No Magic Bullets

By Wendy Gordon

"Eat food. Not too much. Mostly plants. That, more or less, is the short answer to the supposedly incredibly complicated and confusing question of what we humans should eat in order to be maximally healthy." -Michael Pollan

Two years after Pollan made this concise statement at the beginning of his excellent book, "In Defense of Food", it's still not what most Americans want to hear. We remain addicted to our magic bullet approach to nutrition and all that it implies: the unending search for the "right answer"; complicated dietary instructions and restrictions; an evergrowing array of diet books; expensive supplements; over-engineered "food-like substances"; and gallons of guilt.

Yet it's clear the magic bullets aren't hitting the target. In 2009, adult obesity rates increased in 23 states and did not decrease in a single state. The percentage of overweight and obese children is at or above 30 percent in 30 states. The number of obese adults now exceeds 25 percent in nearly two-thirds of states, a startling statistic when you consider that in 1980 the national average of obese adults was 15 percent. The incidence of adult-onset diabetes is also rising dramatically, now encompassing eight percent of the population (23 percent of those over age 60). 10 to 20 percent of Americans suffer from "fatty liver," a form of liver disease directly linked to diet. While mortality rates from heart disease and cancer have dropped, this is a function of better screening and treatment rather than lesser incidence.

Over the years, I've addressed various magic bullets in this column, from high protein to high carbohydrates to raw food diets, generating a fair amount of righteous indignation from their adherents. This time I will turn my attentions briefly to another popular bullet: the "Blood Type" diet. Promoted in a series of books by naturopathic doctor Peter D'Adamo, this theory promotes distinct diets for people with O, A, B and AB blood types, positing one's blood type as a major indicator of immune system differences. "O" is "the hunter", needing a higher protein diet; "A", the cultivator, needs a more vegetarian diet; "Bs" are "nomads" and the only people who can digest dairy; and "AB" is an intermediate between A and B. D'Adamo holds that a substance called "lectins," found in many foods, reacts differently depending on blood type.

This diet confines very complex human beings into just four limiting stereotypes. Even blood type is far more complex than these four categories indicate, with Rh (positive and negative) factors as well as others. O is the most common blood type worldwide (followed closely by A in the United States), but there is no clear linkage between blood type and indigenous dietary habits. For instance, it is a proven fact that Northern Europeans are one of the few populations who tolerate dairy past childhood, but only a small percentage of Northern Europeans have the B ("nomad") blood type. With migrations of populations and the intermingling of ethnicities increasingly common in our interconnected world, the whole concept of indigenous dietary habits is becoming irrelevant. As for "lectins", there is controversy about how many are actively found in food and, even if they are present, how they react with different blood types and if they would have any effect upon weight or general health.

A related diet instructs people to eat according to their "metabolic type." This magic bullet divides people into ten categories, depending on whether their nervous systems are "sympathetic dominant" or "parasympathetic dominant." This plan is also based on one's ethnic background and claims that metabolic type reflects itself in everything from temperament to bowel habits. Each metabolic type has specific dietary requirements. For example, "sympathetic dominant metabolic types" "do not do well on lamb, venison, beef, sardines or salmon" and should "stress wholegrain pasta, breads, cereals, raw goat milk, egg and white fish."

I think our fascination with these diets has less to do with their scientific credibility than with our desire to order and categorize the vast mysteries of our universe. People like the discipline of clear directions to follow. They want to possess the right answer. It's a lot less scary and complicated than believing that the right answer is blowing in the wind.

As Pollan notes, traditional diets (now being replaced by the ubiquitous "Western diet") were strikingly diverse: high fat, low fat, high carbohydrate, all meat, all plants. These populations managed to thrive, suggesting that humans can adapt to many diets.

We would be far better off listening to our bodies than to the latest diet expert. Every one of us is a complex, unique being. Some of us gain weight easily, others do not. Some people can't tolerate dairy, wheat, garlic or tomatoes. Some people feel better on a high protein diet while others do better with complex carbohydrates. Some of us like a large lunch while others prefer a large dinner or to graze all day. As long as we are eating whole, unprocessed foods, chances are we'll do just fine.

Wendy Gordon is a writer and restaurant reviewer who lives in Portland, Oregon. She has a master's degree in clinical nutrition from the University of Chicago.