Vitamin D the Sunshine Factor

In recent years, scientists have learned much more about the crucial role played by Vitamin D in human health. Vitamin D is essential for good health, growth and strong bones.
Numerous studies have contributed to a realization that our bodies require far greater amounts of Vitamin D than had previously been recommended.
Vitamin D aids the absorption of calcium and phosphorus in our diet from the gut. Calcium and phosphorus are essential for the structure and strength of our bones. So, vitamin D is critical for building strong bones. In addition, vitamin D seems to be important for muscles and general health. Scientists have also found that vitamin D may also help to prevent other diseases such as cancer, diabetes and heart disease.
A lack of vitamin D is very common. Most foods contain very little vitamin D naturally, though some are fortified (enriched) with added vitamin D.
Vitamin D is a fat-soluble vitamin. The fact that it dissolves in fat is important, because it means the body can store it for future use. Unlike other vitamins, we do not need to get vitamin D from the food that we eat. This is a good thing because most foods contain very little vitamin D naturally. Foods that contain vitamin D include:
Oily fish (such as sardines, pilchards, herring, trout, tuna, salmon and mackerel). Egg yolk. Fortified foods (this means they have vitamin D added to them) such as margarine, some cereals, infant formula milk. Our main source of vitamin D is that made by our own bodies. It is mostly made in the skin by exposure to sunlight, and 90% of our vitamin D is made in the skin with the help of sunlight.
Ultraviolet B (UVB) sunlight rays convert cholesterol in the skin into vitamin D. Darker skins need more sun to get the same amount of vitamin D as a fair-skinned person. The sunlight needed has to fall directly on to bare skin (through a window is not enough). 2-3 exposures of sunlight per week in the summer months (April to September) are enough to achieve healthy vitamin D levels that last through the year. Each episode should be 20-30 minutes to bare arms and face. This is not the same as suntanning; the skin simply needs to be exposed to sunlight.
Note: The sun's rays can be damaging and sunburn should be avoided at all costs (mainly because it can increase your risk of skin cancer). This awareness has led to a more widespread use of sun screen and protective clothing to shield our skin from these harmful rays.
But in addition to most people spending most of their time indoors, the use of sun screens contributes to Vitamin D deficiency.
A mild lack of vitamin D may not result in obvious symptoms except general aches and pains. A more severe lack can cause serious problems such as rickets (in children) and osteomalacia (in adults), described below:
A recent study found that cases of rickets have been increasing in the UK due to vitamin D deficiency.
Treatment for vitamin D deficiency is with vitamin D supplements. Some persons are more at risk of vitamin D deficiency, and so are recommended to take vitamin D supplements routinely. These include all pregnant women, breast-fed babies, children under 5, and people aged 65 and over. Also, individuals who do not get much exposure to the sun, people with black or Asian skin types, and people with certain gut, liver or kidney diseases.
A recent study published in Environmental Health Perspectives reported that many American children are not getting enough vitamin D from sun exposure alone. Only some Caucasian children, who do not diligently wear sunscreen, were getting enough vitamin D, however this was only during the summer months. Other children had lower vitamin D levels in the summer, and all had lower levels throughout the rest of the year. This means that vitamin D must be supplied from another source.
Because so few foods contain vitamin D naturally, it has been added to many. Despite food fortification, however, the data in this study suggest that many American children still do not get enough vitamin D to meet the recommended dietary reference intake (DRI).
Vitamin D supplements may play an important role in getting to the recommended DRI of 600 IU daily (children ages 1 – 8).
Godar DE, Pope SJ, Burgess Grant W, Holick MF. Solar UV Doses of Young Americans and Vitamin D3 Production. 2011. Environmental Health Perspectives.