Monday, March 4, 2024

Can Phytoestrogens Alleviate Menopausal Hot Flashes and Night Sweats? Exploring the Potential Benefits and Risks


Years ago, while speaking to 120 pharmacy students in an auditorium in Pullman, Washington, I had my first hot flash. First, my scalp suddenly started feeling hot and prickly. Then, two heartbeats later, a shower of sweat gushed down my neck and back. In less than 5 seconds, I was soaking wet!

Can phytoestrogens relieve the physical and social discomfort of menopausal symptoms like sudden hot flashes/flushes or their night-time equivalent, night sweats?

For decades, researchers have noticed how Asian women don’t suffer as much from hot flashes during menopause as Western women do, labeling it the "Japanese Effect." The primary reason for this difference is believed to be diet.

A typical Asian diet contains much more soy than a standard American diet. Foods containing soy and soy concentrates contain phytoestrogens, which are plant-based substances acting in your body in ways and places similar to estrogen.

But eating more soy is only part of the answer. Protection against experiencing hot flushes may also depend on whether your body can change the basic phytoestrogens found in soy into equol, a powerful phytoestrogen. Overall, only 30-50% of North American women can convert soy into equol. Asian and Hispanic women are able to do this more readily. 

Phytoestrogens work by attaching to the same places in your body as other estrogen compounds. These areas of attachment are called estrogen receptors, or ERs. There are two main types of ERs: ER alpha and ER beta receptors. Most estrogens and phytoestrogens bind to ER alpha receptors, which can stimulate breast and uterine cancer.

However, some phytoestrogens bind to ER-beta receptors, which triggers the opposite effect. Binding to ER-beta receptors can BLOCK the action of estrogen on breast tissue. This is similar to how the estrogen-blocking medicines tamoxifen and raloxifene (Evista®) help prevent certain types of breast cancer.

Unfortunately, studying the effects of any one phytoestrogen in the body is challenging. One reason is that foods and herbal sources of phytoestrogens contain different types of phytoestrogens. The two most common types of phytoestrogens are isoflavones and lignans. Soybeans contain isoflavones like genistein and daidzein, while lignans are found in flaxseed, fruits, vegetables, and other foods.

Another reason it's hard to predict the effects of phytoestrogens is because some attach to ER-alpha receptors, some to ER-beta receptors, and some to BOTH, which can create different outcomes. This may explain why phytoestrogens have been shown to encourage weight loss in post-menopausal women in some studies yet weight gain in others.

Depending on their growing conditions, plants can also have variable concentrations of phytoestrogens. An additional complication is how much estrogen is already in place. Phytoestrogens can act differently in pre-menopausal women than in post-menopausal women, whose bodies contain much less estrogen.

How much soy do you need to reduce hot flashes or flushing symptoms? Most clinical studies have used between 40 and 80 mg of phytoestrogens from soy-based products daily. Recent evidence suggests you should start with 2 servings a day of soy foods for 3 months, noting whether you experience fewer episodes of hot flushes/flashes.

One serving of soy food can be 3 ounces of tofu, ½ cup of edamame, ½ cup tofu, ¼ cup soy nuts, or 1 cup of soymilk. Flaxseed, chickpeas, beans, peas, green leafy vegetables, cauliflower, and nuts are good sources of phytoestrogens. After trying soy for 3 months, if you don’t notice any decrease in your hot flashes or hot flushes, you can stop it.

Can eating soy-based food cause breast cancer? If you're not a vegetarian, you're unlikely to get enough soy from your diet to increase your risk of breast cancer.

Be cautious about taking supplements that contain phytoestrogens and estrogen-like compounds. Soy concentrates and herbal products like black cohosh marketed for "menopause support," like Remifemin®, may increase breast cancer risk.

Here are 3 Tips for Taking Phytoestrogens Safely:

1.         You CAN eat food containing soy, even if you have a history of breast cancer.

Moderation is the key. If you are vegetarian or vegan, don't eat tofu or tempeh every day, and watch your consumption of soy milk.

2.         Be cautious with supplements for menopausal symptoms.

If you have a family history or an increased risk of breast cancer, avoid taking supplements containing concentrated phytoestrogens, like soy concentrates or black cohosh, until more is known about their long-term effects.

3.         Stick to phytoestrogens that have had their potency tested.

The exact concentrations of certain phytoestrogens differ depending on growing conditions. The best phytoestrogen supplements measure and standardize every batch to ensure consistent potency.

Dr. Louise Achey, Doctor of Pharmacy, is a 44-year veteran of pharmacology and author of Why Dogs Can’t Eat Chocolate: How Medicines Work and How YOU Can Take Them Safely. Get clear answers to your medication questions at her website and blog,

Ó2023 Louise Achey



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