There have been a lot of news reports about the health risks of meat
eating, but are they justified? Dr Michael Mosley has been investigating the
truth behind the headlines for BBC Horizon.
I like eating meat, but what was once an innocent pleasure is now a
guilty one.
If you believe the headlines, regularly indulging in a steak or a bacon
sandwich raises your risk of heart disease and cancer. The threat to health
comes not from eating white meat, like chicken, but from red and processed
meat. Despite the negative headlines, on average Brits still eat about 70g of
red and processed meat a day, with a quarter of men eating almost twice as
much.
My wife, Clare, who is a GP, has for many years been trying to cut our
family's consumption of red and processed meat. I, however, was resistant. So
we were both delighted when Horizon asked me to investigate what, if any, the
risks really are.
I visited numerous experts, finding out what they themselves eat. I
also decided to go on a high-meat diet to see what effects doubling my intake
to around 130g a day would have.
High fat content
There are lots of good things in red meat. Beef, whole or minced, is a
great source of protein and essential nutrients, like iron and vitamin B12,
which are vital for health. On the downside, however, red and processed meat
tend to be high in saturated fat.
Bacon and sausages have around 16 times more saturated fat per gram
than tofu. If you are a cheese-eating vegetarian you should not feel too smug.
Cheese is, gram for gram, an even richer source of saturated fat than burgers.
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Red and processed meat
Red meat includes steak, lamb, pork and mince. Red meat looks darker
than white meat like poultry because of higher levels of haemoglobin and
myoglobin, the iron and oxygen-binding proteins you find in blood and muscle. Processed
meat includes bacon, sausages, salami and ham.
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But how much does this matter?
One of the best ways to try to assess the impact of particular foods on
our health is by doing cohort studies. You take a large group of people with
varied diets, find out what they eat, then follow them for many years to see
what diseases they develop.
Mortality risk debate
Professor Walter Willett, of the Harvard School of Public Health, heads
a team that have been tracking the diets of tens of thousands of people for
many years.
"We found that those who consumed higher amounts of red meat had a
higher risk of total mortality, cardiovascular mortality and cancer
mortality," he told me in the Harvard cafeteria, while I nonchalantly ate
a large steak.
On the basis of one of the studies he co-authored - Red Meat
Consumption and Mortality, published in Archives of Internal Medicine - he
estimates regularly eating a small amount of unprocessed red meat (85g, around
3oz) is associated with a 13% increased risk of mortality, while eating a
similar amount of processed red meat (a hot dog or two slices of bacon) is
associated with a 20% increased risk.
Not surprisingly, he almost never
eats meat.
He makes an extremely convincing case, yet as I discovered his results
do not match those of a more recent European study published in BMC Medicine in
2013, Meat Consumption and Mortality.
Researchers from the European Prospective Investigation into Cancer and
Nutrition (Epic) followed half a million people in 10 countries for more than
12 years. The researchers found that eating moderate amounts of red meat had no
effect on mortality. The lowest overall mortality rates were in those eating up
to 80g a day.
Although there was a small increase in overall risk for those eating
more than 160g, there was also a higher all-cause death rate amongst the
non-meat eaters. The researchers concluded that "a low - but not a zero -
consumption of meat might be beneficial for health. This is understandable as
meat is an important source of nutrients, such as protein, iron, zinc, several
B-vitamins as well as vitamin A and essential fatty acids."
Dangers of processed meat
Before meat eaters go off rejoicing, there is a significant sting in
the tail.
The Epic study, like almost every other study that has been done, found
that eating processed meat, such as bacon, ham or salami, had a negative effect
on health. Anything over 40g a day and deaths from heart disease and cancer
began to climb.
The science is far from settled. The experts I met have strongly held
but different opinions, reflected in what they themselves eat. In this Horizon
we try to present the facts; where the truth lies is something only you can decide.
Eating lots more processed meat certainly had a bad effect on my body. After a
month of bacon sandwiches and burgers I had piled on the weight and my blood
pressure and cholesterol levels both soared.
I have gone back to my old diet, eating the occasional steak and pork
chop. But there will be fewer burgers and sausages on the BBQ this year.
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Making sense of the statistics
An increased mortality risk of 20% means your risk of dying over the
next year is 20% higher than if you did not eat the processed meat.
Professor Sir David Speigelhalter of Cambridge University says another
way of looking at this is, if the studies are right, that you would expect
someone who eats a bacon sandwich every day to live, on average, two years less
than someone who does not.
Pro rata, this is like losing an hour of your life for every bacon
sandwich you eat. To put this into context, every time you smoke 20 cigarettes,
this will take about five hours off your life.
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Horizon - Should I Eat Meat? The
Big Health Dilemma is broadcast on BBC Two at 9pm on Monday, 18 August.
http://www.bbc.com/news/health-28797106
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