Can Vitamin D 25-OH help with Fruchtbarkeit?

Vitamin D (25-OH) is a key regulator of calcium metabolism and also influences reproductive health. Deficiency has been linked to reduced fertility in both women (ovarian function, implantation) and men (sperm quality). However, evidence that supplementation improves fertility in individuals with adequate levels is mixed. RCTs show inconsistent results. Testing 25-OH vitamin D levels is reasonable to identify deficiency. Supplementation should be targeted to deficiency. Evidence: human-moderate. No specific sources in provided context.