Phytoestrogens in Botanical Dietary Supplements: Implications for Cancer

Abstract

Phytoestrogens are plant constituents that possess either estrogenic or antiestrogenic activity. Although their activities are weak as compared with human endogenous estrogens, the consumption of phytoestrogens may have clinically significant consequences. A number of botanicals, or the compounds contained therein, have been identified as putative estrogenic agents, but consensus in the biomedical community has been hampered by conflicting data from various in vitro and in vivo models of estrogenic activity. Phytoestrogens may serve as chemopreventive agents while at the same time being capable of promoting growth in estrogen receptor positive cancer cell lines. Furthermore, they may exert their estrogenic influence through receptor-dependent and/or receptor-independent mechanisms. These findings have led to speculation that phytoestrogen intake might be ill advised for patients at an increased risk for hormone-dependent cancers, cancer patients, or cancer survivors. This article will attempt to sort out discrepancies between various experimental models and establish whether certain herbs possess estrogenic activity. The review will focus on 5 popular botanical dietary supplements: Trifolium pratense (red clover), Cimicifuga racemosa (black cohosh), Humulus lupulus (hops), Angelica sinensis (dong quai), and Glycyrrhiza glabra (licorice). It will address their mechanisms of action, clinical evidence bases, and implications for use in cancer.

Comparison of the in Vitro Estrogenic Activities of Compounds from Hops (Humulus lupulus) and Red Clover (Trifolium pratense)

“…1B). Red clover has been tested in clinical trials as a menopause therapy (27) with formulations based on the active metabolites and their metabolic precursors (13). In the present study we confirmed the presence of 8-PN as the most potent estrogen in hops using a mass spectrometry-based screening assay developed in our laboratory (28).…”

“…The strobiles of Humulus lupulus L. (hops) are primarily used to flavor beer, although it has been studied since 1953 for a potential estrogenic mechanism of action (13)(14)(15). In the past, the flavonoids, 8-prenylnaringenin (8-PN), 6-prenylnaringenin (6-PN), and the chalcone, isoxanthohumol (IX), have been isolated and reported to be estrogenic in vitro and/or in vivo (16,17).…”

In vivo estrogenic comparisons of Trifolium pratense (red clover) Humulus lupulus (hops), and the pure compounds isoxanthohumol and 8-prenylnaringenin

“…The strobiles of Humulus lupulus L. (Cannabaceae) (hops) are primarily used to flavor beer, and have been studied since 1953 for a potential estrogenic mechanism of action [13][14][15]. In the past, the flavonoids 8-PN and 6-PN, and the chalcone, isoxanthohumol (IX), have been isolated and reported to be estrogenic in vitro and/or in vivo [16,17].…”

Dietary Supplement Use in Cancer Care: Help or Harm

“…Herbal therapies with estrogenic, androgenic, or progesterone-like activity are a theoretic concern for patients with hormone-sensitive cancers, particularly breast, ovarian, endometrial, or prostate cancers [54]. However, the majority of the literature on hormonal effects of herbs focuses on the estrogen activity of herbs commonly used for treating menopause.…”