Tea, Coffee, and Milk Consumption and Colorectal Cancer Risk

1. released online February 15, 2014 Tea, Coffee, and Milk Consumption and Colorectal Cancer Risk Journal of Epidemiology Chadwick John Green, PalinadeDauwe,Terry Boyle,SeyedMehdi Tabatabaei, Lin Fritschi, and Jane Shirley Heyworth 報告組員：施詠譯、陳塏嶙、林蘶峰 指導老師：褚俊傑 IF值：2.113

2. Background • Data regarding the effects of tea, coffee, and milk on the risk of colorectal cancer are inconsistent. We investigated associations of tea, coffee, and milk consumption with colorectal cancer risk and attempted to determine if these exposures were differentially associated with the risks of proximal colon, distal colon, and rectal cancers. • Key words: epidemiological; tea; coffee; milk; colorectal cancer; risk factors

3. INTRODUCTION • Poor diet is a known modifiable risk factor for colorectalcancer(CRC), and many foods and beverages have beenassociatedwith increased or decreased risk of CRC.Thesebeveragesinclude tea, coffee, and milk, which are among the most commonly consumed beverages in the world.

4. Tea leaves are a source of flavonoid antioxidants—apolyphenol subgroup. • Previous reviews have shown that polyphenols inhibit tumor invasion, cell proliferation, and cell transformation, and induce tumor apoptosis

5. Coffee has an antioxidant capacity up to 8 times that of an equal volume of tea, depending on the preparation method used. Unfiltered coffee also contains 2 important diterpenes—cafestoland kahweol—which may reduce cancer risk by altering the way the body metabolizes carcinogens

6. We investigated theassociations of tea, coffee, and milk consumption with CRCrisk and attempted to determine if these exposures weredifferentially associated with the risks of proximal colon,distalcolon, and rectal cancer

7. METHODS • The Western Australian Bowel Health Study (WABOHS) wasa population-based case-control study of CRC. • Information on tumor site was obtained for each case fromthe pathology report stored at the Western Australian CancerRegistry. Tumors arising in the cecum, ascending colon,hepatic flexure, and transverse colon were classified asproximal colon cancers; tumors arising in the splenicflexure, descending colon, and sigmoid colon were classifiedas distal colon cancers; and tumors arising in the rectosigmoidjunction and rectum were classified as rectal cancers.

9. METHODS • Data on tea and coffee consumption 10 years previouslywere collected by self-administered questionnaire • Data on frequency ofconsumption werecollected for hot black tea, tea with milk,hot green tea, hot herbal tea, hot caffeinated coffee, hotdecaffeinated coffee, and iced coffee.

10. Statistical analysis

11. RESULTS

14. DISCUSSION • The results of this study suggest thatconsumption of herbaltea and iced coffee may be associated with the risk of cancersarising in different parts of the colorectum.Consumption ofherbal tea was associated with a significantly decreased risk ofdistal colon cancer, and consumption of iced coffee wasassociated with a significantly increased risk of rectal cancer

15. DISCUSSION • However, neither herbal tea consumption nor iced coffeeconsumption was associated with the risk of proximal coloncancer. Hot caffeinated coffee was associated with a possibleincreased risk of distal colon cancer. Black tea (with orwithout milk), green tea, decaffeinated coffee, and milk werenot significantly associated with CRC risk at any subsite.

16. DISCUSSION • In conclusion, this study found that consumption of black tea (with or without milk), green tea, decaffeinated coffee, and milk were not significantly associated with CRC risk. Hot coffee was associated with a possible increased risk of distal colon cancer; however, this finding is inconsistent with much of the previous literature. An association between iced coffee and increased risk of rectal cancer was internally inconsistent and may be a chance finding. Herbal tea consumption was associated with a significantly decreased risk of distal colon cancer, and this relationship may warrant further investigation.

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