The aim of the present study was to verify the effects of fish oil and a soya-based product on inflammatory markers and endothelial function measured by NO in women with the metabolic syndrome (MetS). A total of sixty-five women (mean age: 47·9 (sd 9·98) years) were studied in a 90-d parallel, randomised design. A control group maintained their usual diet; the second group received 29 g/d of soyabean (kinako); the third group received 3 g/d of fish oil n-3 fatty acids; and the fourth group received fish oil (3 g/d) and kinako (29 g/d). Anthropometric, blood pressure (BP), inflammatory markers, anti-inflammatory marker (adiponectin) and NO concentrations were evaluated. In relation to the baseline values, the group that received fish oil and kinako concomitantly presented a statistically significant decrease in systolic BP (SBP; P < 0·05), whereas there was a significant decrease in diastolic BP (DBP) in the control group (P < 0·05), kinako group (P < 0·01) and fish oil group (P < 0·01) after 90 d. There was a significant increase in adiponectin (P < 0·01) and NO values (P < 0·05) after 90 d in the kinako and fish oil groups. Differences between treatment groups verified a significant decrease (P < 0·05) in DBP in the kinako group after 90 d when compared to the results obtained from the fish oil and kinako groups. In conclusion, the findings of increased serum adiponectin and NO metabolite levels after 90 d, both in the fish oil and soya groups, reinforce the importance of the influence of adiponectin and NO levels on BP decrease in patients with the MetS.