Vitamin D: the sunshine vitamin

Vitamin D is key to maintaining normal blood levels of calcium and phosphate, which in turn are required for normal bone mineralisation, muscle contraction, nerve conduction and overall cellular function in all body cells.

Adequate intake of vitamin D will depend on the lack of exposure to solar irradiation. Our skin pigment, the use of sunscreens, ageing, time of day, clothing, air pollution, season and latitude all directly influence vitamin D3 synthesis. Vitamin D3 (cholecalciferol) becomes an important nutritional factor in the absence of sunlight, and at northern latitudes sunlight is insufficient to maintain adequate levels of vitamin D3 in the skin. Under these conditions, vitamin D3 becomes crucial, so it must be supplemented in the diet on a regular basis.

Populations with high vitamin D requirements.

• Infants and children comprise a population with relatively high vitamin D requirements resulting from their high rate of skeletal growth.
• Puberty is another period where the need for the active form of vitamin D increases due to rapid skeletal growth.
• Changes in vitamin D levels occur during pregnancy and breastfeeding due to hormonal variations and foetal development. Thus, a balanced dietary intake of this vitamin may contribute to foetal growth rate, especially at the bone and muscle levels.
• An age-related reduction in vitamin D has been found. This affects the key role in the synthesis rate in skin, the rate of the process leading to activation of the hormonal form and the response of tissues (e.g. bones). This also influences muscle performance and its associated mass in older adults.