A small study published in 2005 in the Journal of the American College of Nutrition had 24 postmenopausal women eat approximately 390 grams of purple yams (Dioscorea alata) per day for 30 days. After the month was over, researchers found that the women’s hormones had increased, with estrone levels increasing by 26%, estradiol levels by 27%, and sex hormone binding globulin (SHBG) by 9.5%. All three were unchanged in the control.
Yam is one of a few plants containing diosgenin (others include fenugreek, allspice, soy, and bitter melon), a phytoestrogen, which scientists are studying for its hormone-like effects. In a lab diosgenin is synthesized to make horomone therapy.
Other Studies
Research published in 2007 in the Journal of Agricultural and Food Chemistry found that extracts from two varieties of yam triggered responses from estrogen receptors alpha and beta in vitro. The study concluded that naturally occurring compounds in purple yam may exert weak phytoestrogenic effects.
Similarly, a 2018 study on Chinese yam (Dioscorea opposita) found that extracts from the yam also triggered estrogen-related effects. In the study, researchers identified compounds known as adenosine and arbutin as two of the substances in the yam that may have caused this effect. There were interactions observed with ERα and ERβ as well as with GPR30. Researchers noted in the study that Chinese yam can be described as having “estrogen-like effects.”
A Study published in Scientific Reports in 2015 discovered that protein extracts taken from Dioscorea opposita promoted estrogen biosynthesis in ovarian cells harvested from rats.
Keep in mind that the women in the study were eating several hundred grams of yam every single day. That’s way more than your typical slice of ube cake or scoop of ube latte from Starbucks. There’s no concrete evidence that normal servings of ube will influence hormone levels in healthy people.