Modulation of endothelial function by walnuts and sex hormones.

and Sex Hormones To the Editor: We read with interest the recent article by Dr Ros and colleagues1 dealing with the relationship between a walnut diet and endothelial function in hypercholesterolemic subjects. The results of their study demonstrated that the walnut diet significantly improved endothelium-dependent vasodilation. The authors indicated that changes of endothelium-dependent vasodilation correlated with those of plasma cholesterol-HDL ratios. They proposed that the improvement of endothelial function might explain the cardiovascular protective effect of walnut intake beyond cholesterol lowering. Numerous studies have shown that estrogen may also have beneficial effects on cardiovascular functions. One of the mechanisms underlying the protective effect of estrogen may be the enhancement of nitric oxide (NO) production. There is evidence showing that vascular endothelial function is markedly influenced by estrogen and is improved by hormone replacement therapy in postmenopausal women.2 In an in vitro study presented earlier, we demonstrated that 17 -estradiol increased membrane fluidity (a reciprocal value of membrane microviscosity) of erythrocytes and improved the rigidity of cell membranes in postmenopausal women via the NOand cGMP-dependent mechanism.3 Since abnormalities in membrane microviscosity could cause a disturbance in rheological behavior and microcirculation, these findings suggest that estrogen deficiency might be involved in the pathogenesis of vascular complications in women. Recently, the role of estrogen in male physiology has also become evident, and normal physiological estrogen, which is converted from testosterone by aromatase, may confer cardiovascular benefits for men.4 In this context, we speculate that, because nuts are enriched with arginine,5 changes in NO production by sex hormones might modify the effects of the walnut diet on endothelial function and microcirculation both in men and women. It was demonstrated that the endothelium-walnut interplay may differ among the subjects in the present study of Dr Ros and colleagues. Therefore, we would like to know whether the endogenous sex hormones might be related to the magnitudes of the restored endothelial function by the walnut diet. It would be important to assess more precisely the relationships among nut intake, sex hormone status, and NO production, as well as their contribution to the improvement of endothelial function both in men and women.