Vitamin D deficiency

Key learning points: - Vitamin D assays may be inaccurate and imprecise - Low vitamin D status may not be clinically apparent until it is severe - Vitamin D derived from sunlight may have more benefits than vitamin D from supplements Vitamin D deficiency is reportedly common worldwide1 and has been linked to an increased risk of a wide range of diseases.2 There has been a tendency to recommend high blood levels of vitamin D for optimum health,3 and such levels can generally only be achieved with supplementation. However, recent research is challenging much of the past evidence about vitamin D and its relationship with disease outcomes, as well as the level that is needed for good health.4,5 Furthermore, there is some evidence that vitamin D from supplements may not be as effective as vitamin D through sun exposure of the skin.