Paleo 101: How and why you should eat like a Caveman

Carnitine, a compound found in red meats, appeared to be cardioprotective in a systematic review -- a finding that comes barely a week after a Nature Medicine study sounded an alarm about the heart risks of carnitine.

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There are some flaws in Koeth et al.'s hypothesis. They hypothesize that red meat increases heart disease risk because it is high in carnitine, a TMA-containing compound. But, they overlook the fact that many foods have TMA-containing compounds. As they cited in their first paper, choline and betaine contain TMA and are converted to TMAO in mice causing formation of atherosclerosis. Per 100 grams, a steak contains about 95 mg of TMA-containing carnitine. The same amount of Wheaties cereal contains 200 mg of TMA-containing betaine plus 33 mg of TMA-containing choline. Kellogg's All-Bran contains a whopping 360 mg of betaine plus 49 mg choline. Beets contain 260 mg of betaine. Spinach has 120 mg of betaine. If the researchers hypothesis is correct, all of these TMA-containing compounds should increase risk of developing heart disease. A bowl of All-Bran cereal would be of much greater concern than a steak when it comes to risk of heart disease because the bowl of Wheaties contains more TMA-containing compounds.

The researchers showed in their initial paper that mice fed diets supplemented with free betaine or free choline produced more TMAO and developed more atherosclerotic lesions than mice on a normal diet. In the second paper, they showed the same result for mice fed free carnitine. The problem is the amounts of free betaine, choline, and carnitine fed to the mice were much greater than any human could reasonably consume. The dose of choline was 50-100 times the recommended daily amount. The dose of betaine was about 500 times the average human intake. For carnitine, a human would have to eat 5.3 pounds of steak per day to equal the amounts fed to the mice. I suggest that most compounds, when fed in great excess of physiologically relevant amounts, will produce negative health effects.

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aychamo_aycono_sl said:

It's definitely interesting, but I think you're missing the big picture. Can you figure out what that is?

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There is growing interest in the need to improve reliability in science. Many drugs show promise at the design and pre-clinical phases, only to fail (at great expense) in clinical trials. Many of the most hyped scientific discoveries eventually cannot be replicated.

Worryingly for science (but somewhat comforting for my self-esteem as a researcher) this may be because many of the conclusions drawn from published research findings are false.

A major factor that influences the reliability of science is statistical power. We cannot measure everyone or everything, so we take samples and use statistical inference to determine the probability that the results we observe in our sample reflect some underlying scientific truth. Statistical power determines whether we accurately conclude if there is an effect or not.

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