Rebuilding the food pyramid

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"Rebuilding the Food Pyramid" by Walter C. Willett, chair of Harvard School of Public Health department of nutrition, and Meir J. Stampfer, head of the same school's department of epidemiology. Both are also professors of medicine at Harvard Medical School Following is a brief summary of the 6-page article that appeared in the Jan '03 Scientific American. But this summary is no substitute for the entire article, which can be found at www.sciam.com - highly recommended reading!

The original 1992 USDA Food Pyramid, found by the authors to be a dangerous oversimplification. Image from the Scientific American article.

Abstract: The 1992 USDA Food Pyramid (shown here) suggests 6 to 11 servings of bread, cereal, rice and pasta per day at the base, and lumps all fats and oils together at the top as "use sparingly." Current research shows these recommendations are the result of gross oversimplifications that may actually worsen the ratio of bad to good cholesterol and promote obesity/diabetes.

The authors’ research make finer distinctions among types of fats and carbohydrates that are crucially important for anyone seeking to lose weight, prevent type 2 diabetes, and prevent heart disease.

Fats:
Most plant oils are actually good for you, improving the ratio of good to bad cholesterol: olive, canola, soy, peanut, etc. Exceptions include tropical oils such as coconut or palm, which should be avoided.

Animal oils are bad for you as they raise the ratio of bad cholesterol to good: red meat, butter, dairy

Artificially altered fats (trans, or partially hydrogenated fats) actually raise bad cholesterol while lowering good cholesterol! Such fats “have no place in a healthy diet." [Hydrogenated fats are everywhere - be sure to read labels. For example: the authors found peanuts to be beneficial, so you might be forgiven for reaching for the peanut butter. But regular commercial peanut butter has hydrogenated fats to control texture, more than cancelling out the beneficial effect of the peanut oil. Natural peanut butter, while less evenly textured, leaves out the trans fats.]

The authors’ proposed revised food pyramid, draws finer distinctions among types of fats and carbohydrates, and emphasizes exercise and weight control. Image from the Scientific American article.

"The 30 percent limit on fat was essentially drawn from thin air. ... The best way to avoid obesity is to limit your total calories, not just the fat calories." Eating good fats is beneficial as long as you don't exceed the calories you can burn.

Carbohydrates:
Certain carbohydrates break down very fast causing a spike in blood sugar and massive insulin production, followed by a dip in blood sugar that leads to more eating. At the same time, such carbs actually raise triglycerides and lower good cholesterol.

Worst of all, these kind of carbs seem causal to developing type 2 diabetes, with its legion of comorbidities. High levels of physical activity can mitigate this effect somewhat. The effect is worst in those who are already overweight.

Surprisingly, while table sugar is in this group, it is not the worst offender. "Eating a boiled potato raises blood sugar levels higher than eating the same amount of calories from table sugar." The same was true of pasta, white rice, and all refined flour products.

Coarse, whole-grain products resulted in a less pronounced blood sugar spike, again mitigating the ill effects of their more refined cousins.

Fruits and vegetables were not found to substantially affect the risk of cancer, but did help reduce the risk of heart disease. Potatoes do not confer these benefits, and should not be considered as dietarily useful vegetables.

Meat:
The USDA meat group is also oversimplified with red meat contributing to heart disease and type 2 diabetes, and poultry, fish, legumes and nuts either beneficial or not a significant risk factor. Fish, in particular, actually improves cholesterol ratio because of its omega-3 fatty acids. Nuts also improved the cholesterol ratio, and because they are very satisfying, seemed to reduce the craving for other foods. Consuming up to one egg per day was found to be essentially neutral to cholesterol.

Dairy:
High calcium is risk factor in prostate cancer, saturated fat in cholesterol, but the authors felt more research was needed on the epidemiologic effects of dairy products before drawing a conclusion. The total calorie intake, of course, must be controlled with dairy as anything else.

The revised food pyramid
The authors' Revised Food Pyramid attempts to tie current epidemiologic data with what is known now to help prevent obesity, diabetes, and heart disease. It emphasizes total calorie intake, use of correct oils, regular practice of exercise and weight control, and attention to food as an aid to prevention of chronic disease. The authors also believe an ordinary multivitamin would be beneficial for most adults.

Finally, the authors suggest the USDA is too closely linked to the agriculture industry to be in the business of giving diet advice, and that such analysis belongs in the medical/epidemiological community, "...insulated from political and economic interests."

Suggested reading: "Eat, Drink, and be Healthy: The Harvard Medical School Guide to Healthy Eating."