Researchers from the Jean Mayer USDA Human Nutrition Research Centre at Tufts University have found a link between a particular gene, diet and risk factors for heart diseases.
The study, published in Circulation, examined apolipoprotein (APOA5) - a gene that codes for a protein, which in turn plays a role in the metabolism of fats in the blood.
The results showed that people who carry a particular variant of APOA5 may have elevated risk factors that are associated with heart disease, but only if they also consumed high amounts of omega-6 fatty acids in their diets.
The researchers analysed lipid levels and dietary assessment questionnaires of more than 2,000 participants in the Framingham Heart Study and quantified their intake of different types of fats.
Omega-6 fatty acids, as well as omega-3 fatty acids are polyunsaturated fatty acids, and according to a report from the National Institutes of Health Office of Dietary Supplements, most Americans consume about 10 times more omega-6s than omega-3s.
Omega-3s are found in nuts, leafy green vegetables, fatty fish, and vegetable oils like canola and flaxseed, while omega-6s are found in grains, meats, vegetable oils like corn and soy, and also processed foods made with these oils. Both omega-3s and omega-6s, known as essential fatty acids, must be consumed in the diet because the body does not make them.
"We know that some people are genetically predisposed to risk factors for heart disease, such as elevated low-density lipoprotein levels in the blood," says Chao-Qiang Lai, a USDA-Agricultural Research Service scientist.
"And that APOA5 has an important role in lipoprotein metabolism. We wanted to determine if certain dietary factors change the role of APOA5 in metabolizing these lipoproteins and their components, such as triglycerides," Lai added.
Lai and colleagues found that individuals who consumed more than six percent of daily calories from omega-6 fatty acids displayed a blood lipid profile more prone to heart disease.
"Research hasn't shown us yet if there is an optimal ratio for omega- 3s to omega-6s, or if consuming a certain amount of omega-6s might negate the benefits of omega-3s," Jose Ordovas, senior author of the study and director of the Nutrition and Genomics Laboratory at the USDA, said.
"We do know that omega-6s are necessary for the body and can be a source of healthful fat in the diet, but for those who are carriers of the particular APOA5 gene variant, consuming fewer omega-6s in relation to omega-3s may be important, as it might help reduce the risk of developing precursors to heart disease," he added.
The researchers concluded by saying that it may be more important for some people to make preventive dietary and lifestyle changes than others, depending on their genetic makeup.