A higher consumption of phytoestrogens — plant-derived estrogens found in soy and other foods that are similar to the female hormone estrogen — is associated with a reduced risk of endometriosis, an Iranian case-control study suggests.
However, due to the important role of hormones on endometriosis development and progression, these results need to be confirmed in future studies.
The study, titled “Dietary Phytoestrogen Intake and The Risk of Endometriosis in Iranian Women: A Case-Control Study,” was published in the International Journal of Fertility & Sterility.
Phytoestrogens are naturally-occurring plant compounds that share a similar chemical structure and function to the estrogens found in the human body. Foods rich in phytoestrogens include soy, fruits, vegetables, spinach, sprouts, beans, cabbages, and grains.
The effect of diet on hormonal activity, inflammatory markers, and the immune system means that the food choices women make might play a key role in the development of endometriosis. Further, endometriosis has been shown to be related to prolonged exposure to the hormone estrogen in the absence of progesterone.
The main classes of phytoestrogens include isoflavones, coumestans, lignans, and flavonoids. Isoflavones, produced almost exclusively by the members of the bean family, are found in soy. Coumestans may have anticancer effects, while lignans have antitumor and antioxidant effects in mammals. Flavonoids, which also have antioxidant effects, are plant pigments that help give fruits and vegetables their color.
In women with endometriosis, phytoestrogens have an anti-estrogenic effect, meaning they can counter the activity of estrogen. Lignan and isoflavones can be converted in the gut into hormone-like structures.
By binding to estrogen receptors, phytoestrogens can stimulate the production of sex hormone-binding globulin, reducing the ability of the natural free estrogen to interact with estrogen receptors. Further, phytoestrogens can reduce inflammation through many mechanisms, including decreasing the production of inflammatory molecules.
In this study, the researchers assessed the link between phytoestrogen intake and endometriosis risk. The team studied 78 women with endometriosis and 78 with a normal pelvis (control group), all infertile, recruited at the Arash Hospital, in Tehran, Iran. The two groups were matched for multiple parameters, including age, body mass index (BMI), education, marital status, occupation, and income.
The participants’ diets were recorded using a 147-item validated food frequency questionnaire, between May 2016 and February 2017. The type of phytoestrogen in each dietary item was then analyzed using data from the U.S. Department of Agriculture.
The results showed that a higher intake of phytoestrogens was associated with a reduced risk of endometriosis. A greater intake of total isoflavones — specifically the sub-groups formononetin and glycitein — was associated with a decreased endometriosis risk, as was an increased intake of coumestrol. Similar results were found with a higher intake of lignan, specifically the sub-groups secoisolariciresinol, lariciresinol, and matairesinol.
Among food groups, only isoflavin, lignan, coumestrol, and phytoestrogen in dairy products, and coumestral in fruits were related to a reduced endometriosis risk.
“The phytoestrogen content in diet is dependent on environmental and genetic factors for example variety, harvest, food processing, cooking and growth locations,” the researchers noted. “Up to now, Iranian dietary phytoestrogen has not been measured.”
The researchers said that the results, overall, suggest that the impact of phytoestrogens on the level of hormones, and immune and inflammatory markers, is likely to “play an important role in the control and prevention of many diseases.”
“Due to the inflammatory nature of endometriosis and the effect of hormones on the progression of the disease, the role of phytoestrogens consumption in the progression and regression of the disease should be assessed in future works,” they concluded.