Eating fresh fruit and raw vegetables can weaken genetic effects that are strongly linked to heart disease, a study has shown.

The healthy foods appear to modify genetic code variants on the 9p21 chromosome known to increase heart disease risk.

The finding emerged from one of the largest diet and gene heart studies conducted.

Scientists analysed DNA from more than 27,000 people of European, South Asian, Chinese, Latin American and Arab ethnic background. Participants were also questioned about their dietary habits.

The study looked at heart disease risk conferred by several single-letter changes in the genetic code, or single nucleotide polymorphisms, on 9p21.

The chromosome is one of the “packages” of DNA that exist in every cell and contain the genes. Jamie Engert, from McGill University in Canada, one of lead researchers, said: “We know that 9p21 genetic variants increase the risk of heart disease for those that carry it. “But it was a surprise to find that a healthy diet could significantly weaken its effect.”

The findings, reported in the online journal Public Library of Science Medicine, showed the heart benefits of eating a diet rich in raw vegetables, fruits and berries.

People with the high-risk mutations who ate healthily had a similar risk of heart disease as those with low-risk versions of the genetic code variants.

Co-author Sonia Anand, professor at McMaster University in Canada, said: “We observed that the effect of a high-risk genotype can be mitigated by consuming a diet high in fruits and vegetables.

“Our results support the public health recommendation to consume more than five servings of fruits or vegetables as a way to promote good health.”

Ron Do, from Massachusetts General Hospital in the US, another member of the study team, said: “Our research suggests there may be an important interplay between genes and diet in cardiovascular disease.” Judy O’Sullivan, senior cardiac nurse at the British Heart Foundation, said: “This piece of research is certainly an interesting and useful insight into how our risk of developing heart disease is influenced by a number of factors. It should serve as a reminder that while our lifestyle and genes can increase our risk, the way they interact with each other is also very important.”