Vitamin D is required for maintenance of calcium levels and as such is involved in musculoskeletal health. Low levels of Vitamin D cause disorders of muscle and bone.

Vitamin D naturally occurs in food but by far the greatest influence of blood levels of vitamin D comes from the effect of sunlight on the skin in activating pre-vitamin D into something more available to the body.

The current interest in vitamin D concerns research associations between low vitamin D levels and amongst other things, sleep disorders, incidences of cancer and incidences of cardiovascular disease