It’s Not Just the Fat: There’s Another Way Red Meat May Harm the Heart

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Saturated fat? Cholesterol? Sure, red meat has plenty of those, but it also contains a compound that toys with gut bacteria and can lead to clogged arteries.

When it comes to explaining exactly why steaks and hamburgers and other red meats can be so harmful to the heart, the saturated fat that the body breaks down and sequesters in blood vessel walls where they can form dangerous plaques is an easy and obvious culprit. But the high rates of heart disease in the developed world suggest that these fats may not be working alone, say a group of researchers from the Cleveland Clinic who study how microbes and bacteria in our gut influence heart disease.

Our gut is full of bacteria — good strains that don’t cause disease — and recent studies show that these microbes can have a significant impact on our health, affecting our propensity for obesity, asthma, inflammatory diseases and even cancer. Not surprisingly, what we eat can influence which populations of bacteria are more common at any given time, so the researchers of the new study, published in the journal Nature Medicine, focused on how these gut microbes responded to a diet that included meat. Specifically, they looked at a compound called carnitine, which is abundant in meats like beef, lamb, duck and pork, but is also a popular dietary supplement in energy drinks.

In previous work on mice, the scientists found that gut bacteria can transform choline, a vitamin-B-group nutrient, from the diet into a compound called trimethylamine N-oxide (TMAO) that transports cholesterol to arteries where it forms potentially heart-stopping plaques. Carnitine, it turns out, is structurally similar to choline, so the researchers set out to document whether carnitine is metabolized by human gut bacteria in a similar way to gum up heart vessels and cause atherosclerosis.

(MORE: Gut Bugs: They Are What You Eat)

To better understand the relationship between carnitine and TMAO, the researchers conducted a series of experiments with meat eaters and a vegan willing to consume meat for the sake of the study. In the first phase, they documented the boost in TMAO produced after the meat-eating volunteers ate an 8-oz. steak and downed a capsule that would attach to and label the carnitine for easy detection. Consuming high amounts of carnitine from the steak was only associated with a higher level of TMAO in the blood of the five meat eaters, however, and not in the vegan who hadn’t consumed meat in at least a year. That suggests that eating meat can promote larger numbers of bacteria that break down carnitine into TMAO, thus generating more heart-harming cholesterol and establishing a cycle of damage to the heart.

This was confirmed when the researchers then looked at the levels of TMAO and carnitine in the blood of 2,595 patients undergoing heart-disease evaluations who were either omnivores, vegans or vegetarians. Meat eaters tended to harbor higher levels of carnitine and had a higher risk of heart disease, stroke or heart attack compared with the vegans or vegetarians. The bacteria in the gut, then, are heavily influenced by long-term-diet patterns, adding another layer to the understanding of how food can affect our risk for developing certain diseases. “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,” said study leader Dr. Stanley Hazen, of the Cleveland Clinic, in a statement.

(MORE: Fat in Red Meat and Butter May Hurt Your Brain)

In fact, when the meat eaters were given antibiotics for a week to cull some of the intestinal bacteria, levels of TMAO dropped significantly. That finding hints that it may be possible to control some of the heart-harming effects of red meat by suppressing certain populations of bacteria in the gut, although more studies need to be done to confirm exactly which bacterial populations are responsible for breaking down carnitine, and how direct the association between carnitine and TMAO is.

And then there are questions about carnitine supplements. Some energy drinks contain the compound, which is often added to rev up metabolism and increase energy, but if it also promotes the growth of bacteria that contribute to atherosclerosis, then people consuming energy drinks may not be aware that these products may be associated with an increased risk of heart disease.

(MORE: A Surprising Link Between Bacteria and Colon Cancer)

The findings certainly set the stage for more detailed studies on how red meat may contribute to heart disease, but in the meantime, it’s probably not necessary to entirely cut out red meat from your diet. Hazen’s own strategy should serve as a model: once a meat eater who enjoyed about 12 oz. several times a week, he told the New York Times that he now limits himself to eating 4 to 6 oz. once every two weeks. Moderation, it seems, is the best approach until more information becomes available.

17 comments
Techlvr
Techlvr

Everybody has a right to eat what they want, when they want.

I see hundreds of articles being published about what is good and what's not for us. The science will take at least another 20 years to find clear answers.

We may find that meat eaters can live healthier lives, eggs are actually good for us or McChicken gives us essential proteins. We may eat more insects to avoid climate change.

Meanwhile, the only conclusive evidence remains that vegetarians and vegans do live healthier, if not longer lives and cause less damage to environment (google keywords - vegan, heart disease, cancer, diabetes, omnivore).

I think the difference becomes more stark as you cross 50. A low cal, moderate diet with meat and veggies seems to work. Atkin's type of diet doesn't ( from what I have read, mr. Atkins was obese while perching his diet to rest of us).

c41man
c41man

Grass-fed beef...

mjack101795
mjack101795


Wow.

I’m so grateful; now I can enjoy eating my viciously murdered animals with a side of antibiotics.

ArnoldMorgen
ArnoldMorgen

I love this meat but I agree with you . I want to say one more negative about the red meat. I beleive that every meat has negative energy. You khow it is important how the animal grow. Well usually they all are unhappy and that is why the meat from animal gives to the human body negative energy. So my point is that in the red meat there is more negative energy compared to pork and chicken. If you want to eat healthy meat i suggest you to eat only fish. I think i can learn a lot from you. More tips from me you can read at my health blog

azlinaomar6
azlinaomar6

Eating Meat daily makes you a patient of a disease called cardiovascular. One way to avoid this problem is to control your intake of meat. It is better to avoid taking meat one day a week. Replace it with salads, tofu or vegetables. Studies prove that vegetable diet can reduce the risk of heart attack by 32 percent......  http://tiny.cc/zozcvw

JimHannington
JimHannington

EGGSellant article,  Gut Bacteria is becoming a prevalent indicator of disorders and diseases.  It seems all of nature has a balance and order to things.  Too much of anything creates havoc.  Gut Bacteria has also been initially linked by Chinese studies to schizophrenia. 

JonathanLizotte1
JonathanLizotte1

The highest meat consumption (thus carnitine consumption) are countries like the US [120.2](80.5), Canada [94.3](66.2), Australia [115.5](60.3), Argentina [98.3](70.6), Spain [97](43.5), and New Zealand [106.4](76.5).


Low in meat consumption are India [4.4](165.8), Indonesia [11.6](150.8), Pakistan [14.7](222.9), and Bangladesh [4](203.7).

In parenthesis are the death rates per 100k from heart disease. In brackets is annual meat consumption per capita in kilos.

Reference: http://www.worldlifeexpectancy.com/cause-of-death/coronary-heart-disease/by-country/
http://chartsbin.com/view/12730

A couple years ago when the EXACT same TMAO argument was leveled again choline and choline containing products we learned that mouse and human models do not correlate.

see: http://www.westonaprice.org/blogs/cmasterjohn/2011/04/13/does-dietary-choline-contribute-to-heart-disease/

This is but another witch hunt against supplement takers and meat eaters. It's laughably bad science.

BensonChoa
BensonChoa

I still think moderation is the key...


StabbyRaccoon
StabbyRaccoon

It might be important to point out that the very first sentence in the introduction says "The high level of meat consumption in the developed world is linked to CVD risk, presumably owing to the large content of saturated fats and cholesterol in meat1,2" and reference 1 is a single epidemiologial study and 2 is a meta-analysis where only processed red meat and not fresh red meat was associated with coronary heart disease risk. http://circ.ahajournals.org/content/121/21/2271.abstract

So it would appear that right from the starting gates their premise is faulty. It's an interesting study though, I look forward to its examination by more people and their opinions on it. I urge everyone to seek out other analyses of the study before making up their minds about it. Here's one http://examine.com/blog/media-sensationalism:-meat-is-bad-for-your-heart/

midav2752
midav2752

@JanetRiley Janet, I don't think she will but this is well known. Dr. Sinatra (a board certified cardiologist has written many books explaining the "heart saving" virtues of his "awesome foursome" magnesium, Co Q 10, fish oil, and L- Carnitine. I can personally attest to it's merit when I developed intermittent claudication that limited my walking to less than a block. I quit smoking but could not improve my performance by any nutritional means on a plant based diet. My sister (who holds a PHD in nursing suggested I try Propionyl-L-Carnitine and I was immediately able to walk 2 1/2 miles. I have resumed my tough (on my tools) career in construction with the supplementary suggestions by Dr. Sinatra including L-Carnitine. I take home $1200.00 a week at 62 yrs of age ONLY because of this supplement. The severe cramping I used to experience in my calves, thighs and buttocks from the PAD would never allowed me to continue working.( it would not have allowed me to walk from the store parking lot to inside without stopping for 5 or 10 minutes. This person is reporting nonsense.

Techlvr
Techlvr

One more thing, the data being used to show health differences between non and meat eaters is being collected largely from within same geo.

While you can argue that Utah and Alabama are completely different from each other, they are much more alike than US and Somalia or Chad.

Techlvr
Techlvr

That's specious reasoning. Firstly, I love meat eaters but If you notice the data, it doesn't report instances of CVD, but the death rate.

All OECD countries have advanced healthcare that prevent deaths. All low income countries don't even have ambulances that can reach the patient in time leading to higher death rates - not necessarily higher CVD rates.

Secondly, a number of low income countries have moe than 50% of the population in rural areas where data collection is impossible. If that number is added and then normalized, US will have much higher rate of disease.

Finally - visit your local movie theater. Look to your left, then to your right. Then in 6 other directions. 6 out of you 9 will be obese or overweight. All of the obese will be regular meat eaters.