Published : 05 Oct 2026, 11:49 PM
Updated : 05 Oct 2026, 11:49 PM
As the days grow shorter and colder, doctors are warning that most people will not get enough vitamin D from sunlight alone -- and that the effects can be more serious than many realise.
Vitamin D is essential for healthy bones, muscles and immune function. Unlike most vitamins, it cannot be obtained in sufficient quantities through diet, and the body's main source is sunlight on the skin, reports The Independent.
In the UK, sunlight is too weak between October and March to trigger the chemical reaction that produces it.
"Even on a sunny day in the UK autumn and winter you just won't get enough vitamin D from the sun," says Dr Henrik Premasundaram, a GP at HCA Healthcare UK.
A deficiency can cause fatigue, bone pain and muscle weakness, and in severe cases can lead to rickets in children and softening of the bones in adults, The Independent reports.
A 2023 study of more than 12,000 people also found 40 per cent fewer dementia diagnoses among those who took vitamin D supplements.
Nearly one in five adults in the UK are vitamin D deficient, according to national dietary surveys. Yet only around half of people are aware of official guidance recommending a daily 10-microgram supplement from October to March for everyone aged over five.
People with darker skin, those who cover their skin for religious or cultural reasons, and those who spend little time outdoors are advised to take supplements year-round.
Dietary sources such as oily fish, eggs and fortified cereals can help, but experts say they are unlikely to provide enough on their own, according to The Independent.
"It's really, really hard to get enough vitamin D from diet alone," says Premasundaram, who takes the supplement himself. "In the winter months we'd encourage people to take a supplement -- it's just an easy way of getting your daily vitamin D requirement."
