The series covering Natural Expectorants and Allergies will now look at the ingredient licorice, a plant derivative whose flavor people seem to either love or loathe in equal measure. This article will aim to explain what it is, where it is sourced, its recommended daily allowance, the functions/benefits as well as possible side effects from its usage, and in particular, evidence concerning its effectiveness as a treatment for allergies.
What is licorice?
Licorice (a.k.a. liquorice or “sweet root”), the extract obtained from boiling the root of the plant genus Glycyrrhiza and then evaporating the excess water, has been used for both culinary and medicinal purposes for thousands of years. From the ancient Eygptian, Greek, Roman, Indian and Chinese civilizations, through to the Middle Ages of Europe and subsequent later introduction to the America Indians, licorice’s varied qualities continue to be appreciated to the present day. In fact, licorice is now one of the most consumed herbs worldwide; depending on one’s country it may be found in candy and wooden chewable sticks, used in drinks (both soft and alcoholic) and various types of cuisine, valued as a coloring, flavoring and non-sugar sweetening agent and is a common component found in breath fresheners, tobacco and numerous pharmaceutical products.
Licorice Sources
Of the twenty or so species of the genus Glycyrrhiza from the Pea family (Fabaceae or Leguminosae) that are located throughout the Americas, Asia, Australia and Europe, it is Glycyrrhiza glabra (native to parts of southern Europe and Asia) that is most commonly referred to in literature when considering the term licorice. The root of the herbaceous perennial genus Glycyrrhiza is the source of licorice and this is considered to have a flavor similar to anise/aniseed (Pimpinella anisum), star anise (Illicium verum) and fennel (Foeniculum vulgare). Interestingly, as noted by Tyler (1993) in his book ‘ The Honest Herbal’, licorice candy produced nowadays in some countries (e.g. US or UK) derives its flavor primarily from anise.
Common sources of licorice include:
- Europe – Glycyrrhiza glabra var.typica
- Russia – Glycyrrhiza glabra var.glandulifera
- Iran/Iraq – Glycyrrhiza glabra var.violacea
- US – Glycyrrhiza glabra var.lepidota
- China – Glycyrrhiza uralensis and Glycyrrhiza pallidiflora
Recommended Daily Allowance of Licorice
Licorice can be obtained in various forms including whole dried root, powdered root, candice, capsules, deglycyrrhizinated licorice (DGL), extracts, lozenges, syrup, tablets, teas and tinctures, and can be either ingested or used topically for skin problems such as eczema.
It is the odorless, poor oral bioavailability compound called glycyrrhizin (syn. glycyrrhizic acid or glycyrrhizinic acid) and certain flavonoids present in licorice that appear responsible for many of its noted medicinal properties. In addition, glycyrrhizin is significantly sweeter (50x to 170x depending on one’s source) than table sugar (sucrose).
Although there is no official RDA (recommended daily allowance) for licorice root, Isbrucker and Burdock 2006 suggested the following:
“Based on the in vivo and clinical evidence, we propose an acceptable daily intake of 0.015-0.229 mg glycyrrhizin/kg body weight/day.”
They estimated the actual average daily intake of glycrrhizin in the US to be approximately 2 to 15 times higher than their recommended ADI (acceptable daily intake), namely 0.027-3.6 mg glycyrrhizin/kg/day.
Functions and Benefits of Licorice
Glycrrhizin is a natural cough suppressant and expectorant that exhibits corticosteroid-like properties but it is also responsible for many of licorice’s side effects such as hypertension and edema. In order to minimize some side effects, a deglycyrrhizinated form of licorice (DLG) is available, and this is often used for conditions such as canker sores (aphthous ulcer), peptic ulcers and reflux.
The flavonoids, in particular isoflavones, exhibit estrogenic effects; they are photoestrogenic in nature i.e. plant-derived xenoestrogens (type of xenohormone that imitates estrogen) and affect the body’s endocrine system (glands and hormonal secretion).
It may not be without reason that Chinese medicine considers licorice root (Gan Cao) to be the “great harmonizer”. Licorice is said to exhibit an extensive range of medicinal qualities, for example:
- Adrenal gland stimulant (adrenocortical hormone function)
- Antibacterial (Lee et al. 2009)
- Anticancer e.g. prostate cancer (Fu et al. 2004) or Hepatocellular carcinoma associated with Hepatitis C (Arase et al. 1997)
- Anti-fungal (Fatima 2009)
- Antispasmodic (Winston and Maimes 2007) (Crohn’s disease, muscle cramps, irritable bowel syndrome)
- Anti-ulcer: aphthous ulcer/canker sore (Das et al. 1989), stomach (Krausse et al. 2004) or duodenal, and for dyspepsia (heartburn)
- Antiviral: colds, flu, herpes (Curreli et al. 2005), Hepatitis B (Sato et al. 1996) and C and protecting liver (Fujioka et al. 2003), HIV (Ito et al. 1987 and Hirabayashi et al. 1991), SARS (Cinatl et al. 2003), shingles
- Demulcent (coats mucous membranes reducing inflammation and minor pain)
- Emollient (moisturizer)
- Enhances memory and cognition (Dhingra et al. 2004 and Parle et al. 2004)
- Hormonal disorders (polycystic ovary syndrome – Armanini et al. 2007),
- Laxative
- Pectoral (relieves chest or respiratory disorders)
- Premenstrual syndrome and menopause
- Reduces atherosclerosis (‘hardening of arteries’ – Fuhrman et al. 2002)
- Sialogogue (increases saliva flow rate) and possibly helping with
- Weight loss (Armanini et al. 2003, Kamisoyama et al. 2008 and Tominaga et al. 2009).
Furthermore, its touted anti-inflammatory and immune stimulant qualities are said to be beneficial for conditions such as arthritis and eczema, and together with expectorant characteristics, licorice may also assist respiratory problems associated with allergies, bronchitis, congestion, coughs, sore throats and even tuberculosis. From ancient herbal concoctions to modern cough and cold mixtures, licorice is a key ingredient when one needs to:
- Soothe an irritated throat and ease respiratory tract and lung inflammation and congestion.
- Break down and loosen troublesome phlegm, clear congestion and facilitate a productive cough and expectoration, yet
- Comfort a dry, irritating cough by providing relief as a cough suppressant.
There have been many decades of research concerning licorice with early examples including Revers 1948 (side effects of licorice) and Costello and Lynn 1950 (estrogenic substances from plants). Although certain studies may have indicated support for a given trait, others have shown conflicting or inconclusive results and there is currently a lack of in vitro and human clinical trials as well as clinical peer reviewed papers.
Therefore, even though many advocates of natural medicine imply that such claims are indeed fact (based on millennia of anecdotal support and selected scientific papers), the reality is that at present, one should err on the side of caution and apply due diligence. Although certain claims may in time be shown to be valid, there is currently a lack of proven medical worth. As defined in the article CAM Related Terms, proven medical worth implies, “human based scientific studies (in agreement about the effectiveness of the characteristic/trait) which are published in reputable scientific journals and that have passed independent and rigorous scientific review.”
Side Effects of Licorice
Though considered to be generally safe when consumed short-term and in moderate food amounts, various studies have raised concerns about licorice and its health risks and toxicity (Olukoga and Donaldson 2000 and Hesham et al. 2012).
Given licorice’s emmenagogue (stimulates pelvic and uterine blood flow) and potential abortifacient nature (causes miscarriage), it should not be consumed by women who are pregnant or breast feeding. One study, Strandberg et al. 2001 , noted excessive maternal consumption (≥ 500 mg glycyrrhizin per week= ≥ 100 g pure licorice) lead to babies being born earlier and another, Räikkönen et al. 2009, suggested it may affect both the behavior and IQ of offspring.
In addition, licorice also has an estrogenic (Somjen et al. 2004) quality and is therefore usually considered unsuitable for those with hormone-sensitive conditions e.g. breast cancer or endometriosis, and can also cause problems of sexual dysfunction in some men. However, certain studies have suggested possible anticancer properties of certain licorice components such as glabridin (Tamir et al. 2000 and Dong et al. 2007) and glycrrhizin (Niwa et al. 2007) under certain conditions. With regards to hormone effects, one study has also suggested that male serum testosterone decreases by consuming 0.5 g/day glycyrrhizin for one week .
Furthermore, licorice has the potential to interact with various drugs e.g. Coticosteriods, Digoxin, Diuertics etc. leading to reduced levels of potassium in the body (hypokalemia), as well as impact the effectiveness of other drugs, by affecting their function or the way they are broken down in the liver e.g. Diclofenac, Ibuprofen, Phenobarbital, Warfarin.
Although used to treat hyperkalemia (too much potassium in blood), excessive amounts of licorice can result in:
- Hypokalemia (too little potassium in blood – Elinav and Chajek-Shaul 2003 and Francini-Pesenti et al. 2008) and
- Pseudo-aldosteronism (Belhadj et al. 2001) – oversensitivity to adrenal cortex hormone resulting in hypertension (Sigurjónsdóttir et al. 2001) and edema. Therefore, those with heart and kidney problems should be aware of licorice’s hypertensive (raises blood pressure – Sigurjonsdottir et al. 1995 ) and water retentive (edema) propensity.
- Both hyperkalemia and hypokalemia can cause electrical irregularities of the heart leading to cardiac arrhythmia (Böcker and Breithardt 1991), possible cardiac arrest (Campana et al. 2003) and an increased risk of death.
Therefore, if a person intends to take licorice in medicinal quantities or on a medium to long term basis, they should consult a medical practitioner for advice. Infants and toddlers should not be given licorice and older children should avoid consuming it. Finally, though rare, it is possible for some people to be allergic to licorice (Isbrucker and Burdock 2006).
Licorice and Allergies
Licorice is said to be beneficial to allergy sufferers primarily due to its anti-inflammatory (reduce swelling), expectorant (thins mucus secretions facilitating clearing of congestion) and antitussive (decrease the desire to cough) properties.
Even though licorice is a common component of cough mixtures and has amassed considerable anecdotal proof, its effectiveness as a treatment for allergies is still being evaluated scientifically and is subject to ongoing research.
The following represent some examples of studies carried out since the millennium that relate to licorice and allergies:
- Kamei et al. 2003 study into Glycyrrhizae radix, a main component of Bakumondo-to (Mai-men-dong-tang) concluded that their results, “suggest that G. radix contains a potent antitussive compound, liquilitin apioside, whose antitussive effect may depend on both peripheral and central mechanisms.”
- Park et al. 2004 reported that GAMG (18beta-glycyrrhetinic acid-3-O-beta-D-glucuronide) which is produced when glycyrrhizin is metabolized in the body by human intestinal bacteria (Hattori et al. 1985 and Kim et al. 1999), may be useful as an “anti-allergic agent.”
- A review undertaken by Bielory 2004 looked at various studies published between 1980 and 2003 concerning complementary and alternative medicines (CAM) used to treat asthma, allergy and immunologic conditions. The study noted that many of the CAM agents (including licorice root) were, “associated with significant adverse effects” and ”usually in the form of a hypersensitivity reaction.” Furthermore, it went on to recommend,” Allergists and clinical immunologists need to become more knowledgeable about CAM so that they can inform patients about the use and possible abuse of these modalities.”
- Majima et al. 2004 found roasted licorice exhibited superior anti-allergic characteristics compared to un-roasted licorice. The study noted that, “the anti-allergic effect of roasted liquorice was due to glycyrrhizin, its metabolite glycyrrhetic acid, and the Fa fraction.“ In particular, the most potent Fa fraction was found in the roasted licorice.
- A 2006 Chinese study (GuoZhe) observed that, ”Allergic contact dermatitis of mouse can be treated and prevented by GL [Glycrrhizin]”
- Another 2006 study (Ram et al), this time from India, suggested that, “GRZ [Glycrrhizin] alleviates asthmatic features in mice and it could be useful towards developing a better therapeutic molecule in the future.”
- Shin et al. 2007 looked at Glycyrrhiza glabra and its components in vitro and in vivo antiallergic effects in mice. They found certain components, “potently inhibited the passive cutaneous anaphylactic reaction as well as the scratching behavior in mice.” Furthermore, licorice’s antiallergic effects are, “mainly due to glycyrrhizin, 18beta-glycyrrhetinic acid, and liquiritigenin, which can relieve IgE-induced allergic diseases such as dermatitis and asthma.”
- Kim et al. 2010 study into the anti-inflammatory effects of licorice and roasted licorice extracts noted that they,” have benefits in protecting against both acute inflammation and chronic inflammatory conditions including rheumatoid arthritis.” Furthermore, it would appear that roasted licorice extracts may inhibit “acute inflammation more potently than LE [licorice].”
- Houssen et al. 2010 looked at natural anti-inflammatory products for bronchial asthma and concluded, ”The used extract contained Boswellia serrata, Curcuma longa and Glycyrrhiza has a pronounced effect in the management of bronchial asthma.”
- Wu et al. 2011 study related to Nrf2-mediated genes and extracts of tea Chrysanthemum zawadskii and licorice Glycyrrhiza uralensis. The study commented that they both exhibited strong anti-oxidative and anti-inflammatory effects, “which would contribute to their overall health promoting pharmacological effects against diseases including cancer.”
- Li et al. 2011 reported that glycrrhizin promoted beneficial antioxidant and improved immune activity in both blood and nasal mucosa in mice with allergic rhinitis.
