Monday, April 8, 2013

Here We Go Again: Another Meat Kills! Study - Naughton

Here We Go Again: Another Meat Kills! Study

Posted by Tom Naughton

You’ve got to give the anti-meat hysterics credit for their creativity. Since they can’t prove directly that eating meat will kill you, they’ve become quite adept at stringing unrelated results together into what (almost) looks like a chain of causality.

As I explained in my Big Fat Fiasco speech, this technique is referred to as teleoanalysis. In a nutshell, it works like this: we can’t prove that A causes C, but if we can find evidence that A is linked to B and B is linked to C, we’ll go ahead and declare that A causes C.

Teleoanalysis is partly what has kept the Lipid Hypothesis alive. Studies have failed over and over to prove that a high-fat diet causes heart disease – and in fact, low-fat diets have failed to reduce heart disease in clinical trials over and over. So the anti-fat hysterics trotted out a version of teleoanalysis that looks like this:
  • High-fat diets (A) raise cholesterol (B)
  • Raised cholesterol (B) is associated with heart disease (C)
  • Therefore, a high-fat diet must cause heart disease
If this sounds logical to you, consider my own favorite version of teleoanalysis:
  • Drinking lots of water (A) causes frequent urination (B)
  • Frequent urination (B) is associated with diabetes (C)
  • Therefore, drinking lots of water causes diabetes
With that in mind, let’s take a look at yet another Meat Kills! study that’s making a splash in the media. Here are some quotes from a BBC article online:

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.

Can you spot the teleoanalysis? Here it is:
  • Red meat (A) contains carnitine, which when digested kicks off a chain of events leading to higher cholesterol (B)
  • Higher cholesterol (B) is associated with heart disease (C)
  • Therefore, red meat causes heart disease
Here’s the abstract for the study referenced in the BBC article:

Intestinal microbiota metabolism of choline and phosphatidylcholine produces trimethylamine (TMA), which is further metabolized to a proatherogenic species, trimethylamine-N-oxide (TMAO). We demonstrate here that metabolism by intestinal microbiota of dietary l-carnitine, a trimethylamine abundant in red meat, also produces TMAO and accelerates atherosclerosis in mice. Omnivorous human subjects produced more TMAO than did vegans or vegetarians following ingestion of l-carnitine through a microbiota-dependent mechanism. The presence of specific bacterial taxa in human feces was associated with both plasma TMAO concentration and dietary status. Plasma l-carnitine levels in subjects undergoing cardiac evaluation (n = 2,595) predicted increased risks for both prevalent cardiovascular disease (CVD) and incident major adverse cardiac events (myocardial infarction, stroke or death), but only among subjects with concurrently high TMAO levels. Chronic dietary l-carnitine supplementation in mice altered cecal microbial composition, markedly enhanced synthesis of TMA and TMAO, and increased atherosclerosis, but this did not occur if intestinal microbiota was concurrently suppressed. In mice with an intact intestinal microbiota, dietary supplementation with TMAO or either carnitine or choline reduced in vivo reverse cholesterol transport. Intestinal microbiota may thus contribute to the well-established link between high levels of red meat consumption and CVD risk.

Allow me to interpret that gobbledygook:

Humans who eat meat have more carnitine-eating bacteria in their guts and therefore produce more TMAO than vegetarians. TMAO is associated with heart disease. If we pump mice full of carnitine, they also produce lots of TMAO and get heart disease. So humans should cut back on meat.
More teleoanalysis. It’s just another version of this argument, which helped to establish the Lipid Hypothesis: lard raises cholesterol, and rabbits get both high cholesterol and heart disease if they’re force-fed lard, so humans shouldn’t eat lard.

The only problem is that lard consumption was plummeting while heart-disease rates were skyrocketing.

The abstract also mentions the “well-established link” between meat consumption and heart disease. Since vegetarians are often more health-conscious in general and therefore less likely to consume sodas, donuts, candy and other junk, I’d expect them to have lower rates of heart disease than meat-eaters who consume the standard western (crap-filled) diet. But is that association consistent?
As I mentioned out in another post about yet another Meat Kills! study, here’s quote from a study titled Mortality In British Vegetarians:

The mortality of both the vegetarians and the nonvegetarians in this study is low compared with national rates. Within the study, mortality from circulatory diseases and all causes is not significantly different between vegetarians and meat eaters.

And here’s the conclusion from a study titled Dietary protein and risk of ischemic heart disease in women:

Our data do not support the hypothesis that a high protein intake increases the risk of ischemic heart disease. In contrast, our findings suggest that replacing carbohydrates with protein may be associated with a lower risk of ischemic heart disease.

In that study, the women who consumed the most protein ate 16.1% more red meat than women who consumed the least protein, but had lower rates of heart disease.

No consistency, no validity.

Enjoy your steak.
Read the complete article here.
Also read more here.

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