Food Becomes You - Your Personal Nutritional Profile

Every human being is genetically unique. People come in a vast range of sizes and shapes, all with their own blend of talents, weaknesses, dislikes, and preferences. You wouldn't expect everyone to wear the same clothing size. So why should the medical community expect everyone to benefit from one-size-fits-all nutritional recommendations?

These generalities include the USDA food pyramid, optimal caloric intake levels, the demonization of fat, salt, and cholesterol, and the entire recommended daily allowance (RDA). They are the rationale behind iron-supplemented cereal and calcium-supplemented orange juice. All these recommendations are based on extensive study, and, generally speaking, represent the middle of the bell curve. Spit out by government agencies and professional organizations such as the American Dietetic Association, they are then reiterated by the media and medical personnel so frequently that they have become conventional wisdom. Following these suggestions is often beneficial and rarely harmful for the "average person." But they are not the roads to optimal nutrition. For those at the far ends of the bell curve in any respect they are either insufficient or excessively restrictive.

The human species exhibits tremendous variation in height, bone density, skin fold thickness, body fat levels, muscle mass levels, and body fat distribution. Like other animals, humans evolved in response to their external environment. As a general rule, people from tropical regions have a strong hereditary need for diets high in carbohydrate: fruits, vegetables, grains and legumes. Individuals from colder climates generally require more animal protein and fat. In the U.S. we are almost always "genetic mutts" and our predilections fall somewhere in between. Nevertheless, many people distinctly lean towards one tendency or the other.

People's caloric needs fluctuate according to size, physical activity, health and life stage. However, even if all these variables are equal, some people require as much as 800 more calories a day than others to maintain their weight. This is due to a variety of factors: percent of lean muscle mass, type of body fat, and degree of "fidgetiness." (Yes, all that finger tapping uses up a ton of calories!) People from areas of the world where food was scarce or alternated between feast and famine, have an enhanced ability to hoard calories as fat. That was life-saving in the past, but not so in our current food-abundant world.

The body manufactures blood cholesterol for important physiological purposes. Only in excess does it become harmful. The process by which excess dietary cholesterol adheres to and clogs arteries is still unclear. Some people with high blood cholesterol levels respond well to dietary cholesterol restriction; others do not. Some people can eat a three-egg omelet every morning without it having the slightest effect on their blood cholesterol levels.

Vitamin C requirements vary widely from person to person. Individuals also differ in their need for iron. While some individuals, such as pregnant women and long distance runners, often require supplemental iron, others suffer from a relatively common condition known as hemochromatosis, where the body stores too much iron. When undetected, the excess iron causes considerable physiological damage and is potentially fatal.

Excess dietary sodium exacerbates high blood pressure in approximately one quarter of the world's population. For the remaining seventy-five percent, sodium restriction has no effect.

Individuals vary widely in their tolerance to lactose (milk sugar). Typically, Northern Europeans digest lactose readily while those from warmer climates (blacks, Asians, Southern Europeans) have more difficulty, especially beyond childhood. Northern Europeans may also require more calcium, as they are particularly susceptible to osteoporosis. Allergies to gluten, or wheat protein, are also relatively common in certain ethnic groups.

Ethnicity also affects susceptibility to chronic diseases. Type 1 diabetes is most common among Caucasians, while blacks and Mexican-American women are at greatest risk for cardiovascular disease. Blacks are more likely to develop high blood pressure.

Now that we've mapped the human genome, perhaps someday it will be possible for medical practitioners to scan a DNA sample and pop out an optimal personalized diet. Books like "eat for your blood type" are on the right track but overly simplistic. The interrelationship between diet and nutrition is too complex to reduce to one factor like blood type. For now the best method for developing a personal nutritional profile remains trial and error. On what kind of diet do you feel the most energetic, maintain an optimal weight, and get sick less often? If you are following a special diet, is it effective? A doctor or nutritionist can help by taking an extensive family health history and testing for blood pressure, cholesterol, triglycerides, iron, and bone density. More complex and expensive tests for blood nutrient levels and metabolism are also available.

Wendy Gordon is a writer and restaurant reviewer who lives in Portland, Oregon. She has a Masters Degree in Clinical Nutrition from the University of Chicago, and is on the Board of Directors of Food Front Grocery, a co-op in Portland.