Licorice Root For Tooth Decay and Gum Disease - Benefits and Dangers

Licorice (or liquorice) is a perennial herb in the legume family - the same family to which peas and beans belong. The root of the licorice plant is edible when raw and is sweet and very flavorful. In addition to being eaten whole and chopped, the root can be boiled in water to make a licorice extract, which can be concentrated and added to foods or drinks, or used to make a candy, sometimes in combination with other substances. The word "licorice" is used to refer to the plant, the extract or the candy. Licorice has been a popular additive to food and drinks since ancient times, and has also had a long use in traditional medicine.

Today there are many health claims made for licorice. There is preliminary evidence supporting some of these claims, but for others the evidence is mixed, with some experiments showing that licorice has a particular health benefit and others showing that it has no effect. However, the evidence that licorice is beneficial for oral health is slowly growing.

The results of a recent investigation are described in the Journal of Natural Products, which is published by the American Chemical Society. In this investigation scientists discovered that certain chemicals extracted from dried licorice root strongly inhibited tooth decay and gum disease bacteria. Previous experiments have suggested that other chemicals in licorice root may also be antibacterial.

Although the future role of licorice chemicals in oral hygiene looks promising, there are potential dangers to ingesting licorice root or licorice extract, especially for some people. Anyone eating or drinking licorice products or using them in the hope of improving dental hygiene needs to be very aware of these dangers.

According to the research published in the American Chemical Society journal, two antibacterial ingredients in licorice root are licoricidin and licorisoflavan A. The researchers discovered that each chemical strongly inhibited two major tooth decay bacteria - Streptococcus mutans, which is the most important bacterium involved in human tooth decay, and Streptococcus sobrinus. The chemicals also had a major inhibitory effect on two common gum disease bacteria - Porphyromonas gingivalis and Prevotella intermedia. In addition, the licoricidin moderately inhibited a third bacterium, Fusobacterium nucleatum, which is often associated with periodontal disease.

The scientists used an extract made from licorice root and tested it on bacteria which were placed in lab containers. Hopefully the licorice chemicals will have the same effect in our mouths as they did in the lab. If they do, we'll need to find out how much licorice needs to be used and how long it will have to stay in contact with oral bacteria to inhibit their growth.

In a pilot study researchers gave a small group of children sugar-free lollipops that contained a licorice extract. They found that when children at high risk for cavities sucked two lollipops a day for three weeks, the level of Streptocococcus mutans in their saliva was greatly decreased. The bacterial population stayed at a decreased level for twenty two days after the last lollipop was sucked and then began to increase again.

In another pilot study using licorice lollipops, the licorice extract in the lollipops was rich in a substance called glycyrrhizol A. In this study people of different ages sucked two lollipops a day for ten days. Many of the people (but not all of them) showed a big decrease in Streptococcus mutans in their saliva after the lollipop treatment.

Other research suggests that licorice root extracts can reduce the inflammation involved in periodontal disease and even inhibit the bone loss that occurs in the disease.

If you want to start eating and drinking licorice products now for their possible oral health benefits you need to take some precautions. Black and red licorice candy rarely contain real licorice extract. They’re generally flavored with anise oil and/or artificial flavors instead of licorice, and they contain a lot of sugar too, which is bad for oral health. Real licorice candy and products are available, but caution is needed before a person starts chewing licorice root, eating foods containing licorice or drinking licorice tea. In some cases licorice use can raise blood pressure and also lower the potassium level in the blood, leading to fluid and salt retention and possible heart problems. It may also cause muscle weakness, and since it contains isoflavones, which are phytoestrogens, it may affect the function of hormones in the body. Some evidence suggests that it lowers the testosterone level in men. In addition, licorice interferes with the action of some medications. A list of these medications is given at the U.S. National LIbrary of Medicine website.

The consensus of health experts seems to be that for most people licorice root is safe when used occasionally to flavor foods or drinks, provided small amounts are used. It may be safe in some people when used in larger amounts as a medicinal supplement, but mustn’t be used in medicinal doses for longer than four weeks. Ingesting very large amounts of licorice root or the use of licorice as a supplement for longer than four weeks may be dangerous.

The U.S. National Library of Medicine states that consuming thirty grams or more of licorice a day for several weeks can cause severe health problems. As little as five grams (about one sixth of an ounce) of licorice root per day can cause problems in people with high blood pressure, kidney disease, heart disease or a high-salt diet, or in people over forty years of age.

The amount of licorice root that can be safely tolerated depends on body weight as well as pre-existing health conditions and life stage. Pregnant and nursing women and people with estrogen-sensitive diseases shouldn’t eat licorice root. Licorice extract can also be dangerous.

Glycyrrhizin (or glycyrrhizic acid) is the main chemical responsible for the sweetness of licorice. It also seems to be responsible for many of the potentially dangerous effects of licorice consumption. It’s possible to buy deglycyrrhizinated licorice products (DGL products), which have had the glycyrrhizin removed and may therefore be safe. It's not known if ingesting DGL instead of whole licorice eliminates every dangerous effect of licorice, or if DGL has all the health benefits that are attributed to whole licorice.

Anything that decreases tooth decay and gum disease and is also safe to use would be a great addition to an oral hygiene routine. There are already oral hygiene products available that are flavored with licorice root or licorice root extract, but it’s unknown if they contain enough licorice to affect oral bacteria. Perhaps in the future we’ll be able to buy mouthwashes containing effective amounts of the antibacterial chemicals from licorice root (assuming their ability to fight oral bacteria is confirmed by more research), as well as toothpaste and chewing gum that contain known antibacterial licorice chemicals. Until then, we need to be careful when eating licorice products or drinking licorice tea, and keep track of the amount of licorice root that we’re ingesting.