Licorice

Licorice (Glycyrrhiza plants, usually the Glabra species) have been used in Traditional Chinese Medicine to fairly good acclaim for various digestive and health problems, and as a general vitality promoting agent. Licorice is also routinely used as a candy product, and is inherently a functional food rather than just a candy (as the oil containing the traditional licorice flavor also contains some bioactive compounds).

One of the most important compounds in Licorice appears to be Glycyrrhizin, which is the sugar-bound form of Glycyrrhetic Acid (there exists both an alpha and beta isomer, with the latter 18β-Hydroxyglycyrrhetic acid being referred to frequently). This compound is highly relevant when consuming pure licorice extracts due to its good absorption and relatively high content, but also underlies a fairly reliable reduction in testosterone and a highly reliable increase in circulating cortisol after consumption. Both of these effects are dose-dependent and not associated with any toxicological effects (and reversed upon cessation of Licorice), but many persons may want to avoid Glycyrrhizin and Glycyrrhetic Acid due to these reasons.

An ethanolic extract of Licorice, sometimes used in supplements, is able to concentrate flavanoids and isoflavanoid compounds with a relatively low Glycyrrhizin content. Some of these flavanoids, including Glabridol as well as the Liquirtigenin class of flavanoids, appear to be the ones that exert properties that would be seen as 'beneficial'.

Prior to supplementing Licorice, please be aware of Glycyrrhizin (the agent that increases cortisol and reduces testosterone) and, if these results are not desired, try to get products with low Glycyrrhizin content (less than 500mg total dose daily). 150mg has been confirmed to not influence these hormones

Traditional Chinese Medicine recommends a decoction of 8-15g Licorice for health protection and up to 100g for disease states. Consumption of licorice in these doses as a food product does confer the same properties as supplementation, but the caloric and carbohydrate intake from either the root of confectionaries derived from the root need to be accounted for.

With supplementation, intakes of Licorice in the range of 150-300mg daily appear to be most commonly used and intakes of Deglyccyrhizinated (without Glycyrrhizin) up to 1800mg daily for 4 weeks are not associated with toxicity in humans.

The Human Effect Matrix looks at human studies (it excludes animal and in vitro studies) to tell you what effects licorice has on your body, and how strong these effects are.

Grade	Level of Evidence [show legend]
	Robust research conducted with repeated double-blind clinical trials
	Multiple studies where at least two are double-blind and placebo controlled
	Single double-blind study or multiple cohort studies
	Uncontrolled or observational studies only

Level of Evidence ? The amount of high quality evidence. The more evidence, the more we can trust the results.	Outcome	Magnitude of effect ? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.	Consistency of research results ? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.	Notes
	Oxidation of LDL	Notable	Very High See 2 studies	The decrease in oxidation of LDL seen with either licorice of isolated Glabridin appears to exceed 20% and is more than other supplements
	Canker Sores	Minor	- See study	Topical application of licorice is able to reduce canker sore size and pain associated with canker sores
	Cortisol	Minor	Very High See all 3 studies	Appears to increase cortisol at higher doses (500mg or more), with no significant influence at lower doses; this is related to the glycyrrhizin content, and would not occur in deglycyrrhizinated supplements
	DHEA	Minor	- See study	An increase in serum DHEA has been noted following licorice consumption
	Lipid Peroxidation	Minor	Very High See 2 studies	A decrease in lipid peroxidation is noted with licorice consumption, not to a remarkable degree
	Testosterone	Minor	Moderate See all 6 studies	There appears to be a testosterone reduction associated with intake of licorice above 500mg, but the magnitude of this reduction is quite variable and there is no robust information on the topic
	Adiponectin	-	- See study	No significant interaction between adiponectin and licorice
	Fat Mass	-	- See study	No significant influence on fat mass
	HDL-C	-	- See study	No significant influence of licorice on HDL
	Insulin	-	- See study	No significant changes in fasting insulin levels
	Insulin Sensitivity	-	- See study	No significant changes in insulin sensitivity following licorice ingestion
	LDL-C	-	- See study	No significant influence on LDL cholesterol seems apparent
	Lean Mass	-	- See study	No significant alterations in lean mass associated with licorice
	Total Cholesterol	-	- See study	No significant influence on total cholesterol is observed following licorice ingestion
	Triglycerides	-	- See study	No significant influence on triglycerides
	Weight	-	- See study	No significant interactions with body weight associated with licorice ingestion
	Blood Pressure	Notable	Moderate See 2 studies	Has the potential to increase blood pressure secondary to increasing cortisol; this is notable as it seems hypertensives are at greater risk from an adverse reaction to high dose licorice and as such should exert caution when using this herb (related to the glycyrrhizin content, and deglycyrrhizinated supplements should not have the same risk)
	Parathyroid Hormone	Minor	- See study	An increase in parathyroid hormone has been noted with consumption of licorice
	Estrogen	-	Very High See 2 studies	No significant alterations in serum estrogen
	Follicle-Stimulating Hormone	-	- See study	No significant alterations in follicle stimulating hormone seen with licorice consumption
	Luteinizing Hormone	-	High See all 3 studies	More evidence than not suggests no significant changes in lutenizing hormone, although limited evidence suggests an increase of minor magnitude.
	Prolactin	-	- See study	Prolactin appears unaffected following licorice consumption
	Sex Hormone Binding Globulin	-	- See study	No significant alterations in SHBG levels following supplementation

Studies Excluded from Consideration

• Duplication in Pubmed, other duplication added to Table^[1]

• Confounded with other nutrients^[2][3][4][5]

• Pharmacokinetic study^[6]

• No pure licorice group^[7]