Vitamin D has attracted much media coverage of late, following a new government dosage recommendation —but what is it, and what does it, do? Pharma Nord explains more:
Vitamin D: Diet & Sunlight
Vitamin D is essential for human health, as the fat-soluble nutrient plays a key role in protecting our immune system and boosting muscle function and bone health. Although a small proportion of it does come from our diet — 126iu per day on average in the UK — the sun is our main source of vitamin D. The body uses cholesterol to produce vitamin D from sun exposure, but only if there is an adequate amount of UVB light available.
Of course, our dependence on the sun for vitamin D synthesis can be impacted by a number of factors. This includes:
- Season — of course, if there’s less sun available through seasonal factors, the amount of vitamin D we can produce is reduced.
- Age — as we get older, our bodies are less able to convert sun exposure into vitamin D.
- Pigmentation—people with darker skin require greater sun exposure than others to produce the same amount of vitamin D.
- Sunscreen, sun avoidance and covering up — by physically blocking or avoiding the sun, we limit the amount of vitamin D we can produce.
Whether the source is our diet or sunlight, once converted to vitamin D, the nutrient is transported to the liver as calcidiol where it is stored for future use. When required, it is sent to the kidneys to be converted into calcitriol before being sent to tissue all over the body. Calcitriol is responsible for managing calcium levels in the blood, bones and digestive system, as well as helping cells grow, communicate and express genes.
Vitamin D Supplements
When diet- and light-limiting factors are present, many people turn to vitamin D supplements. There are two varieties of vitamin D supplements; D2 and D3. An isomer formed in human skin, D3 (cholecalciferol) is extracted from sheep’s wool to create supplements. On the other hand, D2 (ergocalciferol) is derived from plants and normally extracted from fungi.
D3 is the most common type of vitamin D in modern nutrition science and is often considered the best vitamin D supplement. It is less toxic and more stable than D2, and can bind easily with D receptors in human tissue.
The Scientific Advisory Committee on Nutrition (SACN) recommends a daily dosage of at least 10μg/400iu of vitamin D during autumn and winter. However, this is a recommendation to prevent deficiency, with many experts agreeing that the amount is insufficient for most people.