Smoking, alcohol, hot tea and oesophageal cancer – how are they related?

May1, 2018, Dr Chee L Khoo

We all know that smoking and alcohol are associated with increased risk of oesophageal cancer. A recent large study from China looked at 456,155 people and found 1731 esophageal cancers over 9.2 years. They noticed that there was an interaction of hot tea with smoking. Smokers who drank burning hot tea daily had double the risk of oesophageal cancer compared with non-smokers who only occasionally drank tea.

But the really interesting finding was the effect of hot tea with alcohol. People who drank more than 15 g of alcohol per day and drank hot tea had an oesophageal cancer risk that was five times that of those who did not drink alcohol and only occasionally drank tea. Wow, that’s scary. The only problem with the study is that we don’t really know if it is the tea, the alcohol or the smoking that is causing the five fold increase.

What is the connection between smoking, alcohol and hot tea and their effect on oesophageal cancer? To understand the  connection, we need to understand the patho-physiology of Asian Flushing (their face gets red when they drink alcohol). You see, when alcohol is broken down, it is broken down in two steps:

 

Alcohol ——-> Acetaldehyde ——–> Acetate

Alcohol is converted to acetaldehyde (AA) by alcohol dehydrogenase and AA is converted to acetate by aldehyde dehydrogenase (ALDH). AA is very toxic and can cause DNA damage which is why the second enzyme quickly converts it to harmless acetate. 36% of east Asians (Chinese, Japanese and Koreans) have a defective ALDH enzyme and AA accumulates and causes flushing. So, flushing is a sign that they have a defective ALDH and they are at increased risk of cancer.

 

To thicken the plot, bacteria in the mouth can convert alcohol to AA. In fact, patients with the defective ALDH has three times more AA in their saliva than normal people. They swallow the AA laden saliva which now coats the oesophagus. It is thought that hot tea can damage the protective layer on the oesophagus. Hence, the increase incidence of oesophageal cancer.

Access the abstract here.

Eng MY, Luczak SE, Wall TL. ALDH2, ADH1B, and ADH1C genotypes in Asians: a literature review. Alcohol Res Health. 2007;30(1):22–27.

Brooks PJ, Enoch MA, Goldman D, Li TK, Yokoyama A. The alcohol flushing response: an unrecognized risk factor for esophageal cancer from alcohol consumption. PLoS Med. 2009;6(3):e50.