Zhang Xianglan, associate professor of medicine at Vanderbilt University Medical Center, and colleagues reviewed a study on urine composition and heart health in Chinese middle-aged and elderly volunteers in Shanghai. The researchers compared the levels of soy isoflavones in the urine of 377 patients with coronary heart disease and 753 patients with non-coronary heart disease.
Previous research on soybean and heart health relied heavily on questionnaires asking volunteers to answer the frequency and number of soy consumed. Vanderbilt University researchers believe that, in contrast, urine isoflavone levels more accurately reflect soybean intake. Soybean intake here refers to soybeans ingested from foods such as tofu, soy milk, and green beans, excluding dietary supplements.
The researchers did not find a correlation between the overall level of urinary isoflavones and coronary heart disease, but when they studied the metabolites of equol, a soybean isoflavone, the female volunteers with the highest equol levels were found to have coronary heart disease. The odds are 54% lower than women with the lowest levels of equol in the urine.
The American Fun Science website quoted Zhang Xianglan as saying: “Our results show that high levels of equol in urine are associated with a low risk of coronary heart disease in female volunteers.”
In a paper published in the latest issue of the International Journal of Epidemiology, the researchers wrote that it was the first time that equol was associated with the incidence of coronary heart disease in women.