Another problem for red meat...  

While the recent salami-cancer link has been disputed, new evidence of another culprit is striking even skeptics of the red-meat-cancer linkage.

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.

That, at least, was the theory. So the question that morning was: Would a burst of TMAO show up in people’s blood after they ate steak? And would the same thing happen to a vegan who had not eaten meat for at least a year and who consumed the same meal?

The answers were: yes, there was a TMAO burst in the five meat eaters; and no, the vegan did not have it. And TMAO levels turned out to predict heart attack risk in humans, the researchers found. The researchers also found that TMAO actually caused heart disease in mice. Additional studies with 23 vegetarians and vegans and 51 meat eaters showed that meat eaters normally had more TMAO in their blood and that they, unlike those who spurned meat, readily made TMAO after swallowing pills with carnitine. [More]

This mechanism stikes me as plausible as well. Since Jan has been shifting us to less beef and pork for years, it won't require a major change in our diets. (It doesn't hurt I've become fond of dry white wines either, I suppose.)  Mild adjustments are my kind of lifestyle changes.

I'm not alone.

Well, today I got a big challenge to that theory. Scientists have isolated what looks like a plausible mechanism by which red meat damages your heart: the gut bacteria of frequent meat eaters process carnitine, a chemical found in red meat, into something called TMAO. And TMAO is associated with a higher risk of heart attacks.  

Interestingly, this only happened to frequent meat eaters; vegans who ate a steak did not show elevated blood-levels of TMAO. Over time, their gut bacteria had changed, so they no longer had lots of bacteria that like to eat carnitine.  

I tend to discount dietary fads, but the association between red meat and heart disease is sufficiently long-standing that I'm trying to cut back to once a week. If we see more studies like this, I may cut back even further.
Of course, as many of you will no doubt point out in the comments, it's impossible to be sure. New studies could overthrow these results any time.  
But that's always a problem in this uncertain world. In this case, my best guess is that red meat probably promotes heart disease (which anyway runs in my family). And the cost of eating more poultry and fish and less steak seems relatively small. Much smaller than dying of a heart attack in my sixties. [More from a food-fad skeptic]

This furthers my guess that beef consumption will continue to decline in the US as it climbs elsewhere (areas where folks are "under-beefed). Yet another segment of agriculture with a growing steak (hee-hee) in freer trade.