meat, which in turn elevates a compound called
trimethylamine-N-oxide, or TMAO.^5 TMAO is thought to
contribute to atherosclerosis, the disease process that leads
to plaque-ridden arteries. The ensuing fear was that meat,
independent of its saturated fat or any of the other health
claims previously waged against it, might now promote
heart disease via an entirely new mechanism—microbial
fermentation.
Closer inspection into the research reveals a few
important details. First, the mice were fed very high doses of
supplemental carnitine. This caused a shift in the
microbiome and gave these TMAO-producing bacteria a
competitive edge in the large intestine. Second, low-grain
vegan and vegetarian diets appear to select against carnitine-
loving gut flora, a fact highlighted by microbiome
researcher Jeff Leach.^6 In the human arm of the study,
researchers were able to convince a vegan to consume an
eight-ounce steak to see what it would do to her TMAO
levels, and they didn’t budge. Though a small “n of 1”
experiment, the results suggest that to a certain point, the
overall composition of the microbiome is more important
than the individual food being consumed. A reasonable
takeaway? Don’t give meat a TMAO-out—just eat mostly
vegetables and skip the grains.
Forced to adopt the modern diet, the host-microbe
relationship can become strained. As I mentioned, they only
really like to consume one thing—fiber. Specifically, a form