Why do we need vitamin D?
Unlike most other vitamins, our body is able to make its own vitamin D when the skin is exposed to the sunlight. It converts this vitamin into an activated form that the body can use.
Vitamin D promotes the absorption of calcium and regulates the amount of phosphate in the body. These actions are essential for strong and healthy bones, reducing risk of bone deformations or fractures.
Though vitamin D is best known for its role in bone health, it is thought that it also has other important functions in the body. These may include brain development, muscle function (including the heart), and immune function.
Natural sources of vitamin D
The best natural source of vitamin D is the sun, and the more sun you are exposed to, the more vitamin D is produced. It can be hard to gauge how much vitamin D you are receiving, but generally exposure for around half the time it takes for your skin to begin to turn pink, 2-3 times a week is sufficient. The more skin that is exposed, the more vitamin D is produced, although it is only necessary to expose the hands and face, for example, in order to receive an adequate amount of vitamin D.
There are many health concerns surrounding exposure to the sun, and it is worth bearing these in mind. Once you have been exposed to the sun for about half the time it takes for your skin to turn pink, cover up, sit in the shade, or go inside.
The recommended daily allowance of vitamin D is 10 mcg, however, some health professionals feel that this recommendation can be safely increased to as much as ten times this amount.
Vitamin D is also available through food although it would be difficult to get all the vitamin D you need through diet alone, and it is in a more difficult form for the body to use.
| Food source | Vitamin D content (micrograms, mcg) |
| Mackerel, 85g | 342 |
| Salmon, 85g | 120 |
| Milk, 225ml | 2.5 |
| Almond milk, 225ml | 2.5 |
| Tofu, 85g | 2 |
| Shiitake mushrooms, 85g | 1 |
Vitamin D deficiency
Vitamin D deficiency was extremely common among children throughout the Industrial Revolution, but with an increase of exposure to daylight, this condition was virtually eradicated.
However, it is thought to be on the increase again, as children are spending more time playing indoors than out. Though children are more susceptible to vitamin D deficiency, it is also thought to be an increasing problem among adults.
Initial symptoms of vitamin D deficiency can include low mood, aching joints, and problems with the digestive system. In children, bone deformities, such as bowed legs become common when they begin to walk, as their bones are too soft to support their weight. In adults, weakening of the spine can occur and susceptibility to bone fractures increases.
Too much vitamin D
Too much vitamin D most often occurs when overdosing on dietary supplements. The NHS recommends not taking any more than 25mcg or 1000iu of vitamin D supplements each day. Taking too much vitamin D can cause too much calcium to be absorbed in the body. This excess calcium then risks being deposited in the kidneys, which can damage them. Additionally, calcium can be removed from the bones, which, in a similar way to vitamin D deficiency, can cause them to weaken.
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