Strong bones, a healthy immune system, protection against
some types of cancer:
Recent studies suggest there’s yet another item
for the expanding list of Vitamin
D benefits. Vitamin D, “the sunshine vitamin,”
keeps the heart, the body’s long-distance runner,
fit for life’s demands.
University of Michigan pharmacologist Robert U. Simpson,
Ph.D., thinks it’s apt to call vitamin D “the
In studies in rats, Simpson and his team report the
first concrete evidence that treatment with activated
vitamin D can protect against heart failure. Their results
appear in the July issue of the Journal of Cardiovascular
In the study, treatments with activated vitamin D prevented
heart muscle cells from growing bigger – the condition,
called hypertrophy, in which the heart becomes enlarged
and overworked in people with heart failure. The treatments
prevented heart muscle cells from the over-stimulation
and increased contractions associated with the progression
of heart failure.
About 5.3 million Americans have heart failure, a progressive,
disabling condition in which the heart becomes enlarged
as it is forced to work harder and harder, making it
a challenge even to perform normal daily activities.
Many people with heart disease or poorly controlled
high blood pressure go on to experience a form of heart
failure called congestive heart failure, in which the
heart’s inability to pump blood around the body
causes weakness and fluid build-up in lungs and limbs.
Many people with heart failure, who tend to be older,
have been found to be deficient in vitamin D.
“Heart failure will progress despite the best
medications,” says Simpson, a professor of pharmacology
at the U-M Medical School. “We think vitamin D
retards that progression and protects the heart."
The U-M researchers wanted to show whether a form of
vitamin D could have beneficial effects on hearts that
have developed or are at risk of developing heart failure.
They used a breed of laboratory rats predisposed to
develop human-like heart failure.
The researchers measured the effects of activated Vitamin
D (1,25 dihydroxyvitamin D3, a form called calcitriol)
in rats given a normal diet or a high-salt diet, compared
to control group rats given either of the same two diets,
but no vitamin D treatment. The rats on the high-salt
diet were likely to develop heart failure within months.
The rats on the high-salt diet, comparable to the fast
food that many humans feast on, quickly revealed the
difference vitamin D could make.
“From these animals, we have obtained exciting
and very important results,” Simpson says.
After 13 weeks, the researchers found that the heart
failure-prone rats on the high-salt diet that were given
the calcitriol treatment had significantly lower levels
of several key indicators of heart failure than the
untreated high-salt diet rats in the study. The treated
rats had lower heart weight. Also, the left ventricles
of the treated rats’ hearts were smaller and their
hearts worked less for each beat while blood pressure
was maintained, indicating that their heart function
did not deteriorate as it did in the untreated rats.
Decreased heart weight, meaning that enlargement was
not occurring, also showed up in the treated rats fed
a normal diet, compared to their untreated counterparts.
Simpson and his colleagues have explored vitamin D’s
effects on heart muscle and the cardiovascular system
for more than 20 years. In 1987, when Simpson showed
the link between vitamin D and heart health, the idea
seemed far-fetched and research funding was scarce.
Now, a number of studies worldwide attest to the vitamin
D-heart health link (see citations below).
The new heart insights add to the growing awareness
that widespread vitamin D deficiency—thought to
affect one-third to one-half of U.S. adults middle-aged
and older—may be putting people at greater risk
of many common diseases. Pharmaceutical companies are
developing anti-cancer drugs using vitamin D analogs,
which are synthetic compounds that produce vitamin D’s
effects. There’s also increasing interest in using
vitamin D or its analogs to treat autoimmune disorders.
In more than a dozen types of tissues and cells in
the body, activated vitamin D acts as a powerful hormone,
regulating expression of essential genes and rapidly
activating already expressed enzymes and proteins. In
the heart, Simpson’s team has revealed precisely
how activated vitamin D connects with specific vitamin
D receptors and produces its calming, protective effects.
Those results appeared in the February issue of Endocrinology.
Sunlight causes the skin to make activated vitamin
D. People also get vitamin D from certain foods and
vitamin D supplements. Taking vitamin D supplements
and for many people, getting sun exposure in safe ways,
are certainly good options for people who want to keep
their hearts healthy. But people with heart failure
or at risk of heart failure will likely need a drug
made of a compound or analog of vitamin D that will
more powerfully produce vitamin D’s effects in
the heart if they are to see improvement in their symptoms,
Vitamin D analogs already are on the market for some
conditions. One present drawback of these compounds
is that they tend to increase blood calcium to undesirable
levels. Simpson’s lab is conducting studies of
a specific analog which may be less toxic, so efforts
to develop a vitamin D-based drug to treat heart failure
are moving a step closer to initial trials in people.