By: Eddie Levin
Drop that hamburger, put down the can of
Monster Energy and back away from the body building pills. A nutrient
found in red meat and added to energy drinks and supplements may crank
up people’s risk of heart disease, a new study suggests. Bacteria in the
gut digest the nutrient, L-carnitine, and help turn it into an
artery-hardening chemical — particularly in meat eaters, researchers
report April 7 in Nature Medicine.
The high amounts of saturated fat and
cholesterol in red meat have long been blamed for increasing people's
risk of heart disease. But now, new research points a finger at another
culprit in meat that may be more closely tied to this leading killer.
In a series of experiments in people and
mice, scientists for the first time demonstrated that carnitine from
foods as well as from supplements influenced cardiovascular risk.
The findings show that bacteria living in
the human digestive tract metabolize carnitine — a naturally-occurring
compound in red meat —into trimethylamine-N-oxide (TMAO), a metabolite
previously linked in a 2011 study to the promotion of atherosclerosis in
humans. Additionally, the study shows that a diet high in carnitine
promotes the growth of bacteria that metabolize carnitine, compounding
the problem.
“The bacteria living in our digestive
tracts are dictated by our long-term dietary patterns,” said Dr. Stanley
Hazen, lead researcher. “A diet high in carnitine actually shifts our
gut microbe composition to those that like carnitine, making meat eaters
even more susceptible to forming TMAO and its artery-clogging effects.
Meanwhile, vegans and vegetarians have a significantly reduced capacity
to synthesize TMAO from carnitine, which may explain the cardiovascular
health benefits of these diets.”
Carnitine is naturally occurring in beef,
venison, lamb, mutton, duck, pork and other red meats. It is also used
as a dietary supplement and a common ingredient in energy drinks.
Scientists have long known that eating
red meat jacks up a person’s chances of developing heart disease, but
reliable biomarkers — blood-borne indicators of disease or health — have
been hard to find. One way physicians gauge risk is with blood tests
for cholesterol, a greasy molecule in meat and other foods, which gums
up arteries. But tests for cholesterol and other molecules don’t wholly
explain meat’s link to heart disease, Hazen says. “Cholesterol,
saturated fat and salt only account for a tiny little piece of the
risk.”
Volunteers — a mix of omnivores,
vegetarians and vegans — ate steak and L-carnitine capsules, and then
researchers measured TMAO levels in the blood. Only meat eaters could
make TMAO from L-carnitine, Hazen’s team found, and they needed their
gut bacteria to do it. TMAO production shut down when researchers wiped
out volunteers’ intestinal microbes with antibiotics.
L-carnitine passed right through the guts
of long-term vegans and vegetarians, leaving their blood practically
TMAO-free. When researchers examined volunteers’ stool, they found
different groups of bacteria in people who did and didn’t eat meat.
Hazen’s group also found that blood
levels of TMAO and L-carnitine could predict heart disease risk, which
they learned by collecting blood samples from 2,595 patients and
tracking their health for three years.
The findings are new and exciting but
need to be confirmed, says cardiovascular researcher Ishwarlal Jialal of
the University of California, Davis Medical Center. Molecules proposed
as biomarkers for heart disease often look promising in initial studies
but fizzle out clinically. “We’ve been down this road so many times
before.”
But one message is clear, Jialal says:
“L-carnitine is not good for you. It’s not good as a supplement and it’s
not good in red meat. That’s one thing you can take to the bank.”
Reference:
www.meatpoultry.com
www.sciencenews.org
http://worldtruth.tv
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