After the recent heatwave, it seems scarcely believable: one in five adults in Britain has low levels of vitamin D, the sunshine vitamin.
This may be because we’re covering up more in the sun — think Nigella Lawson and her burkini — and slavishly applying sun cream in response to skin cancer warnings.
Whatever the reason, it has implications for our health.
Last week, Public Health England (PHE) announced that the entire population should consider taking vitamin D — 10 micrograms (mcg) a day — throughout the winter months (from October to March) to prevent bone and muscle disease.
Being overweight has been linked to a lack of vitamin D — a 2013 study in the journal PLOS Medicine suggests that vitamin D may become ‘trapped’ inside fat tissue so that less of it is available to circulate inside the blood
Vitamin D is essential for strong bones and teeth. While it’s found naturally in foods such as oily fish and eggs, its main source is UV light — it is ‘manufactured’ in the skin in the presence of sunlight.
Up until now, only at-risk groups — including children aged one to five, pregnant and breastfeeding women, adults over 65 and those with darker skins — were advised to take vitamin D daily.
But as Dr Louis Levy, head of nutrition science at PHE, explained last week: ‘Everyone will need to consider taking a supplement in the autumn and winter if you don’t eat enough foods that naturally contain vitamin D or are fortified with it.’
But do we really need vitamin D pills, or can we just spend longer in the garden?
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OVER 30 MINUTES IN SUN IS POINTLESS
Exposing skin to sunlight is the best way to boost vitamin D in the body, and is far more effective than popping a pill. For example, it takes just 30 minutes in the sunshine in the summer months for your skin to make 250 mcg of vitamin D — a pill only contains up to 25mcg (this may appear on the label as 1,000 international units, IU).
Wearing sunscreen with an SPF of 10 and above can block UV light from penetrating the skin, so you need to expose the skin without it. But you don’t have to go out in the blazing sun to make vitamin D — to avoid burning, get your rays before 11am or after 3pm.
As for how much skin you need to expose every day, the rule of thumb is around 10 per cent (which is the face, neck, back of the hands and arms) for 15-20 minutes in summer. ‘This should be enough to store up an optimum supply,’ says Susan Lanham-New, a professor of human nutrition at the University of Surrey and a member of the expert committee behind the new guidelines.
In fact, the skin can only make vitamin D for the first 30 minutes of daily exposure, she explains. ‘After that, it stops naturally because it recognises you have all you need.’
As for how much skin you need to expose every day, the rule of thumb is around 10 per cent (which is the face, neck, back of the hands and arms) for 15-20 minutes in summer
COULD A WINTER SUN HOLIDAY HELP?
There is strong evidence that it is impossible for the body to store enough vitamin D during the British summer to last all winter long, says Professor Lanham-New.
‘We have carried out studies that show that the body can store vitamin D in the liver for a certain period of time, but the half-life of vitamin D is only five to six weeks. After that, it is no longer able to play an active role in the body.
‘By mid-November, no one who remains in the UK has sufficient vitamin D stores, however much they soaked up the sun through spring and summer.’
Winter sun in the UK is the wrong wavelength to penetrate the skin and make vitamin D. A simple way to tell if the rays are strong enough is to look at your shadow.
‘If your shadow at noon is shorter than your height, the UVB light will be able to trigger the production of vitamin D in your skin. But in the British Isles in winter, your shadow is typically twice your height,’ explains Professor Lanham-New.
Taking a winter sunshine break could help to top up your vitamin D levels, but the benefit will be lost within two to three weeks of your return, so you will need to continue with your vitamin D supplement — or take more holidays.
Taking a winter sunshine break could help to top up your vitamin D levels, but the benefit will be lost within two to three weeks of your return, so you will need to continue with your vitamin D supplement
ANOTHER REASON TO LOSE WEIGHT
Darker-skinned people, such as those of African, Afro-Caribbean and South Asian origin, are naturally protected from strong sunlight because they have large amounts of the pigment melanin.
But they therefore need at least three to five times longer in the sun to make the same amount of vitamin D as someone with a white skin tone, a 1982 study in The Lancet found.
For similar reasons a tan could reduce the amount of vitamin D made. A Brazilian study presented at the annual meeting of the Endocrine Society in Boston in April found that people who sunbathed regularly could actually be vitamin D deficient because their tans blocked UV light.
More recently, being overweight has been linked to a lack of vitamin D — a 2013 study in the journal PLOS Medicine suggests that vitamin D may become ‘trapped’ inside fat tissue so that less of it is available to circulate inside the blood.
‘Older people are also more at risk of vitamin D deficiency because they become less efficient at making vitamin D in their skin and may also spend more time housebound or indoors,’ explains Professor Lanham-New.
Some medications also reduce absorption, such as corticosteroids, used to damp down inflammation such as osteoarthritis. Professor Lanham-New says that people who take statins for high cholesterol may also be at risk from low levels, although more research is needed.
If your body has a Vitamin D deficiency it may be due to high levels of fat tissue, a 2013 study has suggested
THE LINK TO HEART PROBLEMS
Vitamin D is important not only to maintain strong bones and allow normal growth in children, it’s important for muscle function and a healthy immune system, says Dr William Marshall, a consultant clinical biochemist at The London Clinic.
‘It also helps the body to use the calcium and phosphorus from your food and regulates the process where cells change from one type to another, thus helping to prevent cancer.
‘Other associated conditions include an increased risk of diabetes, heart disease and certain cancers.’
But sceptics aren’t convinced that it’s vitamin D that’s the cause — or the solution.
When Dr Mark Bolland, from the department of medicine at the Auckland University and colleagues analysed the results of nearly 50 trials involving more than 200,000 people in 2013, they found that vitamin D supplements had little or no impact on the risk of heart disease, stroke, cancer or even bone fractures.
Some experts have associated Vitamin D with an increased risk of serious heart disease and certain cancers
DON’T RELY ON A MULTIVITAMIN
Symptoms of vitamin D deficiency may include severe bone pain, lethargy and tiredness, and in older people it can lead to osteoporosis.
A simple blood test can determine if you have low levels of vitamin D — however a GP may start by recommending vitamin D to see if the symptoms ease.
Even if you don’t have any symptoms, the latest advice is that we should all consider taking supplements daily, just in case.
Vitamin D can be taken as a single supplement or in a multivitamin. As well as being cheaper, a single vitamin D supplement is preferable, says Professor Lanham-New.
‘Multivitamins may only contain 5 mcg of vitamin D and we recommend 10 a day. Also, there may be good reasons not to take other vitamins, such as vitamin K, that are found in multivitamins — vitamin K can cancel out the blood thinning properties of warfarin, for instance.’
Buy your supplement in a pharmacist, High Street health store or supermarket, she says, rather than over the internet, where doses may exceed safe levels.
Buy your supplement in a pharmacist, High Street health store or supermarket, she says, rather than over the internet, where doses sometimes exceed safe levels
IS IT POSSIBLE TO TAKE TOO MUCH?
Although levels of vitamin D in supplements vary, they rarely exceed 25 mcg (1,000 international units). The so-called ‘Tolerable Upper Limit’ is 100 mcg (4,000 IU) per day, above which risk for harm begins to increase.
The problem is that vitamin D is fat-soluble, so it is hard for your body to get rid of it (unlike water- soluble vitamin C, which can simply be flushed through the kidneys).
With large amounts of vitamin D, your liver produces too much of a chemical that causes high levels of calcium in your blood, leading to a range of symptoms from nausea to muscle weakness, confusion and exhaustion.
And a 2004 study found a worrying link between vitamin D supplements and higher risk of mortality — increasing the death rate by 6 per cent compared with people who did not take a vitamin D supplement.
The researchers, writing in The Lancet, estimate that for every million people taking the supplements, 9,000 would die prematurely as a result.
However Peter Selby, professor of metabolic bone disease at Manchester Royal Infirmary, says a 10 mcg supplement a day wouldn’t cause harm.
With large amounts of vitamin D, your liver produces too much of a chemical that causes high levels of calcium in your blood, leading to a range of symptoms from nausea to muscle weakness
HOW MANY SAUSAGES WOULD YOU HAVE TO EAT?
Some foods do contain vitamin D, but with many you’d need to eat eyewatering amounts to get the recommended daily amount (10 mcg). Each of the following would provide this:
7 eggs
Some foods do contain vitamin D, but with many you’d need to eat eyewatering amounts to get the recommended daily amount
2 cans (277g) of tuna
2 cans (215g) of sardines
1 herring rollmop
1 fillet (125g) smoked mackerel
4½ packs (1.1kg) butter
12 packs (3.3 kg) Cheddar cheese
38g mushrooms that have been exposed to sunlight*
27 slices Marks Spencer Super Soft White (fortified with vitamin D)
5 glasses (1.3 litres) Alpro soya milk (fortified)
8 tsps (enough to make 2 mugs) Original Horlicks Powder (fortified)
17 (1.1kg) pork sausages
1 medium leg (1.4kg) roast leg of lamb
2 1/7 (½??-sub ) large packets (1.25kg) beef mince
The outer layer of mushrooms is rich in ergosterol, a chemical converted to vitamin D when exposed to sunlight.
Put them upside down on a sunny windowsill for 30 to 60 minutes.