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Drinking coffee and black tea regularly may reduce the risk of basal cell carcinoma and squamous cell carcinoma, two of the most common non-melanoma skin cancers worldwide.
However, caffeinated drinks are not a treatment for the condition. Rather, regular drinking of such beverages provides a protective effect against these common cancers, said Dr Oh Choon Chiat, Senior Consultant, Department of Dermatology, Singapore General Hospital (SGH).
Early experimental studies have indicated that caffeine can kill keratinocytes — the most common type of cells on the top layer of the skin — damaged by ultra-violet (UV) light. Other studies have shown that caffeine can prevent UV-induced carcinogenesis or cancers in animals. While such findings are preliminary, they are important as a proof of concept or feasibility for further studies to examine whether the results can be duplicated in humans, said Dr Oh.
“Three or more cups of coffee a day had the best protective effect against basal cell carcinoma and squamous cell carcinoma. Daily drinkers of black tea also had a reduced risk of non-melanoma cancer compared to non-drinkers,” said Dr Oh. “However, green tea and cola consumption did not demonstrate any protection.”
Non-melanoma skin cancer develops slowly in the upper layers of the skin, unlike the less common but more aggressive melanoma cancer. According to the Singapore Cancer Registry’s 2019 report, non-melanoma skin cancer is the sixth most common cancer among men and the seventh most common cancer among women from 2015 to 2019. The Chinese have the highest incidence of such cancers compared with their Malay and Indian counterparts, who have darker skin tones.
The incidence of non-melanoma skin cancer increases with age, and it is the highest among people with so-called Fitzpatrick skin types I and II, or those whose skin burns, but does not tan, easily in the sun.
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Dr Oh had examined the relationship between coffee, tea and caffeine consumption and the risk of non-melanoma skin cancers among the Chinese in Singapore in a study, “Coffee, tea, caffeine, and risk of non-melanoma skin cancer in a Chinese population — The Singapore Chinese Health Study”. Published in 2019 in the Journal of the American Academy of Dermatology, the study used data from the “Singapore Chinese Health Study”, a prospective cohort of 63,257 men and women between the ages of 45 and 74 years at recruitment from 1993 to 1998.
About 70 per cent of the participants drank coffee daily, 11 per cent drank black tea daily and 12 per cent drank green tea daily. Soda was less frequently consumed, with just 4.3 per cent reported drinking soda three or more times a week.
An eventual 61,321 participants were followed up for an average of 18 years, and the incidence of basal cell carcinoma cancer and squamous cell carcinoma was 427 and 182 respectively. The mean age that skin cancer was diagnosed was 74 years, with men accounting for 48 per cent of all skin cancers, the study found.
The study was prompted by the wide consumption of coffee and tea. “Because of high global consumption of both of these caffeinated drinks, there is much interest in their effects on human health and diseases, including skin diseases with a generally poor prognosis such as melanoma,” Dr Oh said. Other types of skin cancers were not included as the numbers were too small.
“If an individual is a regular coffee drinker, this study and other studies worldwide show that continuing this dietary habit may have protective effect against skin cancers,” said Dr Oh. He added that more studies need to be done to determine which component of coffee and tea — it may not necessarily be the caffeine — is responsible for the protective effect.
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