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Effect of Tea Consumption on Oral and Digestive Tract Health
from Tea & Your Health
by Dilmah
The human digestive tract consists of the oral cavity, pharynx, oesophagus, stomach, small intestine, large intestine and other related organs that work together to convert food through the digestion process into basic nutrients for absorption by the body. Large populations of microorganisms live in all parts of the digestive tract, some harmful and others beneficial to the human body. ‘Commensal microorganisms’ that live in the digestive tract are neither harmful nor beneficial. Different dietary items have different effects on these microorganisms. Some dietary items known as ‘prebiotics’ could increase the beneficial microorganism populations. Choosing such dietary items for regular consumption would contribute to improve the overall health of the individual.
A review of a large number of research studies, carried out to find the effect of tea consumption on the microorganism populations in the digestive tract, reveal that regular tea consumption assists in the reduction of harmful microorganism populations whilst increasing the beneficial microorganism populations. The main beneficial impacts observed are, reducing tooth decay and the risk of diseases with an inflammatory basis such as oral candidiasis, gastritis and peptic ulcers. In addition, high fluoride content in tea helps in the incorporation of fluoride into the teeth, making it more resistant toward tooth decaying bacteria.
The digestive system is a group of organs, working together to convert food through the digestion process into basic nutrients that could be absorbed into the body. The absorbed molecules will provide energy and building blocks to the entire body. Food passes through a long tube inside the body known as the alimentary canal or the gastrointestinal tract (GI tract). The GI tract is made up of the oral cavity, pharynx, oesophagus, stomach, small intestine and large intestine. Each part of the GI tract, assisted by other associated organs, play an important role in the digestion and absorption process.
The type of food consumed by an individual could have an influence, either harmful or beneficial, on the digestive tract. Choosing a diet which has beneficial effect on the digestive system will improve the overall health of the individual.
Oral Cavity
Food begins its journey through the digestive system in the mouth, also known as the oral cavity. Inside the mouth are many accessory organs that aid the digestion of food, tongue, teeth, and salivary glands. Teeth chop food into small pieces, which are moistened by saliva before the tongue and other muscles push the food into the pharynx or throat.
The action of teeth is to facilitate the digestion process and without this action it would be difficult for the other parts of the digestive system to digest large particles of food. Tooth decay is a very common problem which could impair the digestion process, whilst being painful to the individual.
Fluoride and Tooth Decay
The tooth consists of a hard substance called calcium apatite, which forms the inner core called dentine and the outer layer called enamel, the hardest substance in the human body. Fluoride could react with calcium apatite in the teeth to form fluoroapatite, which has a more closely packed structure than apatite and more acid resistant. Fluoroapatite formation could occur during the formation of teeth and, also, when the developed tooth surface comes into contact with solutions such as tea which contain fluoride. Therefore, dietary fluoride will make the teeth more resistant to decay.
Tea is a major source of dietary fluoride and a typical cup of tea could contains 0.14 to 0.34 mg of fluoride. Therefore, regular tea consumption would provide significant amounts of fluoride that would strengthen teeth against decay.1
As the importance of fluoride has been recognised in relation to tooth decay, many countries and cities in the world have implemented fluoridisation of public water supply at the rates of 1 - 1.5 mg/l. 2
Dental and Skeletal Fluorosis
Although fluoride is beneficial in reducing tooth decay, excessive fluoride intakes for long periods, in excess of 10 mg per day, could result in dental
fluorosis and later in skeletal fluorosis.2 Dental fluorosis or mottled teeth will result in brownish patches on the teeth and is mainly an aesthetic issue. However, prolonged intake of excessive fluoride could later lead to skeletal fluorosis, due to accumulation of fluoride in the bones. Skeletal fluorosis could cause pain and also damage to bone and joints.
The main cause for excessive fluoride intake is high fluoride content in the soil in certain regions. This will result in high fluoride levels in ground water and hence in drinking water. Further, agricultural products from these regions also would contain high fluoride, adding to dietary intakes.
Quality of Tea and Fluorosis
As tea contains significantly high fluoride compared to other dietary items, often tea is implicated with dental and skeletal fluorosis. However, it should be emphasized that consumption of good quality tea with normal or fluoridated water would not result in excessive intake of fluoride. The amount of fluoride in such a combination, good quality tea and normal or fluoridised water, would have beneficial effects against tooth decay.
However, as fluoride content increases with leaf maturity, fluoride content of inferior quality tea is higher than that of good quality tea. Typically, for the production of high quality tea, only the bud and the topmost two leaves are carefully hand plucked. This will indirectly ensure that mature leaf containing high fluoride would not come into the finished product. Some tea producing countries such as Sri Lanka, whose product is sold as ‘Ceylon Tea’, practice hand plucking of tea to ensure the production of high quality tea. Certain other countries use mechanical harvesting, where selective plucking of two leaves and bud are not possible.
In fact, in certain countries where mechanical harvesting is practiced, sometimes mature branches are harvested and processed into made tea which would contain excessive amounts of fluoride. Therefore, it is important to choose tea produced in countries such as Sri Lanka to ensure ingestion of normal amounts of fluoride. Further, it is advisable to verify the sources of instant tea and ready to drink tea also, as they too could contribute to excessive intake of fluoride.
Dental Caries (Tooth Decay)
Tooth decay or cavity formation is due to the action of specific bacteria in the oral cavity. Bacteria are normally found in the GI tract including mouth. Harmful bacteria in the oral cavity could convert starch and sugar in the food pieces to acids. All these; bacteria, acid, food pieces, and saliva combine in the mouth to form a sticky substance called plaque which adhere to the teeth. It is most common on the back molars, just above the gum line on all teeth, and at the edges of fillings. If plaque is not removed from the teeth by brushing, it turns into a substance called tartar, or calculus. Plaque and tartar irritate the gums, resulting in gingivitis (inflammation of the gums)
and periodontitis (inflammation spreading into the ligaments and bone that support teeth).
Acid formed in plaque could damage the enamel (outermost layer on teeth) and form cavities. Cavities could further penetrate into the teeth and exposure of nerve tissues of the teeth cause severe pain. However, regular consumption of fluoride containing food such as tea could strengthen the teeth and make them more acid resistant.
Effect of Tea on Tooth Decaying Bacteria
Streptococcus mutans is known as the main cariogenic (cavity forming) bacteria. Many research studies have been carried out to find the effect of tea on the populations of Streptococcus mutans. Recently a study done to assess the effect of mouth rinsing with green tea in comparison with chlorhexidine (a common mouthwash) and plain water, on Streptococcus mutans count in the oral cavity, revealed that green tea was equally effective as chlorhexidine.3
Many other similar studies had been done on the consumption of different types of tea including Black, Oolong and Green tea. A review of these studies have concluded that the flavonoids in black, oolong and green tea have the ability to reduce the Streptococcus mutans populations and thus contribute to reduce the tooth decay.4
Further, many studies have revealed that regular tea consumption reduces the ability of these bacteria to get attached to teeth. These bacteria use an enzyme called glucosyltransferase to convert starch in the diet to sticky, water insoluble, glucans. These insoluble glucans help bacteria and other material in the oral cavity to adhere to the teeth and promote tooth decay. Therefore, glucosyltransferase inhibitors have the ability to reduce tooth decay. Tea had been found to have the ability to inhibit the glucosyltransferase activity.5
Dental plaque formation could irritate the gums, resulting in Gingivitis or the inflammation of the gums. Gingivitis could lead to periodontitis where inflammation spreads into the ligaments and bone that support teeth. The amount of research studies carried out on the effect of tea on gingivitis and periodontal diseases are relatively less. In vitro (outside a living organism) studies have demonstrated the ability of tea flavonoids to inhibit bacteria such as Porphyromonas gingivalis which contribute to gingivitis and periodontal disease.6 Limited number of in vivo (inside a living organism) studies also indicate an inhibitory effect of tea on gingivitis and periodontal disease.7 However, further clinical trials are required to confirm the inhibitory effect of tea on gingivitis and periodontal disease.
Effect of Tea Consumption on Inflammation of the Oral Cavity
Inflammation of the oral cavity is a common disease which affects the mucous membranes in the oral cavity. Diverse factors contribute to the
origin of a range of oral inflammatory diseases. One common form of oral inflammation is caused by the presence of the fungus called Candida. Many species of Candida could live in moist cavities of the human body. A limited number of research studies indicate that tea could inhibit the growth of many species of Candida. 8
Microorganisms live throughout the digestive tract, from the oral cavity up to the anus. Some of these microorganisms are beneficial whilst others are harmful. Yet other microorganisms in the human GI tract, neither harmful nor beneficial, called “commensal microorganisms”, derive a benefit from the host whilst remaining neutral in impact.
Different dietary items have an effect on this large array of microorganisms that live in the GI tract. Some of the dietary items could reduce the harmful microorganisms whilst others may reduce the beneficial microorganisms. Therefore, it is possible to improve one’s health by choosing, for regular consumption, the dietary items which increase beneficial microorganisms and reduce the harmful microorganisms. Such dietary items that encourage the growth of beneficial microorganisms in the GI tract are known as ‘prebiotics’. Certain food items such as fermented milk products could introduce beneficial microorganisms to the GI tract. Such food items are known as ‘probiotics’. Research focused on ascertaining the effect of tea consumption on the microorganisms that live in the GI tract, has revealed that regular tea consumption results in the suppression of harmful microorganisms while increasing the beneficial organisms. A team of scientists from the National University of Singapore found that different strains of intestinal bacteria had varying degrees of growth sensitivity to tea phenolics and metabolites. The growth of certain pathogenic bacteria such as Clostridium perfringens, Clostridium difficile and Bacteroides spp. was significantly repressed by tea polyphenols and their derivatives, while commensal bacteria like Clostridium spp., Bifidobacterium spp. and probiotics such as Lactobacillus spp. were less severely affected. This indicates that tea polyphenols exert significant effects on the intestinal environment through modulation of the intestinal bacterial population, probably by acting as metabolic prebiotics.9
Helicobacter pylori is a harmful bacteria that causes infection in the stomach. It lives in approximately two-thirds of the world population. It is one of the main factors that lead to gastritis, which is caused by the inflammation of the lining of the stomach. Prolonged presence of Helicobacter pylori in the GI tract could lead to peptic ulcer, a sore in the lining of the stomach or duodenum, the first part of small intestine. A pain with a burning sensation in the stomach is the most common symptom of peptic ulcers. Formation of peptic ulcers by Helicobacter pylori increases the risk of developing stomach cancer.
Studies focused on examining the effect of tea consumption on the growth of Helicobacter pylori have revealed that both black and green tea consumption reduces Helicobacter pylori infection, indicating that regular tea consumption could contribute to the reducing of the risk of gastritis, peptic ulcers and stomach cancer.10
Effect of Tea Consumption on Oesophageal Cancer
Incidence of oesophageal cancer is more prevalent in Asian countries. An “oesophageal cancer belt” has been identified, which extends from northeast China to the Middle East through the Himalayan region. Tea consumption in these region is very high compared to the other parts of the world, and could be as high as twenty five cups per day. Therefore, when research began on the oesophageal cancer in this region tea consumption was suspected as the prime culprit. However, detailed research later had proven that tea consumption is not a risk factor, but that it contributed to a lowering of the risk.11 People in this region have the habit of consuming very hot beverages and food, probably to alleviate the cold. Later it had been confirmed that the real culprit was the consumption of very hot food and beverages including very hot tea.12
Conclusions
A large number of microorganisms, some beneficial and others harmful, live in the digestive tract of humans. Another set of microorganisms, known as ‘commensal microorganisms’ have neither beneficial nor harmful effects on humans. Regular dietary items have an effect on the populations of these microorganisms. Review of results from the studies on tea consumption and microorganisms of the digestive tract, indicate that it generally results in the reduction of harmful microorganism populations, while increasing the beneficial microorganism populations. Main effects of this activity are reduction of tooth decay, and the risk of diseases with an inflammatory basis, such as oral candidiasis, gastritis and peptic ulcers.
• Regular tea consumption reduces the risk of tooth decay by reducing the populations of tooth decaying bacteria and also by reducing their ability to adhere to the teeth. In addition, fluoride in tea contributes to strengthen teeth and making them more resistant towards decay. • Although fluoride helps in strengthening teeth, excessive fluoride consumption for a long period of time could lead to dental fluorosis (mottled teeth) and later skeletal fluorosis causing pain and also damage to bone and joints. • Consumption of good quality tea with normal or fluoridated water would not result in excessive intake of fluoride. However, fluoride content of inferior quality teas are higher than that of good quality tea as mature leaves are used for the production of inferior quality tea.
Therefore, tea should be selected from a source such as Sri Lanka where only the tender shoots are carefully hand plucked for processing into high quality end product. • Regular tea consumption results in the reduction of harmful microorganism populations throughout the digestive tract, while increasing the beneficial microorganism populations. Main effects observed due to this are reducing tooth decay, reducing the risk of diseases with an inflammatory basis, such as oral candidiasis, gastritis and peptic ulcers.
REFERENCES
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