Many women today are searching for safe and effective alternatives to Hormone Replacement Therapy (HRT), largely due to the increased health risks associated with their usage. Inevitably, somewhere along this search they come to discover “phytoestrogens”. The short story with phytoestrogens is that they can be very helpful for menopausal concerns and they should be considered extremely safe. The full story requires a bit more explanation because there is a great deal of misinformation that exists surrounding their efficacy and safety. Let’s take a closer look.
What are phytoestrogens?
The term “phytoestrogen” can literally be translated into “plant estrogen”. In the 1950’s this estrogenic activity was discovered in plants when researchers investigated the cause of infertility in a specific group of Australian sheep. Researchers noticed that these infertile sheep were grazing in pastures of clover, subsequently labeling genistein as the active ingredient and the constituent responsible in clover for having estrogen-like activity. Since this discovery, hundreds of foods have been identified as phytoestrogens – each possessing varying potencies. Here is a brief list of some popular phytoestrogen plants, along with their main active ingredients:
- Soy (isoflavones; genistein and daidzein)
- Alfalfa (coumestans, coumestrol)
- Clover, especially red clover (coumestans, coumestrol)
- Flaxseed (lignans)
- Hops (8-prenylnaringenin)
How do phytoestrogens actually work?
Despite the literal translation to “plant estrogen”, it’s important to note that no actual estrogen exists in phytoestrogenic plants (i.e. the principle human estrogen, 17B-estradiol, is not present). Instead, plants that are described as phytoestrogens simply have effects on the human body similar to the effects of our bodies’ natural estrogen. In the most basic sense, all phytoestrogenic plants contain some type of active ingredient that actually interacts with and activates estrogen receptors. The human body interprets this chemical signal in the same way that it would if natural estrogen had triggered the receptor. In other words, the switch gets turned on regardless of what initiated the action.
It is also very important to recognize that, even though phytoestrogens activate estrogen receptors, they do so in a much weaker manner. Using our on/off switch analogy, phytoestrogens simply turn on fewer switches than true estrogen because they don’t bind strongly enough to the switch. This results in similar physiological responses that are much milder.
Lastly, to fully understand the action of phytoestrogens, we must recognize that there are two different types of estrogen receptors in the body: alpha-estrogen receptors (ER-a) and beta-estrogen receptors (ER-b). Each receptor is distributed more heavily in certain tissues (i.e. bone versus breast tissue). This is important because all phytoestrogens are actually “selective estrogen receptor modulators” (SERMs), meaning they affect either the ER-a or ER-b preferentially. Most bind more strongly to ER-b than ER-a, but the story is very complex as this is not always the case.
But what does the research say?
On the whole, research examining the ability of phytoestrogens to alleviate menopausal ailments is positive, yet still mixed. Beneficial results have been shown for improving hot flashes, vaginal dryness, sleep disturbances, cognition and bone density in menopausal women. However, many studies have also shown very little or no effect of phytoestrogens on menopausal symptoms. With this in mind, it’s important to know that there is a tremendous amount of variability in terms of the amount of active ingredient used in each study. Moreover, individual differences in intestinal microflora can further lead to mixed results by altering the ability to break down and use phytoestrogens in the human body.
A comprehensive 2013 review study evaluating the efficacy of isoflavones, coumestans and lignans found that “current research is sufficiently conclusive that findings are positive”. Interestingly, the same researchers confirmed a significant placebo effect for treating hot flashes, yet still found phytoestrogens to be superior. In other words, a positive psychological outlook is very well known to improve hot flush symptomatology; so even the act of taking a phytoestrogen supplement and the belief that it’s working provides subjective improvement in menopausal symptoms. Even considering this psychological impact, researchers have found additional benefit in treating menopausal hot flashes from using phytoestrogens.
Hops (Humulus lupulus), a less well-known phytoestrogen that is better known as a sedative herb, has also been found to be extremely useful in reducing the intensity of hot flashes and night sweats. Hops can be considered a relatively “new” phytoestrogen as the active estrogenic ingredient, 8-prenylnaringenin (8-PN), was only recognized in 1999. Despite being the new kid on the block, hops is worth mentioning because comparison against the active ingredients found in other phytoestrogens (such as genistein and diadzein from soy) show that 8-PN is actually one of the most potent! Two clinical studies using standardized hops extract have been conducted, both of which elucidated the rapid and effective relief of hot flashes. Considering the large proportion of menopausal women with sleep disturbances and hot flashes, hops is an ideal ingredient to target this population for its estrogenic and sedative properties.
The take home message here is that there are many different phytoestrogens, in varying capacities, that have demonstrated their benefits for treating menopausal complaints: including hot flashes, vaginal dryness, sleep disturbances, cognition and bone density. Numerous active ingredients, inadequate potency, and variations in individual metabolisms may lead to mixed results, but many women have found tremendous relief from menopausal ailments by using phytoestrogens and much of the research supports this claim.
Are phytoestrogens safe?
One of the greatest attributes of phytoestrogens is their extremely high safety profile. A literature review in 2010 analyzed twenty years of soy research and found that there were no serious side effects – only a slightly higher incidence of gastrointestinal disturbances (such as gas or bloating) in those consuming higher amounts of dietary soy. Similarly, there have been studies examining the safety of soy consumption for up to 3 years in length that failed to expose any serious adverse effects. Research on the use of lignans from flaxseeds, 8-prenylnaringenin from hops and coumestrol from both alfalfa and red clover have all shown comparable safety profiles.
Some research has raised concerns surrounding the use of soy and its possible negative effects on thyroid health. It’s important to clear the air on this point: research has only shown that genistein from soy can exacerbate low thyroid function in individuals with pre-existing suboptimal thyroid function (specifically deficient in iodine). Put another way, there is currently no evidence to suggest that healthy people consuming soy are at increased risk for hypothyroidism.
As aforementioned, HRT has also raised various concerns regarding their use and possible risk of increased blood clotting, liver disease and certain cancers. Interestingly, not only have phytoestrogens been found to not increase the risk of endometrial cancer, but also some studies actually suggest a possible protective effect for this type of cancer. In addition, soy consumption in the whole food form has actually been found in many human populations to be protective against breast cancer (directly opposing animal studies that many people reference to show the potential harms of soy with breast cancer).
All in all, phytoestrogens appear to be a very safe substitute for HRT that can alleviate women’s health concerns and aid their transition into menopause. Still, to be cautious, it is advised to only utilize phytoestrogens for shorter-term use and at reasonable dosages, as long-term use (i.e. years) of high-potency extracts have not been explicitly studied.
Phytoestrogens in dietary form or standardized extracts may be beneficial for your menopausal symptoms. However, as the mixed evidence suggests, each phytoestrogen doesn’t necessarily work for everyone – you must find the combination or product that works best for you. Additionally, it’s clear that the type and potency of the phytoestrogen used alters the physiological effects on the body. One thing you can be sure of is that phytoestrogens are safe.
To meet the growing needs and concerns of menopausal women, AOR is currently developing a product to alleviate commonly associated menopausal symptoms according to the newest and best research. Speak with a qualified health care practitioner to find out if this product or any phytoestrogen is safe and right for you.
You may also be interested in: "Hops for Hormonal Support"
Bedell S, Nachtigall M, Naftolin F. The pros and cons of plant estrogens for menopause. J Steroid Biochem Mol Biol (2013) http://dx.doi.org/10.1016/j.jsbmb.2012.12.004
Chadwick LR, Pauli GF, Farnsworth NR. Humulus lupulus L. (hops) with an emphasis on estrogenic properties. Phytomedicine 2006;(13):119-131
Erkkola R, Vervacrcke S, Vansteelandt, et al. A randomized, double-blind, placebo-controlled, cross-over pilot study on the use of a standardized hop extract to alleviate menopausal discomforts. Phytomedicine 2010;(17):389-396
Marini H, Polito F, Adamo EB, Bitto A, Squadrito F, et al. Update on genistein and thyroid: an overall message of safety. Front Endocrinol (Lausanne). 2012;3:94