Two new reports that analysed research on vitamin
D supplements found there's no reason to get excited yet about any possible
One review, from international researchers, found hardly any
benefit. The other analysis suggested it may have what a specialist called a
"huge" effect on lifespan, but the findings aren't definitive.
"For now, the vitamin D story is intriguing," said
Naveed Sattar, a professor of metabolic medicine at the University of Glasgow
in Scotland, who co-wrote an editorial accompanying the studies. But more
research is required before any definitive recommendations should be made, he
said, since "there may yet be unexpected risks to supplementation".
There's been intense debate about the value of vitamin D
supplements in recent years, specifically over whether they contribute to
Vitamin D does for you?
Only one benefit
In one of the new reports, researcher Evropi Theodoratou, at
the University of Edinburgh in Scotland, and colleagues examined a series of
studies and found that scientists had only examined vitamin D's effects on 10
health issues, a far cry from the 137 that have been linked to vitamin D.
They found only one "benefit" from the vitamin, a
seeming link between vitamin D
levels late in pregnancy and the birth weight of children. The review also
raised questions about whether vitamin D is as important as previously believed
when it comes to bone
The other new report, from Oscar Franco, at Erasmus
University Medical Centre Rotterdam, in the Netherlands, and colleagues looked
at studies analysing links between vitamin D and the likelihood that subjects
would die during the study follow-up periods of three to seven years.
Together, 14 of the most reliable studies – known as
randomised controlled trials linked vitamin D3 supplements to an 11% reduction
in risk of death. However, there was a slight increase in the death rate among
those who took vitamin D2 supplements.
The 11% reduction in the death rate "seems
remarkable", Sattar and a colleague wrote in their editorial. In an
interview, he said the reduction is "huge", potentially putting vitamin
D deficiency in the same health-harming league as smoking and physical
A complicated picture
However, the studies are relatively small and mostly look at
the elderly, Sattar noted.
The whole picture is complicated, he said. "There is an
assumption that low blood vitamin D levels are causing or contributing to risk
for many diseases but recent research tells us that, in fact, the opposite is
the case and that having the disease in first place leads to people having low
vitamin D levels," he said.
"Furthermore, many of the risk factors which cause
disease – namely, obesity, smoking and poor
diet, can also lower vitamin D levels, and it is these risk factors and not
necessarily the low vitamin D we need to correct," Sattar said. "To
resolve these issues, we need big trials to tell us once and for all whether
vitamin D supplements make any difference to health."
When it comes to taking vitamin D supplements, "the
best advice is to wait for study findings to be reported," a process that
should only take a few more years since a big study will be finished by 2017,
The Council for Responsible Nutrition, which represents the
supplement industry, issued a statement on the findings.
"As we've seen in other studies, there is something
about certain diseases that seems to either be depleting the body of normal
levels of vitamin D, or the low levels are contributing to the disease,"
said Duffy MacKay, senior vice president for scientific and regulatory affairs
at the council. "In either case, where patients present with insufficient
levels of this critical nutrient, supplementing with vitamin D makes sense –
whether it actually slows the progression of the disease or rather helps to
replace the depleted nutrient levels being caused by the disease."
MacKay went on to say that in its "latest review of
vitamin D, the Institute of Medicine [a scientific advisory board to the US
government] raised the recommended levels for vitamin D."He added "In a recently released proposed rule
from the US Food & Drug Administration on nutrition and supplements facts
labels, the agency identified vitamin D as a 'nutrient of public health
significance', advising that vitamin D content be listed on food labels."
Lona Sandon, an assistant professor of nutrition at University
of Texas South-western Medical Centre at Dallas and a spokeswoman for the
American Dietetic Association, said the recommended amount of vitamin D per day
for people aged 1 to 70 is 600 international units. It jumps to 800 IU after
"About 15 minutes in the sunlight during peak hours a
few times per week is sufficient for most people to get enough vitamin D
production," she said. "People with darker skin may need longer sun
As for dietary sources,
mackerel, beef liver, egg yolk and mushrooms all contain vitamin D, Sandon
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