[Usefulness of phyto-oestrogens in reduction of blood pressure. Systematic review and meta-analysis]

To determine whether treatment with phyto-oestrogens or soya protein succeeds in lowering blood pressure.

A systematic review, evaluating all the observation studies and clinical trials, was conducted, followed by a meta-analysis to evaluate blood pressure variations in patients treated with phyto-oestrogens. SEARCH: The search strategy adopted used the terms "phyto-oestrogens," "soya meals," "hypertension," and "blood pressure."

The data bases MEDLINE, EMBASE, Cochrane, OVID were used, without time or language restrictions. References in the relevant articles were searched for manually.

Two independent reviewers analysed the studies found in the search.

The Jadad scale was used for the clinical trials and the numerical data in the text or referred to in tables were extracted. Evaluation was made of which observational and experimental articles showed a drop in blood pressure with phyto-oestrogens and which did not. In the meta-analysis, data on sample size, difference in blood pressure before and after intervention and standard deviation were extracted from each study. The weighted difference of means was used with the model of randomised effects. The Review Manager v4.2.9 programme was used.

No significant variations in blood pressure were found, whether systolic (-1.20 mm Hg; 95% CI, -2.80 to 0.41 mm Hg) or diastolic (-1.31 mm Hg; 95% CI, -2.73 to 0.11). If there were any variations, they are clinically of little importance. There was also an important degree of both statistical and clinical heterogeneity.

There are no statistically significant or clinically important differences in blood pressure between patients treated with phyto-oestrogens and those not treated.