A New Reason Why Red Meat, and Some Energy Drinks, May Be Bad for Our Heart

ScienceNOW ^ | 7 April 2013 | Jennifer Couzin-Frankel

[neverdem]

Our guts are awash in bacteria, and now a new study fingers them as culprits in heart disease. A complicated dance between the microbes and a component of red meat could help explain how the food might cause atherosclerosis. The work also has implications for certain energy drinks and energy supplements, which contain the same nutrient that these bacteria like chasing after.

Red meat is considered bad news when it comes to heart health, although studies aren't consistent about how much can hurt and whether it always does. Furthermore, it's not clear which components of meat are doing harm. Various studies have considered saturated fat or sodium but the results are inconsistent and sometimes depend on whether meat has been processed or not. Stanley Hazen, the section head of preventive cardiology and a biochemist at the Cleveland Clinic in Ohio, wondered whether another ingredient might be harmful: L-carnitine, a nutrient that helps transport fatty acids into the cell's energy powerhouses, the mitochondria. L-carnitine is a popular additive to energy drinks and supplements that claim to boost energy levels. In food, the highest levels of L-carnitine are in red meat.

Hazen's focus on L-carnitine was something of a wild guess based on earlier work he'd done. Two years ago, he and his colleagues published a paper in Nature identifying a compound in the blood called trimethylamine N-oxide (TMAO). It seemed to correlate with future heart disease risk and cause heart disease when fed to mice. TMAO is created when intestinal bacteria break down certain compounds in foods. Hazen wondered if the bugs might also convert L-carnitine to TMAO, which, in turn, could put the heart at risk.

To find out, Hazen, his Ph.D. student Robert Koeth, and their colleagues bought a George Foreman grill and started cooking steaks. "People lined up for the study," Hazen says, and participants "tended to be young, hungry students." Blood tests administered afterward revealed a rise in TMAO levels. This showed that something was converting L-carnitine to TMAO, but the researchers couldn't say yet that the culprits were bacteria. To pin this down, they gave five of their volunteers broad-spectrum antibiotics for a week to suppress gut microbes and then repeated the experiment. This time, there was virtually no TMAO in the blood or urine after the volunteers ate steak, suggesting the conversion couldn't happen without bacteria present.

"When you measure things in people's blood, you don't think of [them] as coming from bacteria," Hazen says, but in this case that appears to be what's happening. The finding is the latest in a series of studies that have shown that the population of bacteria in our guts—collectively known as the gut microbiome—can influence everything from weight loss to brain chemistry.

As the researchers describe today in Nature Medicine, mice fed a diet supplemented with L-carnitine for 15 weeks had much higher levels of TMAO than control animals. Animals getting extra L-carnitine had about double the burden of atherosclerosis in their arteries compared with mice eating a normal diet.

And the intestines of the mice getting extra L-carnitine also adapted, becoming enriched for various classes of bacteria that could more readily convert L-carnitine to TMAO. This hinted that people who eat lots of red meat might be especially efficient at converting L-carnitine to TMAO and that consuming the food in moderation could be less harmful because the conversion might be more sluggish. Twenty-three vegans and vegetarians given L-carnitine supplements were, Hazen's group found, less able to synthesize TMAO than those who regularly ate red meat.

It's still unclear why TMAO seems to promote atherosclerosis. Work by Hazen's group hints that TMAO seems to make it easier for immune cells in the arteries to accumulate cholesterol. Another mystery is how other foods containing L-carnitine might impact TMAO levels. For example, fish, which is thought to lower cardiovascular risk, also contains much lower levels of L-carnitine, as do chicken and milk, notes Dariush Mozaffarian, an epidemiologist at the Harvard School of Public Health in Boston who has studied meat and heart disease, in an e-mail. Inconsistencies also remain about how harmful red meat really is. That said, although more work needs to be done to tease apart the L-carnitine-microbe connection in people, "these findings may turn out to be seminal in the field," Mozaffarian writes.

"It tells a very compelling story," says Daniel Rader, a preventive cardiologist at the University of Pennsylvania. The best way to determine exactly how L-carnitine affects cardiovascular disease, he says, is with a clinical trial that manipulates how much L-carnitine people are taking in. Whether a trial like that is feasible, though, this study "at least would suggest—well, even if you've controlled your LDL [cholesterol]" with medication, "eating red meat might still be bad for you."

[illiac]

They also said at one point in time that eggs and shell fish were bad for heart patients...only to recant later...

In the meantime, many heart patients lost weight due to malnutrition....which was also considered good...

[Gen.Blather]

“They also said at one point in time that eggs and shell fish were bad for heart patients...only to recant later...

In the meantime, many heart patients lost weight due to malnutrition....which was also considered good...”

Mark Twain says about Huckleberry Finn’s aunt that she read every magazine about health, ignoring that the following issue reversed the findings of the one she just read. I noticed in reading study after study that sometimes they’re based on one or two observations. Whatever happened to double blind studies and peer review?

[HangnJudge]

However...
Not having carnitine can be a very bad thing

The carnitines exert a substantial antioxidant action, thereby providing a protective effect against lipid peroxidation of phospholipid membranes and against oxidative stress induced at the myocardial and endothelial cell level

Carnitine is primarily used for heart-related conditions. Several clinical trials show that L-carnitine and propionyl-L-carnitine can be used along with conventional treatment for angina to reduce medication needs and improve the ability of those with angina to exercise without chest pain

it is required for the transport of fatty acids from the cytosol into the mitochondria during the breakdown of lipids (fats) for the generation of metabolic energy.

[who_would_fardels_bear]

That settles it.

I'm now marinating my steaks in energy drinks before grilling them up!

[NoGrayZone]

Here's an idea. Why don't they stop feeding the cows crap, antibiotics and growth hormones and dead cows?

How about we let them live and eat in their natural environment?

“These” people keep messing with our food sources, then turn around and blame the food.

They keep saying “there is an obesity problem”. Perhaps it has to do with all the growth hormones they inject our food supply with, let alone all the thing we don't know about. All these hormones being injected into our food supply could very well explain the "gender confusion" that seems so rampant these days.

[GraceG]

The solution is not to stop eating red meat or energy drinks.

But to fix the gut bacteria so they don’t do this bad thing.

I have to wonder is some cultures fare better with heart ddisease because they have different gut flora.

[Uncle Miltie]

We have chickens, so I eat a ton of eggs. Can you show me the research that says eggs are not bad for your cholesterol, please?

[elcid1970]

Steak Tartare shall never die........

[WVKayaker]

I have to wonder is some cultures fare better with heart ddisease because they have different gut flora.

I had a friend, a heart surgeon, who explained to me how I should live. He told me to enjoy my life. He also informed me of many studies of the diet and lifestyles in France and Italy, where heart disease is not the big problem.

Though high in fats, sugars and other SUPPOSEDLY/ALLEGEDLY bad-for-you foods, they also drink lots of red wine. He told me to drink red wine every day. I do.

I have twin brothers who are 3 years older. They both have had multiple heart attacks, and one is having liver problems from excessive alcohol use. He can kill a bottle of Jim Beam in a night.

I buy cheap boxes of Merlots and Cabs. I usually have a glass or two every evening. I'm 65, and God-willing, should follow many of my predecessors to be 100 or thereabouts when I die (unless I get run over by a Mack truck first!). I have moderately high BP, have not had any heart conditions, and enjoy eating a good steak, ENC-style PORK BBQ, and must finish that one with a good banana pudding or slice of pecan pie!

I am now living in the Philippines, and have a difficult time finding good beef, but pork and seafood here are fresh and most excellent. I may import some cows and let some of my new family members here on Leyte make me a fortune!

[aft_lizard]

You like paying $15 a pound for ground beef and 30 for steaks? Thats what we would pay if followed your plan.

[muir_redwoods]

Any L-carnitine to be found in cheesecake, Stilton or ice cream?

[freekitty]

Makes you think why don’t these fools make up their minds?

[JoeProBono]

[dfwgator]

“I’m the enemy because I like to think. I like to read. I’m into freedom of speech and freedom of choice. I’m the kind of guy that could sit in a greasy spoon and wonder, gee, should I have the T-bone steak or the jumbo rack of barbecue ribs or the side order of gravy fries? I want high cholesterol. I would eat bacon and butter and buckets of cheese. Okay? I want to smoke Cuban cigars the size of Cincinnati in the nonsmoking section. I want to run through the streets naked with green Jell-O all over my body reading Playboy magazine. Why? Because I might suddenly feel the need to. Okay, pal?” - Dennis Leary Demolition Man

[JoeProBono]

Why? Because I suddenly might feel the need to, okay, pal? I’ve SEEN the future. Do you know what it is? It’s a 47-year-old virgin sitting around in his beige pajamas, drinking a banana-broccoli shake, singing “I’m an Oscar Meyer Wiener”.

[dfwgator]

Best rant, ever.

[neverdem]

It appears that diet, gut microbes and the immune system are involved atherosclerosis which is at the root of coronary artery disease, CAD, also called coronary heart disease, CHD, cerebrovascular disease, CVD, i.e. strokes, and peripheral vascular disease, PVD.

Red meat also appears to increase the risk of colorectal cancer.

Red meat + wrong bacteria = bad news for hearts - Microbes turn nutrient in beef into an artery-clogging menace.

New culprit for red meat health risks

Gut flora metabolism of phosphatidylcholine promotes cardiovascular disease FReebie

"We next examined the impact of dietary choline and gut flora on endogenous formation of cholesterol-laden macrophage foam cells, one of the earliest cellular hallmarks of the atherosclerotic process."

Those cells are often called foamy macrophages or just foam cells. Macrophages are part of the innate immune system.

"The human intestinal microbial community is an enormous and diverse ecosystem with known functions in nutrition, gut epithelial cell health, and innate immunity31. Intestinal flora also has recently been implicated in development of some metabolic phenotypes such as obesity and insulin resistance, as well as alterations in immune responses 11,32–34."

They didn't really describe the gut microbes, just how they wiped them out: "An antibiotic cocktail (0.5 g/L vancomycin, 1 g/L neomycin sulfate, 1 g/L metronidazole, 1 g/L ampicillin) previously shown to be sufficient to deplete all detectable commensal bacteria37 was administered in drinking water ad lib."

[BfloGuy]

Whatever happened to double blind studies and peer review?

I think they still exist, but they don't make good Facebook comments.

[Wonder Warthog]

"I have to wonder is some cultures fare better with heart ddisease because they have different gut flora."

The effect on different mixes of GI flora on many areas of health is a hot topic right now. It affects many things, including weight gain or loss. One theory says that the reason heart disease "runs in families" isn't genetics, but that family members have similar gut flora mixes.