The often dull British weather is the source of much complaint, but is it actually having a negative impact on our health? According to the government’s Scientific Advisory Committee on Nutrition (SACN), the lack of sunshine is leaving many of us with worryingly low levels of vitamin D.

It is estimated that one in five British adults, and one in six children, have low levels of the vitamin. SACN investigated the link between such deficiency and various health problems, including musculoskeletal health problems, heart disease, type 1 diabetes, cancer and multiple sclerosis. Those deduced to be most at risk of health problems related to vitamin D deficiency were pregnant women, children up to the age of 5, and adults over the age of 65. Those with darker skin and those who generally do not expose their skin to sunlight very often are also less likely to have healthy levels of vitamin D.

SACN says that it is important for those high-risk groups to be boosting their vitamin D intake with supplements. As there is no easy way to assess who is getting enough, the committee has proposed a blanket recommendation for everyone, because the risk of getting too much of the vitamin is considered to be extremely low.

“Before this, the general assumption was that adults were able to make all the vitamin D they needed from sunshine, and didn’t need to have any dietary or supplementary intake,” says Dr Adrian Martineau, an expert of vitamin D at the London School of Medicine and Dentistry. “The action of sunlight on the skin in the UK is highly variable for different populations depending on the time of year and the latitude – you’ll get more UVB in Brighton than in John o’Groats – and finally how much skin is exposed and the colour of skin. SACN was right to say that we can’t rely on sunshine in the UK to meet the vitamin D requirements. That’s a major and important change. It’s a big step forward that this is now officially recognised.”

The National Institute for Health and Care Excellence (NICE) has also raised awareness of the need to counter hidden epidemics of vitamin D deficiency, calling for more free supplements and low-cost options in supermarkets.

Vitamin D deficiency has been linked to various health problems, but most notably causes rickets and brittle bones. Supplements to help you avoid these problems are widely available, and the NHS recommends that adults in need of supplementation take 10 micrograms a day.