July 3, 2012 — Coffee — and the caffeine it contains — may reduce the risk of developing basal cell carcinoma (BCC), according to new prospective data from more than 110,000 healthcare professionals who participated in 2 large, surveillance studies.
Study participants who drank more than 3 cups of caffeinated coffee a day had a 17% reduction in their relative risk of BCC compared with individuals who drank less than 1 cup per month.
Women benefited a bit more than men from drinking 3 cups a day, but in each case, the dose-response relationship was significant when compared with that noted in people who rarely drank coffee (Ptrend < .0001 in women; Ptrend = .003 in men).
A protective association was also found with other dietary sources of caffeine (chocolate, tea, and cola). "However, decaffeinated coffee consumption was not associated with a similar decrease in BCC risk," report the authors, led by Fengju Song, PhD, of Harvard Medical School, in Boston, Massachusetts, and Tiajin Medical University Cancer Institute, in China.
Their new study appears in the July 1st edition of Cancer Research.
These authors used data from the Nurses' Health Study (NHS; women) and the Health Professional Follow-up Study (HPFS; men) to explore a possible association between caffeine and skin cancers.
It is interesting to note that they did not find an association between consumption of coffee and other caffeine products and either squamous cell carcinoma (SCC) or melanoma.
The authors call for confirmatory studies to validate their findings. "BCC is increasing by 4% to 8% per year in the United States," they say, "and accounts for approximately 80% of newly diagnosed skin cancers and 30% of all newly diagnosed cancers. The prevalence of BCC will soon equal that of all other cancers combined," write Dr. Song and colleagues.
Animal studies have shown that oral or topical caffeine administration "markedly reduces the risk of skin cancer," say the authors. However, the triggering effect of caffeine on apoptosis, which eliminates damaged skin cells, "may be apparent only in basal cells but not in squamous cells," they speculate. Furthermore, with regard to melanoma, there is no scientific evidence that caffeine eliminates damaged melanocytes in the way it has been shown to eliminate keratinocytes, the precursors to nonmelanoma skin cancers, they say.
The new study provides an important addition to the literature, according to the authors.
An inverse association between coffee and nonmelanoma skin cancer risk was reported as early as 1986, but various studies have not distinguished between caffeinated and decaffeinated coffee or tea. "Therefore, it was unknown whether the inverse association was due to caffeine or other components of coffee," explain the authors.
A total of 112,897 eligible participants (72,921 female nurses and 39,976 male health professionals) were included in the analyses. As participants in their respective cohort studies, the men and women completed self-administered questionnaires biennially with updated information on their lifestyle, diet, and medical history.
Skin cancer identification was conducted routinely in both the NHS (24 years of follow-up from 1984) and the HPFS (22 years of follow-up from 1986).
Coffee consumption was categorized into 5 groups: less than 1 cup per month, 1 cup per month to 1 cup per day, 1 to 2 cups per day, 2 to 3 cups per day, and more than 3 cups per day.
Compared with individuals who consumed less than 1 cup of caffeinated coffee per month, study participants who consumed more than 3 cups per day had the lowest risk (relative risk, 0.83; 95% confidence interval, 0.77 - 0.87).
Coffee accounted for 78.5% of all caffeine consumption. "Caffeine from other dietary sources (tea, 18%; cola, 3%; and chocolate, 0.5%)...was also inversely associated with BCC risk, with nonsignificant relative risk comparable with that of caffeine from coffee," report the authors.
The authors admitted that their data on tea drinking — and a "number of possibly relevant issues" — were limited. They were unable to differentiate between green and black tea, brewing strength, and other matters because of "lack of detailed information about tea consumption on the food frequency questionnaires."
The study was supported by the National Institutes of Health. The authors have disclosed no relevant financial relationships.
Cancer Res. 72(13) July 1, 2012; doi: 10.1158/0008-5472.CAN-11-3511
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