Sex differences in selenium metabolism played a considerable role in the heart health outcomes of the KiSel-10 study. In that randomized controlled trial, the researchers administered 200 mcg/day selenium and 200 mg/day Coenzyme Q10 or matching placebos to elderly Swedish study participants with low selenium status. The combined supplementation significantly improved heart function and reduced cardiovascular mortality [Alehagen 2013].

Note that, on average, the baseline selenium status in the KiSel-10 study participants was at a deficiency level, 67.1 mcg/L. The elderly citizens’ CoQ10 level was only borderline satisfactory, 0.82 mg/L at the study start. Prof. Urban Alehagen and the KiSel-10 research team knew that a low selenium intakes and an aging-related decline in CoQ10 bio-synthesis are associated with increased risk of cardiovascular disease [Alehagen 2013; Alehagen 2020].