Red meat chemical 'damages heart', say US scientists

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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.

Red meat meals versus daily guidelines

Composite image of various red meats
Meal or processed meat Cooked weight Within guideline?

Source: NHS/World Cancer Research Fund

1. Cooked breakfast



Assumes two standard sausages and two thin rashers of bacon

2. Spaghetti bolognese



Standard portion of minced beef

3. 5oz rump steak



A 5oz steak is smaller than a typical restaurant serving

4. Doner kebab



Typically comprising several slices of processed marinated lamb

5. Big Mac



Contains two thin burgers

6. Sunday roast



Assumes three slices of beef, lamb or pork

Victoria Taylor, Senior Dietitian at the British Heart Foundation, said: "This is certainly an interesting discovery and sheds some light on why red meat might have an impact on heart health.

"While the findings won't necessarily mean a change to existing recommendations, these scientists have served up a good reminder for us to think about alternative sources of protein if we regularly eat a lot of red or processed meats."

Catherine Collins, a dietitian at St George's Hospital, said: "It's a very persuasive argument, but we know that eating a couple of portions of red meat weekly is of no risk, heart wise.

"There's no need to change our dietary recommendations from this - a Mediterranean-style diet with modest meat, fish, dairy and alcohol intake, coupled with more pulses, vegetables fruits, wholegrains and mono-unsaturated fats, remains the nutritional blueprint for a healthy and healthful life.

"But 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.

"If the evidence is confirmed these supplements would do more to damage arteries than provide health benefits."


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  • rate this

    Comment number 453.

    Naturally produced meats have evolved to provide those that consume them with the essential ingredients to enable the body to function, they are designed that way to allow animals to eat them. It is the manmade style 'meats' that cause the problem when other ingredients have been added. As only humans eat this kind of rubbish that is where the unhealthy meats lie, not steak/chicken etc.

  • rate this

    Comment number 250.

    Why does anyone listen to this rubbish. We've been eating red meat since the dawn of time yet we're still living longer and longer. If we believe this "research" we should all be dead before we're born.

    Some scientific research is important, but this is just nonsense. What is the point of producing a report that clearly flies in the face of evolution and common sense.

  • rate this

    Comment number 240.

    This study does not address the quality of the meat products being assessed. I would suggest that naturally processed meats without the nitrites are not so harmful. Nor is an organically reared animal as potentially risky to human health. A study factoring in these variables may have greater validity.

  • rate this

    Comment number 237.

    Personally, I don't eat a great amount of red meat, mainly because I can't afford it. I do though, take medical research seriously.
    I still question why the many elderly living beyond 80 whom where brought up on plentiful supplies of red meat, beef dripping, smokey open fires etc. have survived.
    They worked harder, had less scaremongering research available, or are they just lucky?

  • rate this

    Comment number 210.

    Very interesting study that finally explains the increased risk of cardiovascular disease associated with eating red meat. Obviously red meat is neither a major cause, nor the biggest risk factor, so people do not have to change their lifestyles as a result of this, and instead focus on factors such as weight, smoking habits and exercise.


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