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Genetic factors may be derailing healthful diets Low-fat regime backfires in some

By Jon Van Tribune staff reporter Published September 3, 2001

People who drastically limit how much fat they eat may be surprised to learn that their dieting habits might actually raise their risk for heart disease.

While many believe a low-fat, high-carbohydrate diet is the most healthful way to eat, it probably isn't for some because of genetic factors.

Researchers don't yet have the full story on how genes can work against what sounds like a healthful diet, but they have done studies that demonstrate how a low-fat diet can have unwanted results in a substantial number of people.

A report on the perils of low-fat dieting was presented last week in Chicago at the national meeting of the American Chemical Society as part of a new development that factors genetics into nutritional science.

Researchers predict that the food industry is on the verge of a new era where companies will design foods and market them to consumers according to their genetic makeup. Eating a designer diet could help individuals avoid coronary disease, diabetes, cancer, central nervous disorders and other afflictions with much greater precision than possible today, say backers of this new approach to diet, called nutrigenomics.

`Concept is not drastic'

"This concept is not drastic," said Nancy Fogg-Johnson, a nutrition consultant who described nutrigenomics at the chemical society meeting. "Surveys show that 85 to 93 percent of consumers already believe that food is tied to health. They know about the positive effects of some foods such as broccoli, soy and green tea."

In the future, Fogg-Johnson said, genetic studies will help identify which individuals will benefit the most from particular foods. And genetic engineering also will modify foods to make them more beneficial to the health of people who eat them.

There is much work left to do until it happens on a large scale, Fogg-Johnson acknowledged. The case of low-fat diets and coronary disease illustrates the complexities that researchers face in unraveling the many connections between diet and genetics.

Ronald Krauss, a researcher at the University of California's Lawrence Berkeley National Laboratory, described work that he and others have done in trying to understand why when people eat exactly the same things, it can affect individuals differently.

Krauss' report centered in the so-called bad cholesterol, known as LDL, that most health authorities agree is associated with coronary artery disease. When people eat diets that consist of only 10 percent fat, on average, their LDL levels drop, but the average hides a lot of individual variation, Krauss said.

When looking closer at what happens to individuals, researchers find that some people on low fat diets have a real and significant drop in LDL. But others experience a conversion of their LDLs in such a way that their exposure to coronary artery disease probably rises, Krauss said.

Further investigation has found several genes that seem to dictate how someone's LDL profile will change when dietary fat is drastically reduced, he said. Researchers suspect that when some people stop eating fats, the other things they eat, especially carbohydrates, somehow trigger the changes in LDL makeup.

"We hypothesize that certain genes get turned on by carbohydrates," Krauss said. "But this needs more study."

When a physician puts a patient on a low-fat diet, there are chemical markers that can be monitored to provide a good idea of whether the diet is helping reduce the patient's risks, said Krauss.

But healthy people who aren't being watched by a physician really have no way of telling whether extreme dieting is beneficial or risky, said Krauss, who played a key role in writing dietary guidelines for the American Heart Association.

"That's why the Heart Association guidelines call for a diet with 30 percent fat instead of 20 percent or 10 percent," he said. "We know that 30 percent is OK for the general population."

Before food companies begin designing diets for genetic subsets of customers, researchers will have to know a lot more about the specific effects of many genes, Fogg-Johnson said.

Also, there will have to be an inexpensive way for consumers to learn their genetic profiles.

"Some small companies have already started that hope to commercialize genetic profiling," she said.

The field will also raise new ethical and legal issues, Fogg-Johnson said. For instance, she asks, "who gets to know your genetic profile?"

If there is a particular diet for an individual proven to be healthful, but that person doesn't want to follow it, there may be ramifications from an insurance company or employer, she said.

Even though there are many hurdles, several speakers at the chemical society meeting suggested that the health and commercial benefits of nutrigenomics are such that it is bound to take hold.

Supplements already popular

John Finley, a chemist at Kraft Foods who helped organize the symposium, said that to an extent, it is already happening. Many people are taking food supplements extracted from grape juice and spices that have been shown to cut the risk of colon cancer, he said.

"If you ask the average person, he's probably never heard of the COX-2 gene, but you see it mentioned in some advertisements now, and many people who suffer from arthritis know about it," Finley said. "Resveratrol, an ingredient from grape juice, inhibits COX-2 and people with inflammatory diseases are learning about these relationships.'

The lead in promoting foods to fight specific diseases will probably come from small, innovative companies, Finley said.

"I expect someone will start marketing beverages with five times the resveratrol as is found in red wine," he said. "If a product like that succeeds, then the larger companies will notice and this type of marketing will become more mainstream."

-- Anonymous, September 03, 2001