Does Drinking Hot Tea Increase Cancer Risk? - Chromatography Investigates

It is one of the most popular drinks in the world. But a recent study published in the journal has looked at whether drinking tea could be a cause of cancer in certain regions of Africa. Could drinking tea, or be a cause of esophageal cancers?

ESCC - geographic regions?

The study was published in the journal Cancer Epidemiology and considered two main factors in the investigation. The researchers, from universities and hospitals in Kenya and the USA, considered drink temperature and exposure to polycyclic aromatic hydrocarbons, or PAH, in chai drinkers in rural Kenya.

The cancer they were studying was a type of esophageal cancer called esophageal squamous cell carcinoma or ESCC. Esophageal cancer is the sixth most common cause of cancer death worldwide with ESCC being the most common histologic type of the cancer. But ESCC has an unusual geographic distribution with high risk areas across central Asia and from eastern to southern Africa. The cancer is often only diagnosed late on during its development which leads to a poor diagnosis, a problem with most cancer types. Hence the need for research into possible causes of ESCC.

Drinking tea in Kenya - a risky business

In rural Kenya the drink of choice is chai - a mixture of black tea leaves, water and milk. The same ingredients used all over the UK every morning, in fact, chai is simply the Swahili word for tea. But, it is made by a different method and is consumed at very hot temperatures Could there be a correlation between the high rates of ESCC in Kenya and the drinking of chai? The researchers set out to study two main risk factors that could be associated with chai drinking in Kenya.

PAHs and temperature, a lethal combination?

Previous work has shown the presence of polycyclic aromatic hydrocarbons in drinks, and PAHs have also been found in the epithelium of ESCC patients. The researchers decided to analyse the content of PAH of tea leaves. The researchers used gas chromatography-mass spectrometry to analyse the PAH in leaves - a technique discussed in the article, Detection of molecular markers in aquatic sediments by ion profiles obtained by GC/MS system.

Consumption of hot beverages has been proposed as a risk factor for esophageal cancer in other regions - but the drinking of chai, and in particular, the temperature at which it is consumed has not been studied. The method of making chai - all the ingredients are mixed and then heated - means it is consumed at a high temperature when compared with how tea is made in the UK.

The team report that the PAH levels in Kenyan tea are very low when compared with other drinks that are associated with cases of ESCC. They also report sever limitations in their study. But conclude that the study: ‘demonstrated that temperature, but not PAH content, should be examined as potential a risk factor’.

The question remains unanswered.