“Scientists have known for some time that isoflavones protect
against the buildup of plaque in arteries, known as atherosclerosis, in
monkeys, and are associated with lower rates of heart disease in people
in Asian countries,” said senior author Akira Sekikawa, M.D., Ph.D., an
associate professor of epidemiology
at Pitt Public Health. “We were surprised when a large trial of
isoflavones in the U.S. didn’t show the beneficial effects among people
with atherosclerosis in Western countries. Now, we think we know why.”
All monkeys can produce equol, as can 50 to 60 percent of people in
Asian countries. However, only 20 to 30 percent of people in Western
countries can.
Sekikawa and his colleagues, who include scientists in Japan,
recruited 272 Japanese men aged 40 to 49 and performed blood tests to
find out if they were producing equol. After adjusting for other heart disease
risk factors such as high blood pressure, cholesterol, smoking and
obesity, the team found that the equol-producers had 90-percent lower
odds of coronary artery calcification, a predictor of heart disease,
than the equol non-producers.
The daily intake of dietary isoflavones—found in traditional soy
foods such as tofu, miso and soymilk—is 25 to 50 milligrams in China and
Japan, while it is less than 2 milligrams in Western countries. Equol
is available as a supplement—bypassing the need for gut bacteria to
produce it—though no clinical trials have been performed to determine a
safe dosage for heart protective effects, or if it even does provide
such protection.
“I do not recommend that people start taking equol to improve their
heart health or for any other reason unless advised by their doctor,”
said Sekikawa. “Much more study is needed.”
Sekikawa and his team are pursuing funding for a much larger
observational study to expand on their findings and eventually a
randomized clinical trial to examine the effect of taking equol on
various medical conditions and diseases.
“Our discovery about equol may have applications far beyond heart
disease,” said Sekikawa. “We know that isoflavones may be associated
with protecting against many other medical conditions, including
osteoporosis, dementia, menopausal hot flashes, and prostate and breast
cancers. Equol may have an even stronger effect on these diseases.”
Additional authors on this research include lead author Vasudha
Ahuja, Ph.D., of Pitt Public Health; and co-authors Katsuyuki Miura,
M.D., Ph.D., Akira Fujiyoshi, M.D., Ph.D., Maryam Zaid, Ph.D., Naoko
Miyagawa, M.D., Ph.D., Aya Kadota, M.D., Ph.D., and Hirotsuga Ueshima,
M.D., Ph.D., all of Shiga University of Medical Science in Japan;
Abhishek Vishnu, M.D., Ph.D., and Rhobert Evans, Ph.D., both of Pitt
Public Health; Takashi Hisamatsu, M.D., Ph.D., of Shiga University of
Medical Science and Shimane University in Japan; and Tomonori Okamura,
M.D., Ph.D., of Keio University in Japan.
This research was funded by National Institutes of Health grant R01 HL68200, Japanese Ministry of Education, Culture, Sports, Science and Technology grants B16790335 and A13307016, and a small grant from Pitt Public Health’s Department of Epidemiology.