Vitamin D supplements not needed by healthy adults
Vitamin D supplements not needed by healthy adults
The widespread use of vitamin D
supplements to prevent osteoporosis in healthy adults is not
necessary, according to a study by one of New Zealand’s
leading medical scientists.
The study, led by
Professor Ian Reid from the University of Auckland’s Bone
Research Group, found that taking vitamin D supplements does
not improve bone mineral density in adults with a normal
Vitamin D level.
Professor Reid and his
colleagues conducted a systematic review and meta-data
analysis of the effects of vitamin D supplements on bone
mineral density. The data from more than 4000 healthy
adults in 23 randomised trials was analysed and the results
published this week in leading medical journal, The
Lancet.
The study found that taking vitamin D
supplements did not improve bone mineral density at the hip,
spine, forearm, or in the body as a whole.
“Most
healthy adults do not need vitamin D supplements” says
Professor Reid. “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.”
“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 inappropriate,” says Professor
Reid in the Lancet article.
Analysis of the data
from the 23 studies did not identify any effects for people
who took vitamin D for an average period of two years, apart
from a small but statistically significant increase in bone
density (0.8%) at the femoral neck. According to the
authors, such a localised effect is unlikely to be
clinically significant.
“In North America and
Europe particularly, more than half the adult population
have their vitamin D level assessed and take vitamin D
supplements,” says Professor Reid. “Some advocates
have suggested that the indicator level for needing vitamin
D supplements has been quite high.”
“We believe
that vitamin D supplements are only indicated for people
with very low levels, (such as those who are frail, are
confined rest-home residents, or women who are veiled, and
some dark skinned people),” he says. “This review
study suggests that the high use of vitamin D supplements by
most healthy adults is a waste of money and
resources.”
Others at risk of vitamin D
deficiencies, such as children without access to a
conventional diet, especially dark-skinned children, may
need vitamin D supplements to avoid conditions such as
rickets that affects the growing skeleton causing bowed legs
and knock knees.
“Most healthy adults, especially
in New Zealand, who live a normal, active life and get out
regularly for activities such as walking, shopping and
gardening, get vitamin D from the sun, and do not need
vitamin D supplements”, says Professor
Reid.
“We do know that maintaining good blood
vitamin D levels is important for promoting absorption of
calcium from the diet,” he says. “Very high levels of
Vitamin D may have the opposite effect, and take calcium out
of the bone and weaken the skeleton. There is a sweet spot
in the middle, where not too much and not too little is a
good
level.”
ENDS