People who drink herbal tea, even as little as once a week, may have a reduced risk of distal colon cancer, according to local collaborative research.
The study explored the effect of hot coffee, iced coffee, herbal tea and black tea on the risk of proximal colon, distal colon and rectal cancers.
Curtin University Professor Lin Fritschi says the relationship between herbal tea and decreased risk of bowel cancer was their most statistically significant finding and may warrant further investigation.
"Whether or not the relationship between the herbal tea and decreased risk of cancer is a "real" effect needs to be confirmed in other studies," Prof Fritschi says.
"One of the reasons people who drink herbal tea may have a reduced risk is that overall, they have a healthier diet than those who don't.
"The tea might just be a marker for that, not the actual protective factor.
"In addition, herbal tea comprises many types, for example peppermint, camomile etc."
Prof Fritschi says to obtain a better understanding of the effects of beverages on the bowel, it would be beneficial to explore types of tea that people consume.
"A better way to study it would be in a cohort study in which detailed information on tea consumption is obtained and people are followed for many decades," she says.
Data from 854 incident cases and 948 controls were analysed in a case-control study of colorectal cancer in Western Australia during 2005–07.
Differences between teas
Multivariable logistic regression was used to analyse the associations of black tea (with and without milk), green tea, herbal tea, hot coffee, iced coffee, and milk with colorectal cancer.
Consumption of black tea (with or without milk), green tea, decaffeinated coffee, and milk were not significantly associated with colorectal cancer risk.
Hot coffee was associated with a possible increased risk of distal colon cancer; however, this finding is inconsistent with previous literature.
An association between iced coffee and increased risk of rectal cancer was internally inconsistent and may be a chance finding.
Prof Fristchi says although their study was in part inconclusive, it would serve as a starting point for research into the relationship between cancer risk and beverage consumption.
"One strength of this study was the use of pathology reports for accurate determination of site-of-cancer origin in the large bowel," Prof Fritschi says.
"A further strength was the measurement of tea and coffee, which included the type, frequency and amount consumed."
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"Tea, coffee, and milk consumption and colorectal cancer risk." Green CJ, de Dauwe P, Boyle T, Tabatabaei SM, Fritschi L, Heyworth JS. J Epidemiol. 2014;24(2):146-53. Epub 2014 Feb 15. www.ncbi.nlm.nih.gov/pubmed/24531002