Studies of whether polyunsaturated fatty acids in fish oil--in particular, eicosapentaenoic and docosahexaenoic acids--lower blood pressure have varied in design and results. We conducted a population-based, randomized, 10-week dietary-supplementation trial in which the effects of 6 g per day of 85 percent eicosapentaenoic and docosahexaenoic acids were compared with those of 6 g per day of corn oil in 156 men and women with previously untreated stable, mild essential hypertension. The mean systolic blood pressure fell by 4.6 mm Hg (P = 0.002), and diastolic pressure by 3.0 mm Hg (P = 0.0002) in the group receiving fish oil; there was no significant change in the group receiving corn oil. The differences between the groups remained significant for both systolic (6.4 mm Hg; P = 0.0025) and diastolic (2.8 mm Hg; P = 0.029) pressure after control for anthropometric, lifestyle, and dietary variables. The decreases in blood pressure were larger as concentrations of plasma phospholipid n-3 fatty acids increased (P = 0.027). Dietary supplementation with fish oil did not change mean blood pressure in the subjects who ate fish three or more times a week as part of their usual diet, or in those who had a base-line concentration of plasma phospholipid n-3 fatty acids above 175.1 mg per liter. We conclude that eicosapentaenoic and docosahexaenoic acids reduce blood pressure in essential hypertension, depending on increases in plasma phospholipid n-3 fatty acids.
Objective: To examine the relation between consumption of ®sh and ®sh products registered by a comprehensive food frequency questionnaire and the composition of fatty acids in serum phospholipids. Design: Cross-section study. Setting: Cardiovascular screening centre in Trondheim, Mid-Norway. Subjects: Of 256 eligible women 242 agreed to participate in the present study. Altogether 234 middle-aged women (91.4%) completed the questionnaire and gave a valid blood sample. Results: Total frequency consumption of ®sh for dinner showed only weak association with serum phospholipid fatty acid composition. In separate analyses of lean and fatty ®sh, consumption of fatty ®sh was negatively associated with n-6 and positively associated with n-3 fatty acids in serum phospholipids, while no signi®cant associations were found for lean ®sh consumption. Cod liver oil consumption was strongly related to the phospholipid fatty acid composition. The associations improved moderately when adding portion size information. Spearman's correlation coef®cient between dietary intake of eicosapentaenoic acid (EPA) and serum phospholipid EPA was 0.58, and Spearman's correlation coef®cient between intake of docosahexaenoic acid (DHA) and serum phospholipid DHA was 0.53. Conclusions: This study suggests that in populations with a high consumption of ®sh and cod liver oil, habitual intake can be re¯ected in serum phospholipids. However, as the fat content of ®sh is highly variable, separate registration of lean and fatty ®sh consumption is needed. Sponsorship: Erna and Olav Aakre's Foundation, Tromsù, and the Norwegian Cancer Society (E96071). Descriptors: ®sh; cod liver oil; n-3 fatty acids; food frequency questionnaire; serum phospholipid fatty acids.
Ecological and case-control studies have demonstrated a positive correlation between consumption of fat and the risk of prostate cancer. Two recent human studies have focused on a-linolenic acid as a risk factor for prostate cancer. Animal experiments have shown that dietary v-6 polyunsaturated fatty acids have generally stimulated tumour development, whereas v-3 polyunsaturated fatty acids have diminished it. The aim of our study was to investigate the association between these fatty acids and the subsequent risk of prostate cancer. Blood donors to the Janus serum data bank in Norway, who later developed prostate cancer, were matched to blood donors without prostate cancer (141 matched sets); the proportional level of fatty acids measured before diagnosis in the donors' serum was examined. The risk of later prostate cancer was analysed by conditional logistic regression. Increasing risk for prostate cancer was found with increasing quartiles of palmitoleic, palmitic and a-linolenic acid. An inverse risk association was found with increasing levels of tetracosanoic acid, for the ratios of linoleic to a-linolenic acid and arachidonic to eicosapentaenoic acid. There was no clear association between the risk effect of total v-3 and total v-6 fatty acids. There were no indications of a relationship between fatty acids and more aggressive cancers. Our results verify recent findings of a positive association between a-linolenic acid and a negative association between the ratio of linoleic to a-linolenic acid and the risk of prostate cancer. Int.
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