Dangers of Hot Tea

As Sri Lankan most of us start our day with a cup of tea. Some like to have lukewarm tea while others needs very hot tea. Both green tea and black tea are beneficial for our health since they contain plenty of health-related chemical compounds. Tea is considered as a health-promoting beverage. It is believed to be able to prevent cancer, cardiovascular diseases and metabolic abnormalities. However, according to recent research studies, drinking very hot tea is unhealthy because it can contribute to esophagus cancer. This week I am going to discuss this topic broadly.

What is Tea?

Tea is one of the most ancient and popular beverages consumed around the world. There are 03 major types of teas namely Green tea (non-fermented tea), Oolong tea (semi-fermented tea) and Black tea (fermented tea). Tea contains polyphenols, alkaloids (caffeine, theophylline, and theobromine), amino acids, carbohydrates, proteins, chlorophyll, volatile organic compounds, fluoride, aluminum, minerals, and trace elements. The polyphenols, a large group of plant chemicals that includes the catechins, provide health benefits that have traditionally been attributed to tea; especially green tea. The most active type of catechin in green tea is epigallocatechin-3-gallate (EGCG) while Black tea contains much lower concentrations of these catechins compared to green tea. 

Anticancer properties of tea

Catechins in green tea have substantial free radical scavenging activity and may protect cells from DNA damage, caused by reactive oxygen species. Many of the potential beneficial effects of tea have been attributed to the strong antioxidant activity of tea polyphenols. Tea polyphenols have the ability to inhibit tumor cell multiplication, as shpwn in laboratory and animal studies. In addition, tea polyphenols may protect against the damages caused by ultraviolet B (UV) radiation. They may modulate the the functioning of the immune system. Furthermore, Green tea has been shown to activate detoxification enzymes such as glutathione S-transferase and Quinone Reductase that may help protect against tumor development. 

Esophageal cancer

Esophagus is an organ of our digestive tract which is a long, hollow tube that runs from throat to stomach. It helps move the swallowed food from the back of throat to the stomach where digestion takes place. Esophageal cancer usually begins in the cells that line the inside of the esophagus. Esophageal cancer is classified according to the type of cells that are involved. There are 03 major  types of esophagus cancer such as Adenocarcinoma (Adenocarcinoma begins in the cells of mucus-secreting glands in the esophagus and occurs most often in the lower portion of the esophagus ), Squamous cell carcinoma (The squamous cells are flat, thin cells that line the surface of the esophagus and Squamous cell carcinoma occurs most often in the upper and middle portions of the esophagus) and Other rare types (Some rare forms of esophageal cancer include small cell carcinoma, sarcoma, lymphoma, melanoma and choriocarcinoma). Among these 03 types, esophageal squamous cell carcinoma is the sixth most common cause of cancer deaths worldwide.

How hot tea causes esophageal cancer

Tea is a healthy beverage. However when we consume very hot tea, it will adversely effect on esophagus of digestive tract due to potential thermal injury that can be caused. This is because very hot beverages were identified to be Group 2A carcinogens by IARC (International Agency for research on cancer) monographs. Moreover, scientist Mirvish in 1995, discovered that release of N-Nitroso compounds (NOCs), which are formed as a result of an inflammatory processes, is associated with chronic thermal irritation of the esophageal mucosa. It may also contribute to the development of carcinogenesis of the esophagus. But in experiments involving animals, there was also limited evidence for carcinogenicity with very hot water. 

Research studies in International Agency for Research on Cancer have reported that very hot tea, served above 60 degrees Celsius (140 degrees Fahrenheit) when drunk over a period of over 10 years, had nearly double the risk for esophageal squamous cell carcinoma compared to those who drank lukewarm tea and less tea in general.  The World Health Organization’s International Agency for Research on Cancer has classified drinking “very hot” beverages, above 65°C, as “probably carcinogenic” to humans. 

Tea is a healthy beverage. However when we consume very hot tea, it will adversely effect on esophagus of digestive tract due to potential thermal injury that can be caused

Hot tea, alcohol, tobacco use and esophageal cancer

Tobacco smoking and alcohol consumption, as well as the chemical compounds and adverse thermal effect of high temperature tea, considerably complicate the association between hot tea consumption and esophageal cancer risk.  As concluded by Chinese ( Jun Lv and others ) research study in 2018, there is a significant relationship of high-temperature tea consumption with excessive alcohol consumption or smoking on esophageal cancer risk. Those who had assembling habits of consuming high-temperature tea, excessive alcohol, and tobacco had a risk of developing esophageal cancer over five times as high as those who consumed none.

The consumption of very hot tea and also other hot foods and beverages process the esophageal cancer due to the chronic thermal irritation of esophageal mucosa might stimulate the  endogenous formation of reactive nitrogen species and subsequently form carcinogenic nitrosamines. It has  been assumed that the repeated thermal injury may impair the barrier function of the esophageal epithelium, thereby making it more vulnerable to the damage by intraluminal carcinogens especially in esophagus squamous cell carcinoma.  Moreover, researchers have found that swallowing hard food without sufficient chewing due to dental problems may cause physical irritation to the esophageal epithelium and increase the risk of cancer. Furthermore, there are increase in esophageal cancer risk with a combination of consuming high-temperature tea, excessive alcohol, and tobacco. Therefore, we have to stop those attitudes in order to preserve our health for longer lime without any illness. 

The writer is a medical laboratory technologist at a private hospital and holds a MSc Degree in Industrial and Environmental Chemistry from the University of Kelaniya and a BSc in Food Production and Technology Management degree from the Wayamba University of Sri Lanka.