A few months ago, experts insisted that we should all be taking vitamin D
Now, experts have revealed the supplements may be bad for your health
Just four months ago, the advice on vitamin D seemed as clear as the sky on a hot summer’s day.
After an exhaustive, five-year review, Public Health England finally announced that everyone needed 10 micrograms a day ‘in order to protect their bone and muscle health’.
The advice had been a long time coming.
It was based on the recommendations of the Scientific Advisory Committee on Nutrition (SACN), a team of independent experts set up by the Government to consider all the available evidence and review the decades-old public guidance on vitamin D.
After an exhaustive, five-year review, Public Health England finally announced that everyone needed 10 micrograms of Vitamin D a day
Vitamin D is made in the skin by the action of sunlight. In spring and summer, when the sun is sufficiently strong, this is the main source for most people and any excess we make is stored in the fat and liver.
However, these stocks are steadily depleted during the colder months.
And while vitamin D can be found in some food — oily fish, liver, egg yolk and fortified cereals, for instance — it’s hard to get enough this way, which is why SACN recommends everyone should take the daily 10mcg supplement during the autumn and winter.
Those whose skin is rarely exposed to sunlight, such as the elderly, should take this amount every day of the year.
But now researchers writing in the British Medical Journal have thrown a spanner in the works.
After analysing the results of hundreds of trials involving tens of thousands of patients, they concluded there was ‘no consistent evidence that vitamin D supplementation improves musculoskeletal outcomes’ if you’re not in the at-risk groups such as older people and certain ethnic groups.
Meanwhile, other experts are now saying that official advice is actually causing some people to take far too much vitamin D, which can lead to a range of serious health problems and may even weaken rather than strengthen bones.
Experts are now saying that some people actually take far too much of the supplement, which can lead to a range of health problems
Confused? It’s easy to see why. So which experts are right — and should you keep taking those vitamin D pills?
The debate has split the medical and scientific communities into those who believe that one in three of the population is deficient in vitamin D, and sceptics who say supplementation is a ‘cure’ for an invented disease that doesn’t actually exist.
‘We are seeing an over-obsession with something that isn’t a real disease,’ says Tim Spector, a professor of genetic epidemiology at King’s College London and a consultant rheumatologist who runs an osteoporosis clinic at Guy’s and St Thomas’ Hospital, London.
IT’S FASHIONABLE TO TEST YOUR LEVELS
He’s in the sceptic camp, and last week wrote a comment article for the BMJ, in support of the new paper.
‘Now we’ve created this new fashion of measuring vitamin D, with arbitrary ‘deficiency’ levels, and suddenly a third of the population is deficient and you have a whole new industry,’ he told Good Health.
‘It’s a bit sad really, a modern phenomenon.’
That phenomenon is being helped along by the growth of the home finger-prick blood-test industry.
Levels of vitamin D in the blood are measured in nanomoles per litre. Current NHS guidelines say anything under 15 nmol/L is ‘severe deficiency’
Levels of vitamin D in the blood are measured in nanomoles per litre. Current NHS guidelines say anything under 15 nmol/L is ‘severe deficiency’
Kits cost anything from £30 to £50; you send off your blood for analysis and within a couple of days you receive the result — and, if you are ‘deficient’, an invitation to buy vitamin D supplements.
Levels of vitamin D in the blood are measured in nanomoles per litre. Current NHS guidelines say anything under 15 nmol/L is ‘severe deficiency’ and a level of 15-30 is regarded as ‘deficiency’.
From 50 to 100 is ‘adequate’ and 100-150 is regarded as ‘optimal’.
But there is no international agreement.
In the U.S. a reading over 125 (which the NHS says is ‘optimal’) is regarded as actually being too high — with ‘potential adverse effects’, says the National Institutes of Health.
And while the NHS says vitamin D blood levels shouldn’t fall below 25 at any time of year, the European Food Safety Authority has just set a target of 50 for everyone.
In other words, what’s regarded as adequate in the UK, is seen as deficient in Europe.
Professor Tim Spector says we’ve created a new fashion of measuring vitamin D, with arbitrary ‘deficiency’ levels, and suddenly a third of the population is deficient
In fact, says Professor Spector, all these categories ‘were arbitrarily decided by clinical societies and international bodies without consensus’.
He agrees there would ‘be some concern’ if someone’s reading was under 20 nmol/L, but ‘true clinical deficiency’ — where the lack of vitamin D is beginning to affect the bones — probably only occurs when it’s under 10, he told Good Health.
‘There is no evidence that people in the 20 to 50 range are suffering any problems, and yet that is most of the population currently being labelled as having a disease.’
But Dr Louis Levy, head of nutrition science at Public Health England, suggests the idea that people with these levels are seen as somehow ill is a misinterpretation.
He says that while levels shouldn’t drop below 25, if they did, it doesn’t mean you have a disease — rather it is a level that the majority of the population should achieve, or surpass, ‘in order to protect their musculoskeletal health’.
Arguably, that’s a subtle difference most people wouldn’t spot.
CHILDREN SHOULD TAKE SUPPLEMENTS
Vitamin D is important because it helps the body absorb calcium from food, and a true deficiency can lead to weak or soft bones — known as rickets in children and osteomalacia in adults — and can weaken muscles, which, in turn, can lead to falls.
In multiple studies, low levels of vitamin D have also been linked to a host of other conditions, from diabetes, irritable bowel syndrome and arthritis to multiple sclerosis, Parkinson’s disease and even cancer.
Vitamin D is important because it helps the body absorb calcium from food, and a true deficiency can lead to weak or soft bones
But as yet, there is no conclusive evidence to say whether low levels of vitamin D are a cause, or a symptom of these illnesses, or that taking a supplement will cure them.
In any event, says Professor Spector, dangerously low levels of vitamin D are seen only in cases of rickets and osteomalacia, of which there are only a handful a year.
The NHS recommends that all babies under a year old should have a daily supplement of 8.5 to 10mcg, and children aged one to four 10mcg (babies on more than 500ml of fortified infant formula a day don’t need additional vitamin D).
No one disagrees with the recommendation that children should receive supplements.
But for the vast majority of the population, says Professor Spector, taking vitamin D ‘doesn’t work and is actually distracting people from having a healthier lifestyle, going out in the sunshine and eating properly’.
Dr Natalie Carter, head of research liaison at Arthritis Research UK, agrees.
The BMJ paper, she says, is ‘interesting, high-quality research which improves our knowledge about optimum vitamin D levels and no doubt during its next review Public Health England will take this study into consideration’.
No one disagrees with the recommendation that children should receive supplements. But for the vast majority of the population, says Professor Spector, taking vitamin D ‘doesn’t work’
Clinicians, she says, ‘can’t take a ‘one-size-fits-all’ approach when recommending supplementation to prevent vitamin D deficiency, as the amount needed will vary according to your age, gender, health status and location’ — people who live in more northerly latitudes get less sun.
Arthritis Research UK does not recommend that most peope take supplements, saying: ‘The best form of obtaining vitamin D is through exposure to sunlight.’
MOST ADULTS GET ENOUGH FROM SUN
‘Safely exposing skin to the sun for just 15 minutes a day during the summer months should give you the right amount of vitamin D for the winter months,’ they say.
This was shown in 2009 by an Australian study of 120 people who spent a year in Antarctica, where they were deprived of sunlight from March to August.
The study, published in the journal Osteoporosis International, found those who arrived with vitamin D levels of 100 nmol/L or higher (achievable with a healthy outdoor summer lifestyle) had enough reserves to get through the six months until the sun returned.
‘Safely exposing skin to the sun for just 15 minutes a day during the summer months should give you the right amount of vitamin D for the winter months,’ they say
Last year, a statement by seven specialist UK groups, including Cancer Research UK and the National Osteoporosis Society, said most people who kept their vitamin D topped up in the sun in summer ‘should [be able to] keep levels greater than 25mmol/l in winter even without supplements’.
Indeed, even in the at-risk groups, supplements should be considered on an ‘individual basis’, said the BMJ authors.
Until July, the advice in the UK on taking vitamin D supplements hadn’t changed for 25 years, and it was categorical: vitamin D supplements were ‘not necessary for most of the UK population aged four to 64 years’.
Only those at risk of vitamin D deficiency — including pregnant and breast-feeding women, infants, adults over 65 and those with limited exposure and women and children of Asian ethnic origin — should take between 7 and 10 mcg a day.
This recommendation was reviewed, but remained unchanged in 1998 and again in 2007.
Seven specialist UK groups said most people who kept their vitamin D topped up in the sun ‘should [be able to] keep levels greater than 25mmol/l in winter even without supplements’
Then, in 2011 the SACN revisited the recommendations, partly because people were taking heed of advice about skin cancer and staying out of the sun and wearing sunscreen; the concern was that they were depriving themselves of sufficient sun to generate enough vitamin D.
But there was no evidence of this.
Studies had found that ‘although sunscreens can significantly reduce the production of vitamin D under very strictly controlled conditions, their normal usage does not generally prevent vitamin D synthesis’, the SACN concluded.
TOO MUCH CAN WEAKEN BONES
Professor Spector acknowledges that taking 10mcg of vitamin D a day will not harm anyone.
‘But my experience is that as soon as you tell people they’ve got to take something they say ‘I’ll take more because the more I take the healthier I’ll be’.’
Trials show people with very high levels of the sunshine vitamin are more likely to fracture and more likely to fall over
The problem, he says, is many people are already eating foods fortified with vitamin D, such as cereals, bread, milk and yoghurt, and then taking ‘dangerously high doses’ of a supplement on top.
In his clinic, he says: ‘I am now seeing people with extremely high levels of vitamin D.
‘They hear the advice and, because they think it’s going to help them, they take what the doctor prescribes them and then go and get a top-up on the internet.
‘In fact, trials show people with very high levels are more likely to fracture and more likely to fall over.’
Indeed it’s easy to find vitamin D tablets or capsules containing 20 times the recommended daily dose of 10mcg, more than would even be prescribed in the most extreme cases of deficiency.
With very high doses of vitamin D there is a danger of hypercalcaemia, the build-up of excessive levels of calcium in the blood, which can cause lethargy, high blood pressure, heart problems, hardening of the arteries and kidney damage.
With very high doses of vitamin D there is a danger of hypercalcaemia, the build-up of excessive levels of calcium in the blood, which can cause lethargy and high blood pressure
In 2014 the Food Standard Agency’s Committee on Toxicity concluded: ‘High intakes of vitamin D from medication or dietary supplements (often over prolonged periods) have caused toxicity in humans, and many cases of such poisoning have been reported’.
It said 110mcg is the highest amount that could be consumed every day over a lifetime by an adult or child aged 11 to 17 without risk to health (it’s 50 mcg for children aged one to ten, and 25 for infants).
PILLS WON’T STOP HEART DISEASE
When it comes to what constitutes a deficiency in vitamin D, gaps in the evidence mean ‘we don’t know how low levels need to be to make people really at risk’, explains one of the authors of the new BMJ paper, Professor Alison Avenell, clinical chair of health services research at the University of Aberdeen.
She adds the evidence behind the new paper comes from comprehensive systematic reviews of well-conducted clinical trials: ‘These show vitamin D does not prevent important medical problems such as falls and fractures in older people.’
So should we all be taking supplements?
She suggests they’re only needed by people ‘who never go out in the sun, such as old people in nursing homes, and those who rarely go outside or have clothing that means they are mostly covered up when in the sun, will also be at risk’.
Some research suggests supplements are only needed by people ‘who never go out in the sun, such as old people in nursing homes
People with dark skin from African, African-Caribbean and South Asian communities are also in danger ‘because their skin will not make vitamin D so effectively in the UK’.
And if you’re not in these groups, and are thinking about taking vitamin D to ‘prevent fractures, heart disease, diabetes, or cancer, or many other conditions, we don’t have evidence that it will be helpful’ — in other words, don’t bother.
The authors of the new paper and the NHS do agree on one thing: over the years vitamin D has been credited with being a miracle cure for many conditions but both conclude that there is no evidence taking the pills can help with any non-musculoskeletal condition.
They also agree no one is likely to actually come to grief following Public Health England’s advice to take 10mcg a day.
As Professor Avenell puts it: ‘We think very few people will benefit and many will take unnecessary supplements.’
Source: Daily Mail
