Fish oil, selenium and mercury in relation to incidence of hypertension: a 20-year follow-up study

Abstract. Xun P, Hou N, Daviglus M, Liu K, Morris JS, Shikany JM, Sidney S, Jacobs DR, He K (Department of Nutrition, Gillings School of Global Public Health and School of Medicine and Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC; Department of Preventive Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL; Research Reactor Center, University of Missouri-Columbia, Columbia, MO; Division of Preventive Medicine, School of medicine, University of Alabama at Birmingham, Birmingham, AL; Division of Research, Kaiser Permanente Medical Care Program, Oakland, CA; Division of Epidemiology and Community Health, School of Public Health, University of Minnesota, Minneapolis, MN; and Department of Nutrition, University of Oslo, Oslo, Norway). Fish oil, selenium and mercury in relation to incidence of hypertension: a 20-year follow-up study. J Intern Med 2011; doi: 10.1111/j.1365-2796.2010.02338.x. Objectives. Long-chain omega-3 polyunsaturated fatty acids (LComega3PUFAs), selenium (Se) and mercury (Hg) are three important components in fish. The cardioprotective effect of LComega3PUFA intake has been recognized; however, the hypothesis that this benefit may be greatest with high Se and low Hg levels has not been investigated. Design. A cohort of 4508 American adults aged 18-30, without hypertension at baseline in 1985, were enrolled. Six follow-ups were conducted at examinations in 1987, 1990, 1992, 1995, 2000 and 2005. Diet was assessed by a validated interviewer-administered quantitative food frequency questionnaire at exams in 1985, 1992 and 2005. Incident hypertension was defined as first occurrence at any follow-up examination of systolic blood pressure (BP) >/= 140 mmHg, diastolic BP >/= 90 mmHg or taking antihypertensive medication. Toenail clippings were collected in 1987, and Se and Hg levels were quantified by instrumental neutron-activation analysis. Result. Participants in the highest LComega3PUFA intake quartile had a significantly lower incidence of hypertension (hazard ratio: 0.65; 95% CI: 0.53-0.79; P(trend) < 0.01) compared to those in the lowest quartile after adjustment for potential confounders. Docosahexaenoic acid showed a greater inverse association than eicosapentaenoic acid. The inverse association of LComega3PUFA intake with hypertension appeared more pronounced at higher Se and lower Hg levels, although interaction tests were statistically nonsignificant. Conclusions. Our findings indicated that LComega3PUFA intake was inversely associated with incidence of hypertension. The prior hypothesis that the potential antihypertensive effect of LComega3PUFA intake varies depending on joint levels of Se and Hg received modest support and cannot be ruled out.

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