Thursday, December 13, 2018


A recent press release reported on a link between high blood levels of a compound called TMAO (trimethylamine N-oxide) and heart disease. Then they said high TMAO levels are linked to a diet rich in red meat, and such people have TMAO levels three times as high as those who eat mostly white meat or no meat.

The authors defined "rich in red meat" as about 8 ounces of steak daily.

Horrors! Sounds as if we should all avoid red meat and try to lower TMAO levels.

But wait! Another recent press release says we should all eat more vegetables and fish because these foods increase our TMAO levels, and "low-dose treatment with TMAO reduced heart thickening (cardiac fibrosis) and markers of heart failure in an animal model of hypertension."

The authors of the second study write, "It was previously thought that TMAO blood plasma levels--and heart disease risk--rise after the consumption of red meat and eggs. However, "it seems that a fish-rich and vegetarian diet, which is beneficial or at least neutral for cardiovascular risk, is associated with a significantly higher plasma TMAO than red meat- and egg-rich diets, which are considered to increase the cardiovascular risk."

Is it any wonder that people are confused about which diet is best to follow in order to reduce the risk of heart disease?

The effects of diets are complex. For one thing, different people may react differently to the same thing, and rodents may also react in a different way. For another, it's not usually just one component of a diet that is important; it's the diet as a whole. A red-meat and chocolate cake diet is different from a red-meat, vegetable, and salad diet. A 16-ounce steak has a different effect from 4 ounces of steak.

And TMAO could have a U-shaped effect so that small increases were beneficial but large increases were not, or vice versa.

Rat experiments don't always translate into effects on humans, but they're suggestive. Also, the second study was done in an animal model of hypertension.

Today, certain memes are popular, including "eat more fruits and vegetables" and "avoid red meat." But most fruits raise blood glucose levels in people with diabetes, and also to some degree in those without the disease. Sometimes it seems as if research is designed to prove these memes rather than to learn something new. It's easier to get research grant money if you are supporting the current dogma. Not long ago, that was low-fat, and people who didn't support that concept had trouble getting research grants. The South African scientist Tim Noakes, was accused of "unprofessional conduct" for advising a mother to wean her infant onto a low-carbohydrate diet. He was eventually found not guilty of any wrongdoing.

So we don't yet know if TMAO is beneficial or detrimental. As most research papers say, "More research is needed."

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