What is vitamin D and where does it come from?
If you want to get all scientific, vitamin D comprises a group of fat-soluble seco-sterols, which enters the human circulatory system in two forms; vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D2 is largely human-made and added to foods (like in ‘fortified’ cereals and margarine) and makes-up a relatively small amount of out vitamin D, whilst vitamin D3 is synthesized in the skin as a result of the action of ultraviolet light from the sun.
Why is vitamin D important?
Vitamin D is really important for bone health and more recently wider roles of vitamin D have been described. Deficiency of vitamin D has been linked to increased risk of falling, poor bone health and poor bone healing (Brinker et al. 2007) and poor muscle performance (Pfeifer et al. 1999). Some have even reported that vitamin D deficiency may even in part be responsible for increased risk of several cancers and MS.
It’s difficult to prove that deficiency is the cause of these diseases; data are measured in populations that already have the disease/condition and compared to the required levels of optimal health.
Correction of vitamin D deficiency by supplementation (often by high dose tablets taken in conjunction with calcium) has been shown to reduce the risk of falling in frail individuals, increase muscle performance and improve bone healing and bone mineral density in people who have suffered a fracture.
Extent of problem?
Sunlight is responsible for vitamin D production and the efficiency of this conversion is reduced with age, skin pigmentation, where you live (latitude) and potentially with the extensive use of sunscreens (Institute of Medicine, 1997). So, particular problems have been identified in Northern countries, such as Scandinavia, and even as close to home as Scotland. You wouldn’t believe though that Australia could report a vitamin D deficiency problem given the climate would you?
In fact a recent study reported that vitamin D deficiency is common in Australia, affecting nearly one-third of adults aged ≥25 years (Daly et al. 2012). It seems that the efficiency of their programme to reduce skin damage and skin cancer has had a negative effect on vitamin D production.
There are some groups of people who are more likely to be vitamin D deficient than others. These include:
People with darker skin
Those who spend limited time outside and, or don’t expose their skin to the sun
People who live in cloudy climates and in Northern territories
Next time I’ll talk more about supplementation. If you want more information on vitamin D, the Vitamin D Council is a really useful resource.
Brinker MR et al. (2007). Metabolic and endocrine abnormalities in patients with non-unions. J Orthop Trauma, 21(8):557-570
Daly RM et al. (2012). based study. Clin Endocrinol (Oxf). 77(1):26-35
Pfeifer M. (1999). Vitamin D and hip fracture. Trends Endocrinol Metab. 10(10):417-420.