Phytoestrogens are a group of bioactive compounds found in various plant-based foods. They can be classified into different subclasses, including isoflavones, lignans, coumestans, and flavonoids. These compounds have a similar structure to the hormone estrogen and can bind to estrogen receptors in the body, thereby exerting estrogenic or antiestrogenic effects. The specific effects of phytoestrogens can vary depending on the type of compound and the receptor it interacts with.

Research suggests that phytoestrogens may act as selective estrogen receptor modulators (SERMs), [1] meaning they can selectively activate or down-regulate cellular responses depending on the tissue and receptor involved. For example, they may activate estrogen receptors in bone and cardiovascular tissue, promoting bone health and cardiovascular protection. On the other hand, they may down-regulate estrogen receptors in breast and uterine tissue, potentially reducing the risk of certain hormone-related cancers. [2]

Foods High In Phytoestrogens in the Diet

Phytoestrogens can be found in various foods, with some sources containing higher amounts than others. Here are some major dietary sources of phytoestrogens:

Soy, Edamame and Soy Products

Soybeans and edamame, which are green, immature soybeans, are well-known sources of phytoestrogens. These legumes are rich in isoflavones, a type of phytoestrogen that can produce estrogen-like activity in the body. Isoflavones may have varying effects on blood estrogen levels, potentially increasing or decreasing them. Research suggests that soy isoflavones may help reduce the frequency and severity of hot flashes in menopausal women. [3] Additionally, a diet rich in soy early in life may lower the risk of breast cancer. However, it's important to note that the protective effects of soy isoflavones seem to be more pronounced in Asian diets, where soy consumption is higher compared to Western diets.

Flaxseeds

Flaxseeds are small, golden or brown seeds that are rich in lignans, a type of phytoestrogen. They contain up to 800 times more lignans than other plant foods. Lignans have been associated with a decreased risk of breast cancer, particularly in postmenopausal women.[4]  Flaxseeds can be sprinkled on various dishes, added to baked goods, or blended into smoothies to incorporate them into your diet.

Sesame

Sesame seeds, often used in Asian cuisine for their nutty flavor and delicate crunch, are another potent source of phytoestrogens. These small seeds are rich in various nutrients and have been found to affect estrogen levels in postmenopausal women. A study showed that consuming 50 grams of sesame seed powder daily for 5 weeks increased estrogen activity and improved blood cholesterol levels. Including sesame seeds in your diet can be as simple as sprinkling them on salads, stir-fries, or roasted vegetables.

Legumes

Legumes, such as beans and lentils, are another good source of phytoestrogens. These plant-based proteins contain isoflavones, coumestans, and other phytoestrogenic compounds. Incorporating legumes into your meals can help increase your phytoestrogen intake while providing other essential nutrients. [5]

Whole Grains

Whole grains, including wheat, oats, barley, and rice, contain varying amounts of phytoestrogens. They are a healthy addition to your diet, providing fiber, vitamins, minerals, and other beneficial compounds. Choosing whole grain options over refined grains can help boost your phytoestrogen consumption. [6] 

Fruits and Vegetables

Certain fruits and vegetables also contain phytoestrogens, although in lower amounts compared to soy and flaxseeds. Examples include berries, apples, carrots, and cruciferous vegetables like broccoli and cabbage. While these may not be the primary sources of phytoestrogens, incorporating a variety of fruits and vegetables into your diet can contribute to overall phytoestrogen intake and provide other health benefits. 

Dried fruits tend to be higher than normal fruit and can provide a significant amount of phytoestrogens. Dates, prunes, and dried apricots are among the dried fruits with the highest phytoestrogen content. These fruits are also packed with fiber and other essential nutrients, making them a healthy addition to your diet. Incorporate dried fruits into your meals or enjoy them as a standalone snack to reap the benefits of their phytoestrogen content. [7] 

Garlic: A Flavorful Herb with Phytoestrogenic Potential

Garlic, a popular ingredient known for its pungent flavor and health benefits, may also influence estrogen levels in the body. Animal studies have suggested that garlic may affect blood estrogen levels, although human studies are limited. Additionally, garlic supplements have been associated with lower inflammation levels in [8] postmenopausal women. This anti-inflammatory effect may offer protection against bone loss related to estrogen deficiency. While more research is needed, incorporating garlic into your meals can add both flavor and potential health benefits. Interestingly Garlic seems to have the opposite effect in men, with some evidence suggesting it can raise testosterone in these cases.

Herbs and Spices

Some herbs and spices, such as black cohosh, licorice, red clover, and hops, contain phytoestrogens and have been used traditionally for their medicinal properties. These can be consumed in the form of herbal teas, supplements, or incorporated into cooking to add flavor and potential health benefits. Liquorice being one of the most notable examples. 

Liquorice

Some research suggests that phytoestrogens in liquorice may help alleviate symptoms of menopause, such as hot flashes and mood swings. However, it's important to note that the effects of phytoestrogens can vary between individuals, and more research is needed to fully understand their impact on health. Research suggests that phytoestrogens found in liquorice may have a positive impact on menopausal symptoms. A study published in the journal Climacteric found that women who consumed liquorice extract experienced a significant reduction in the frequency and severity of hot flashes compared to a placebo group. [9] Another study published in the Journal of Obstetrics and Gynaecology Research reported that liquorice extract improved vaginal dryness and overall quality of life in postmenopausal women. {10]

Peaches: A Sweet and Phytoestrogen-Rich Fruit

Peaches, with their sweet and juicy flesh, are not only a delightful summer fruit but also a source of phytoestrogens. These fruits contain lignans, a type of phytoestrogen that has been linked to a decreased risk of breast cancer in postmenopausal women. While more research is needed to fully understand the potential benefits of lignans, incorporating peaches into your diet can be a refreshing and nutritious choice. [11]

Role of Phytoestrogens in Hormone Balance

Phytoestrogens have the ability to interact with estrogen receptors in the body, leading to various effects on hormone balance. Estrogen receptors, known as alpha and beta receptors, play distinct roles in cell proliferation and apoptosis. Phytoestrogens can bind to both receptors, albeit with lower affinity compared to endogenous estrogen.

The binding of phytoestrogens to estrogen receptors can influence gene expression, DNA transcription, and other cellular processes. Phytoestrogens may also modulate the activity of enzymes involved in hormone metabolism, such as aromatase, which converts androgens to estrogen. This modulation can have implications for hormone-dependent conditions, including hormone-related cancers.

Phytoestrogens and Reproductive Health

Phytoestrogens have been studied for their potential effects on reproductive health. For women approaching menopause, phytoestrogens may offer a natural alternative to hormone replacement therapy. These compounds can help alleviate symptoms such as hot flashes and improve overall well-being during this transitional phase. [12]

Research suggests that phytoestrogens may influence progesterone levels, stimulate the production of estradiol, and affect oocyte maturation and zygote development. However, the effects of phytoestrogens on reproductive development and health require further investigation, particularly in relation to infant formula intake and long-term consequences.

Cardiovascular Benefits of Phytoestrogens

Studies have shown that phytoestrogens may have protective effects on cardiovascular health. These compounds can help reduce total cholesterol levels and improve heart function. In particular, isoflavones found in soy products have been associated with lower LDL cholesterol, increased HDL cholesterol, and reduced blood pressure.

Phytoestrogens can also influence blood sugar regulation, with some evidence suggesting a potential benefit in reducing fasting blood sugar levels and insulin resistance. The consumption of soy-based products, rich in phytoestrogens, has been linked to a lower incidence of chronic diseases in East Asian populations. [13]

Phytoestrogens and Weight Loss

Phytoestrogens have been linked to weight loss and body composition changes. By inhibiting the life cycle of adipocytes, the cells responsible for storing fat, phytoestrogens may promote fat-free mass and reduce fat accumulation. These compounds may also have anti-inflammatory effects, contributing to weight loss and improved metabolic health. [14]

Studies have shown that phytoestrogens, particularly those from soy products, can have a significant impact on weight loss in both animal and human studies. For instance, soy-based meal replacement formulas have been associated with significant weight loss in obese individuals. Particularly in populations suffering from post menopause weight gain, making them interesting as a potential supplemental treatment for menopause. However, further research is needed to fully understand the mechanisms and long-term effects of phytoestrogens on weight management.

Phytoestrogens and Hormone-Dependent Tumors

The potential role of phytoestrogens in hormone-dependent tumors, such as breast and endometrial cancer, has been a topic of interest. Research has yielded conflicting findings regarding the impact of phytoestrogens on cancer risk. Some studies suggest that phytoestrogens, particularly those from soy foods, may have a protective effect against breast cancer recurrence and death. [15] 

However, the relationship between phytoestrogens and cancer is complex and may depend on various factors, including the stage of menopause. While phytoestrogens may offer potential benefits, it is essential to consult with a healthcare professional before considering them as a cancer prevention or treatment strategy.

Phytoestrogens and Bone Health

The role of phytoestrogens in maintaining bone health has been a subject of investigation. While some studies have shown a weak link between increased intake of soy isoflavones and improved bone mineral density, the overall evidence is inconclusive. More research is needed to fully understand the effects of phytoestrogens on bone health, particularly in postmenopausal women who are at a higher risk of osteoporosis. [16]

Side Effects of Phytoestrogens: Risks and Safety Considerations

The safety of phytoestrogens, particularly in supplement form, remains a topic of debate. While natural phytoestrogens obtained from a balanced diet are generally considered safe, the use of phytoestrogen supplements may carry potential risks. The quality, purity, and dosage of these supplements are not regulated by the FDA, making it important to exercise caution and consult with a healthcare professional before using them.

Some concerns have been raised regarding the potential impact of high soy consumption on ovarian function. However, research has not conclusively established a link between soy intake and negative effects on ovarian function or other health outcomes.

Individual Variability

The effects of phytoestrogens can vary among individuals due to genetic factors, gut microbiota composition, and overall health status. Some individuals may be more responsive to the effects of phytoestrogens, while others may not experience significant changes. It's important to listen to your body and make personalized choices based on your specific health needs.

Hormonal Imbalance

In individuals with existing hormonal imbalances or conditions such as estrogen-sensitive cancers, it's crucial to consult with a healthcare professional before increasing phytoestrogen intake. While phytoestrogens can have antiestrogenic effects in certain tissues, excessive amounts may still interact with estrogen receptors and potentially disrupt hormonal balance.

Source and Quality of Phytoestrogens

The source and quality of phytoestrogens can vary, and some processed foods or supplements may not provide the same benefits as whole food sources. It's recommended to focus on consuming phytoestrogens from natural, unprocessed foods whenever possible.

Optimal Dosage and Timing

The optimal dosage and timing of phytoestrogen consumption are still areas of ongoing research. While there are general guidelines available, individual needs may vary. It's important to discuss dietary changes and potential supplementation with a healthcare professional who can provide personalized guidance.

Allergies and Sensitivities

Certain individuals may have allergies or sensitivities to specific phytoestrogen-rich foods, such as soy or legumes. If you have known allergies or intolerances, it's important to choose alternative sources or avoid these foods altogether.

Phytoestrogens are bioactive compounds found in various plant-based foods that have gained attention for their potential health benefits. While the research on phytoestrogens is still evolving, there is growing evidence to suggest that they may play a role in preventing chronic diseases such as certain cancers, cardiovascular problems, and menopausal symptoms. Incorporating phytoestrogen-rich foods, such as soy, flaxseeds, legumes, and whole grains, into a balanced diet could contribute to overall health and well-being, although the efficacy of different foods is dependant on their particular compounds and more research is needed in most areas to confirm any of the current hypotheses. 

References

1 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4995266/

2 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3767174/

3 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7539339/

4 - https://pubmed.ncbi.nlm.nih.gov/14749240/

5 - https://pubmed.ncbi.nlm.nih.gov/20100387/

6 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6412439/

7 - https://pubmed.ncbi.nlm.nih.gov/37049451/

8 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6390141/

9 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3832176/

10 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9806245/

11 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2781234/

12 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7468963/

13 - https://pubmed.ncbi.nlm.nih.gov/10807439/

14 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7071386/

15 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7759898/

16 - https://pubmed.ncbi.nlm.nih.gov/27710141/