Antioxidants have been studied for OSA, since it is associated with increased levels of oxidative stress. Although oxidative stress is reduced by CPAP therapy[1], the relationship between antioxidant levels in the body and OSA isn’t well-understood.[2]. One small cohort study noted an improvement in OSA symptoms after 8 weeks vitamin D supplementation in participants with mild OSA and low vitamin D levels at the start of the trial.[3] This particular study lacked appropriate blinding and controls to yield conclusive results, however, and studies examining associations between vitamin D levels and OSA have reported inconsistent results.[4] Nitrate supplements have also been studied for OSA, and were found in one randomized crossover trial to reduce the OSA-induced increase in early-morning blood pressure.[5]