Have any supplements been studied for obstructive sleep apnea?

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]