GMartin

Healthiest Diet for Humans

3 posts in this topic

Dr. RJM

Is there a scientifically proven optimum diet for humans?

Scientists seem to have this worked out for cats and other animals.

Is there a perfect food or balance of foods that would give optimum health and longevity to humans? I realize that there are other factors involved such as genetics, exercise, and stress.

Glenn Martin

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Dear Glenn,

There are several points I would like to make on this subject:

1. As a topic, "Nutrition and Health" (how and what to eat to avoid disease and premature death) should be distinguished from "Nutrition and Aging" (how and what to eat to slow down the aging process and live beyond the normal life span).

2. Concerning optimum diet, there are important differences amongst individuals, with obvious examples being infants or people with health problems. Particularly in the latter case, the best source of individually tailored advice is a medical professional, generally one's own doctor.

3. With those first two points in mind, I am willing to offer some opinions which may be of use to a fair number of readers. These comments are rather general, for the following reasons: (a) I am primarily a gerontologist, not a nutritionist, which means that I am commenting broadly within my field, but not within my specialty; (B) the aforementioned differences amongst individuals make the best specific advice for one reader unsuitable for others; and ( c) I think that a typical, healthy adult needs only general guidance rather than very specific instruction on what to eat.

With points 1-3 as preamble, I offer the following opinions on the subjects of Nutrition and Health (points 4-6) and Nutrition and Aging (point 7).

4. Assuming a generally healthy reader, with no specific food allergies or intolerances, I see no reason to eliminate any specific food from one's diet. Conversely, I see no reason to force oneself to eat any individual substance if one dislikes the taste. There are plenty of good sources of nutrition available today. I make this comment specifically because many diet plans offer very regimented instructions on what to eat, and how much, and what not to eat at all. This approach seems unnecessarily puritannical to me. It appears to decrease, rather than increasing the quality of life for many (most?) people, and not to be sustainable without very strong will power.

The real issues are how much one should eat, and what should be the relative amounts of different types of food.

5. Nutrition and health - how much should one eat? - For most people, the answer is "somewhat less than the average person eats today". Obesity is a major cause of premature ill-health and death, particularly because it enhances the risk of cardiovascular disease and adult-onset diabetes. Increasing abdominal obesity at young and middle ages is associated with increased risk of disease, but I should note that weight loss - the anorexia of aging - is an important predictor of frailty and death at older ages. Thus, some people argue that weight maintenance and weight stability become more important goals than weight loss, beyond about age 60.

6. Nutrition and health - relative amounts? - In general, I agree with the mainstream advice to eat less sugar, salt and saturated fat than the current average, and more fruit, vegetables and dietary fibre, in order to decrease the risk or delay the onset of various diseases. Please note the word choices: "less" and "more", not "none" or "masses"; "decrease" rather than "eliminate" the risk; "delay" rather than "prevent" the onset.

In other words, although I am not willing to endorse any specific diet plan, my leanings are toward the Pritikin approach (low fat, high complex carbohydrate) and against the Atkins approach (high fat, low carbohydrate). It will be very difficult to persuade me that a boiled potato or a slice of wheat bread is not good food. Even if it is true that low carbohydrate diets can cause weight loss - and I think the key is consumption of fewer calories - that is not the best or only standard of health.

Concerning vitamin and mineral supplements, I doubt very much that megadoses of any single nutrient have beneficial effects (again, assuming the context of a healthy reader, and with a reminder to anyone who needs it: your doctor knows you better than I do). Luckily, for most people, the body is hardy and consuming large doses of vitamins is a comparatively harmless folly, but there are limits (which vary among vitamins and individuals). A daily multivitamin/mineral pill is less likely to do much harm, and it might actually be beneficial in some cases, e.g. for elderly people or those with dietary deficiencies. However, the risk of disease is minimized by obtaining vitamins from food, particularly various fruits and vegetables, rather than from pills. It is not yet clear to me whether that is primarily because these foods contain additional nutrients or because the form, concentration and availability of the nutrients differ between food and pills. I suspect that all of these factors are involved.

7. Nutrition and aging. All of my comments above concern nutritional choices intended to minimize the likelihood of premature death. No dietary supplement and no adjustment of relative amounts of foods in the diet can stop or slow down the aging process. On a more positive note, the discovery was made 70 years ago that caloric restriction - limiting the total food intake of laboratory rodents to 30-40% less than the normal level, while avoiding malnutrition - extended both the average and maximum life span. Some rather dubious reports have been published suggesting that caloric restriction (CR) also slows down the aging process of simpler organisms, e.g. yeast, worms, and some kinds of flies. Of greater interest to me is an ongoing study of CR in nonhuman primates. Studies of CR in monkeys began about 15 years ago, and any extension of life span will become apparent after another 15 years.

Meanwhile, a small number of people have undertaken CR self-experimentation. I must emphasize that these individuals ("CRONies" - practitioners of Caloric Restriction with Optimal Nutrition) are very attentive to the various nutrient deficiencies and other ill effects which could arise from this practice, and I recommend against CR for anyone who has not done enough reading to assess the potential risks and benefits for himself (see http://calorierestriction.org/howto for more information). If CR extends the human maximum life span, then the effect is likely to become apparent 50-60 years from now. Meanwhile, those individuals who are willing to tolerate the inconveniences appear to be healthy and happy after as long as 19 years on the CR diet (I base this statement on the personal testimony of a colleague, and documentation in the following report:

Fontana L, Meyer TE, Klein S, Holloszy JO. Long-term calorie restriction is highly effective in reducing the risk for atherosclerosis in humans. Proc Natl Acad Sci U S A. 2004 Apr 27;101(17):6659-63.)

To conclude, the relationship of nutrition to health and aging is very complex and not yet fully understood. I hope this lengthy answer justifies the lengthy wait (> 2 months since your question was posted).

Sincerely,

RJM

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Dr. RJM,

Thank you for your interesting and imformative reply.

Glenn Martin

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