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Globe and Mail Update Published on Thursday, Mar. 04,
2010 5:40PM EST Last updated on Thursday, Mar. 04, 2010
6:05PM EST
forwarded by Tim Uuksulainen
Clinical Trials on
Vitamin D
Two major clinical trials are just beginning in the United
States that will likely settle, once and for all, whether
everyone living at northern latitudes should pop a vitamin
D pill every day to help ward off cancer, heart disease,
and a host of other serious ailments.
The trials will also test the benefits of calcium supplements
and omega-3 fatty acids, two other nutrients that also have
gained a widespread following over their purported health
benefits.
Hopes are high that the research studies will end the debate
over the sunshine vitamin because they will be using relatively
high doses – 2,000 International Units – a day,
and involve more than 22,000 people, a large enough group
to uncover any benefits or risks.
Both trials have been designed specifically to test the
nutrient’s possible role in preventing cancer, perhaps
the most dramatic medical claim that has been made about
the vitamin.
“We’re not going to change formal public policy
[about taking vitamin D] until we have at least one randomized
trial with a primary outcome being cancer,” says Joan
Lappe, a professor at Creighton University in Nebraska,
and the lead researcher on one of the trials.
Dr. Lappe’s review will involve 2,300 postmenopausal
women, who will be tracked for four years to check whether
the vitamin reduces cancer rates, along with the incidence
of cardiovascular disease and diabetes. Some of the women
will also be given calcium.
The other trial, which will involve 20,000 people, is being
run jointly by Harvard Medical School and the Brigham and
Women’s Hospital in Boston. It will also test the
theory that fish oils are good for heart health and stroke
prevention, and will run for about seven years.
Both studies are receiving funds from the U.S. National
Institutes of Health.
Vitamin D has acquired its health-cult status because many
studies have found that people with more of the nutrient
circulating in their blood have lower rates of some cancers.
As well, other research – based on epidemiology or
the study of disease distribution in large populations –
has found that there is more cancer, diabetes, and other
chronic ailments among those living at northern latitudes
than among people living further south.
This peculiar south-to-north pattern of increasing incidence
of many diseases suggests a possible role for vitamin D
because most of this nutrient is made in the skin when cholesterol
in it is exposed to strong, ultraviolet light – hence
the sunshine vitamin moniker.
Light isn’t intense enough to make the vitamin the
natural way in northern countries like Canada for nearly
six months every fall and winter, causing many people who
aren’t supplementing to have seasonal deficiencies
and possibly putting them at risk of illness.
While epidemiology has been suggestive of benefits from
vitamin D – it was the research technique used to
finger cigarettes as a cancer risk – it has the drawback
of not constituting proof in the same way as a drug-style
clinical trial involving some people taking medication and
others a dummy pill, the gold standard for proving the efficacy
of any treatment.
The idea that a vitamin deficiency may cause cancer and
many other illnesses is also such an unconventional one
that it has prompted disputes within the medical research
community, with doctors who are skeptical arguing that before
people start taking large amounts, physicians should be
certain both of its efficacy and potential side effects.
The researchers involved in the trials are also urging
caution.
“We have to be careful before jumping on the bandwagon
to take megadoses of supplements before we have conclusive
answers from randomized trials,” says JoAnn Manson,
co-leader of the Harvard/Brigham study and a professor of
medicine at Harvard Medical School.
Another factor suggesting a careful approach is that many
nutrients, such as vitamin C and beta-carotene, once as
hyped as vitamin D, failed to live up to initial, hopeful
research after drug-style trials didn’t find the value
in taking them, according to Dr. Manson.
But those who have been urging wider usage of vitamin D
say the evidence is already compelling and that people shouldn’t
wait for the trial results to start supplementing.
“People should not remain vitamin D deficient,”
says John Cannell, head of the Vitamin D Council, a California-based
non-profit group that has been advocating widespread use
of the nutrient as a public health measure.
Dr. Cannell says that when it comes to vitamin D, physicians
have an obligation to “act based upon what is currently
known, not waiting for what is going to be known in the
future.”
But Dr. Manson says that there may be early indications
of the results from her research. For ethical reasons, those
participating in the study will be monitored for both harmful
effects and benefits, which if found, may cause the trial
to be altered.
How much vitamin D should you take?
The doses used in the clinical trials checking vitamin
D’s anti-cancer properties will be 2,000 International
Units a day, Health Canada’s maximum safe level. This
is the equivalent of two typical over-the-counter pills
and is designed to raise blood levels of the nutrient to
concentrations associated with lower cancer risk in previous
epidemiological research.
The Canadian Cancer Society has been recommending 1,000
International Units a day, with whites taking that amount
in fall and winter and those with dark skin year-round because
non-whites don’t make the vitamin as quickly in Canada’s
relatively feeble sunlight.
The cancer society made the recommendation following the
publication of study in 2007, the first of its kind, finding
that about 1,100 International Units taken daily had anti-cancer
properties.
Health Canada says people need take only 200 International
Units to 600 International Units a day, depending on age,
a recommendation based on vitamin D’s well recognized
role in promoting bone health.
There are very few dietary sources of the nutrient, making
it hard to get large amounts from food. Fortified milk has
100 International Units per cup. Wild salmon is one of the
best natural sources, at about 800 International Units per
serving. Eggs contains about 25 International Units per
yoke.
Previous research has found that a vitamin D intake of
around 400 International Units per day doesn’t have
anti-cancer properties
Vitamin D 'triggers and arms' the immune system
http://www.telegraph.co.uk/health/healthnews/7379094/Vitamin-D-triggers-and-arms-the-immune-system.html
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