Can a DNA Test Tell You How to Live Your Life?

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Scientists who specialize in nutritional genomics have only begun to decipher the relationship between DNA sequences, diets and ailments like diabetes, heart disease and cancer. Their hope is that someday your own nutritional geneticist will be able to scan your DNA and tell you exactly how to plan your diet given the genes you've been bequeathed.

But that day isn't here yet, and not by a long shot, according to the Government Accountability Office. Last week the agency reported to the Senate Special Committee on Aging the results of its probe of four Internet-based firms that — for prices ranging from $99 to more than $1,000 — promise personally tailored "nutrigenetic" advice. Customers provide the firms with a DNA sample in the form of a cheek swab and a detailed description of dietary and lifestyle habits. According to the agency, the reports peddled by these firms are in equal parts misleading, vague to the point of uselessness and based on scientifically dubious claims. The GAO sent in profiles for 14 mock customers — each with a unique lifestyle and physical profile — but derived from only two DNA sources. According to the GAO, the companies sent back a variety of reports. That suggested, in the GAO's opinion, that the advice had very little to do with genetic screening.

Rosalynn Gill-Garrison couldn't disagree more. The chief scientific officer of Colorado biotech Sciona, one of the companies probed by the GAO, says her firm's reports differed for each fictional customer because each report is a function of both the genetic and the lifestyle information provided. Change half the function, she says, and you’re bound to get a different result. And although she concedes that nutrigenomics is a young field, she disagrees vehemently with the GAO’s claim that her company cannot back up its reports with sound science. "Can we tell you that in 30 years you won't get heart disease?" asks Gill-Garrison. "No we cannot say that. But we are not predicting risk, and we're not diagnosing disease."

So what exactly is Sciona doing? The company, says Gill-Garrison, tells its customers if any of the 19 genes they screen reveal a metabolic problem that has been clearly associated with disease. If the tests suggest the customer has a gene that promotes, say, a bad cholesterol profile, it can tell that person, based on his dietary and lifestyle profile, how to modify his diet and habits to keep his good (HDL) and bad (LDL) cholesterol in healthy balance. Ditto for other genetic markers. Sciona, says Gill-Garrison, makes sure that each nugget of advice it offers is built on a firm scientific foundation. And a bibliography on the company’s web site, she says, backs up that claim.

So how dangerous is direct-to-consumer nutrigenetics? It depends. Two of the firms probed by the GAO coupled their reports with a pitch for what they claimed were supplements designed to address the deficiencies in the DNA profiles of their customers. The supplements, one of which would have cost $1,880 a year, were not substantially different from those available for $35 a year at any drug store. It's not just about money, but safety too. As the GAO points out, not all supplements are harmless to all people.

On the other hand, if all a company is doing is essentially telling its customers to stop smoking and start eating more broccoli, it probably isn’t putting them in grave danger. "You may not be getting the full value out of every dollar you spend on your test," says Ray Rodriguez, director of the Center of Excellence in Nutritional Genomics at the University of California, Davis, "but it won't do you any harm — and you might actually start taking your nutrition more seriously." The only question is whether you really want to shell out $1,000, or even $99, for that sort of advice.