Licorice More Estrogenic Than Estradiol: Some of the Flavonoids in Glycyrrhiza Glabra Roots Turn Out to Be Superinductors of the Estrogen-α & -β Receptors

Image 1: In view of the fact that most confectionary licorice contains no more than ~3% of the roots of the licorice plant, I would rather bother about the tricks the ~74g of carbohydrates (on a 100g base) of this treat may play on your insulin levels than about any potential negative effects the consumption of a few or even a whole bunch of these licorice wheels may have on your testosterone levels or overall manliness ;-)
You probably have heard about licorice, the root of Glycyrrhiza glabra, a legume with a slightly sweet taste and one of the ingredient of the eponymous candy being a potent adrenal "revitalizer" that is used and advocated my many naturopathic doctors. If you frequent any of the major health and fitness boards on the Internet, you will yet also be familiar with some of its unwanted side-effects, first and foremost its scientifically validated anti-androgenic (specifically testosterone reducing) effects (Zamansoltani. 2009). While Zamansoltani et al. yet still speculated, whether the reduction in serum testosterone they observed as a result of administration of 150-300mg/kg of licorice extract (HED ~ 40-80mg/kg; 3.2-6.4g for a 80kg human) to male rats still speculated, whether these reduction were the result of "[i]ncreas[es] in T metabolism, down-regulation of androgen receptors or activation of oestrogen [sic!] receptors", a recent study that was published in the Annals of Bioanalytical Chemistry shows that the latter, i.e. the (profound!) activation of both types of estrogen receptors probably was the underlying cause of the emasculation of the licorice treated bucks (Simons. 2011).

Estrogen receptor superinductors were not invented by Dr. Spock

In a pretty meticulous analysis, Rudy Simons et al. found that several fractions of an ethyl acetate extract from licorice root displayed estrogenic activities at either the estrogen-alpha or estrogen-beta receptor that were more pronounced than the ones of the reference "drug", estradiol (E2).
Figure 1: Relative estrogenic activity (in % of estradiol = E2) of 51 fractions that were isolated from an ethyl acetate extract from licorice root (data adapted from Simons. 2011).
If you take a closer look at the 51 fractions the scientists identified by liquid chromatography-massspectrometry and analyzed for their activity by the means of yeast estrogen bioassays, you will recognize that not just one or two, but a whole host of these "fractions", which themselves were complex mixtures of similar compounds, exhibit partly profound estrogenic activity. In that it is particularly noteworthy that the superinduction (activity >E2=100%) was not caused by a post-translational stabilization of the firefly luciferase reporter enzyme, which would have disqualified these results as shortcomings of the yeast essay Simons et al. had used - a effect which has been previously described for genistein, one of the phytoestrogens in soy and soy products.
Figure 2: Relative content and estrogenic activity of individual fractions F1-F5, F6-F21 and F22-F51 from the ethyl acetate extract from licorice root used in the study (calculated based on Simons. 2011).
Of all the fractions, the scientists isolated from the licorice extract, which was supplied by Frutarom US, fraction 41 (F41) with an estrogen-alpha receptor activity of 159.9% at the low (3µg/ml) and 186.9% at the high (10µg/ml) concentrations was by far the 'worst offender'. In view of the fact that we do not know how much of these flavonoids actually make it into the bloodstream, the 103.1, 97.9, 95.5, 74.6, 68.7, 57.2 and 57.3% estrogen-beta activity of fractions F24-F30 at a much lower concentration of 0.3µg/ml is probably more of a concern and most likely the underlying cause of the anti-androgenic effects of licorice, which have also been established in a human study on seven 22-24 year old healthy male subjects by Decio Armanini et al. in 1999 (Armanini. 1999):
Figure 3: Changes in testosterone, androstenedione and 17-hydroxy-progesterone levels (ng/dl) in 7 healthy men upon oral adminstration of 7g of a commercial licorice preparation (data based on Armanini. 1999)
As you can see in figure 3, the 7 g of a commercial preparation of licorice (containing 0.5 g of glycyrrhizic acid) the men in the Amanino study received in the form of tablets (Saila, Bologna, Italy) on a daily basis had an immediate and pretty profound anti-androgenic effect (-44% total testosterone within 2 days!) resulting from the negative feedback of the phytoestrogenic components from Glycyrrhiza glabra. The levels of androstenedione and 17-hydroxy-progesterone on the other hand did not change.
Image 2: Licorice could help with menopause symptoms such as hot flashes, but it has potential corticosteroid-like side effects you should keep an eye on.
Update: Evelyn from CarbSane asked in the comment section whether licorice would not make a good addition to any natural menopause treatment. In fact, she is right that the very estrogenicity of the licorice extracts that is detrimental to men could be of great use for women going through menopause. A cursory search of the databases (how else could it be in view of the fact that you cannot patent licorice) does yet reveal that no one appears to be willing to invest serious money into studies on the effects of licorice / licorice extracts in menopausal women. Nevertheless, there is evidence for estrogen-like bone-building effects (Somjen. 2004) and a -2.4% reduction in the dreaded hot flashes over placebo (Nahidi. 2011).

Moreover, licorice appears to act as an SSRI (selective serotonine reuptake inhibitor) and may thus also help with moodswings and neurotransmitter-imbalances (Ofir. 2003), which can also cause sugar cravings and thusly induce weight gain. If you add to that the growth-inhibitory action the glabridins in licorice exhibit on breast-cancer cells (Tamir. 2000), it may be well worth to try to alleviate menopause symptoms with licorice. In that, it is yet important to know that the glycyrrhetinic acid in licorice has mineralocorticoid-like side effect (i.e. it works like cortisol), which can become problematic especially if licorice is taken as part of one of the typical pharmacological protocols conventional doctors tend to prescribe to their patients (e.g. Inada. 2007). My advice would thus be to carefully monitor your reaction, Ladies ;-)
Against the background of the results of both the initially mentioned rodent study by Zamansoltani et al. (Zamansoltani. 2009), as well as the certainly more relevant data from the 1999 study by Armanini et al. (Armanini. 1999) the 'test-tube' findings by Simons et al. gain a degree of practical significance many of the likewise bio-essay based studies, the manufacturers of purported (!) testosterone boosters like to cite to underline the scientific validity of their products, are lacking... you may want to keep that in mind before you try to counter the unwanted side-effects of a licorice-based "adrenal optimizer" by popping a few servings of the latest and greatest "scientifically proven testosterone booster" ;-)
Disclaimer:The information provided on this website is for informational purposes only. It is by no means intended as professional medical advice. Do not use any of the agents or freely available dietary supplements mentioned on this website without further consultation with your medical practitioner.