Vitamin D is mainly created through direct exposure to sunlight when outdoors. The nutrient plays an essential role in keeping bones, teeth and muscles healthy. A lack of the vitamin can lead to bone deformities such as rickets in children, and bone pain caused by a condition called osteomalacia in adults. It may come as a surprise to hear that it can impair the immune system too.
A couple of large observational studies have identified a link between deficiency and respiratory tract infections like colds, children, and bone pain caused by a condition called osteomalacia in adults.
Further bolstering the findings, a number of studies have found that taking vitamin D supplements at a dosage of up to 4,000 IU daily may reduce a person’s risk of respiratory tract infections.
In one study in people with the chronic lung disorder COPD, only those who were severely deficient in vitamin D experienced a significant benefit after taking a high-dose supplement for one year.
It can also cause this unsettling symptom.
Who is at risk?
Fortunately, from about late March/early April to the end of September, most people should be able to get all the vitamin D they need from sunlight, according to the NHS.
Some people won’t get enough vitamin D from sunlight because they have very little or no sunshine exposure, however.
Risk factors include people who:
- Aren’t often outdoors – for example, if you’re frail or housebound
- Are in an institution like a care home
- Usually wear clothes that cover up most of their skin when outdoors
- If a person has dark skin – for example if they have an African, African-Caribbean or south Asian background – they may also not get enough vitamin D from sunlight.
According to Dr Oz, people with pre-existing health conditions may also run the risk of a vitamin D deficiency.
As he explained: “People who have trouble absorbing fat in their diet, like those with inflammatory bowel diseases or those who have had gastric bypass surgery.”
Topping up vitamin D
The Department of Health recommends people at risk take a daily supplement containing 10 micrograms of vitamin D throughout the year.
People can buy vitamin D supplements or vitamin drops containing vitamin D (for under 5s) at most pharmacies and supermarkets, explained the NHS.
10 micrograms a day will be enough for most people.
The NHS advised against exceeding this dose: “Taking too many vitamin D supplements over a long period of time can cause too much calcium to build up in the body (hypercalcaemia).”
It added: “This can weaken the bones and damage the kidneys and the heart.”
Vitamin D is also found in a small number of foods.
- Oily fish – such as salmon, sardines, herring and mackerel
- Red meat
- Egg yolks
- Fortified foods – such as most fat spreads and some breakfast cereals
“In the UK, cows’ milk is generally not a good source of vitamin D because it isn’t fortified, as it is in some other countries,” added the NHS.