Britain in winter is not a sunny place. And our levels of vitamin D, the “sunshine vitamin” produced by the action of light on skin, tend to run low. The government is now recommending that we all take a daily supplement throughout the winter. But do we really need it? What about eating more oily fish? Would a lightbox help? And who needs it most?
Vitamin D is essential for healthy bones, teeth and muscles. Around one in five adults and up to one in four children have low levels throughout the year. Severe deficiency is much rarer, but can result in rickets in kids and osteomalacia in kids and adults, which cause bone deformity and pain. Vitamin D also plays an important role in the immune system. Low levels have been linked to cancers, multiple sclerosis and heart disease. A recent report by the Scientific Advisory Committee on Nutrition (SACN) said there isn’t enough evidence yet to draw any firm conclusions about these links.
Most of us get a bit low in vitamin D in the winter months but some groups are at risk of more serious deficiency. The at-risk groups include: pregnant and breastfeeding women (particularly teenage mums); children under five (because they need more vitamin D for bone growth); anyone who doesn’t get much exposure to sun; people over 65 who are frail and lack a varied diet or opportunity to get outdoors much; and people with darker skin tones, which block UV rays more effectively than paler ones.
The majority of our vitamin D is produced when UV rays penetrate the skin and activate an inactive form of the vitamin. The active vitamin plays a vital role in calcium and phosphate balance in the body. The SACN couldn’t recommend how much sun exposure we need to keep our vitamin D levels topped up because individuals vary in their response. From October until the end of March, the sun in the UK isn’t strong enough to ensure adequate vitamin D levels even if you’re outdoors all year round.
One option is to use a lightbox; a study of people with severe vitamin D deficiency due to underlying disease such as cystic fibrosis showed that regular use of a UV lightbox boosted vitamin D levels effectively.
We also get a bit of vitamin D from our diet: oily fish (salmon, sardines, herring, mackerel), red meat, and liver and egg yolks. Some breakfast cereals and fat spreads also have added vitamin D.
So the latest advice from Public Health England is that everyone over the age of one should “consider taking a daily supplement of 10mcg (400 iu) of vitamin D, particularly during autumn and winter”. People at higher risk of deficiency, children aged one to four and breastfed babies under one, should take it all year round. Babies under one who are bottle-fed don’t need supplements because formula milk has vitamin D added. You can buy supplements over the counter at pharmacists and supermarkets; health visitors can advise about vitamin D drops for babies and they are available free to low-income families through the Healthy Start scheme.
Health professionals in England are being told they should only test vit D status (with a blood test) if people have symptoms of deficiency (such as suspected rickets), are considered to be at particularly high risk of deficiency or have a specific clinical reason, such as recent falls. There’s no need for a test before taking supplements; the risk of overdose on 10mcg a day is next to nothing.
