First red meat was bad because of cholesterol.
Then it was saturated fat.
When that evidence fell apart, red meat haters found a new reason not to eat it: TMAO.
Trimethylamine N-oxide, or TMAO, is a compound that has been
associated with a higher risk of heart disease. (Note the emphasis on “associated.” No research has yet proven that TMAO
causes heart disease.)
Here’s a typical explanation for how TMAO in red meat contributes to heart disease, pulled from the Cleveland Clinic website:
Here’s how it works: When people ingest certain nutrients, such as choline (abundant in red meat, egg yolks, and dairy products) and L-carnitine (found in red meat as well as some energy drinks and supplements), the gut bacteria that break it down produce a compound called trimethylamine (TMA). The liver then converts TMA into the compound trimethylene N-oxide (TMAO).
The trouble with TMAO is that data show high levels contribute to a heightened risk for clot-related events such as heart attack and stroke—even after researchers take into account the presence of conventional risk factors and markers of inflammation that might skew the results.
There’s just one problem with this story.
Red meat and eggs are minuscule sources of TMAO in the diet. I wrote about this
several years ago. If you look at a chart of TMAO sources in the diet, red meat and eggs are barely even visible.
So what is the biggest dietary source of TMAO?
Seafood!
And countless studies show that seafood consumption is inversely associated with heart disease. In other words, those that eat the
greatest amount of seafood have the
lowest levels of heart disease.
How could this be if TMAO is bad for our heart?
That’s a question none of the advocates of the red meat–TMAO hypothesis have answered.
A
new study just published adds even more doubt to the TMAO hypothesis. Researchers found that
high levels of TMAO may
reduce hypertension-related heart disease symptoms.
Yes, you read that correctly.
And check out this gem, from the
Science Daily article summarizing the paper:
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.”
Here’s what we can take away from this:
- Red meat and eggs won’t increase your TMAO levels—but seafood will!
- TMAO may be good for you.
This should be a cautionary tale for putting too much weight on mechanistic studies and on agenda-driven science that sets out with a goal (to prove red meat is bad).
In health,
Chris
Chris Kresser <info@chriskresser.com> |
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Dec 27, 2018 |
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