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TMAO and Heart Disease

by Simon Bridge
Tags: disease, heart, tmao
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Simon Bridge
#1
Apr8-13, 11:33 PM
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Come to my attention vie the NYT article:
Culprit in Heart Disease Goes Beyond Meatís Fat
... The researchers had come to believe that what damaged hearts was not just the thick edge of fat on steaks, or the delectable marbling of their tender interiors. In fact, these scientists suspected that saturated fat and cholesterol made only a minor contribution to the increased amount of heart disease seen in red-meat eaters. The real culprit, they proposed, was a little-studied chemical that is burped out by bacteria in the intestines after people eat red meat. It is quickly converted by the liver into yet another little-studied chemical called TMAO that gets into the blood and increases the risk of heart disease.

The paper seems to be:
Koeth R. A., Wang Z. et al. Intestinal microbiota metabolism of L-carnitine, a nutrient in red meat, promotes atherosclerosis Nature Medicine (2013) doi:10.1038/nm.3145

So it appears we should be adopting a vegan diet or take antibiotics with our steak?
My reading of what I can follow is that everything is very iffy still... the researchers have proposed another mechanism that may link red meat to heart disease that differs from the previously supposed mechanism.

Presumably not eating red meat also has um side effects?

What is this really all about? Is the science reporting over-hyped again?
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Evo
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Apr9-13, 12:04 AM
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Quote Quote by Simon Bridge View Post
Come to my attention vie the NYT article:
Culprit in Heart Disease Goes Beyond Meatís Fat
... The researchers had come to believe that what damaged hearts was not just the thick edge of fat on steaks, or the delectable marbling of their tender interiors. In fact, these scientists suspected that saturated fat and cholesterol made only a minor contribution to the increased amount of heart disease seen in red-meat eaters. The real culprit, they proposed, was a little-studied chemical that is burped out by bacteria in the intestines after people eat red meat. It is quickly converted by the liver into yet another little-studied chemical called TMAO that gets into the blood and increases the risk of heart disease.

The paper seems to be:
Koeth R. A., Wang Z. et al. Intestinal microbiota metabolism of L-carnitine, a nutrient in red meat, promotes atherosclerosis Nature Medicine (2013) doi:10.1038/nm.3145

So it appears we should be adopting a vegan diet or take antibiotics with our steak?
My reading of what I can follow is that everything is very iffy still... the researchers have proposed another mechanism that may link red meat to heart disease that differs from the previously supposed mechanism.

Presumably not eating red meat also has um side effects?

What is this really all about? Is the science reporting over-hyped again?
I just read (a month ago) a study that red meat is not harmful because stearic acid isn't bad for you. It's the same type of spin they use for coconut oil, even though it's a highly saturated fat it has a dab of good fat. Now does that mean that dab of good fat makes it healthy? No! But marketers want you to think it does.

You really have to look long and hard at what the studies are saying. If something is 90% bad, 10% of something good in it does not make it healthy. It seems every new study contradicts the last. Maybe this is a new career opportunity, interpreting what nutrition studies really mean.
zoobyshoe
#3
Apr11-13, 01:43 PM
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Quote Quote by Simon Bridge View Post
Presumably not eating red meat also has um side effects?
This is anecdotal, but I went without eating any kind of meat for ten years and did not notice any difference of any kind except a tendency toward less body fat.

The only risk I know of is that, if you don't make up for it from other sources, your iron levels may become too low and you'll become anemic.

http://www.irondisorders.org/iron-deficiency-anemia

Simon Bridge
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Apr11-13, 09:04 PM
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TMAO and Heart Disease

I've heard there are long term effects - iron deficiency being one, and vitamin B12 deficiency being another, with women being more susceptible than men. I've also heard that humans don't make taurine so well either so we need small amounts in our diet.

The article compares red meat eaters with those on a vegan diet.

What I'm mostly interested in is what the actual science is behind the article.
It seems that every day someone is telling me that some common food is terrible in some way and backing it with some luck-warm science that managed to get published someplace that doesn't really say so much.
Evo
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Apr11-13, 09:28 PM
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I know what you mean Simon. It seems that contradictory reports come out monthly. Sometimes I notice that the outcome comes out in favor of the source doing the funding.
Simon Bridge
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Apr11-13, 09:39 PM
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Or in favor of some pet fad or something on the part of the researchers ... the comparison to veganism raised an alarm bell on this one for that reason: why pick vegan diet? Why not some other vegetarian diet? What about finding people who only eat white meat?

"maybe a targeted antibiotic" though, suggests the researcher is fishing for funding.

Most of the studies seem to be surveys ... people keeping track of their diet and stuff like that.
Many are qualitative at heart - at least this one measures something.

The actual research appears to just notice that people who are used to eating meat produce more of substance X than people who are not ... and this is of interest because other studies show a corellation between substance X and heart disease in rats.

This is supposed to support a conclusion that substance X is the main cause of heart disease in humans.
I don't think the evidence presented is good support for the conclusion ... but it is the press that is emphasizing the conclusion isn't it?

But it is well outside my field so I may be reading it wrong.
jim hardy
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Apr11-13, 11:35 PM
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back around 1980 I read this book
http://www.amazon.com/Type-A-Behavio.../dp/0394480112


and saw myself .

In 1995 at age 48 I went to ER with a heart attack. Flatlined for the ER folks but they got me going again. As they wheeled me out of ER one of the medics asked: "You're not overweight, you don't smoke and don't drink, you are cracking jokes and seem lighthearted - why are you here?
I responded quite honestly "I'm a closet type A". They immediately burst into unanimous agreement "That'll do it"...
A couple days later they ran the angiogram scans. My three arteries were 70, 90, and 100% blocked.
My co-workers were amazed - I was known as the "health nut" who ate salads for lunch.

Those two surgeons who wrote that book are on to something.
They say stress changes how we metabolize cholesterol.
It's not what you eat, it's what's eating you.
Something has to be pretty true to achieve platitude status.

So does this TMAO affect how we metabolize cholesterol?

http://en.wikipedia.org/wiki/Trimethylamine_N-oxide
TMAO alters cholesterol metabolism in the intestines, in the liver, and in artery wall. In the presence of TMAO, there is increased deposition of cholesterol in, and decreased removal of cholesterol from, peripheral cells such as those in the artery wall.[8] Vegans and vegetarians appear to have fewer gut bacteria that convert carnitine to TMAO.[9][10]
How about worry-warts ?

A quick search on 'TMAO stress' turned up some studies on heat stress in sharks but I don't understand them.
But I am interested so will keep an eye out for more.

Thanks for the alert, guys.
Simon Bridge
#8
Apr11-13, 11:55 PM
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It is well known that stress kills - stressing out about your diet will do it too.
IIRC the "type A - type B" personality type idea has been debunked but it remains a useful metaphor.

So what we are saying is that TMAO is a plausible main-contributor anyway?
That would be a serious buzz-kill for those "paleolithic diet" people then wouldn't it?


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