Evidence check: Vitamin D 25-OH in the context of Allergie

The evidence linking vitamin D (25-OH) to allergies is moderate but not conclusive. Observational studies suggest that low vitamin D levels are associated with an increased risk of allergic conditions such as asthma, eczema, and food allergies. Vitamin D is involved in immune regulation, particularly in balancing Th1 and Th2 responses, which may influence allergic reactions. However, randomized controlled trials (RCTs) on supplementation have not shown consistent preventive or therapeutic benefits. The evidence is primarily based on observational data and mechanistic reasoning, not strong clinical endpoints. For consumers: measuring 25-OH vitamin D is useful to identify deficiency, but using it alone to predict or treat allergies is not well-supported. Individual allergy susceptibility is influenced by many factors including genetics, environment, and diet. Therefore, vitamin D should be considered part of a healthy lifestyle rather than a specific anti-allergy intervention. Evidence: human-moderate.