Vitamin D: are you taking the right kind? And will it keep you out of hospital?
We explain the difference between D2 and D3, whether liquids are better than tablets, and if a higher dose is always better.
We explain the difference between D2 and D3, whether liquids are better than tablets, and if a higher dose is always better.
Vitamin D is crucial for good health, including building strong bones and muscles, as well as maintaining a robust immune system. But surveys suggest that one in 10 people over the age of 65 in the UK are vitamin D deficient.
“We don't have enough sunlight in the UK during the winter months for our bodies to make enough vitamin D,” says Susan Lanham-New, professor of human nutrition at the University of Surrey, and a leading authority on the vitamin.
In the six months between October and March in the UK, the sun’s angle is too low for UVB rays to break through the atmosphere effectively.
“The best way of telling whether you’re in the right sunlight or not is checking that your shadow is shorter than your height – which it is between April and September. But in the winter, even if it’s a sunny day, your shadow will be double your height, so that means you won’t be getting enough sunlight for your body to make vitamin D,” says Professor Lanham-New.
The Department of Health and Social Care (DHSC) recommends a 10mcg daily supplement for everyone aged four years and over between October and March.
Some people, such as those living in care homes or those who don’t go out much and cover up when they do, and people who have darker Asian or Black skin, are advised to consider taking a supplement all year round.
“The evidence does not show convincingly that the skin becomes less efficient at making vitamin D as we get older,” says Professor Lanham-New.
“It’s just that older people sometimes go out less and feel the cold more, so they tend to cover up more when they do go out, and so reduce their direct sun exposure on the skin.”
Vitamin D is vital for maintaining bone health and muscle strength. It does this by regulating levels of calcium and phosphorus.
It plays a role in activating white blood cells in the body’s immune system, too, helping us to fight infections.
There’s also some evidence that vitamin D can help with some mental health conditions, including cognitive decline and low mood, says Priya Tew, a registered dietitian and spokesperson for the British Dietetic Association.
“Fatigue is also common in winter and can be a symptom of low levels of vitamin D,” she explains.
A new study led by the University of Surrey and published in the American Journal of Clinical Nutrition in January 2026 found that people with a severe vitamin D deficiency were 33% more likely to be admitted to hospital with respiratory infections such as pneumonia and bronchitis.
The study was based on data from the UK Biobank, and found that for each 10 nmol/l increase in vitamin D levels, hospitalisation rates for respiratory infections dropped by 4%.
“Vitamin D is vital to our physical wellbeing,” says Abi Bournot, lead author of the study and a PhD researcher in nutritional immunology at the University of Surrey.
“Not only does it keep our bones and muscles healthy, but its antibacterial and antiviral properties are also thought to reduce the risk of respiratory tract infections that can lead to hospitalisation.
“Taking a vitamin D supplement, especially in the winter months when our exposure to sunlight is limited, is an effective way of reducing the risk of serious respiratory tract infections.
“This is particularly important for older people who are at higher risk of death from such infections, and ethnic-minority communities in the UK, who are at higher risk of vitamin D deficiency.”
Bournot says that vitamin D has also been shown to reduce inflammation in the body: “Too much inflammation in the body could lead to more severe respiratory infections, so it’s thought that vitamin D could be beneficial for this reason, too.”
There are two types of vitamin D supplement – vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) – but research has shown that vitamin D3 is much more readily absorbed by the body.
D3 is the form your skin makes from sunlight, and is also found in meat. D2 comes from plant fungal sources such as mushrooms exposed to UVB light and yeast, and is suitable for vegans.
“The molecular structure of vitamin D3 seems to mean that the body can make much better use of it, but both D3 and D2 will increase your vitamin D levels,” says Professor Lanham-New.
“Some studies have found that D2 may also blunt the effectiveness of circulating D3.”
“There isn’t any difference in effectiveness between sprays, tablets or liquids when it comes to supplements,” says Professor Lanham-New.
“It really just comes down to your personal preferences and what’s easiest for you to take. The important thing is that you take it.
“A study led by Dr Pamela Magee from the University of Ulster in Northern Ireland showed that oral sprays were as effective as tablets.”
“Although vitamin D is also found in certain foods, such as oily fish, egg yolks, liver, mushrooms and fortified foods (such as orange juice and breakfast cereals), it’s very difficult to get enough from diet alone,” says Tew.
"It's one of the few situations where we wouldn’t recommend a food-first approach to tackling a vitamin deficiency.”
Professor Lanham-New adds: “Even with a diet rich in oily fish, you’d still only get around 3 to 5mcg a day, which is way short of the 10mcg daily amount recommended.
“This might be possible in the future if we fortified more foods with vitamin D, as countries such as Finland do, but at the moment this isn’t happening enough in the UK.”
Professor Lanham-New says that vitamin D deficiency in older people can cause a condition called osteomalacia, an adult version of rickets where bones become soft and painful.
Symptoms of osteomalacia include lower back pain, pain in the shoulder, ribs, pelvis or legs, muscle pain and weakness, plus a waddling gait.
You might also notice difficulties climbing stairs or getting out of a chair because of muscle weakness.
Tingling, cramping and twitching of muscles is another symptom.
“We think there are millions of people with mild osteomalacia in the winter months in the UK alone,” says Professor Lanham-New.
“The symptoms include bone pain, muscle ache, lethargy and tiredness, all of which are worse in the winter, as well as catching more infections.
“These are symptoms of vitamin D deficiency and can be treated with supplementation by your doctor – at a higher level at first to restore normal levels.”
Frequent fractures due to the fragile bone condition osteoporosis may also be linked to low vitamin D levels.
The upper safe limit for daily intake of vitamin D is 100mcg. “Mega doses of vitamin D are not needed,” explains Professor Lanham-New. “What you are trying to do is just avoid being deficient.
“Taking high doses can cause too much calcium to build up in the body, which can weaken bones and damage the kidneys and heart. For most people, taking 10mcg a day is enough and safe.”
“The latest advice is that it’s safe for adults to have 15 to 20 minutes of unprotected sun exposure a day (without suncream), with 10 to 20% of your body exposed, between April and September, without burning, in order for your skin to make vitamin D in spring and summer,” says Professor Lanham-New.
“But if you have a history of skin cancer, don’t do this – just take a vitamin D supplement in the summer as well as in winter.”
Guidance from NHS England to Integrated Care Boards (ICBs) in 2024 advised that vitamin D supplements shouldn’t be prescribed routinely on the NHS to prevent deficiency.
However, supplements can be prescribed to people with vitamin D deficiency, including those who've had surgery for malabsorption due to chronic conditions or for the management of osteoporosis.
Supplements are fairly inexpensive to buy from pharmacies and supermarkets – 90 x 10mcg D3 tablets cost £2.75 from Boots.
(Hero image credit: Getty)
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