Vitamin D is known as ‘the sunshine vitamin’. “Most of our vitamin D is manufactured in the skin after exposure to summer sun radiation,” says Antony R Young, Emeritus Professor of Experimental Physiology at King’s College London, whose research interests include mechanisms of UV-induced skin damage.
Does suncream block vitamin D?
“That’s why in theory sunscreens might be expected to reduced Vitamin D production; in practice that’s not the case. There are several reasons for this, but the most important is that the amount of sun needed for vitamin D production is much lower than that which causes sunburn.”
Young directs us to a 1995 Australian study that showed no difference in Vitamin D levels between adults randomly assigned to use sunscreen one summer and those assigned a placebo cream.
Why is Vitamin D important?
Vitamin D’s importance can’t be understated. Working with calcium, it helps to strengthen your bones and protect adults from osteoporosis. It also reduces inflammation, which is linked to restricting cancer growth; boosting immune function to prevent illness; and improve glucose metabolism that has beneficial effects on complications of type-2 diabetes.
Should you take a Vitamin D supplement all-year-round?
The sun and Vitamin D are clearly inextricably linked, which begs the question: should you take a Vitamin D supplement all-year-round? “There should be no need to take supplements in summer if you enjoy regular non-sunburning sun exposure wearing summer clothes,” says Young. “It’s a good idea to take supplements once the sun is no longer effective at making vitamin D. I take 25mg (1000 international units (IU)) daily from about mid-October to late April.”
Ideally, you should take a vitamin D3 supplement. That’s due to the process by which the body converts sunshine to vitamin D, namely the sun’s ultraviolet B (UVB) rays interact with a protein called 7-DHC in the skin, converting it into vitamin D3, which is the active form of vitamin D.
You can also obtain vitamin D from foods like oily fish, egg yolks and liver, but at very low levels, so a winter supplement is still recommended.
Can you check your Vitamin D levels?
You can check your Vitamin D levels via a simple blood test. Vitamin-D insufficiency is defined as levels below 30nmol/L. It’s worth noting that there a number of factors that influence vitamin-D levels. These include…
Skin colour. Melanin is the substance – more precisely, a family of biomolecules as oligomers or polymers – in skin that makes it dark or light. Melanin battles for UVB with 7-DHC that stimulates the body’s vitamin-D production.
That’s why darker-skinned people tend to need greater UVB exposure than lighter-skinned people to generate the same amount of Vitamin D.
Weight. Studies have shown that obesity is correlated with low vitamin-D levels. Being overweight may also affect the bioavailability of vitamin D.
Age. In general, older people have lower levels of 7-DHC which UVB light converts into the vitamin-D precursor. There’s also evidence that older people are less-efficient vitamin-D producers than younger people.