Yet Another Reason to Eat More Vegetables (And Fish)

By Jane Farrell

A naturally occurring compound could be a new weapon in the fight against heart disease and hypertension.

Researchers working with an animal model found that elevated levels of the compound, trimethylamine N-oxide (TMAO), may reduce hypertension-related heart disease symptoms. Treatment with TMAO also reduced heart thickening (cardiac fibrosis) and markers of heart failure in in the animal model of hypertension.

The study, from researchers at the Medical University of Warsaw and the Polish Academy of Sciences, was published in the American Journal of Physiology–Heart and Circulatory Physiology.

TMAO levels in the blood significantly increase after eating TMAO-rich food such as fish and vegetables. Additionally, the liver produces TMAO from trimethylamine (TMA), a substance made by gut bacteria. But the compound’s effects on the heart and circulatory system are unclear, and earlier research has been contradictory.

This newest study may help clarify the issue. The researchers studied the effect of TMAO on rats that have a genetic tendency to develop high blood pressure (spontaneously hypertensive rats). One group of hypertensive rats was given low-dose TMAO supplements in their drinking water, and another group received plain water. They were compared to a control group of rats that does not have the same genetic predisposition and received plain water. The dosage of TMAO was designed to increase blood TMAO levels approximately four times higher than what the body normally produces. The rats were given TMAO therapy for either 12 weeks or 56 weeks and were assessed for heart and kidney damage and high blood pressure.

The study could underscore the heart-healthy benefits of following a Mediterranean-style diet.

TMAO treatment did not affect the development of high blood pressure in any of the spontaneously hypertensive rats. However, condition of the animals given the compound was better than expected, even after more than a year of low-dose TMAO treatment. “A new finding of our study is that [a] four- to five-fold increase in plasma TMAO does not exert negative effects on the circulatory system. In contrast, a low-dose TMAO treatment is associated with reduced cardiac fibrosis and [markers of] failing heart in spontaneously hypertensive rats,” the researchers wrote.

“Our study provides new evidence for a potential beneficial effect of a moderate increase in plasma TMAO on [a] pressure-overloaded heart,” the research team wrote. The investigators acknowledged that further study is needed to assess the effect of TMAO and TMA on the circulatory system. But an indirect conclusion from the study could underscore the heart-healthy benefits of following a Mediterranean-style diet rich in fish and vegetables.