Phytoestrogens
Phytoestrogens are naturally occurring compounds found in various plants that mimic the effects of estrogen in the body. They are classified into three main categories: isoflavones, lignans, and coumestans. These compounds are primarily sourced from foods such as whole grains, seeds, legumes, vegetables, fruits, and certain herbs. Notably, soy products like tofu and soy milk are rich in isoflavones.
Phytoestrogens have been studied for their potential role in reducing the risk of hormone-related cancers, including breast, prostate, and ovarian cancers. They may help modulate hormonal levels and could enhance the effectiveness of certain cancer treatments like chemotherapy. While some research supports their protective effects, the findings are not universally conclusive, and more extensive studies are needed to fully understand their impact.
Consuming phytoestrogens through a balanced diet is generally considered safe, but caution is advised for individuals undergoing hormone therapies, as these compounds may interfere with treatment. The FDA does not regulate phytoestrogen supplements, and their safety remains unestablished. Overall, phytoestrogens present an intriguing area of study for their potential health benefits and impacts on hormone-related conditions.
On this Page
Subject Terms
Phytoestrogens
ALSO KNOWN AS: Soy isoflavones (genistein, daidzein, glycitein, formononetin), lignans (secoisolariciresinol, matairesinol, pinoresinol, lariciresinol), coumestans (coumestrol)
DEFINITION: Phytoestrogens are naturally occurring, estrogen-like chemicals found in many plants. There are three basic categories of phytoestrogens: isoflavones, lignans, and coumestans. They come primarily from food sources.
Cancers treated or prevented: May mitigate hormone-dependent cancers like breast, prostate, ovarian and uterine cancers
Delivery routes: Oral through diet, pill, or capsule
How these compounds work: Phytoestrogens have been touted as natural substances that may help prevent certain types of cancer, especially hormone-related cancers such as breast, prostate, and uterine cancer. Studies have also indicated they may be beneficial to ovarian cancer as well. Phytoestrogens may provide hormonal modulation, which naturally regulates hormones. Though not conclusive, some studies demonstrate that phytoestrogens may also provide some protection against lung and colon cancers.
Phytoestrogens can be absorbed into the body chemistry either to act as estrogens at low levels or to block the estrogen effect at high levels. These substances can mimic a weak estrogen to stimulate or inhibit the growth of cells. Research has shown that increased exposure to certain hormones can increase the risk of cancer. Phytoestrogens appear to protect the body from hormones that can produce cancer. A 2020 review of studies by the National Institutes of Health appeared to confirm that soy's phytoestrogens reduced the risk of breast, ovarian, and prostate cancers. Further, phytoestrogens were not just beneficial in preventing cancer. When used alongside cancer treatments, such as chemotherapy, radiation, and hormone therapy, phytoestrogens appeared to increase the effectiveness of those treatments. More studies are needed to understand the relationship between cancer and phytoestrogens.
The best sources of phytoestrogens occur naturally in plants. Hundreds of foods contain phytoestrogens. The most common ones are whole grains such as oats, wheat, and corn; edible seeds such as flax and sesame; legumes such as lentils, soybeans, sprouts, black beans, and chickpeas; vegetables such as leafy greens, fennel, celery, asparagus, carrots, parsley, and seaweed; fruits such as oranges, bananas, and strawberries; olive, safflower, and pumpkin oils; nuts such as pistachios, chestnuts, and walnuts; and other sources such as garlic, onions, and red wine. Soy foods such as tofu (bean curd), soy milk, tempeh, and soy yogurt are well-known sources of isoflavone phytoestrogens. Certain herbs also contain phytoestrogens, such as red clover, green tea, hops, alfalfa, licorice, citrus peel, and flax seeds. Herbal teas are considered a longevity tonic, and red wine contains resveratrol, a phytoestrogen that may inhibit cancer cell growth. Beer and coffee, in moderation, may also be beneficial.
Phytoestrogens are also marketed in pill and capsule form as food supplements. The US Food and Drug Administration (FDA) does not regulate food supplements for safety and effectiveness; these supplements are not recommended, as their safety has not been established and could increase the incidence of cancer.
Phytoestrogens consumed in food are generally considered safe when taken in moderate amounts. Though some research studies have shown that phytoestrogens may protect against cancer, others dispute this effect. More double-blind studies are needed to fully assess the impact of specific phytoestrogens on the body chemistry.
Side effects: Patients taking hormone therapies for cancer, such as tamoxifen or other antiestrogenic drugs, should seek the advice of their healthcare providers before taking supplementation of phytoestrogens, as some studies suggest that these phytonutrients may interfere with drug therapy.
Bibliography
Bacciottini, Lucia, et al. "Phytoestrogens: Food or Drug?" Clinical Cases in Mineral and Bone Metabolism, vol. 4, no. 2, 2007, pp. 123-130, www.ncbi.nlm.nih.gov/pmc/articles/PMC2781234/. Accessed 25 June 2024.
Heber, David, et al., editors. Nutritional Oncology. Burlington: Elsevier, 2006.
Krishna, Devarakonda R., and Masuram Somashekhar. "Pharmacokinetics of Phytoestrogens." Phytoestrogens in Functional Foods. Edited by Fatih Yildiz. Boca Raton: CRC, 2006, pp. 99–122.
Marengo, Katherine, and Amy Richter. “Phytoestrogens: Benefits, Risks, and Food List.” MedicalNewsToday, 20 May 2024, www.medicalnewstoday.com/articles/320630. Accessed 25 June 2024.
“Prostate Cancer, Nutrition, and Dietary Supplements (PDQ®).” National Cancer Institute, 5 Apr. 2024, www.cancer.gov/about-cancer/treatment/cam/hp/prostate-supplements-pdq. Accessed 25 June 2024.
Simon, Stacy. “Soy and Cancer Risk: Our Expert's Advice.” American Cancer Society, 29 Apr. 2019, www.cancer.org/cancer/latest-news/soy-and-cancer-risk-our-experts-advice.html. Accessed 25 June 2024.
Torrens-Mas, Margalida, and Pilar Roca. "Phytoestrogens for Cancer Prevention and Treatment." Biology, vol. 9, no. 12, 2020, doi.org/10.3390/biology9120427. Accessed 25 June 2024.
Wan-Shui Yang, et al. "Soy Intake Is Associated with Lower Lung Cancer Risk: Results from a Meta-Analysis of Epidemiologic Studies." American Journal of Clinical Nutrition, vol. 94.6, 2011, pp. 1575–83.