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Are the clues to diet success in your genes?

With 'nutrigenomics,' eating plans are based on DNA. Some experts question the advice.

April 11, 2005|Hilary E. MacGregor | Times Staff Writer

Some day, we may move beyond the one-size-fits-all food guidelines. A doctor could prick a finger, send the blood to a lab, predict the genetic likelihood of certain diseases -- and tailor a preventive diet exactly to those unique needs.

This is the goal of a new field known as nutritional genetics -- or nutrigenomics. The field, which barely existed five years ago, studies how nutrition interacts with genes and how that interplay ultimately affects health. Applied correctly, researchers believe, it could help prevent certain chronic diseases.

Many scientists, even those specializing in nutrition and genetics, agree that won't be for a while yet.

But high above Los Angeles, at a high-end holistic clinic with white orchids, New Age music and views from downtown to the ocean, the Center for Health Enhancement in Santa Monica is already offering eating plans tailored to clients' genetic profiles.

The center's directors call their nutrition service the DNA Diet, a name trademarked and copyrighted by licensed nutritionist Carolyn Katzin.

For $595, Katzin takes a swab from a patient's mouth (just like in "CSI," only it takes longer to get the results, she explains), places it in a tiny test tube and sends it off to a lab.

The lab looks for the presence of variations in 19 genes that determine some of the body's essential metabolic processes, including those believed to play a major role in cardiovascular health, insulin sensitivity, the ability to transform food into energy and dispose of waste products, antioxidant capacity, tissue repair and bone density.

Before prescribing a diet for patients trying to prevent illness or lose weight, Katzin conducts a lengthy interview with the client, paying particular attention to family history, current eating habits and stresses. She also weighs and measures the client, performs a body-fat analysis and measures his or her waist.

"This is so motivating," said Katzin. "We're all fascinated by ourselves."

The center is one of the few places in the country offering a DNA analysis combined with personal counseling by a nutritionist, its directors say. (The clinic also provides a range of complementary and alternative medicine options, such as executive physicals, acupuncture, reiki, aromatherapy, yoga and stress reduction programs.)

A few other companies market DNA testing kits -- for nutrition purposes -- directly to consumers. One Person Health Sciences Inc., a Vancouver, Canada-based company, uses the results to recommend vitamins and supplements; Boulder, Colo.-based Sciona Inc., and Market America Inc., an Internet company based in North Carolina, sell DNA screening analysis kits, and make diet and lifestyle recommendations.

Many genetics and nutrition researchers are skeptical that a diet now can be prescribed based on an analysis of a person's DNA.

"Most experts predict that by 2010 we will have enough information to make geno-based diet recommendations," said Raymond Rodriguez, a professor of molecular and cell biology and director of the Center of Excellence for Nutritional Genomics at UC Davis.

To date, too little is known, Rodriguez said, about the interplay among the body's tens of thousands of genes, much less how specific disease risks might be affected or managed with food.

Other scientists say such diet prescriptions probably aren't harmful -- especially if administered by a nutritionist or dietitian -- but that the analyses probably don't offer enough information to be helpful.

"The genes that they are looking at, the mutations they are looking at, there is evidence in the literature that supports what they are trying to do," said Jose M. Ordovas, professor of nutrition and molecular genetics, and director of the Nutrition and Genomics Laboratory at Tufts University. "But if you are trying to draw the whole picture of an individual based on 19 genes, I think it is a little bit naive to believe that can tell us much. If we have more than 20,000 genes, the others are also doing something."

Ordovas said he believed it would take a panel of about 200 genes before doctors and nutritionists could give reliable diet advice.

Rodriguez, of UC Davis, agrees such tests are still too primitive to say much. For example, he said, there are about 30 types of obesity, with an estimated 300 to 400 genetic markers. What matters, he said, is the form of obesity a person has, which of their genetic markers are predictive and which will allow effective adjustments to a diet. Many chronic diseases involve the interaction of many genes and environmental factors, he said.

"It is hard to say they are wrong," he said of the DNA Diet's creators, "but it is a question of completeness."

Nutritionist Katzin and Dr. Alan Heilpern, who bought the Center for Health Enhancement with his wife, Michelle, in 2000, concede that the DNA Diet can offer no preventive promises.

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