Researchers at Johns Hopkins are reporting what is
believed to be the most conclusive evidence
to date that inadequate levels of vitamin D, obtained from
milk, fortified cereals and exposure to
sunlight, lead to substantially increased risk of death.
In a study appearing in the Archives of Internal
Medicine online Aug. 11, the Johns Hopkins
team analyzed a diverse sample of 13,000 initially healthy
men and women participating in an ongoing
national health survey and compared the risk of death
between those with the lowest blood levels of
vitamin D to those with higher amounts. An unhealthy
deficiency, experts say, is considered blood
levels of 17.8 nanograms per milliliter or lower.
Of the 1,800 study participants known to have died by
Dec. 31, 2000, nearly 700 died from
some form of heart disease, with 400 of these being
deficient in vitamin D. This translates overall to
an estimated 26 percent increased risk of any death, though
the number of deaths from heart disease
alone was not large enough to meet scientific criteria to
resolve that it was due to low vitamin D
Yet researchers say the finding does highlight a
trend, with other studies linking shortages of
vitamin D to increased rates of breast cancer and
depression in the elderly. And earlier published
findings by the team, from the same national study, have
established a possible tie-in, showing an 80
percent increased risk of peripheral artery disease from
vitamin D deficits.
Researchers note that other studies in the last year
or so in animals and humans have identified
a connection between low levels of vitamin D and heart
disease. But these studies, they say, were
weakened by small sample numbers, lack of diversity in the
population studied and other factors that
limited scientists' ability to generalize the findings to
the public at large.
"Our results make it much more clear that all men and
women concerned about their overall
health should more closely monitor their blood levels of
vitamin D, and make sure they have enough,"
said study co-lead investigator Erin Michos.
"We think we have additional evidence to consider
adding vitamin D deficiency as a distinct and
separate risk factor for death from cardiovascular disease,
putting it alongside much better known
and understood risk factors such as age, gender, family
history, smoking, high blood cholesterol levels,
high blood pressure, lack of exercise, obesity and
diabetes," she said.
Vitamin D is well-known to play an essential role in
cell growth, in boosting the body's immune
system and in strengthening bones.
"Now that we know vitamin D deficiency is a risk
factor, we can better assess how aggressively
to treat people at risk of heart disease or those who are
already ill and undergoing treatment," said
Michos, who added that test screening for nutrient levels
is relatively simple. It can, she said, be
made part of routine blood work and be done while
monitoring other known risk factors, including
blood pressure, glucose and lipid levels.
Heart disease remains the nation's leading cause of
death, killing more than a million Americans
each year. Nearly 10 percent of those with the condition
have not one identifiable, traditional risk
factor, which the experts say is why a considerable extent
of the disease goes unexplained.
Michos, an assistant professor at the Johns Hopkins
University School of Medicine and its
Heart and Vascular Institute, recommends that people
boost their vitamin D levels by eating diets
rich in such fish as sardines and mackerel, consuming
fortified dairy products, taking cod-liver oil and
vitamin supplements and in warmer weather briefly exposing
skin to the sun's vitamin D — producing
Aware of the cancer risks linked to too much time
spent in the sun, Michos says that as little as
10 to 15 minutes of daily exposure to the sun can produce
sufficient amounts of vitamin D to sustain
health. The hormonelike nutrient controls blood levels of
calcium and phosphorus, essential chemicals
in the body.
Michos says that if vitamin supplements are used,
there is no evidence that more than 2,000
international units per day do any good. Study results show
that heart disease death rates flattened
out in participants with the highest vitamin D levels
(above 50 nanograms per milliliter of blood),
signaling a possible loss of the vitamin's protective
effects at too-high doses.
The U.S. Institute of Medicine suggests that an
adequate daily intake of vitamin D is between
200 and 400 international units (or blood levels nearing 30
nanograms per milliliter). Previous results
from the same nationwide survey showed that 41 percent of
men and 53 percent of women are
technically deficient in the nutrient, with vitamin D
levels below 28 nanograms per milliliter.
Michal Melamed, study co-lead investigator, who
started the research as a clinical fellow at
Johns Hopkins, says that no one knows yet why or how
vitamin D's hormonelike properties may protect
the heart, but she adds that there are plenty of leads in
the better known links the vitamin has to
problems with muscle overgrowth and high blood pressure, in
addition to its control of inflammation,
which scientists are showing plays a stronger role in all
kinds of heart disease. But more research is
needed to determine the nutrient's precise biological
Researchers say their next steps are to test various
high doses of vitamin D to find out if the
nutritional supplementation results in fewer deaths and
lower incidence of heart disease, including
heart attack or moments of prolonged and severe chest
The team also plans to investigate what biological
triggers, such as obesity or hypertension,
might offset or worsen the action of vitamin D on heart
muscle, or whether vitamin D sets off some
other reaction in the heart.
Melamed says that because vitamin D levels are known
to fluctuate in direct proportion with
daily physical activity, the growing epidemic of obesity
and indoor sedentary lifestyles lend more
urgency to act on the vitamin D factor.
Funding for this study was provided by the National
Institutes of Health, P.J. Schafer
Cardiovascular Research Fund and Paul Beeson Physician
Faculty Scholars in Aging Program. Michos has
received previous consulting fees from vitamin D
therapeutics manufacturer Abbott Pharmaceuticals.
The terms of these arrangements are being managed by The
Johns Hopkins University in accordance
with its conflict of interest policies.
Other Johns Hopkins researchers involved in this
study, conducted solely at Johns Hopkins,
were Wendy Post and Brad Astor. Melamed is now an assistant
professor at the Albert Einstein
College of Medicine of Yeshiva University.