A chemical found in
red meat helps explain why eating too much steak, mince and bacon is bad for
the heart, say US scientists.
A study in the journal Nature
Medicine showed that carnitine in red meat was broken down by
bacteria in the gut. This kicked off a chain of events that resulted in higher
levels of cholesterol and an increased risk of heart disease. Dieticians warned
there may be a risk to people taking carnitine supplements. There has been a
wealth of studies suggesting that regularly eating red meat may be damaging to
health.
In the UK, the
government recommends eating no more than 70g of red or processed meat a day -
the equivalent of two slices of bacon. Saturated fat and the way processed meat
is preserved are thought to contribute to heart problems. However, this was not
thought to be the whole story.
“Start Quote
I would strongly
recommend that unless you're a vegetarian or vegan, there is a potential risk
from taking L-carnitine, lecithin, choline or betaine supplements in an attempt
to ward off cognitive decline or improve fat metabolism ”
End Quote Catherine Collins Dietitian
"The cholesterol
and saturated fat content of lean red meat is not that high, there's something
else contributing to increases in cardiovascular risk," lead researcher Dr
Stanley Hazen told the BBC.
Gut bugs
Experiments on mice
and people showed that bacteria in the gut could eat carnitine.
Carnitine was broken
down into a gas, which was converted in the liver to a chemical called TMAO.
In the study, TMAO was
strongly linked with the build-up of fatty deposits in blood vessels, which can
lead to heart disease and death.
Dr Hazen, from the
Cleveland Clinic, said TMAO was often ignored: "It may be a waste product
but it is significantly influencing cholesterol metabolism and the net effect
leads to an accumulation of cholesterol.
"The findings
support the idea that less red meat is better.
"I used to have
red meat five days out of seven, now I have cut it way back to less than once
every two weeks or so."
He said the findings
raised the idea of using a probiotic yogurt to change the balance of bacteria
in the gut.
Reducing the number of
bacteria that feed on carnitine would in theory reduce the health risks of red
meat.
Vegetarians naturally
have fewer bacteria which are able to break down carnitine than meat-eaters.
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