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Licorice root has long been used in herbal medicine and its properties in terms of dental health are now being acknowledged. Specific properties found in licorice which can be antibacterial and assist oral health but side effects can also be possible.

The name “licorice” refers to extraction from the root of a plant (although officially classified as a weed) called Glycyrrhiza glabra, which is a legume and so comes from the same family as peas, beans, lentils, and chickpeas. Licorice extract has long been utilized in herbal and traditional medicine and as a flavoring in foods and confectionary.

It is thought to originate from southern Asia and subsequently spread to the Middle East and into Europe. The ancient Egyptians used it medicinally and early manuscripts (from 360 A.D.) from a variety of countries cite licorice as being used for eye and skin conditions, coughs, gastrointestinal complaints and for loss of hair; and both Chinese and Indian (Ayurvedic) medicine systems consider it a key herb. 

The plant root is edible and is naturally sweet with a strong flavor; it can be eaten whole, chopped, or boiled in water to make an extract. This extract has often been associated with candy, being used to flavor confectionary. However, what is now sold as licorice candy in the U.S. is actually flavored with anise oil which (along with fennel) contains the same compound (anethole) as licorice, despite being botanically distinct.

Dried licorice root may assist with keeping teeth healthy

Despite once being the key ingredient in classic candy, the news is that licorice may actually be good for you! This is welcome news as tooth decay is reported to be the most common long-term condition in the U.S.A - an estimated 92% of American adults and seniors report having had tooth decay in some form, while 59% of teens and 42% of children aged 11 and under suffer from it.

A study reported that dried licorice root may help maintain tooth health: the authors stated that two particular compounds found in the dried root may help both prevent and treat tooth decay and gum disease. The compounds licoricidin and licorisoflavan A are thought to impact upon the growth of bacteria (specifically streptococcus mutans and streptococcus sobrinus) thought to lead to tooth decay.

These chemicals also inhibited two common gum disease bacteria—Porphyromonas gingivalis and Prevotella intermedia; and also a third bacterium, Fusobacterium nucleatum, often associated with periodontal disease.

Oral bacteria and the antibacterial compound found in licorice

Researchers have examined another chemical called trans-chalcone, in terms of its effect on oral bacteria; trans-chalcone is related to chemicals found in licorice root called chalcones and have antibacterial properties.

It is purported that trans-chalcone stops an enzyme needed by Streptococcus mutans so it is unable to form biofilms. Biofilms in the mouth are known as plaque and they protect the bacteria within them, which makes it harder to eliminate them.

While interesting, laboratory-produced results are not always replicated in the real world.  There are two problems associated with the use of licorice products for oral health:

  • substances in the mouth are diluted by saliva and

  • are quickly swallowed so perhaps don't remain in the required area for long enough to have an effect.

Other researchers have proposed a solution to this difficulty. Their study utilized a licorice lollipop and, as the lollipop was repeatedly sucked, there was a continual addition of potentially beneficial compounds to the oral cavity.

Studies with licorice lollipops and their impact on oral bacteria

In a pilot study, a small group of children was given sugar-free lollipops containing licorice extract. These children were at high risk for cavities and sucked two lollipops a day for three weeks, during which the level of Streptocococcus mutans in their saliva was considerably decreased. The number of bacteria remained at a decreased level for twenty-two days after the last lollipop before increasing again.

A further pilot study using lollipops, people of different ages sucked two lollipops a day for ten days. The licorice extract was high in a substance called glycyrrhizol A. Many displayed a considerable decrease in Streptococcus mutans in their saliva after the protocol.

Other research indicates that licorice root extracts may be anti-inflammatory and so assist with periodontal disease - even inhibiting the bone loss occurring in the disease, which could be very helpful for assisting with oral health.

Exercise caution, however - licorice may have side effects

Although licorice potentially has benefits for oral hygiene, ingesting the root or extract may be problematic for some people so aware of any dangers is key for those who plan to use them to improve dental hygiene.

According to experts in complementary and alternative medicine, licorice root supplements may not be safe to take for more than four to six weeks as they may lead to sodium retention, low potassium, and elevated blood pressure.

Therefore those with heart or kidney disease, diabetes or glaucoma should exercise caution and only supplement under supervision. The reason for side effects is that forms of the supplement contain glycyrrhizin, which apart from affecting potassium and sodium levels, sets off a chain reaction of chemical reactions which can also increase blood pressure. 

Therefore people with high blood pressure or heart disease need to be careful using licorice.

It is reported that children as young as 10 years old have experienced hypertension sufficient to require hospitalization after consuming too much licorice. Low potassium is a problem as it can cause muscle cramps, twitching or weakness and even lead to arrythmia or irregular heartbeat;  this condition is known as hypokalemia.

Pregnant women are also advised to avoid supplementing with licorice and should not consume large amounts of licorice in food.

Furthermore, some studies report that participants who ingested an excess of licorice root over just a two-week period suffered from fluid retention and metabolism abnormalities.

Therefore it is recommended that there is a maximum intake of 2 mg glycyrrhizic acid per kg of body weight per day as this amount is unlikely to cause adverse effects, although sensitive people may still respond adversely. Licorice is thought to contain 0.2% glycyrrhizic acid by weight so in real terms, the advice is not to eat more than 57g (2 ounces) of black licorice per day for more than a two-week period. 

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