Abstract—Sesamin, the major lignan found in sesame, has been shown to increase vitamin E levels by inhibiting its metabolism via the cytochrome P₄₅₀ isozyme CYP4F2. CYP4F2 and CYP4A11 are the predominant human isoforms that synthesize 20-hydroxyeicosatetraenoic acid (20-HETE) from arachidonic acid. Considerable evidence suggests that 20-HETE may play a role in the pathogenesis of hypertension. We hypothesized that sesamin could be an inhibitor of 20-HETE synthesis. This study investigated the effects of sesamin on 20-HETE synthesis in vitro and the effect of sesame supplementation on plasma and urinary 20-HETE concentrations in humans. Human microsomes were used to investigate the potency and selectivity of sesamin inhibition of 20-HETE synthesis. Sesamin inhibited human renal and liver microsome 20-HETE synthesis with IC₅₀ <20 µmol/L. It was selective toward CYP4F2 (IC₅₀: 1.9 µmol/L) and had reduced activity toward CYP4A11 (IC₅₀: >150 µmol/L), as well as cytochrome P epoxygenation of arachidonic acid (IC₅₀: >50 µmol/L). In a randomized, controlled crossover trial, overweight men and women (n=33) consumed 25 g/d of sesame (50 mg/d of sesame lignan) or an isocaloric matched control for 5 weeks each. Relative to control, sesame supplementation resulted in a 28% decrease in plasma and a 32% decrease in urinary 20-HETE (P<0.001). Urinary sodium, potassium, and blood pressure were not affected. This study demonstrates for the first time that sesame supplementation in humans reduces the plasma and urinary levels of 20-HETE, likely via inhibition of CYP4F2 by sesame lignans. These results suggest that sesame lignans could be used for the investigation of potential roles of 20-HETE in humans.