Modest Intake of DHA/EPA found to Significantly Lower Blood Pressure
Minihane, A. M. et al., Journal of Nutrition, in press, 2016
Norwich Medical School, Univ. of East Anglia, Norwich, United Kingdom
Numerous studies have shown the ability of supplemental DHA plus EPA omega-3 fatty acids to lower blood pressure. A considerable proportion of such studies have utilized doses of DHA/EPA which are much higher than can readily be obtained from dietary sources (eg., 3 grams/day or more). The present trial was designed so as to determine if much lower levels of daily supplementation (such as could be fulfilled by dietary sources such as fish/seafood) could significantly lower blood pressures. For this purpose, healthy adults (312 men plus women, average age of 45 years) were assigned to receive a ‘control’ supplement (no DHA/EPA present) each day or fish oil providing 0.7 grams (700 mgs) or 1.8 grams of DHA/EPA (DHA:EPA ratio of 1.4:1) for a period of 6 weeks. Baseline and post-supplementation blood pressures were measured along with fatty acid analyses of the blood plasma phospholipid (phosphatidylcholine) which confirmed the resulting rise in circulating DHA/EPA levels when fish oil was supplemented.
The final results showed a statistically-significant reduction of systolic blood pressure (by 5 mm Hg (mercury) overall in those subjects from the group receiving 0.7 grams DHA/EPA daily who had systolic hypertension (mean systolic blood pressure of 146 mm Hg) at the beginning but not in those who had normal blood pressures (incl. mean systolic blood pressure of 119 mm Hg). No further significant reduction in systolic blood pressure was found in those with systolic hypertension who were assigned to the higher DHA/EPA intake (1.8 grams/day). The subjects assigned to the ‘control’ supplement exhibited no significant lowering of blood pressure. The authors concluded that daily intakes of DHA/EPA as low as 0.7 grams (700 mgs) daily are capable of showing clinically meaningful blood pressure reductions. At the population level, such reductions could be associated with a lower risk of cardiovascular disease.
Dr. Holub's Comments:
It is noted that the extensive MRFIT study from the US on 347,978 men indicated that a 91 % increase in coronary heart disease (CHD) risk was associated with a 25 mm Hg elevation in the systolic blood pressure range of 120-159 mm Hg (Kannel et al., Hypertension, 42: 453-456 (2003)). Thus, a 1 mm Hg elevation would be associated with a 3.6 % increase in CHD risk. It can therefore be estimated that the 5 mm Hg reduction with 700 mg DHA/EPA as found in the present study in those with systolic hypertension would yield an 18 % reduction in the risk of CHD. Such relatively modest intakes of DHA/EPA of 700 mg/day can readily be obtained from the selection of appropriate fish/seafood sources and/or enriched functional foods containing DHA/EPA and/or via supplementation. It is noted that DHA/EPA intakes from dietary sources in North America currently are in the range of only 110-150 mg/day.