Subhuti Dharmananda is a well-known practitioner of TCM in the US. He is also well versed in biochemistry. This text has been compiled from an e-mail correspondence with Severin Bühlmann.
The term phytoestrogens is usually misleading and your confidence that phytoestrogens prevent women from many problems including impact of aging is possibly misplaced. The term combines the origin of chemical substances, namely plants, with an animal substance, specifically estrogen. The implication is that the substances in plants behave, when consumed, like estrogen. In the field of herbal medicine, two types of plant substances have come under this heading: those that have a chemical structure similar to estrogen, namely a steroidal structure, and those that have a different structure but are claimed to behave like estrogen, or stimulate production of estrogen.
If you look at the chemical structures of cholesterol, estrogen, progesterone, and testosterone, as examples, you will see that they are remarkably similar but for small attachments to the steroidal backbone. These very small differences make for remarkably different physical effects. The difference between the plant steroidal structures and the animal ones is even greater and thus the impact of the plant substances is also expected to be markedly different, and it is, namely markedly less. Naturopathic doctors insist on women taking “bioidentical hormones” rather than the animal derived ones or the synthetics (obtained from plant steroids), and here the difference in the molecules is even less than the difference between, for example, estrogen and progesterone, and so tiny differences become of concern while the vast difference between these and plant steroids is perhaps given too little attention.
The synthesized hormones are made from steroid compounds found in abundance in “wild yam,”, the Mexican Dioscorea. This plant has been used as an herb, but it has little if any anti-aging effect or hormonal action (despite what some western herbalists would have you believe), and it takes four synthetic steps to get from the plant steroid to the human hormone type compound.
Steroidal compounds in plants (as well as the somewhat similar triterpenoids, do have physiological activities, but hormone action is not one of them.
Some compounds are reputed to have hormone-like action with different structure, the main example being isoflavones from soy, such as genestein. This compound became of interest because of claimed differences in health from high soy diets found in Asia (compared to low soy diets in the west), implying that women had both lower menopausal symptoms (suggesting a pro-estrogen effect) and lower breast cancer incidence (suggesting an anti-proliferative effect). Women flocked to products with soy isoflavones for a while to get menopause alleviating action and, just as quickly, left those products when there was a suggestion that anything pro-estrogen was pro-cancer. In fact, genistein had disappointing effects on menopausal symptoms, making it easier to put aside.
In the laboratory, any of the phytoestrogens can be placed on cancer cells and may show either cancer promoting or cancer inhibiting actions. Both of these actions are irrelevant to clinical effects as the amount of the substance contacting cells in the body is so much less. Chinese studies, of poor quality, indicated that Chinese herbs could reverse the decline of hormones with aging, as support of antiaging claims. They stopped doing that when concern was raised about higher hormone levels and cancer. There is, in fact, little evidence for those hormonal effects.
Put simply, the story of phytoestrogens has been overblown, both for positive effects and negative effects in relation to hormones. Large doses of steroidal compounds from plants may slightly lower cholesterol and through similar mechanism may reduce BPH. Large doses of steroidal compounds from plants may be mucolytic or sedative. Chinese herbal formulas generally do not provide sufficient amount of hormone-affecting substances to be of concern positively or negatively with regard to hormone action. The possible exception is when licorice is used in high dose (as opposed to typical low dose use in most formulas). Thus, when using the decoction equivalent of 6 grams or less per day, it should not be problematic, but higher doses, such as 9-15 grams per day (for long-term use, which is unusual) might have some impact, including some hormonal effect.
At our two clinics in Portland, cancer patients are our dominant group, and women with reproductive system cancers are the largest subgroup of cancer patients. They use the modern medical therapies and they use Chinese herbs and naturopathic supplements; we do not contraindicate any herbs or formulas. The one thing I recommend against, in most cases, is trying to specifically use acupuncture and herbs to prevent cancer recurrence (after remission from initial cancer) over the long term. There is no evidence that any particular procedure or herb formula is indicated for that. Acupuncture and herbs can be used during that time to address diseases, disorders, and symptoms as per usual TCM practice.
(in an e-mail to Severin Buehlmann July 2016)