Phyto-estrogens at menopause: what should we think?

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In the diet or in food supplements, soy isoflavones are of interest to women seeking to relieve their hot flashes without taking hormone treatment of menopause. But are these natural estrogens effective and safe?

Phyto-estrogens at menopause: what should we think?

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Many food supplements intended for menopausal women contain phyto-oestrogens from soybean, sage, alfalfa, clover or hops. These natural compounds are sought after because their action in the body resembles that of female hormones. Among these phytoestrogens, isoflavones are the most interesting for menopausal women.

Which foods are rich in isoflavones?

In the diet, isoflavones are present in legumes like chickpeas. “But the most significant quantities are found in soy,” says Dr. Jean-Michel Lecerf, head of nutrition and physical activity at the Institut Pasteur in Lille.

Yes soy is a food rich in isoflavones, its phyto-estrogen content is not the same depending on the type of product:
– soya juice: 10 mg per 100 ml;
– Soy dessert: 8 mg per 100 g;
tofu : 22 mg per 100 g;
soy steak : 22 mg per 100 g;
– cooked soybeans: 10 mg per 100 ml

Source: Sojaxa (association of leading soyfood manufacturers, France, 2016).


Are natural estrogens as effective as female hormones?

Estrogens Provided by Hormone Treatment for Menopause Have Proven Their Efficacy against hot flashes. But phyto-oestrogens are not equivalent.


“In the body, phytoestrogens act on the same estrogen receptors, present in the bone, brain or blood vessels. But they are much less powerful, “says Dr. Lecerf.

Consequently, their action on symptoms of menopause is not guaranteed. “Studies have shown a reduction in intensity and number of hot flashes. But efficiency is not at the rendezvous in all cases, “says the nutritionist.

Indeed, isoflavones are more or less well metabolized in the body. About 30% of individuals can transform them into active molecules. Factors such as intestinal microbiota and genetics have their influence.

Should we prefer the diet or capsules?

For Dr. Lecerf, a woman who wants to stop her hot flashes is unlikely to achieve it with only soy:


” The doses of isoflavones that can be achieved with soy foods remain weak. It is difficult to exceed 20 to 40 mg per day. However, to obtain an effect on hot flashes, it would require a higher intake, of the order of 60, 80 or 100 mg per day, according to women, “he says.

The taking a dietary supplement allows to reach these daily doses. But, the National Agency for Food Safety (ANSES) recommends not to exceed 1 mg per kilogram per day, or 60 mg for a woman weighing 60 kg. However, with these levels of isoflavones, there may be effects on the breast.

What is the risk of breast cancer with phytoestrogens?

At dietary doses, 10 to 20 mg per day, isoflavones pose no risk to the breast. On the contrary. “Studies have shown that consuming soy reduces the risk of breast cancer, the risk of recurrence, and mortality,” says Dr. Lecerf. On the other hand, with dietary supplements, the situation is more complex.


“It is necessary to be careful at menopause with isoflavones taken in high doses (more than 60 mg per day), and for prolonged (approximately one year)”, insists the nutritionist.

A recent study shows that, in this context, the risk of breast cancer varies, for each woman, according to her estrogen impregnation and estrogen receptor status. It increases after menopause and in women whose estrogen receptors are “negative”, much more so after ER-breast cancer. These women at risk may consume soy, but should avoid isoflavone-based dietary supplements.

In contrast, the risk is decreased in premenopausal and early menopause, in women with no history of breast cancer.

At menopause, the estrogen deficiency increases risk of osteoporosis. Soy isoflavones have a protective effect on the bone by binding to estrogen receptors. But less important than thecalcium intake. “At menopause, vegetarians need to eat 3 dairy products a day,” says Dr. Lecerf. To privilege also: mineral waters rich in calcium (Hépar, Courmayeur, Contrexeville …).