How Long Does It Take for Vitamin D Supplements to Work
Low levels of vitamin D have been linked to a range of serious conditions
Vitamin D
Dr Sarah Jarvis discovers why almost a fifth of her medical colleagues take vitamin D It's almost impossible to eat enough vitamin D to keep levels topped up, so most of us absorb up to 90% of vitamin D we need from sunshine through our skin. Sufficient blood levels of vitamin D are 70 and over (nanomoles per litre). Insufficient is classed as 40 to 70, and below 40 is deficient. Vitamin D is essential for strong bones, and low levels in later life raise the risk of bone thinning. It was this that worried the female doctors in our poll most. But there is increasing evidence for a link with breast cancer (in one review of studies, women with the highest levels of vitamin D were 50-70% less likely to suffer than those with the lowest levels), heart disease and depression. A consultant chemical pathologist in the survey, whose job is interpreting blood samples, said that 'low vitamin D is common across the UK in winter, and all year round anywhere north of Birmingham', while a consultant cardiologist talked of an 'epidemic' of vitamin D deficiency.
In a nutshell:
• Unless you get plenty of sunshine, consider a daily 25mcg (1,000 units) vitamin D supplement.
• If you keep sun exposure to a minimum for your skin's sake, talk to your GP and get your levels tested
For years we've been told to cover up, stay out of the sun and slap on factor-50 sun screen. It's become a mantra for all of us wanting to protect ourselves against skin cancer. But now some experts are admitting they got it wrong, and that overdoing the safe-sun message could be contributing to a worrying new health epidemic – vitamin D deficiency.
As well as osteoporosis, low levels of vitamin D have been linked to a range of serious conditions from heart disease to diabetes. So has a lifetime of covering up put us all in danger? To learn the truth, we asked 12 members of the Good Housekeeping team, chosen at random, to undergo a simple blood test to check their levels. The tests were carried out by Harley Street GP, Dr Richard Cooper. To his – and our – disbelief, every single one of these apparently healthy women had low blood levels of vitamin D, and nearly 50% were clinically deficient. Good Housekeeping's own Dr Sarah Jarvis was stunned when she discovered her own level was staggeringly low.
'I was absolutely horrified and really shocked – particularly by my own results,' she says. 'I do actively avoid sunbathing and burning, but I don't actively avoid being outside. I was astonished my result was so low – I am not constantly covered up or indoors all the time. I've been aware for a while that there is an issue with vitamin D, and that it could be a ticking time bomb for osteoporosis in later life. It has made me rethink the way I look at my patients, and on a personal level I am so deficient that I am now having injections to get my vitamin D levels back to normal. Then I will think seriously about taking supplements.'
And there's growing evidence that the Good Housekeeping results are a snapshot of what's happening among women in general. Studies show that around half of us have inadequate vitamin D levels and, during winter and spring, one in six is severely deficient even at the very low minimum level set by UK authorities. For the first time in many years, cases of rickets – a childhood bone disease caused by vitamin D deficiency – are on the rise. So what's the explanation?
Unlike other nutrients, where our intake comes almost exclusively from food, we get around 90% of our vitamin D from the action of sunlight on our skin. And, for a variety of reasons, we're not getting nearly enough, says Simon Pearce, professor of endocrinology at Newcastle University.
'Appropriate sunlight exposure is key for vitamin D synthesis, and the sun-safe message has been overstated. Other important factors are that women in particular are unlikely to work outside. And people are eating far less fish, which is a good source of vitamin D.'
It's hardly surprising levels are low when sunlight is so scarce, especially in the north of Britain. In fact, people in Scotland get only a little more sun than Eskimos inside the Arctic Circle, but without the same vitamin D-rich fish diet.
The missing health link
Scientists have known since the 1920s that vitamin D is crucial for building strong bones, but in the past 30 years there's been an explosion of knowledge about the nutrient. 'We now know vitamin D is present in at least 38 tissues in the body – and probably present in all of them,' says Anthony Norman, emeritus professor of biochemistry at the University of California, Riverside, who has spent almost 50 years studying vitamin D.
'It's been shown to play an important role in the immune system, in the heart and blood vessels, in the pancreas, in muscle development and strength, and in brain development.'
A study last year, funded by the Medical Research Council, found vitamin D has a direct influence on 229 genes involved in disease – particularly those associated with multiple sclerosis, Crohn's disease and type 1 diabetes. Scientists at the University of Copenhagen found that the vitamin plays a crucial role in activating our immune defences by triggering and arming the body's T cells, which seek out and destroy invading bacteria and viruses.
And it doesn't stop there. The evidence linking low levels of vitamin D with many common diseases is stacking up.
Colds and flu
According to American research, vitamin D supplements reduced the incidence of colds and flu by 70% over three years in Afro-Caribbeans, who are more vulnerable to deficiency because of their darker skin.
Heart disease
After analysing 28 different studies involving nearly 100,000 people, researchers concluded that middle-aged and elderly people with high levels of vitamin D in their blood stream had a 43% reduced risk of heart disease and diabetes. Some researchers have linked the lack of sunlight in Scotland to the country's high rates of heart disease.
◆ Diabetes
When vitamin D supplements were given to babies in Finland, their risk of type 1 diabetes was reduced by 80%. Other research has found low vitamin D levels in children newly diagnosed with diabetes.
◆ Multiple sclerosis
The idea that sunlight – and vitamin D – may be protective came about because MS is more common in countries further from the equator. Chicago has higher rates than Florida, and Scotland has one of the highest rates in the world. 'There is some evidence that vitamin D deficiency during pregnancy and in the early years of life may play a role in the development of MS,' says Dr Doug Brown, head of biochemical research at the MS Society.
◆ Cancer
A growing number of research studies links low vitamin D levels with an increased risk of breast, bowel and prostate cancer. One analysis of 63 different scientific papers concluded that a daily dose of vitamin D could halve the risk of breast cancer and there is growing evidence linking higher vitamin D levels to a reduced risk of bowel cancer. It may even protect against melanoma, the most dangerous form of skin cancer. One study of melanoma patients found that those with the lowest vitamin D levels were 30% more likely to relapse after treatment than those with the highest levels.
◆ Pregnancy complications
Researchers at the University of South Carolina found that pregnant women taking very high daily doses of vitamin D were 50% less likely to experience pre-term labour, pre-eclampsia, gestational diabetes and infections than those on the lowest dose.
Who is at risk?
The vast majority of us, say experts who point at the high prevalence of deficiency. The Government already recommends supplements for pregnant and breast feeding mothers, children under four, people over 64 and those with darker skin or whose skin is not exposed to the sun very much. People of African or Asian origin, for example, are particularly vulnerable, as they need more sun to make the same amount of vitamin D. Older people have a reduced ability to make vitamin D and people who are obese are also at greater risk. 'Because vitamin D is fat soluble it will go into the fat cells, so very little is released into the blood stream,' explains Dr Inez Schoenmakers, senior research scientist at the MRC Human Nutrition Research Centre in Cambridge.
So why aren't we told to take supplements?
For many experts the jury is still out because, although the vitamin D link to bone health is proven, there isn't solid evidence that vitamin D deficiency causes other diseases, or that supplementation would make a difference. 'The idea that vitamin D deficiency, easily combated with a supplement, could be the miracle cure for cancer, heart disease, diabetes and MS, is certainly attractive. But while individual studies have raised hopes, the research evidence isn't conclusive, and more work needs to be done,' says Dr Nita Forouhi, clinician scientist programme leader at the MRC Epidemiology Unit in Cambridge.
What we don't know
And there are still many unanswered questions. What is the optimal vitamin D level and how much do we need on a daily basis? It's a complex issue because we know that there is no 'one size fits all' answer because age, weight and skin colour can all affect the amount that we might need. Currently, unlike other countries, the UK has no recommended daily intake level for people aged four to 65. The Government's Scientific Advisory Committee on Nutrition's working group is currently reviewing the evidence on vitamin D and this will form the basis for new UK recommendations, which are expected later this year.
Professor Pearce thinks we need to add vitamin D to food. 'Fortification, particularly of milk and orange juice, is needed and a major change in policy by major cereal manufacturers would be helpful. Although Kellogg's supplements Special K and Bran Flakes with vitamin D, it doesn't supplement the ones targeted at kids, although own-brand cereals like rice pops do have added vitamin D.'
How much sun is enough?
The current advice is to regularly spend a few minutes in the middle of the day without sun screen. But again there is no standard answer, as the level of sun exposure needed to make enough vitamin D depends on your skin type, amount of skin exposed, time of day, latitude, altitude and cloud cover. What we do know is that our need for vitamin D isn't a green light to fry in the sun. 'We know that vitamin D production stops well before the skin starts to become red,' says Dr Schoenmakers. So never allow your skin to redden or burn. Darker-skinned people will be able to spend more time in the sun than those with fairer skin, who burn more easily.
What's now needed are large-scale clinical trials that use high doses of vitamin D to raise blood levels while measuring the impact on disease. The good news is that it's starting to happen around the world.
What it means for you
Until we have the definitive answers, where does this leave the rest of us? 'While we shouldn't overreact, the impact of vitamin D on bone health is a certainty – and on that basis alone those with lower levels need to address the issue,' says Dr Cooper. Although vitamin D is found in fortified margarines, oily fish, eggs and some breakfast cereals, food is only a small part of the equation, and anyone who gets very little sun should consider supplements.
The Canadian Cancer Society now recommends all Canadians take 1,000 iu (25mcg) of vitamin D in winter and Bupa has urged people to take vitamin D3 supplements to reduce their cancer risk. Current UK advice is that taking up to 25mcg of vitamin D3 daily is safe (if you have trouble swallowing tablets or with absorption, you can buy vitamin D3 in liquid form), though some campaigners argue that two to four times that amount is needed for disease prevention. Ultimately it's a personal decision. As professor Norman says: 'We know that long-term trials are the only way of proving supplements will make a difference, but are you going to wait 10 years for the results or make a decision to protect you and your family's health now based on what we know is safe?'
What our tests revealed
Many vitamin D experts consider a blood level of 75 and over (measured in nmol per litre) to be optimal. Levels below 25 are classified as clinically deficient. None of our Good Housekeeping volunteers – aged from 24 to 63 – had vitamin D blood levels even approaching 75. And the two with the highest scores had just returned from sunny holidays. Incredibly, almost 50% of our 12 volunteers had scores below 25, showing they were clinically deficient.
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How Long Does It Take for Vitamin D Supplements to Work
Source: https://www.goodhousekeeping.com/uk/health/a531258/vitamin-deficiency-vitamin-d-deficiency-low-vitamin-d/