A large new study in the US found no sign that vitamin D lowers
the overall risk of dying from cancer, injecting a note of caution to
the latest vitamin craze.
The exception: People with more vitamin D in their blood did have a
significantly lower risk of death from colourectal cancer, supporting
Getting enough of the so-called sunshine vitamin - the skin makes it
from ultraviolet rays - is vital for strong bones.
But vitamin D has made headlines in recent years because of research
saying it may be a powerful cancer fighter, sparking a push for people
to get more than currently recommended amounts, either through diet or
Far from settled
National Cancer Institute researchers analysed vitamin D levels
measured in almost 17 000 people as part of a national study that
tracked their health. About a decade after enrolling, 536 of those
people had died of cancer.
The first-of-a-kind US government study released Tuesday shows the
issue is far from settled.
Whether people had low or high vitamin D levels played no role in
their risk of dying from cancer in general, they reported Tuesday in
the Journal of the National Cancer Institute.
Then the researchers examined different types of cancer. There were
just 66 deaths from colourectal cancer. Still, people with high levels
of vitamin D appeared 72 percent less likely to die of colourectal
cancer than people with the lowest vitamin D levels.
"While vitamin D may well have multiple benefits beyond bone, health
professionals and the public should not, in a rush to judgment, assume
that vitamin D is a magic bullet and consume high amounts," Johanna
Dwyer, a dietary supplement specialist at the National Institutes of
Health, cautioned in an accompanying editorial.
Indeed, there are numerous risk factors for colourectal cancer,
including obesity and low physical activity, and it's unclear if low
vitamin D levels play an independent role or are just a marker for
those other risks, she said.
Scientists have been interested in vitamin D's effects for decades,
since noticing that cancer rates between similar groups of people were
lower in sunny southern latitudes than in northern ones. A handful of
studies since then have found people given vitamin D supplements have
less risk of developing certain cancers, but much of the evidence is
Experts are cautious because other vitamins and nutrient supplements
once widely thought to prevent cancer didn't pan out when put to
The NCI's study is the first to compare blood levels of vitamin D to
cancer mortality, and "it's the best research we have on this topic,"
said Dr Len Lichtenfeld of the American Cancer Society.
But a big weakness: It measured vitamin D at just one point in
participants' lives, when levels can vary widely with dietary changes
and especially the seasons.
Overall, most research "seems to be pointing in the direction that
there is a role of vitamin D," Lichtenfeld said. Tuesday's study "puts a note of caution in there that says with all the explosion of information and advocacy on behalf of vitamin D, we need to be cautious. ... We really need some further studies that are well done to answer the question." – (Sapa-AP)
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