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Vitamin D

2 min read

Simon Körösi

Reviewed by: Joanna Elmes

Vitamin D is an essential, fat-soluble vitamin that plays a significant role in the absorption and retention of calcium and phosphorus — both critically important for bone construction. In fact, your body can only absorb calcium, the primary component of bone, in the presence of vitamin D.

Interestingly, vitamin D is a hormone that isn't naturally abundant in many foods. However, you can obtain it from fatty fish like salmon, mackerel, and sardines. Moreover, your body synthesises vitamin D when in contact with UVB radiation through direct sunlight, by converting a chemical in your skin (7-dehydrocholesterol) into another form of vitamin D (cholecalciferol/vitamin D3). Cholecalciferol will convert into another form of vitamin D (calcifediol/25-hydroxycholecalciferol) in your liver and finally into the active form of the vitamin (calcitriol/1,25-dihydroxycholecalciferol) in your kidneys.

Apart from bone health, vitamin D also regulates many other cellular functions in your body. It boasts anti-inflammatory, antioxidative, and neuroprotective properties which support immune health, muscle function, and brain cell activity.

The amount of vitamin D your skin produces is contingent on numerous factors, with sunlight being the primary source. The extent of sun exposure you receive, especially to areas of uncovered skin, influences the volume of vitamin D your skin generates. Vitamin D synthesis is most efficient when the sun is at its zenith, typically between 10 am and 3 pm. During this period, UVB rays penetrate the atmosphere more directly, thereby enhancing the production of vitamin D in the skin.

Although sunscreen can diminish vitamin D production, its merits in preventing skin cancer far outweigh this drawback. Consequently, it's always advised to wear sunscreen to safeguard your skin.

But what if you reside in the northern hemisphere, where sunlight is a scarce commodity for significant portions of the year? Vitamin D deficiency is prevalent in northern latitudes and can give rise to a host of health complications, including bone loss, muscle weakness, and an increased risk of certain diseases. Given that very few foods naturally contain vitamin D, supplementation can prove beneficial, particularly for individuals who have limited sun exposure or reside in regions with scarce sunlight.