Genes Are Only Part of the Story

Two studies published last week in the journal Science revealed that three common variations in genes more than doubled the risk of having a heart attack in men who were less than 50 years old and women less than 60 years old. In the first study, scientists at deCODE Genetics in Iceland examined blood samples from more than 17,000 people and compared those who had heart disease with those who did not. They found that there were very small gene variations in those who had heart disease—just single letters of the DNA code, called SNP's (pronounced "snips"), or single nucleotide polymorphisms. People with this variant on both chromosomes rather than on just one—20 percent of Caucasians—had more than double the risk of developing heart disease at an early age.

In the second study , also published in the same issue of Science (it's interesting how different investigators in other parts of the world often make the same discovery at the same time), researchers at the University of Ottawa Heart Institute in Canada looked at DNA changes in more than 28,000 people. They identified another SNP on the same chromosome as the Iceland group that increased the risk of developing early heart disease. People of European descent who had this DNA variant on one chromosome had a 25 percent greater risk of developing heart disease at an early age, and those who had it on both chromosomes had a 40 percent increased risk. In both studies, this increased risk of heart disease was not found in those of African descent.

Another recent study identified seven SNP variants that increase the risk of diabetes. Interestingly, the people who are at highest risk for diabetes also may show the most improvement from making comprehensive lifestyle changes. More research is likely to identify other genes that are associated with an increased risk of illness.

Not surprisingly, genes appear linked to obesity as well. In a study published a month ago, researchers at the University of Oxford found that another common gene variation markedly increased the risk of obesity. Approximately 50 percent of white Europeans have one defective copy of the gene, which increased the risk of obesity by about one third. However, approximately 16 percent of people have two altered copies of this gene, and these people have a 70 percent increased risk for obesity and were an average of 6.6 pounds heavier.

These findings are consistent with a classic study of adoptees conducted in Denmark and a study of twins conducted in Sweden. Researchers led by Dr. Albert Stunkard found that there was a strong relation between the weight of adoptees and their biological parents, but not between adoptees and their adoptive parents. They also found that the body-mass index of twins reared apart was only slightly lower than those reared together, whereas there was more variation in fraternal twins who share only some of the same genes.

So, what does this mean to you? Some people may say, "Well, looks like it's all in my genes, there's not much I can do about it." It's tempting to take a nihilistic view since it absolves us of any personal responsibility. But it also means we're powerless, and I don't like feeling that way. Besides, it's not true. Our genes are only part of the story.