In other words, getting sufficient vitamin D during the summer may not secure vitamin D status in the winter months and early spring. 1-15.Īs the half-life of vitamin D is three to six weeks, there is a seasonal peak of vitamin D status in northern latitudes in September, with the lowest point in early spring. Notably, in the elderly the skin produces 4-times less vitamin D when exposed to the sun, as compared to younger people Holick, M.F., Sunlight, UV-radiation, vitamin D and skin cancer: how much sunlight do we need? Adv Exp Med Biol, 2008. However, how much vitamin D is produced from sunlight depends on the time of day, geographic latitude, the colour of the skin, the age and use of sunscreen, among other variables. In children and adults, exposure of the hands, face and arms to the sun for 10 to 15 minutes per day is usually sufficient for most individuals. Food sources include oily fish such as salmon, sardines and mackerel, eggs, liver, and in some countries fortified foods such as margarine, dairy foods and cereals. Very few foods are naturally rich in vitamin D. The type of vitamin D made in the skin is referred to as vitamin D3 (cholecalciferol), whereas the dietary form can be vitamin D3 or a closely related molecule of plant origin known as vitamin D2 (ergocalciferol). The primary source of vitamin D comes from sun exposure: vitamin D is made in the skin when it is exposed to ultraviolet B rays. It increases bone mineral density Bischoff-Ferrari, H.A., et al., Dietary calcium and serum 25-hydroxyvitamin D status in relation to BMD among U.S.It has a direct stimulatory effect on muscle tissue and thereby may reduce the risk of falling Bischoff-Ferrari, H.A., et al., Fall prevention with supplemental and active forms of vitamin D: a meta-analysis of randomised controlled trials.It ensures correct renewal and mineralization of bone Priemel, M., et al., Bone mineralization defects and vitamin D deficiency: histomorphometric analysis of iliac crest bone biopsies and circulating 25-hydroxyvitamin D in 675 patients.Ceglia, L., et al., Multi-step immunofluorescent analysis of vitamin D receptor loci and myosin heavy chain isoforms in human skeletal muscle. Resulting in reduced bone loss Bischoff-Ferrari, H.A., et al., Fall prevention with supplemental and active forms of vitamin D: a meta-analysis of randomised controlled trials. It has a downward regulatory effect on parathyroid hormone level Steingrimsdottir, L., et al., Relationship between serum parathyroid hormone levels, vitamin D sufficiency, and calcium intake.It assists in calcium absorption from food in the intestine Heaney, R.P., et al., Calcium absorption varies within the reference range for serum 25-hydroxyvitamin D.
Vitamin D has a beneficial effect on bone health throughout life, through several key functions:
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