London - Taking vitamin D supplements does not improve bone strength and is a waste of time for women trying to stave off osteoporosis, claim researchers.
A new review of studies involving more than 4 000 healthy adults concludes that supplements fail to increase the density of bone at the hip, spine, forearm, or in the body as a whole.
Taking steps to increase bone mineral density is widely thought to be essential in preventing fractures in later life.
Hundreds of thousands of women take supplements in the UK either prescribed by their doctor for osteoporosis - thinning bones - or bought over the counter as “bone insurance”.
Professor Ian Reid from the University of Auckland in New Zealand, who led the study published in The Lancet medical journal, said close to half of adults aged 50 and older use vitamin D supplements, but for many people it will not make any difference.
He said “Most healthy adults do not need vitamin D supplements.
“Our data suggest that the targeting of low-dose vitamin D supplements only to individuals who are likely to be deficient could free up substantial resources that could be better used elsewhere in healthcare.”
Prof Reid and colleagues carried out a systematic review of 23 randomised trials examining the effects of using vitamin D supplements to boost bone mineral density in 4 082 healthy adults aged 59 on average up to July 2012.
The results did not show any effects for people who took vitamin D for an average period of two years, apart from a small increase in bone density at the femoral neck (forming part of the hip joint).
But this change would be unlikely to provide any real medical benefits to the individual, says the report.
It said “This systematic review provides very little evidence of an overall benefit of vitamin D supplementation on bone density.
“Continuing widespread use of vitamin D for osteoporosis prevention in community-dwelling adults without specific risk factors for vitamin D deficiency seems to be inappropriate.”
Vitamin D is essential for the immune system, strong healthy bones and teeth, and the absorption of calcium, and there is growing evidence that vitamin D deficiency may be responsible for triggering a range of diseases, including several cancers.
The body makes most of its vitamin D from sunlight, although oily fish is a good dietary source.
Older women are more at risk of osteoporosis because the rate of bone loss is accelerated by the menopause.
One in two women and one in five men over the age of 50 will break a bone mainly because of the disease.
Dr Claire Bowring, medical policy manager of the National Osteoporosis Society said “Vitamin D is essential for good bone health. this latest study supports what the National Osteoporosis Society has been saying for years: the best source for most people is safe summer sunlight exposure, and that only people at risk of vitamin D deficiency should take a supplement.
“The Department of Health identifies the following groups: pregnant and breastfeeding women, under 5s, people with darker skin, older people aged 65 and over and those with low or no exposure to the sun, as being at risk of vitamin D deficiency.”
Dr Carrie Ruxton, from the Health Supplements Information Service, said “Vitamin D deficiency continues to be a major problem in the UK where up to a quarter of adults have inadequate blood vitamin D levels, according to government data.
“This is due to our turbulent weather and dark winters, which restrict how much vitamin D our bodies can make, as well as low intakes of oily fish which is the best natural source of vitamin D.
“In terms of bone health, vitamin D promotes calcium absorption and its utilisation by bone, having the strongest impact on bone density when taken alongside dietary calcium.
“Therefore, it is unsurprising that the meta-analysis found no significant impact of vitamin D when taken alone. It is also worth remembering that vitamin D is needed for more than bone health.
“Emerging evidence suggests a role in immune function, maintenance of heart health and even prevention of chronic conditions such as multiple sclerosis.
“This is why I disagree with the findings of the Lancet study and would actually recommend that more people consider a daily vitamin D supplement, particularly with winter approaching.”
In the UK, the Food Standards Agency does not recommend a specific daily dose of vitamin D unless you are elderly, pregnant, Asian, get little sun exposure and eat no meat or oily fish when 10mcg is advised.
It says daily supplements of 25mcg are unlikely to cause harm.
The danger with taking excessive doses for long periods is that the body absorbs too much calcium, which could weaken bones and possibly damage liver and kidneys. - Daily Mail