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Science-Based Nutrition

One of the most successful propaganda campaigns within health care in the last few decades has been the re-branding of nutrition as “alternative” or out of the mainstream of scientific medicine. I have marveled at how successful this campaign has been, despite all the historical evidence to the contrary. I suppose this is partly a manifestation of the public’s short-term memory, but it also seems to reflect basic psychology.

Some History

There is evidence that most ancient cultures recognized the importance of diet in health. The Greeks recognized both the benefits of a varied diet and the negative health consequences of obesity, for example. But knowledge of nutrition was limited to these broad observations and was mixed with superstition and cultural beliefs.

The science of nutrition probably dates back to 1614 when scurvy (the disease that results from vitamin C deficiency) was first recognized as a dietary deficiency, one that could be cured by eating fresh fruits and vegetables. In 1747 Lind conducted what might be the first clinical trial – systematically comparing various diets for the treatment of scurvy and finding that citrus fruits were the key to treatment.

From 1928 to 1933, two research teams independently isolated ascorbic acid (the chemical name for Vitamin C): a Hungarian research team of Joseph L Svirbely and Albert Szent-Györgyi and the American researcher Charles Glen King. Albert Szent-Györgyi was awarded the 1937 Nobel Prize in Medicine for his part in the discovery.

Prior to that, in 1912, Casimir Funk developed the concept of vitamins (so named because he thought that chemically they were all amines – therefore “vital amines” or vitamins). Vitamins are not, it turns out, all amines, but are defined as micronutrients that are essential for biological function but cannot be sufficiently synthesized by an organism and therefore must be obtained in the diet.

Other components of a healthful diet include other micronutrients, such as minerals and trace elements, and the macronutrients – those that give us our calories and major building blocks. The macronutrients include carbohydrates, fats, and proteins.

Nutrition in Medicine

There have been three major conceptual trends (not mutually exclusive) in the thinking about nutrition in medicine and health. The first was the concept of deficiency – that an insufficient amount of a critical nutrient can cause disease. Nutrition science and intervention in the 19th and earth 20th centuries focussed on malnutrition, identifying specific nutrients and the diseases caused by their dearth, and on the role of supplementation in public health. This approach resulted in iodine in salt, vitamin D in milk, and on the recommended dietary allowances (which are basically the minimum necessary to avoid deficiency).

As an extension of the malnutrition model was the recognition that certain disease states or situations come with increased nutritional requirements. For example, when battling cancer individuals typically have significantly increased nutritional and caloric demands. Increased nutrition may therefore stave off weight loss as a result of the cancer, and help fight off the disease and weather the stress of chemotherapy. It is also recognized that wound healing after injury or surgery requires vitamin C in particular and increased nutrition in general.

In the latter half of the 20th century and continuing into the 21 century science-based nutrition has added two new conceptual frameworks. The first is thinking about excess nutrition – meaning getting too much of something in our diets as a risk factor for disease. Here the focus has been on the macronutrients – too much of the wrong kind of fat as a risk factor for vascular disease and too many carbohydrates as a risk of Type II diabetes are prominent examples. But also too much salt as a risk for hypertension, and even the possibility of too much iron in the diet of men and non-menstruating women.

The other concept that has been added to the scientific approach to nutrition is the recognition that specific nutrients may decreased the risk of developing certain diseases and may even treat an existing disease. To give some examples from my own specialty – vitamin B2 and Coenzyme Q10 have been shown to reduce migraines, vitamin B6 may be helpful in nerve healing (for example from carpal tunnel syndrome), and folate is essential for pregnant women to reduce the risk of spina bifida.

Therefore, to summarize, science-based nutrition includes the recognition of nutritional deficiencies, the increased need for nutrition in situations of physiological stress, the risks of dietary excess, and the role of specific nutrients in mitigating specific diseases and conditions. This is all part of standard medical training, ongoing medical research, and everyday practice. The examples I gave above are meant to be representative, and not exhaustive. Also, specific conclusions are tentative and will change as new data is gathered.
Nutritional Pseudoscience

Nutritional claims are prominent among health products and services that lie outside of science-based medicine. Part of the reason for this is regulatory – supplements are often regulated as food, rather than as drugs, and therefore subject to less regulation and oversight. Nutritional supplementation is also highly marketable, because it seems less invasive and less risky than other modalities.

There are many legitimate health benefits for specific nutrients. However, the claims for nutritional therapy often go far beyond the evidence or scientific plausibility. Some promoters go as far as to claim that poor nutrition is the cause of most or even all disease and illness, and therefore all human disease can be treated with supplementation.

Because such claims are not supported by current science, it seems that the industry has decided to make a pre-emptive strike against scientific criticism. Therefore they have created, as part of their marketing strategy, the notion that the medical community does not understand, value, or study the role of nutrition in health. Some even go as far as to claim that there is a conspiracy to conceal real scientific information about nutrition.

Conclusion

Nutrition is an essential part of health and medicine, and nutritional science is a vibrant and successful research program. However, nutrition is also a common target of dubious marketing and harmful medical pseudoscience. Readers are encouraged to have healthy skepticism toward nutritional claims that seem to good to be true, take a hostile approach toward mainstream science and medicine, and especially those that claim there is a conspiracy to silence the truth about nutrition.

Posted in: Herbs & Supplements, Nutrition, Public Health, Science and Medicine

Leave a Comment (15) ↓

15 thoughts on “Science-Based Nutrition

  1. Hayden Jones says:

    The link to Quackcast is now broken. I’d just change it to the home page: http://www.quackcast.com/

  2. Hayden Jones says:

    I’d love to hear you comment more on things that vegetarians or vegans get right and wrong about nutrition (particularly a group like pcrm.org, who started a misleading anti-vivisection petition a while back).

  3. Egaeus says:

    There it is. The salt bogeyman sticks out his head again.

    I know that salt increases blood pressure. Anyone who understands the concept of osmotic pressure knows this. I’ve seen a recent study touted on the CSPI website that demonstrated this quite effectively. I don’t understand why it got published, since I learned the concept in high school, but that’s beside the point.

    I understand that for people with reduced renal function, or those who have a problem with hypertension, the reduction in blood pressure that comes from reducing salt intake can be very important in reducing the strain on the heart.

    What I want to know is where is the evidence that salt, independent of diet, is a risk factor for anything? Poor diets tend to have a high salt content, but the contrapositive is not necessarily true. Correlation is not causation, which I’m sure you already know and preach.

    I’ve seen mentioned a study (mentioned above) that control the diet and vary the salt content, and demonstrate osmotic pressure quite nicely. I’ve seen mentioned a study that followed high-risk patients long-term, and their salt intake correlated with mortality, but with no mention of any other aspects of their diet. I would hypothesize that those who reduced salt intake altered most aspects of their diet, and the inverse as well.

    Where is the good science that establishes this risk? I’m not saying that it’s not out there, but from the limited amount I’ve read, it looks like the science behind the low-salt diet is as good as that behind the low-fat diet. I understand the difficulty of producing such a study, but if it hasn’t been done, shouldn’t EBM practice what it preaches?

  4. daedalus2u says:

    There is some variability in sodium metabolism. In some parts of Africa there is very little sodium in the environment because rain has leached it away. In one place elephants have found a vein of sodium containing mineral that they use as a nutrient source. Over many generations elephants have mined sufficient material that they have excavated caverns.

    http://gsa.confex.com/gsa/2003AM/finalprogram/abstract_63240.htm

    http://www.travelafricamag.com/content/view/246/56/

    There is some thought that variability in human sodium metabolism derives from people living in sodium depleted regions. That is likely part of why salty foods taste good. If sodium is always scarce, there isn’t a need to evolve pathways to deal with too much. But some of this variability may be epigenetic, determined in utero and not necessarily genetic.

    A major metabolic load on the kidney is the pumping of sodium ions. If your kidneys have the metabolic capacity to pump as much sodium as your diet requires them to without going into metabolic stress, salt isn’t going to bother you. If they don’t, then it will.

  5. Oldfart says:

    Hunter-Gatherers moved around, eating different foods with the seasons from different areas. When meat was available, they binged out on it, when it was not they lived on roots and other veggies and fruits. They did quite well.

    “Civilized” peoples, on the other hand, did not do so well at first. Living in the same spot year-round and on one single food did not do the human body good. Disease, famine, malnutrition took their toll. It took centuries to learn the tricks of living “Civilized” and agricultural rather than hunter-gatherer.

    However, our nutritional system, being slower to respond, is still largely hunter-gatherer. We were h-g for how long? 200,000 years? and we have been civilized for how long? 10,000 years? maybe.

    So, the Greek advice of variety is probably very very good advice. Eat a variety of foods, veggies, fruits, meats, fats, grains, roots, tubers, insects if you like. If there is anything else the human body needs for good nutrition it is likely to be in those foods and not in little bottles on the vitamin shelves of Wal-mart.

    Note: I am completely unqualified to make any of the above statements in a scientific sense. Those are my OPINIONS by which I have lived for 66 years.

  6. Just one side note on EBM – it does not recommend that in the absence of solid scientific evidence we do nothing. Rather, it acknowledges that we often lack definitive evidence, and so recommends that the best risk vs benefit assessment be made given existing evidence.

    The salt and hypertension issue is certainly a complex moving target. I did not mean to imply it was a simple or direct relationship – I was just referring to it “as a risk factor.” I think the evidence supports that there is a subset of people who may have so-called salt-sensitive hypertension. Recommending a modest cut back in salt intake and monitoring the effects on HTN in an individual is a reasonable EBM approach.

  7. Egaeus says:

    Yes, I agree that is a reasonable approach. What I have a problem with is things like the gigantic load of garbage found at the Center for Science in the Public Interest: http://www.cspinet.org/salt/

  8. pec says:

    For people who do not have artery disease or chronic hypertension, it makes no sense to limit dietary salt. And even if blood pressure is somewhat above whatever is considered normal at the moment, there still may be no artery disease. So a person with hypertension does not necessarily have to limit salt.

    The early salt – heart disease connection was made from observations of tribal people who ate very little salt and had no heart disease. This correlation was used as a basis for the idea that a high-salt diet can cause heart disease.

    Subsequent research has not been conclusive. It’s possible that, for some individuals, a low-salt diet can be harmful. It’s also possible that dietary salt can help fight certain infections.

  9. pec says:

    The connection between refined carbohydrates and artery disease (via type 2 diabetes) is so much stronger than the salt connection. Yet doctors have emphasized restricting salt rather than sugar and white flour.

    As far as I know, the dietary sugar – artery disease insight comes from CAM.

  10. weing says:

    Very good post. I recall another Greek, Aristotle, I think, who stated that one man’s meat is another man’s poison. People are always looking for a one size fits all solution especially with diet. I’ve been finding a lot of gluten sensitivity lately in adults and quite a few have no symptoms except for osteoporotic fractures.

  11. starflyer says:

    Related: Yesterday Airborne was forced to repay swindled customers: http://www.webmd.com/cold-and-flu/news/20080304/cold-remedy-airborne-settles-lawsuit
    A victory, but it probably won’t change much.

  12. FeelGood365 says:

    I wish more people would listen and make up their own minds before they start taking any medication when having a challenge.

    Taking ANY medication can be risky no matter what the doctor says, so you need to be aware of the side effects, add them all up, READ the labels and be responsible.

    It is YOUR life and it is YOUR future. Die early or wait to later, I like the word later.

    Life has NEVER been this great as it is now and we enjoy it to the fullest thanks to our own judgement.

    Are we talking Nutraceutics not just Nutrition? YEP and what a difference.

    This is why we say FeelGood365 it’s all in the name you know!

  13. nwtk2007 says:

    I know this is a late post and this thread has apparently run it’s course but I am bored.

    The salt issue is over rated and reduced salt intake might actually be risky for the hypertensive patient.

    In Guyten, the physiology book used by many med schools, it is shown that if salt intake is reduced, there is a transient decrease in Bp with subsequent rise back to previous levels. The reverse is also shown, that an increase in salt intake causes an transient increase in Bp followed by a gradual return to previous levels.

    The problem is this, if a person with greatly reduced salt intake partakes of a meal with elevated salt content (lets face it, we don’t have control of all of our meals) there will be a transient increase in the Bp. The transient increase will be pronounced in the person who has reduced salt intake and thus an elevated sensitivity. This transient increase could very well be dangerous.

    If a person has regular salt intake, there will be no reaction.

    This is just food for thought. No pun intended. OK yes there was.

    I also find it interesting that in modern science, the only thing that has ever shown any effect on increasing longevity has been reduction in caloric intake, to the tune of about 50% decrease from the average.

    Nine tenth of the time any discussion of nutrition centers on weight loss. People who want to lose weight need to do one thing in particular. EAT LESS and CONSUME LESS. It is that simple and also that difficult. And that all depends upon how much you really was to make the change in order to lose the weight.

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