Liquorice (Glycyrrhiza glabra) has a divisive flavor and salted versions of its confectionary form even more so. However, it is likely that humans have been consuming liquorice roots since prehistoric times. Consumption of liquorice in various forms is intertwined with a lot of human history spanning Eurasia and North Africa. Notable examples include documentation in Egyptian hieroglyphics (~1300 BCE), under the mythological Emperor Shennong (~2300 BCE) which later became integrated in Chinese medicine, Ayurveda (~200 BCE), and heavily documented by Theophrastus in Ancient Greece (~300 BCE)(Fiore, Eisenhut et al. 2005, Lee 2018). Liquorice was brought to the UK after the crusades where it was cultivated in Pontefract, West Yorkshire (Lee 2018). This later became the main ingredient of Pontefract Cakes, a confectionary which can still be purchased to this day in “The Oldest Sweet Shop in the World”.
The main ‘sweet’ tasting component of liquorice (Glycyrrhiza glabra) is the molecule glycyrrhizin. It is of particular interest as it has come under recent investigation for antiviral properties against coronaviruses (such as SARS-COV2) and hepatitis B. Ingestion of glycyrrhizin and liquorice appear to impact a whole range of responses and so the complete mechanisms are not fully understood (Sato, Goto et al. 1996, Banerjee, Baidya et al. 2023). Viruses are parasitic and need to enter host cells to replicate and in the case of COVID19, it was shown that glycyrrhizin can block the point of entry of the SARS-COV2 virus (ACE2 receptor), stop viral replication, as well as modulate the immune system favorably (Murck 2020). As a consequence, glycyrrhizin and indeed whole liquorice extracts are being tested under clinical trial conditions. Interestingly, glycyrrhizin has also been shown to work synergistically (complimentary) with many other therapies, including chemotherapy for cancer treatment and asthma (Wang, Yu et al. 2022). The multitude of effects that can be elicited by glycyrrhizin makes it harder to study mechanistically however there is both historical and modern precedent to explore these potentially beneficial properties further.
Liquorice has also been considered in oral health. Here the bioavailability (availability for absorption by human cells into circulation) is low, so a whole host of plant chemicals including glycyrrhizin can readily impact the many microorganisms that lead to disease. As a consequence, potential beneficial effects of liquorice have been discussed across many oral health complications (gingivitis, periodontitis, dental caries, oral candidiasis, ulcers, oral cancer) (Sidhu, Shankargouda et al. 2020). Liquorice has been added to some oral healthcare products including Reuterdent dental tablets to support their function.
Due to the potency of bioactive molecules in liquorice, it is important to note that the food safety authorities around the world caution excessive ingestion due to toxicity (~60 g). But small amounts go a long way, are perfectly fine and eaten all over the world for millennia with even some of history's notorious emperors encouraging its consumption.