disgusting. Please don’t generalize.

    Last night I had a cup of chipotle black bean soup and a roasted red pepper multi-grain panini last night (with spinach, roasted garlic and sundried tomato, black olives, provalone.) The bread was perfectly crispy, the cheese melty, the soup spicy. You can eat vegetarian food and be perfectly satiated flavor-wise.

  21. passionlessDrone,

    Good question. Animal models are used all the time in nutrition. Dogs have very similar digestive systems to ours and have traditionally been used to model diabetes; guinea pigs model vitamin C metabolism. Recommendations for human dietary changes are not made until there are many animal and human studies to back them up.

    The issue is partly evaluating the impact of proposed and current recommendations. For a tiny example, if people are supposed to eat less hamburger, what do people who rely on fast-food outlets eat instead? Batter-fried fishburgers? Fishburgers are more expensive than hamburgers, so is that person also going to have to give up part of their food budget and sacrifice variety in their diet? In that case, we might expect that following the recommendation to eat less red meat could actually raise their risk of cardiovascular disease.

    We need to know not just what effects different kibbles have on lab animals, but also what patterns of dietary choices people make in the real world and how that seems to correlate with real-world outcomes. In the studies above, consumption of red meat (basically hamburger) correlates with poverty, lower education, smoking and diabetes. Not hugely surprising when you think about it, but not something that a lab rat could tell you.

  22. Todd W. says:

    @pD

    While animal studies would give a bit more control, it still would only be suggestive of the effects of those diets and would not necessarily correlate to humans. At best we could say, “This is the effect in this animal. This effect might apply to humans, but further research is necessary.”

  23. Ken Shim on good news: “Surprising that vegans aren’t much better off than the rest of us.”

    Vegans are a mixed lot. Some of them are anorexics using principled veganism as a cover; others have mental illnesses or are just feeble old people who live on tea and biscuits. There are the traditional South Asian vegans who are cooking from scratch and probably doing very well indeed if they are also maintaining traditional family relationships. A significant number of “vegans” may not be principled at all, but just be flat-out poor. There are the nontraditional vegans living a busy modern life with all the junk food but without the meat and cheese who may not be getting a well-balanced diet. And then there are the educated, principled slow-food vegans.

    Many people find it hard to get enough concentrated calories without animal input, so even the vegans otherwise eating a well-balanced nutritious diet tend to go heavy on the desserts. (Pushap, the most beloved vegan restaurant in Montreal, does most of its business catering traditional Indian sweets.) Other studies report that vegans have higher rates of dental caries, possibly partly for this reason.

    The best dietary recommendations I have ever seen are Michael Pollan’s: “Eat food. Not too much. Mostly plants.” http://www.nytimes.com/2007/01/28/magazine/28nutritionism.t.html

    (Disclosure: I’m a principled vegan wannabe. Cutting out eggs is easy; cutting out dairy is harder. But I still eat some fish.)

  24. khan says:

    Red meat is not bad for you; blue-green fuzzy meat is bad for you.

  25. qetzal says:

    Alison,

    Thanks very much for the excellent reply to my questions!

  26. BobbyG,

    The death of a child is tragic. People pretending that they can eliminate tragedy by eliminating fruit juice are in some sort of fairyland. I’m so sorry.

    The “healing burger” is not so far off the mark. An actual helpful dietician will want you to eat. Eat, eat, eat! My friend dying of cancer has been told that his job is to keep from starving to death long enough to allow the cancer to kill him. The not-starving-to-death part is within his control; the cancer is not. So he needs to focus on what he can do. If you like fruit juice, great! Lots of calories. Calories are good. Feel like a burger? Wonderful! Calories, protein and comfort. Then go home and have some scrambled eggs and ketchup and cookies.

    Real clinical dieticians think like this doctor:
    http://dinosaurmusings.blogspot.com/2010/02/master-of-analogy.html

  27. rork,

    So a disappointing attenuation of 0.1 comparing FFQ data to biomarkers would mean… ?

    From the paper on validity of intake measurement methods:

    “If the aim is to correct for the ‘attenuation’ effect of measurement error on estimates of disease risk then two independent measurements are required, one of which must be unbiased. If the aim is to completely characterize the error properties of the dietary assessment methods then three independent measurements are required. The difficulty is in finding three independent estimates of dietary intake.

    In practice, three main categories of dietary assessment can be distinguished: questionnaires for assessment of habitual, long-term intake; methods based on recording of actual food intake on one or more days (e.g. weighed food records, 24-hour diet recall interviews), and biomarkers of diet. It is clear that the measurement errors of instruments in the first two categories are correlated, not least because the same food tables must be used when converting foods to nutrients. This leaves only certain biomarkers as a possible alternative. One set of biomarkers of particular interest consists of those based on the urinary recovery of chemical substances from diet. Such recovery-based markers allow the computation of absolute daily intakes of nutrients in time. They also have the advantage that repeat measurements may be assumed independent, if the repeats are sufficiently widely spaced, so that the necessary statistical assumptions for validation studies may be fulfilled. Recovery-based markers are currently available for energy expenditure, and for protein, sodium, and potassium intake.”

  28. qetzal,

    I did a BSc in Nutrition (incomplete) back in the 80s. Never worked in the field, but it’s fun to be able to pull some of that knowledge out of a hat.

  29. Mark P says:

    the increased risk per 50 gram serving of processed meats per day

    Lordy that is a lot of processed meat!

    I’m not even close to vegetarian, but my total meat consumption a day is not 100g. I doubt I would eat 5g per day of bacon, ham etc, and I really like them and don’t do anything to avoid them.

    If a person is eating 50g of processed meat a day then I would suggest the main risk to their health is that they are plain over-eating.

    Modern people don’t eat too much meat. We just eat too much.

  30. 50 g is less than 1.8 ounces. The standard ADA serving size for meat is 3 ounces (85 g) and is about the size of a deck of cards. One hot dog is about 1.6 ounces or 45 g.

    While it’s true that 45 g of hot dogs per day is 45 g too many, I don’t think it’s evidence in itself that Americans eat too much.

  31. Sorry, that should be “that modern people eat too much.”

  32. rork says:

    I want to be useful to those I admire, even when it’s dull (for me), but am dying under a data avalanche right now. Isn’t there another nerd in the house?

  33. Zoe237 says:

    Excellent analysis! I agree ftmp. I would say one reason some become vegetarians is because it’s easier to just say “no meat” rather than cut back. Kind of like quitting anything cold turkey. The governor in our state had her ass handed to her because she declared a day a few months ago a “meatout” day. I’m not vegetarian myself, but I admire those who are.

    So happy to see some helpful topics addressed on sbm!

    I’ve heard that vegans can have serious problems from lack of B12, don’t know if that’s true. It’s not something I would try.

    I believe not eating or reducing the amount of meat eaten is one of the top two most influential environmental choices we can make, according to the Union of Concerned Scientists. The others are transportation choices (walking, biking, gas mileage) and political activism. Supposedly things like paper vs plastic are pretty meaningless.

  34. IndianaFran says:

    Wow, I’m having some cognitive dissonance here….
    I’m glad to see Harriet saying things like:
    “But correlation and plausibility are not enough to establish causation.”
    and
    “Could it be this constellation of factors, rather than xxxxx itself, that leads to higher mortality? ”
    and
    “I don’t think this can be determined from the data. They haven’t reliably ruled out all possible confounding factors”

    And then I remember that last fall when we discussed “the tragic death toll of homebirth” http://www.sciencebasedmedicine.org/?p=2392#more-2392
    , I made almost precisely the same arguments about the “dataset” which was exhibited as “evidence” of a causal relationship. And you defended Amy’s position that “Homebirth with a homebirth midwife dramatically increases the risk of neonatal death.”

    So what gives? Can you reread that post now, with the same skeptical mindset, asking the same types of questions, and come to the conclusion that the data presented there, with little or no true statistical analysis, identification of confounders, or any form of peer review, comes anywhere close to the quality of scientific work on nutrition that you reviewed here in this post? Or is it easier to overlook the logical flaws in an argument when you have your own confirmation bias?

    So no use beating a dead horse now, but I would have liked to get an answer to the question I posed back then:
    Do you really think that it is quibbling to insist that when comparative statistics are presented as “scientific evidence”, those statistics should be based upon well-matched cohorts?

  35. peter.m says:

    I was interested in this article as I am an advocate of the Paleolithic Diet (a science-based concept which looks at diet in the context of the modern western diet versus the diet we adapted to over several million years of evolution). To me this concept shines out like a beacon in the rather dark and hugely fraught area of diet and nutrition.

    It seems to me that many of the studies which show red meat to have a negative effect on health come from North America where the majority of red meat comes from cattle which are force fed an unnatural grain-based diet plus piles of growth hormones etc. This results in very fatty meats (cattle fed a grain-based diet become obese just like people fed a grain-based diet!) with high saturated fat and low omega-3 fatty acids compared to the lean, grass-fed meat (and organ meats) regularly consumed by our hunter-gatherer ancestors and to which our genome is clearly adapted.

    From a purely logical point of view it would seem incongruous that a food (ie lean red meat) which made up such an important part of the human diet for at least two million years would be bad for us.

    Did the author of the article come upon any information which can shed light on this aspect of red meat consumption?

  36. littlejohn says:

    Is it reasonable to assume the problem with processed meat is the known carcinogens (sodium nitrate and sodium nitrite) used in their preparation?
    If so, it’s a shame. Nothing smells or tastes better in the morning than fried bacon.

  37. peter.m – just because we’ve evolved to eat it, doesn’t mean we’ve evolved to eat LOTS of it! If it was rare and difficult to obtain, and now is easy, that’s a good start before you even get to considering details like fat grain fed vs lean pastured animals. And Americans are reputed to eat a huge amount of meat compared to my non-vegetarian moderately healthy Australian diet. (I eat too much sugar but I’m OK with my meat consumption.)

  38. peter.m says:

    Dear Cath

    I am also Australian (from Adelaide actually), where our red meat is mostly pasture fed. The thing is that humans eat substantially less protein now than our ancestors did, including red meat. Finding edible vegetable matter in the natural environment is actually very difficult which is why humans became such good hunters – we needed meat to fuel our huge brains, and we needed big brains to become smart at hunting (seeing as we didn’t have big teeth and claws). There is evidence that during the last ice age we ate a diet of pretty much all meat – much like the Inuit in modern times – as there just wasn’t much edible plant food around. It is a fact that people can survive on an all meat diet but cannot survive on an all vegetable diet unless certain supplements are taken, and a significant portion of the diet is made up of foods that our ancestors could never have eaten (such as soy beans) in order to get sufficient protein. I am still waiting for a supporter of the “red meat causes sickness” camp to explain this dilemma to me.

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