Tea consumption may not be linked to development of colorectal cancer; more research needed
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Key takeaways:
- Meta-analysis of 15 global studies showed tea reduces CRC risk by 24%, but researchers called this estimate “uncertain.”
- The actual effect on risk varies by regional and population differences.
Although previous data has demonstrated a possible link between tea consumption and a reduced risk for colorectal cancer, researchers reported the actual effect on risk ranges from a reduction of 51% to an increase of 18%.
“It has been found that tea polyphenols, one of the most abundant components in tea, can inhibit tumor development by promoting tumor cells apoptosis, inhibiting proliferation and angiogenesis via regulating some signaling pathways such as Ras-MAPK,” Yu Huang, of the Third Hospital of Hebei Medical University in China, and colleagues wrote in BMC Gastroenterology. “Despite this, the findings remain controversial.”
They continued, “Over the past few decades, numerous studies have evaluated the association between tea consumption and CRC morbidity and mortality; however, the conclusion is inconsistent and no consensus has been reached.”
In a population-based meta-analysis, researchers reviewed data from 15 studies (n = 2,693,030 participants) to assess the association between tea consumption and the risk for CRC. Eleven studies were cohort-based, three were case-control and one was a randomized controlled trial, and all demonstrated an “inherent relationship” between tea consumption and risk for CRC. Studies were conducted in Asia, North America, Europe and Oceania.
Using a random effect model for data analysis, researchers reported no statistically significant association between tea consumption and CRC risk (RR = 0.758; 95% CI, 0.489-1.176) based on combined results of all tests.
They then conducted subgroup and sensitivity analyses by geographic region, amount and type of tea consumption, sites of cancer and other factors to account for significant heterogeneity between studies.
According to results, while data from the American subgroup analysis suggested tea consumption “might protect against” CRC (RR = 0.326; 95% CI, 0.11-0.908), data from the U.K. (RR = 1.454; 95% CI, 1.031-2.05) and Italian (RR = 1.151; 95% CI, 0.079-1.229) subgroups had opposite results. By tea type, green tea consumption was significantly associated with a reduced risk for CRC (RR = 0.049; 95% CI, 0.031-0.067).
“Based on the studied samples of patients, the meta-analysis shows that tea reduces colon cancer risk by 24%, but the estimate is uncertain,” Huang and colleagues wrote. “The actual effect on risk can range from a reduction of 51% to an increase of 18%, but regional and population differences may cause differences.”
Sensitivity analyses, which excluded any single study, yielded overall results ranging from 0.49 (95% CI, 0.46-0.66) to 1.18 (95% CI, 1.07-1.34), which the study authors called “robust.”
They continued: “Taken together, this meta-analysis suggests that tea consumption may not be linked to the development of CRC. These relationships still need to be confirmed by additional well-designed large prospective studies and randomized clinical trials.”
Perspective
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Amanda Bode, RDN, LD
The main active component in tea that is thought to be protective against cancer is the antioxidant polyphenol. A tea’s antioxidant level depends on the type of tea and the method of preparation. Green tea generally has a higher level of antioxidants than black tea.
What we can glean from this meta-analysis is that green tea is still thought to have a protective effect against colorectal cancer. Other teas may lower cancer risk, but this study found no statistically significant association between tea consumption and CRC risk. However, this may be because the types of tea evaluated in this meta-analysis included a variety from 15 different studies with different aims. This study did not include data that evaluated herbal or fruit teas.
Other variables that were not included in this study are organic tea vs. nonorganic, brewing method and amount of tea consumed between studies analyzed.
In my practice, I usually support consuming tea as a healthy beverage, especially green tea, and I discuss that with my patients as part of their nutrition plan.
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