The antihypertensive effect of fish oil was estimated from randomized trials using metaregression analysis. Modification of the blood pressure (BP) effect by age, gender, blood pressure, and body mass index was examined.
A total of 90 randomized trials of fish oil and BP were identified through MEDLINE (1966–March 2001). Trials with co-interventions, patient populations, non-placebo controls, or duration of < 2 weeks were excluded. A total of 36 trials (50 strata) were included, 22 of which had a double-blind design. Original reports were retrieved for data collection on sample size, study design, duration, fish oil dose, BP changes and baseline characteristics of trial populations. Pooled BP estimates were obtained by metaregression analysis, weighted for trial sample sizes. Stratified analyses according to population characteristics were performed.
Intake of fish oil was high in most trials (median dose: 3.7 g/day). Fish oil reduced systolic BP by 2.1 mmHg [95% confidence interval (CI): 1.0, 3.2;P < 0.01] and diastolic BP by 1.6 mmHg (95% CI: 1.0. 2.2;P < 0.01). Restricting the analysis to double-blind trials yielded BP reductions of 1.7 mmHg (95% CI: 0.3, 3.1) and 1.5 mmHg (95% CI: 0.6, 2.3), respectively. BP effects tended to be larger in populations that were older (> 45 years) and in hypertensive populations (BP ≥ 140/90 mmHg).
High intake of fish oil may lower BP, especially in older and hypertensive subjects. The antihypertensive effect of lower doses of fish oil (< 0.5 g/day) however, remains to be established.
aDivision of Human Nutrition and Epidemiology, Wageningen University, The Netherlands, bJulius Center for Health Sciences and Primary Care, Utrecht University, The Netherlands and cCenter for Biostatistics, Utrecht University, The Netherlands.
Sponsorship: J.M.G. was supported by an unrestricted grant from the European Branch of the International Life Sciences Institute (ILSI-Europe), Brussels (http://www.ilsi.org).
Correspondence only (no reprints will be available) to J.M. Geleijnse, Wageningen University, Division of Human Nutrition and Epidemiology, P.O. Box 8129, 6700 EV Wageningen, The Netherlands. Tel: + 31 317 482574; fax: + 31 317 483342; e-mail: firstname.lastname@example.org
Received 22 October 2001
Revised 15 March 2002
Accepted 12 April 2002