Lower incidence of hypertension associated with greater omega-3 fatty acid intake

Tuesday October 4, 2011. The August, 2011 issue of the Journal of Internal Medicine published the findings of American researchers of a reduction in the incidence of high blood pressure in men and women who consumed higher amounts of long-chain omega-3 polyunsaturated fatty acids from fish. While the cardiovascular benefits of long-chain omega-3 fatty acids (which include EPA and DHA) are well known, the current research sought to determine potential interactions with the body's levels of selenium and mercury, elements that also occur in fish.

The study involved 4,508 men and women enrolled in 1985 in the ongoing Coronary Artery Risk Development in Young Adults (CARDIA) Study. Dr Ka He of the University of North Carolina in Chapel Hill and colleagues utilized responses to dietary questionnaires conducted upon enrollment and at the seven and twenty year follow-up examinations to determine average omega-3 fatty acid intake. Blood pressure was measured at all six follow-up visits, and incidences of high blood pressure or initiation of antihypertensive medication were noted. Selenium and mercury levels were determined by measuring the amounts contained in toenail clippings collected in 1987.

Dr He's team found a 35 percent lower adjusted risk of developing hypertension among men and women whose EPA and DHA levels were among the top 25 percent in comparison with those whose intake was among the lowest fourth. When the fatty acids were separately evaluated, DHA was associated with the greatest protective effect. The benefit for omega-3 fatty acids appeared to be greater among those with higher selenium and lower mercury levels.

"To the best of our knowledge, no study has investigated three-way interactions of selenium, mercury and long-chain omega-3 polyunsaturated fatty acids in relation to incidence of hypertension," the authors write. "The possible mechanisms explaining the modification of selenium and mercury on the antihypertensive effect of long-chain omega-3 polyunsaturated fatty acids may lie in that both selenium and mercury are somehow involved in the process of oxidative stress and cardiac function through the same pathway by which long-chain omega-3 polyunsaturated fatty acids regulate blood pressure."

"Additional studies are warranted to elucidate the complex interactions amongst selenium, mercury and long-chain omega-3 polyunsaturated fatty acids, three important components in fish, in terms of hypertension prevention," they conclude.