- Although its name may indicate so, Vitamin D is NOT a VITAMIN! By definition vitamins are essential compounds that cannot be synthesised by the body and must be obtained in the diet. However, our body is able to synthesise and make adequate amounts of this valuable vitamin when the skin is exposed to sunlight; without the need to obtain it through the diet.
- The best known action of Vitamin D is to help absorb calcium into the bloodstream. Without this Vitamin, most of the calcium consumed in the diet would be lost; eventually leading to rickets in children and osteomalacia in adults (fragile and easily deformed bones).
- Unlike other vitamins which can be found in a wide range of foods, Vitamin D food sources are very limited. The only rich sources of Vitamin D include oily fish such as salmon and mackerel, while eggs and mushroom contain smaller amounts.
Figure 1. Dietary sources of Vitamin D. Besides sunlight, fish oil and oily fish are the richest dietary Vitamin D sources that can be found. Additionally, some mushrooms that have been exposed to sunlight can also provide large sums of this vitamin, while eggs only contain small amounts.
- Simultaneously as we age, the skin loses its capacity to generate Vitamin D when exposed to sunlight. This means that older people need to rely more on dietary sources in order to meet their daily Vitamin D requirements.
- Skin pigmentation does matter when making Vitamin D: Individuals with very pale skin colour are the best at synthesizing Vitamin D when exposed to sunlight; while people with darker skin need more time in the sun to generate the same amount of vitamin D.
- Sunscreens Interfere with Vitamin D production. Since Vitamin D is produced when our skin is exposed to Ultraviolet B (UVB) light and sunscreens absorb this radiation before it penetrates the skin, this vitamin cannot be made.
- In order to make Vitamin D, you must be OUTSIDE! When you are next to a closed window indoors you do not make any Vitamin D because the UVB radiation is blocked. This is why in order to synthesise D you must enjoy the sunshine and leave the house!
Figure 2. a) When a person is indoors no Vitamin D can be made as the UVB radiation is blocked by the windows and walls. b) Whereas, when the individual is outside the UVB is able to reach the skin and consequently allow Vitamin D synthesis.
- While chronic Vitamin D deficiency leads to diseases such as rickets and osteomalacia, having excessive amounts is far worse. Nevertheless, Vitamin D toxicity is a 20th century phenomenon and is extremely rare: the only possible way of getting it is by consuming too many supplements or fortified foods. Meanwhile, our bodies will never generate an excess of Vitamin D when exposed to the sun, regardless of how many hours we may spend outside.