Monday, December 20, 2010

Nutritional Relativism Versus Facts

By Diana Hsieh

A new article in the LA Times -- A Reversal on Carbs -- reports on the increasing awareness that cutting carbohydrate intake improves health. For example:

"Fat is not the problem," says Dr. Walter Willett, chairman of the department of nutrition at the Harvard School of Public Health. "If Americans could eliminate sugary beverages, potatoes, white bread, pasta, white rice and sugary snacks, we would wipe out almost all the problems we have with weight and diabetes and other metabolic diseases."
That's great, but why focus on white bread rather than just bread? (Too many people just can't challenge the mantra of hearthealthywholegrains, unfortunately.)

Even the big kahunas in the American Heart Association seem to be hedging their bets in face of the growing evidence that their low-fat, high-carb dietary recommendations have failed miserably:
Though the movement to cap carbs is growing, not all nutritional scientists have fully embraced it. Dr. Ronald Krauss, senior scientist at Children's Hospital Oakland Research Institute and founder and past chair of the American Heart Assn.'s Council on Nutrition, Physical Activity and Metabolism, says that while he fundamentally agrees with those advocating fewer dietary carbs, he doesn't like to demonize one food group.

That said, he adds, those who eat too many calories tend to overconsume carbohydrates, particularly refined carbohydrates and sugars. "It can be extremely valuable to limit carbohydrate intake and substitute protein and fat. I am glad to see so many people in the medical community getting on board. But in general I don't recommend extreme dietary measures for promoting health."
In fact, whether some practice or principle counts as "extreme" depends on the cultural context. Consider that to advocate the rights of Jews during the Third Reich was "extreme." Today, just the opposite it true: to advocate the extermination of Jews in Germany would be "extreme." What counts as "extreme" depends wholly on the dominant ideas and values of one's culture: it doesn't tell you what's right or wrong. So to criticize some practice or principle as "extreme" is to implicitly adopt a standard of cultural relativism: other people's collective opinions trump the facts. That's wrong in theory -- and often disastrous in practice. Such matters should be discussed in terms of the relevant facts, e.g. that every human person, whatever his religion or origin, deserves to have his rights recognized, respected, and protected.

Similar considerations apply to questions about nutrition. To speak in terms of certain diets being "extreme" presupposes cultural relativism. On that all-too-common approach, the facts are not important, not in face of majority opinion or standard practice. Again, that's wrong in theory -- and often disastrous in practice. And in this case, it's quite myopic too, since apparently the kind of diet that most people have eaten throughout most of human history, even up to 100 years ago, now qualifies as "extreme."

In fact, the critical questions in the science of nutrition should be whether the consumption of that food tends to promote human health or not, what kinds of costs and benefits accure with different quantities of that food, and what kind of variation in effects people experience in eating that food. In other words, facts about foods should be our sole concern in nutrition -- not whether eating or not eating some food is "extreme" relative to our current eating habits.

Finally, I'm particularly pleased with the end of the article, which suggests an evolutionary approach to diet:
As nutrition scientists try to find the ideal for the future, others look to history and evolution for answers. One way to put our diet in perspective is to imagine the face of a clock with 24 hours on it. Each hour represents 100,000 years that humans have been on the Earth.

On this clock, the advent of agriculture and refined grains would have appeared at about 11:54 p.m. (23 hours and 54 minutes into the day). Before that, humans were hunters and gatherers, eating animals and plants off the land. Agriculture allowed for the mass production of crops such as wheat and corn, and refineries transformed whole grains into refined flour and created processed sugar.

Some, like Phinney, would argue that we haven't evolved to adapt to a diet of refined foods and mass agriculture — and that maybe we shouldn't try.
For me, low-carb or not isn't so important. The critical issue for health is not macronutrient ratios, but rather food quality. As it happens, however, the worst-quality foods that people eat are very high in sugar and wheat, and hence, eating low-carb is often a step in the right direction. Of course, macronutrient ratios can be important to achieve particular goals (like weight loss, muscle gain), and eating low-carb can reverse metabolic derangement. But at the beginning, middle, and end of the day, food quality should be king.

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