Which Meal Is Better for You?

Once, the battle of the bulge seemed so simple.

Fat was bad. Chicken, fruit, vegetables - all good, all the time.

It was the classic one-size-fits-all approach, with an almost Calvinist ethos of dietary rights and wrongs.

In retrospect, it made about as much as sense as saying every human should wear the same size pants.

With all of these areas where we had a dogma that this or that was good for everybody, we're now realizing that individual differences in our genetic makeup make that untrue,'' said Dr. Bertram Lubin, a specialist in studying such variability and president of Children's Hospital Oakland Research Institute in California.You and I might eat the same thing at dinner, but that diet for me could increase susceptibility to heart disease while for you, it might even prevent heart disease.''

That understanding has given rise to a new branch of medical research poised at the crossroads of nutrition and genetics. Called nutrigenetics, it is being pioneered in places such as Tufts University by researchers exploring the exquisitely complex relationship between the food we eat and the most basic building blocks of life, our genes.

Now, scientists are examining our genes to figure out why one diner can tuck into a plate of pancakes slathered in butter and remain trim and healthy, and why another must scrupulously avoid any dish hinting of dietary decadence. In fact, the emerging field could finally explain why so many of the billions of dollars spent on fad diets - think Atkins or Ornish - go to waste, as some people see little change while others thrive.

And the resulting knowledge could spawn a revolutionary way of viewing food - not just as sustenance, but as a pharmaceutical capable of reversing disease and stalling the rigors of aging.

``You have to be able to provide individuals with the right dietary approach to prevent chronic diseases - heart disease, cancer, obesity, diabetes, osteoporosis,'' said Jose M. Ordovas, director of the nutrition and genomics laboratory at the Tufts School of Nutrition Science and Policy in Boston.

But doing that requires a detailed understanding of the human genetic map. And while the Human Genome Project provided a global view of the genes that make us who we are, scientists are honing in on a more street-level perspective, looking for the chemical quirks that make us individuals and that define how food acts once it gets inside our bodies.

Scientists experience moments of great elation when they discover that a disease - cystic fibrosis is one example - can be blamed on a single gene mutation. But as genetic exploration intensifies, researchers increasingly recognize that few medical conditions can be so easily unraveled. For instance, 71 genes are implicated as suspects in the epidemic of obesity.

And, when it comes to nutrition and genes, just understanding the wiring isn't enough.

It's going to be even more important to determine which circuits in the wiring are being activated,'' said Dr. Ronald Krauss, who directed the committee that drafted dietary guidelines for the American Heart Association.How our circuits actually function is very much dependent on environmental factors, including the food we eat.''

Certain diets can turn certain genes on and off and recognizing that can allow doctors to intervene. That's already happening to a limited extent as scientists identify genetic mutations that place patients at risk of disease.

Here's one scenario, provided by Ordovas: A patient comes to see the doctor after a genetic screening, which can cost hundreds of dollars. That test identified a specific gene mutation related to the interplay between diet and cholesterol. Separately, a blood screening diagnosed the patient with dangerously low levels of the good form of cholesterol, HDL, which provides a protective shield against heart disease.

Research has shown that patients with that specific gene mutation can actually raise their level of HDL by boosting the amount of polyunsaturated fat they consume. So the patient leaves with a prescription to eat more vegetable oil, nuts, and fish such as salmon and tuna.

But such a diet in other people would result in the converse - a potent illustration of the individuality of nutrition.

One of the reasons that dietary advice has confused the public and that the public doesn't have a lot of faith in which nutrients are good and which are not is because nutrients interact differently on different genetic backgrounds,'' said Patrick Stover, director of the Cornell Institute for Nutritional Genomics.If we understand the science of why that happens, then we can better target dietary guidelines to specific genetic backgrounds.''

When that will happen routinely is subject to considerable conjecture.

Ordovas estimated that an expensive version of genetic testing for nutritional purposes could be available within three to five years, with more universal use eight years away.

But Barbara Olendzki, senior nutritionist at the University of Massachusetts Medical School, remains more measured.

``I would really like to see this genetic information used to help people's lives, but I don't think it's going to happen in my lifetime,'' said the midcareer scientist.

Already, though, commercial interests have begun exploring how they can profit. A handful of companies sell consumers genetic tests and, with them, recommendations on the food and supplements people should use to be fit.

Jim Kaput's Chicago firm, NutraGenomics, intends to offer such tests - but not yet. Kaput said he believes that genetic science is still too immature to promise such sweeping prescriptions for health. Instead, his company is in the midst of trials to determine groups of genes responsible for some of the nation's deadliest diseases.

Once those culprits are identified, Kaput said, doctors will be able to address the specific causes of a patient's illness with equally specific remedies. But fears about invasion of privacy and potential backlash from employers and insurers dictate that genetic testing must proceed gingerly, he said.

Pioneers in the field are confident that sufficient similarities exist among humans that it won't be necessary to come up with billions of different diets. The point, Ordovas said, is not to find the ``blue elephant'' but, instead, to develop strategies to help large swaths of people.

By providing people with the right tools, we can tilt the slope in their favor,'' Ordovas said.Of course, we all have to die at some point. But at least we can die healthier.''

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c.2003 The Boston Globe