Phytohormones (plant hormones), particularly phytoestrogens, have generated a great deal of interest in the consumer and scientific community for a number of years. Phytoestrogens, or plant estrogens, are very weak estrogens that occur naturally in many foods and herbs. The chemical structure of phytoestrogens is similar but not identical to the estrogens produced by the body.

The body is not able to convert phytoestrogens into estrogen, however, anecdotal evidence indicates there may be benefits from phytoestrogens for women during perimenopause because of weak estrogenic-like qualities. Some women report relief from minor symptoms such as hot flashes, anxiety, and irritability.

Types of Phytoestrogens

• Isoflavones
• Flavanols
• Flavones
• Flavanones
• Lignans

Each of these classes contains many categories and subcategories.

Isoflavones

Isoflavones, plant estrogens found in legumes such as soybeans, have generated the most excitement because it appears they may have estrogenic effects in the body. Studies have already demonstrated eating soy foods can decrease levels of cholesterol, low-density lipoproteins (LDLs), and triglycerides. Animal studies have shown that the isoflavones have a beneficial effect on some cancers. And isoflavones have been shown to work as potent antioxidants and free radical scavengers.

Finding Phytoestrogens

Not a soy fan? Not to worry. There are plenty of ways to add phytoestrogens to your diet.

Where To Start

"Diet is the best place to start if a woman is interested in adding phytoestrogens," says Steven Krems, M.D., an internist at Daniel Freeman Marina Hospital in Marina Del Rey, California. But loading up on supplemental phytoestrogens won't undo the effects of a poor diet, he cautions.

''You can get the beneficial effects from phytoestrogens with very small amounts per day,'' notes Hope Ricciotti, M.D., an OB/GYN at Beth Israel Deaconess Medical Center in Boston and associate professor at Harvard Medical School. ''Two to three ounces of tofu or a glass of soy milk [daily] is enough to add 40 to 60 mg of isoflavones to your diet,'' she says.

Popular Supplements

Along with soy powders and capsules, other popular phytoestrogen supplements include:

• Red clover, a source of isoflavones
• Dong quai or angelica, which contains coumarin, an anti-coagulating agent
• Flaxseed, source of lignans

Some ''women's'' supplements or formulas combine several of these, along with black cohosh, which is heavily marketed as a menopause supplements, but contains no known phytoestrogens.

There's scanty evidence about either the safety or effectiveness of supplemental phytoestrogens, particularly in dosage ranges that go far beyond what we would normally eat in food. And, Dr. Noel Bairey Merz, medical director and endowed chair of the Women's Health Program, Preventative and Rehabilitative Cardiac Center, at Cedars-Sinai Medical Center, points out, studies done to date show that phytoestrogen supplements produce less impressive results than phytoestrogens found in food. ''We don't know why yet,'' she says. ''It could be the wrong supplement [was studied]. Or it could be a case where a woman doesn't absorb and metabolize phytoestrogens well.''

Claims

With millions of dollars in sales at stake, it's not surprising that hundreds of phytoestrogen products have flooded the market, some of which claim to strengthen bones, sharpen the mind, protect the heart, and lower breast cancer risk. The fact that Japanese women have a high soy diet and lower incidence of breast cancer than other populations is often cited in marketing material for soy products, in particular.

However, the link between a high-soy diet and lower incidence of breast cancer is still conjectural. While soy does appear to lower cholesterol and prevent bone loss, it's not clear how much you need to eat to achieve the beneficial effects. And, preliminary studies suggest that soy or other phytoestrogen supplements--capsules, powders, or other formulas--are not as effective as adding soy from food to your diet.

Although it is known that phytoestrogens have antioxidant effects, reduce inflammation, and bind with estrogen receptors in the body, researchers haven't yet untangled the extent to which phytoestrogens affect the body or how. Studies are underway to measure how certain phytoestrogens influence cardiac function and bone strength, among other things.

How Much

With phytoestrogens, more isn't necessarily better. For example, the average Japanese diet includes 25 to 50 mg of isoflavones a day. Some supplements on the market contain five to ten times that amount. There is no scientific evidence documenting the need for the higher amounts, and some experts worry that overdosing with phytoestrogen supplements could lead to too much estrogenic stimulation in the breasts or uterus.

Cautions

• A large amount of anti-nutrients are found in soy. Which means that soy contains plant chemicals and if not removed first by slow cooking or fermentation it can cause serious health problems when too much is consumed.
• More soy is not necessarily better as research has not shown a conclusive link between soy and relief of vasomotor symptoms associated with menopause. In one comprehensive study from the Bowman Gray School of Medicine in North Carolina, researchers looked at the effects of soy phytoestrogens on women aged 45 to 55 with menopausal symptoms. This study made the news because the women who took a phytoestrogen-rich soy supplement reported a 50 percent decrease in the severity of their hot flashes. However, the placebo group reported a 35 percent reduction. Furthermore, the study showed only a small reduction in the severity of hot flashes and none on their frequency.
• Soy contains five different types of plant chemicals that can be toxic to humans if not removed by a special process. These toxins include phytates, protease inhibitors, genistein, goitrogens and allergens.
• Allergens to soy can cause severe allergic reactions in some individuals.
• Phytates tightly bind up essential minerals, including zinc, preventing them from being absorbed into the body. Zinc is an important factor for cell functions in the bones, skin, muscles, eyes and kidneys.
• Phytochemicals found in soy inhibit the enzymes that digest protein into simple building blocks of amino acids.
• Protease inhibitors are what AIDS patients currently take and a good lesson learned the hard way from the use of protease inhibitors is that they inhibit the pancreatic enzymes. Protease inhibitors prevent you from digesting food.
• Note that if you are estrogen dominant or taking birth control pills, you already have problems with high copper and low zinc levels. Which means protease found in soy can have adverse effects.
• Genistein blocks glucose transportation into cells by inhibiting an enzyme calledl GLUT-1. GLUT-1 is a major glucose transporter that is found in the brain cells, red blood cells and other areas of the body. Its function is to transport glucose into the cells.
• Goitrogen is a chemical that latches onto iodine, preventing it from absorbing into the body from the gastrointestinal tract. Iodine is needed to make thyroid hormone.
• Research on soy products for the prevention of breast cancer is inconclusive. While a 2001 study showed phytoestrogens in the amount commonly consumed by American women appear to have little effect on the risk of breast cancer, to date, research on the connection between soy products and breast cancer has been inconclusive.