Taking a daily vitamin D supplement can improve mood and energy levels, according to a GP, as experts warn the UK autumn and winter sun is too weak for the body to produce the vitamin naturally.
Vitamin D is essential for healthy bones, muscles and immune function. The body produces it when sunlight hits the skin, but from October to March in the UK, the sun’s rays are not strong enough. Deficiency can cause tiredness, bone pain, muscle weakness and, in severe cases, affect mood.
Why sunlight is not enough in winter
Dr Henrik Premasundaram, a GP and health screener at HCA Healthcare UK, said: “You can get most vitamins within a balanced diet, so if you’re having lots of good veg, fruit, etc, you can get the majority of your vitamins. But with vitamin D you simply can’t, because the main production is from the sun. Vitamin D is essential for healthy bones, muscles, and normal immune function, and if you’re deficient, it can lead to things like tiredness, and in really low cases it can affect your mood.”
Bridget Benelam, a nutrition scientist from the British Nutrition Foundation (BNF), explained: “Vitamin D is unique among the essential vitamins because our main source is from sunlight, not the foods and drinks we consume. Sunlight on our skin triggers a vital chemical reaction, allowing the body to produce vitamin D. During the summer, short periods of sunlight exposure are enough for most people to make vitamin D. But in the UK from October to March the sunlight isn’t strong enough to make vitamin D, and the body relies on stores built up during the summer and on dietary sources of vitamin D.”
Signs of deficiency and who is at risk
Benelam said: “Vitamin D deficiency doesn’t always cause obvious symptoms straight away. But low levels over time can lead to bone pain, muscle weakness and an increased risk of falls in older adults.” In children, severe deficiency can result in rickets, while in adults it can cause osteomalacia, a condition that leads to soft, weak bones.
A 2023 study by the universities of Exeter and Calgary of more than 12,000 people, some of whom took vitamin D supplements and some who didn’t, found 40% fewer dementia diagnoses in the supplement-taking group.
Benelam pointed out that people with darker skin, those who cover their skin for religious or cultural reasons, and those who don’t get outside regularly, are at higher risk of vitamin D deficiency, so it’s recommended that they take a supplement all-year round.
Dietary sources and recommended intake
The exact amount of sunlight needed varies depending on skin type, age, clothing and weather conditions. Premasundaram said: “Most people can maintain their vitamin D levels through sunlight, especially during the spring and summer, but definitely not through the autumn and winter, just because of the way the UVB rays come through in the UK – they’re essentially just too low because of either the clouds or the sun exposure. Even on a sunny day in the UK autumn and winter you just won’t get enough vitamin D from the sun.”
He added that getting sunlight just on the face is unlikely to produce the required amount: “It’s not necessarily just sunlight on your face that’s enough. You actually need a bigger surface area, so it’s quite hard to get the amount you really need simply from sun exposure.”
Benelam said: “There aren’t many good sources of vitamin D in the diet – oily fish such as salmon, mackerel and sardines provide the most, and you can also get vitamin D from eggs, fortified cereals and fat spreads, plus vitamin D-enriched mushrooms.” A 140g portion of baked salmon provides about 10 micrograms, a 30g portion of fortified cereal about 1.4 micrograms, one egg about 1.6 micrograms and an 80g portion of enriched mushrooms 3.2 micrograms.
Supplement advice and impact on wellbeing
The Government recommends a daily 10 microgram vitamin D supplement for everyone aged over five years from October to March. The NHS also recommends supplements for babies and young children, with amounts depending on whether babies are breastfed or bottle fed, and on the child’s age.
The National Diet and Nutrition Survey shows nearly one-in-five adults (18%) are vitamin D deficient. Benelam said BNF surveys suggest only around half of people are aware of the recommendation to take a supplement during autumn and winter. “A daily 10 microgram supplement is a simple and inexpensive way to help maintain adequate vitamin D levels when sunlight exposure is limited,” she stressed.
Asked if people are likely to notice a difference, Premasundaram said: “Yes, definitely. It can even help with moods, and help people feel more energetic. I take vitamin D regularly, and I feel a lot better – I feel less tired. Is it a placebo? Maybe a small percentage of that, but I think it definitely has a good impact on patients’ wellbeing.”
