By: Thomas Pickering, MD, DPhil, FRCP, Director of Integrative and Behavioral Cardiology Program
of the Cardiovascular Institute at Mount Sinai School of Medicine, New York.

“Natural” estrogens, also referred to as phyto-estrogens (phyto means plant) are a group of substances derived from plant products, which are converted into estrogen-like substances in the bowel, and which are present in certain food products such as soy. They are becoming increasingly popular as food supplements, on the grounds that they can provide the health benefits of synthetic estrogens, without their adverse effects. But what is the evidence for this?

A recent review in the authoritative medical journal, the Lancet, has looked at the evidence. The first point to consider is that the term phyto-estrogen includes a number of different compounds, such as isoflavones (the ingredient is soy products), lignans, and coumestans. This means that what is found for one phyto-estrogen does not necessarily apply to the others. A big boost to the use of phyto-estrogens was provided by the official approval by the Food and Drug Administration of the United States for the use of soy proteins to lower total and LDL cholesterol and triglycerides, and hence to help to protect against heart disease. However, it takes a lot of soy (47 grams a day, or three servings) to get this benefit. Another study showed that isoflavones derived from red clover can reduce the stiffness of the arteries of menopausal women.

Oriental diets tend to be rich in phyto-estrogens, and Asian women have less hot flashes, heart disease, and osteoporosis than European and American women, but giving phyto-estrogens does not reduce the flashes, and it remains to be seen if phyto-estrogens in general actually do prevent heart disease.

Some of the phyto-estrogens that are marketed as “natural” products are in fact synthetic, and both natural and synthetic products can have harmful effects as well as beneficial ones.

The bottom line is that “natural” estrogens and “phyto-estrogens” should not be taken as a catch-all category of products that can be assumed to have benefits but no risks for menopausal women. We simply do not know enough about them to make any general recommendations for their wider use.