Healthy adults do not need to take vitamin
D supplements, suggests a study in The
Lancet which found they had no beneficial
effect on bone density, a sign of
osteoporosis.
But experts say many other factors could be at
play and people should not stop taking
supplements.
University of Auckland researchers analysed 23
studies involving more than 4,000 healthy
people.
The UK government recommends children and
over-65s take a daily supplement.
The New Zealand research team conducted
a meta-analysis of all randomised trials
examining the effects of vitamin D
supplementation on bone mineral density in
healthy adults up to July 2012.
The supplements were taken for an average of
two years by the study participants.
Bone mineral density is a measure of bone
strength and measures the amount of bone
mineral present at different sites in the body.
It is often seen as an indicator for the risk of
osteoporosis, which can lead to an increased
risk of fracture.
The trials took place in a number of different
countries including the UK, the US, Australia,
Holland, Finland and Norway.
Although the results did not identify any
benefits for people who took vitamin D, they
did find a small but statistically significant
increase in bone density at the neck of the
femur near the hip joint.
According to the authors, this effect is unlikely
to be clinically significant.
Free up resources
Prof Ian Reid, lead study author, from the
University of Auckland, said the findings
showed that healthy adults did not need to
take 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."
Writing about the study in The Lancet, Clifford
J Rosen from the Maine Medical Research
Institute agrees that science's understanding of
vitamin D supports the findings for healthy
adults, but not for everyone.
"Supplementation to prevent osteoporosis in
healthy adults is not warranted. However,
maintenance of vitamin D stores in the elderly
combined with sufficient dietary calcium
intake remains an effective approach for
prevention of hip fractures."
The Department of Health currently
recommends that a daily supplement of
vitamin D of 10 micrograms (0.01mg) should
be taken by pregnant and breastfeeding women
and people over 65, while babies aged six
months to five years should take vitamin drops
containing 7 to 8.5 micrograms
(0.007-0.0085mg) per day.
Additional factors
Dr Laura Tripkovic, research fellow in the
department of nutritional sciences at the
University of Surrey, said the study was
important but very specific.
"I'm not surprised they didn't find any
evidence of the effects of vitamin D on bone
density because there are so many other
factors involved in osteoporosis, like genes,
diet and environment.
"To pin it all on vitamin D... it's difficult to do
that."
Dr Tripkovic said it was no good taking vitamin
D supplements if people didn't also maintain a
healthy, balanced diet containing calcium and
take plenty of exercise.
She said most healthy people should be able to
absorb enough vitamin D naturally, through
sunshine and diet.
"But if people are worried about their vitamin
D levels then a multi-vitamin tablet would do.
If you have bone pain and muscle aches then
you should go and see your GP and discuss it."
We get most of our vitamin D from sunlight on
our skin, but it is also found in certain foods
like oily fish, eggs and breakfast cereals.
However, taking too much vitamin D in the
form of supplements can be harmful because
calcium can build up and damage the kidneys.
Experts advise taking no more than 25
micrograms (0.025mg) a day.
The UK guidance is currently being reviewed.
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