Diets designed for your DNA

SACRAMENTO, Calif.

Deep in each person's genetic code may lie the answers to which medicines can help them, which environmental toxins can kill them and even which foods they should eat to live well.

The tantalizing prospect of personally tailored diets, dictated by our genetic makeup, drew hundreds of scientists and dietitians from around the world to the University of California-Davis in October for a conference on nutritional genomics.

The fast-growing field "will be huge," said Jim Kaput, who next month will take over as head of the U.S. Food and Drug Administration's division of personalized nutrition and medicine. "We are definitely not ready for it."

In interviews, Kaput and other conference speakers said that as the cost of creating individual genetic profiles drops, doctors, dietitians and consumers will be able to get massive amounts of data about themselves.

The challenge will be figuring out what to do with it.

"Eating for your genotype is probably decades away," said Judith Gilbride, a nutrition professor at New York University who last year was president of the American Dietetic Association.

Genes interact with each other and with the environment in so many ways that it will be a long, slow slog toward advice so specific that you're told to eat more broccoli while your neighbor is advised to opt for oranges.

What's likely to come first are potentially valuable snippets of information.

In a study that made headlines last year, researchers zeroed in on a genetic variation that affects how quickly different people process caffeine.

They found that people who drink lots of coffee but metabolize caffeine slowly face a greater risk of heart attacks than those who drink just as much coffee but clear caffeine from their bodies faster.

Ahmed El-Sohemy, co-author of that study, said this could help explain some of the conflicting results from earlier research into coffee and heart disease.

If a substance can be bad for people with one set of genes, but harmless or beneficial for people with different genes, it's easier to see why studies that lump everyone together can be unclear or misleading.

In one way, today's cutting-edge nutritional research is pointing back toward older truths, said Ray Rodriguez, who heads UC Davis' nutritional genomics center and who organized the weekend conference.

"People don't always respond the same way to the same diet. I think our ancestors knew that, our grandmothers knew that, but experts assumed we really all did respond the same," Rodriguez said.

One of his favorite examples is a low-fat diet. Most people with high cholesterol see it drop when they consume less fat. But a smaller group, roughly 30 percent, see it increase instead.

A few companies have already begun offering diets based on genetic testing for the general public, but Rodriguez dismisses them as "infotainment."

It's not that the science behind them is bad or sloppy, he said. It's simply that so far, we don't know enough yet to leap from a few genetic details to truly individualized diets.

There is a danger, too, in relying too much on genetics to predict how healthy we can be, said heart health researcher and author Dr. Dean Ornish.

In a talk underscoring his long exploration of lifestyle and heart disease, Ornish noted that new research is focusing on ways our behaviors can change how our genes work.

Exercise in older people, for example, was recently shown to affect about 300 different genes, increasing activity in some and dampening it in others.

"You're not a victim of your genes," Ornish said. "You can actually change to a much larger degree than we once realized."

In time, he predicted, doctors will be able to tailor recommendations much more precisely, using genetic testing to help each person find the right mix of diet, exercise and medication.