Q: Are phytoestrogens safer than prescription estrogens for treating hot flashes?
Not necessarily. Phytoestrogens are plant-based substances that can act just like estrogen in our bodies. Although they aren’t exactly the same, they can do some of the same things estrogen can because they way they are shaped allows them to fit into the same places as both prescription estrogens we take, called exogenous estrogen, and the estrogens we make in our own body, called endogenous estrogen.
There are approximately 20 phytoestrogen compounds found in various foods and herbs, with soy products and flaxseed having the highest concentration. Herbal products such as black cohosh and red clover also contain phytoestrogens.
Phytoestrogens can behave just like other types of estrogen, but are about 100-10,000 times weaker than our own enodgenous estrogen. They can also have the opposite effect. Phytoestrogens can act just like the prescription medicines tamoxifen or raloxifine (Evista®) which block estrogen’s effect on breast tissue, which helps prevent breast cancer.
For example, in women with a low level of endogenous estrogen such as in menopause, soy phytoestrogens will act just like our own estrogens on bone and breast tissue. But in premenopausal women who have normal endogenous estrogen levels, soy phytoestrogen has the opposite effect. How does this happen? The phytoestrogen in soy can kick our bodies’ own estrogen off of its binding place on the breast cells, replacing potent estrogen that we made with the much, much weaker phytoestrogen.
Soybeans and soy products such as soy nuts, soy milk, tofu and tempeh are particularly high in a particular type of phytoestrogen called isoflavone. Because they are the most concentrated and available source of phytoestrogen, soy foods and soy concentrates have been studied the most.
Phytoestrogens are interesting to researchers because they can relieve hot flashes during menopause in some women. Researchers have noted that Asian women don’t suffer from hot flashes during menopause as commonly as Western women do. One major difference is believed to be their diet; a typical Asian diet contains a lot more soy than a typical American diet.
One particular isoflavone called genistein is the main phytoestrogen in soy-based foods. In research studies, an increased intake of genistein has been associated with a 10% reduction in hot flash symptoms.
How much soy does it take to experience a reduction in your hot flash symptoms? Most clinical studies have used 40-80 mg daily of phytoestrogens, particularly genistein. You can get 40 mg of genistein from ½ cup tofu, ½ cup soy nuts, or 1 cup of soy milk. Flaxseed, chickpeas, beans, peas, green leafy vegetables, cauliflower and nuts are other food sources of phytoestrogens.
Are phytoestrogens actually safer than estrogen in treating hot flash symptoms in menopause? Not always. In susceptible individuals soy extracts may actually trigger breast cancer. Soy has been shown to stimulate increased cell production in normal breast tissue, and the phytoestrogens found in soy and red clover may interfere with the effectiveness of tamoxifen, a medicine used to prevent breast cancer.
If you have a family history of breast or endometrial cancer, or have had breast cancer, you should avoid consuming large amounts of soy based foods and soy supplements. If you are vegetarian or vegan, don’t eat tofu or tempeh every day, and restrict your consumption of soy milk.
If you are not vegetarian, it’s unlikely that you’ll get enough soy in your diet to increase your risk of breast cancer. That’s not the case if you take supplements containing soy concentrate or herbal products marketed for “menopause support” such as Remifemin®. If you have a family history or an increased risk of breast cancer you should avoid taking supplements containing soy concentrates, black cohosh or other phytoestrogens as well as restricting your intake of soy-based food products.
