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Scientists look to DNA for personalized diets

/ Source: The Associated Press

As a registered dietitian, Ruth DeBusk has eaten a healthy diet for a long time. As a geneticist, she wondered if she could do better.

So earlier this year, she had her DNA tested by a company that gives personalized nutrition advice based on genetics. The results indicated she needed more folate.

So DeBusk doubled her minimum amount of folate, a B vitamin found in leafy greens and citrus.

“I’m more diligent about being sure that I get it every day if possible, because it really matters,” said DeBusk, who has a private practice in Tallahassee, Fla., and has written a book on nutrition and genetics.

“I’ll actually make an effort to drink a glass of orange juice or eat an extra big salad in the evening, being aware it hasn’t been one of my better folate days.”

Personalized dietary advice

That’s the way it’s supposed to work in a field called nutritional genomics or nutrigenomics. The basic idea is this: There are genes that affect the risk of getting illnesses like heart disease, cancer, osteoporosis and diabetes, and the impact of those genes can be modified by what you eat. Everybody carries one version or another of each of those genes. So why not find out what gene versions you have and base dietary advice on that?

“Every time we go to the supermarket we’re using educated guesses about what we should eat and what we shouldn’t eat,” says Raymond Rodriguez, director of the National Center of Excellence for Nutritional Genomics at the University of California, Davis.

In the future, more of that guesswork may be replaced with accurate, personal DNA-based dietary advice, which Rodriguez says is “rapidly emerging on the horizon.”

But that time isn’t here yet, most experts say. Nutrigenomics is still in its infancy, with plenty to be learned, and it’s not yet clear what role it may play in standard medical practice.

Most of the research targets heart disease and cancer, and scientists may be ready to deliver personalized diet recommendations in those areas within five years, said Jose Ordovas, director of the nutrition and genomics laboratory at the U.S. Department of Agriculture Nutrition Research Center at Tufts University in Boston.

“We have scientific evidence that the concept is right, that we can provide something along those lines in the future,” Ordovas said. “We are not there yet.”

DNA test kit

No? You can walk into some pharmacies or grocery stores right now and pay $99 for a DNA test kit that will get you personalized diet advice for heart health, bone health, or any of three other areas. It’s from Sciona Inc., a small company based in Boulder, Colo., that started offering DNA-based diet advice in 2001. Such tests are also available by mail order and on the Internet.

Sciona customers collect their own DNA with a cheek swab, complete a diet and lifestyle questionnaire and send it all in for analysis. Sciona encourages customers to review its advice with a doctor.

The company acknowledges that some scientists say it’s too soon to offer such a service, but says its testing is based on solid research. Current testing focuses on 19 genes and the company is studying others, said Rosalynn Gill-Garrison, chief scientific officer and a company founder.

Sciona’s approach basically starts with standard healthy-eating recommendations and modifies them when genetic analysis indicates a need for something more, Gill-Garrison said.

After a DNA test, Sciona may recommend steps like eating more broccoli or omega-3 fatty acids, she said, or limiting caffeine to protect against bone loss.

Gill-Garrison said studies show that people with a certain version of a gene called MTHFR tend to have high blood levels of a substance called homocysteine, which has been linked to a higher risk of heart disease and stroke. Studies also show that people with this gene version can reduce their homocysteine levels by taking in more folate, she said. So that’s the advice Sciona customers with that gene version get.

High levels of homocysteine also can be spotted with a standard blood test at a doctor’s office.

A work in process

Ordovas said the trouble with anybody providing gene-based dietary advice now is that scientists don’t yet have the whole picture of what genes should be considered. With current tests, it’s like trying to size up a landscape by looking through a keyhole, he said. You can’t tell what you’re not seeing.

“At least in that very narrow region of our genome that they are looking, they have potential that they may provide some valuable information, and it could benefit some people,” he said. But advice based on current tests “can also be misleading because you are ignoring pieces that are very important,” he said.

Rodriguez said he doubts anybody will be harmed by the current tests, and that they’re beneficial because they get people to think about diet and lifestyle. But he said they remind him of the first VCRs or CD players to hit the market.

“It is an expensive new technology ... and it will probably, in my estimation, become more efficient, more accurate and more affordable with time.”

DeBusk, who said she has no financial ties to any of the companies, figures the time for DNA-based diet advice has come.

“The scientist in me says we shouldn’t do this now, we need to wait another 20 years until many studies have been done,” she said. But her clients want to know what the best science is right now, and “it’s difficult to say, 'Come back in 20 years.' You can’t do that.

“Do we know everything we’d like to know? No. ... Do we know enough to start introducing this type of technology and start the long process of educating people? I would say yes.”