Eating According to Your Genome

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TR: One of the current nutrition debates is over the benefits of omega-3 fatty acids--different studies have produced conflicting results regarding omega-3's ability to protect against heart disease. Can nutrigenomics help sort this out?

JO: We have found that some people are more susceptible to the negative effects of omega-6 [a related fatty acid] than others. Those with a certain variant in the apolipoprotein A, or APOA, gene show a rise in triglycerides, a risk factor for cardiovascular disease, when they eat a diet high in omega-6. In these cases, the protective effect of omega-3 may be overwhelmed by overconsumption of omega-6.

This allele is much more common in Asia, and those who have it are more susceptible to the effect of omega-6 consumption. That may explain the rising rates of cardiovascular disease in Asian populations.

TR: What are the major hurdles in identifying how our genes affect our body's response to food?

JO: There are so many combinations of genes and environmental factors, you need huge populations to study. Most studies in the field are underpowered. We've done studies with 5,000 people, but that's just not enough. We need to do studies on the order of 100,000 people to take into account all the different factors.

We also need better statistical tools. Currently, we are borrowing analysis tools from situations that are much simpler, such as Medelian genetics, where a single gene leads to a certain phenotype. But applying those methods to huge networks of interactions is just not feasible.

TR: Is the nutrigenomics community using new genetic tools, such as the large gene chips that can detect 500,000 genetic variations in a single experiment?

JO: Yes, those chips do help to accumulate data. But because we need to run thousands of subjects, the cost is still prohibitive.

TR: A few consumer nutrigenomics tests are already on the market. What do you think of them?

JO: These tests may point people in the right direction, but they are not by far a final answer. Their worth also depends on the feedback the consumer gets. If the test is accompanied by prudent recommendations on diet and does not make snake-oil promises, then they probably don't have much potential to harm. And they may even have some benefit. One study found that people who took the test and went to a dietician did better than people who just went to a dietician. I think it's the placebo effect. People will pay better attention because they feel they are getting advice that is just for them.