10/11/2011 05:30 EDT | Updated 12/11/2011 05:12 EST

High fruit-and-vegetable diet can overcome genetic risk for heart disease: study

TORONTO - It may be true that we're pretty well stuck with the genes we were born with. But for people carrying a common genetic signature that predisposes them to cardiovascular disease, it appears there's a way to get around their DNA.

A pair of studies involving about 27,000 subjects has shown that people with the genetic anomaly can reduce their chance of having a heart attack or stroke with a diet rich in fruits and vegetables, especially those eaten raw or lightly cooked.

"Despite potentially having a family history of heart disease, or an implied genetic increased risk, you can actually turn off the bad genes by adopting healthy dietary patterns," said co-principal author Dr. Sonia Anand of the Population Health Research Institute at McMaster University.

"And I think this is important because sometimes people feel that their family history and their genes are not modifiable, so they just have to live with it," Anand said Tuesday from Hamilton. "So this kind of gives them that message that you actually can change supposedly non-modifiable risk factors."

Scientists have known for some time that a region of genetic variants called 9p21 is a strong predictor for cardiovascular disease and is commonly found in different ethnicities around the world.

In their study, published is this week's issue of PLoS Medicine, the researchers analyzed the effects of various types of diets on subjects from five ethnicities — European, South Asian, Chinese, Latin American and Arab — both those who carry the 9p21 variants and those who don't.

Their results suggest that individuals with the genetic variation who consumed a "prudent diet," composed mainly of raw vegetables, fruits and berries, had a similar risk of heart attack to those with a low-risk genetic profile.

“We know that 9p21 genetic variants increase the risk of heart disease for those that carry it,” said Jamie Engert, a cardiovascular geneticist at McGill University and joint principal investigator of the research. “But it was a surprise to find that a healthy diet could significantly weaken its effect.”

That effect was seen in all the ethnic groups except those of Arab ancestry, but that may have been because the number of participants in that cohort was comparatively small, Engert said from Montreal.

"Everybody already knows that a prudent diet will help you avoid heart disease," he said. "But the important part of our paper was that we showed a specific genetic variant for which the susceptibility could be reduced."

Anand said it's not known how diet could overcome the power of DNA.

"But we hypothesize that in some way a diet high in fruits and vegetables, and all of the good things that are contained in them, somehow modifies the expression of this particular gene," she said.

"From the purely scientific perspective, it's interesting to see this interaction and do future studies to understand the mechanism, because everyone is always looking for drug targets or some way to modify the expression of genes."

Dr. Beth Abramson, a cardiologist at St. Michael's Hospital in Toronto who was not involved in the research, said people with a close family relative who experienced early heart disease, such as a parent or sibling, have double the risk of having a heart attack or other cardiovascular event as those in the general population.

"What this study seems to imply is that you shouldn't throw in the towel if you have a family history or are at risk for heart disease because healthy living with a healthy diet, in addition to other lifestyle changes such as exercise and maintaining a healthy body weight, can take away from the risk that genes give you," she said.

Still, the advice to eat a diet high in fruit and vegetables — 10 servings a day is recommended — is good for everyone, said Abramson, who is also a spokeswoman for the Heart and Stroke Foundation of Canada.

Her diet advice doesn't just stress the consumption of lots of fruits and vegetables, but also includes keeping fat intake to a minimum.

While public health advocates have long been hammering home the recommendation to eat more fruits and vegetables, Anand suggests that only a minority of the population "takes this advice to heart."

Engert agreed, adding that as personal genomic testing becomes more affordable and common, those who learn they have this genetic propensity for cardiovascular disease may be motivated to adopt the diet and behaviour changes to lower their risk.

"That doesn't mean that they won't get heart disease," he said, explaining that there are likely multiple areas of DNA involved in boosting an individual's likelihood of having a heart attack or stroke. "It just means their increased risk because they carry this susceptibility gene is no longer there."