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In the latest statistical salvo of an ongoing debate, people who consumed more than four cups of caffeinated coffee daily had a lower risk of head and neck cancer (HNC), according to a meta-analysis of 14 published studies.

The relative risk of any HNC declined by 17%, including statistically significant declines in the risk of oral cavity (30%) and oropharyngeal cancers (22%). People who reported drinking three to four cups of coffee daily had a 41% lower risk of hypopharyngeal cancer. Drinking decaffeinated coffee and drinking more than zero but less than one cup daily were associated with 25% and 34% reductions in the risk of oral cavity cancer, according to Yuan-Chin Amy Lee, PhD, of the University of Utah and Huntsman Cancer Institute in Salt Lake City, and colleagues.

Tea consumption also claimed a couple of spots in the data, consisting of a 29% reduction in the risk of hypopharyngeal cancer and a 9% reduction in the risk of any HNC cancer in association with more than zero but no more than one cup. Drinking more than one cup of tea daily boosted the risk of laryngeal cancer by 38%, as reported in .

The data on relationships between coffee and tea consumption with specific types of HNC distinguished the analysis from previous work, according to Lee.

"The main difference from past studies is that we were able to have a large enough study population to look at oropharyngeal and hypopharyngeal separately," said Lee. "In addition, I believe tea drinking was also not investigated to look at oropharyngeal and hypopharyngeal separately. With these results we defined the protective association with coffee drinking, both regular coffee and decaffeinated coffee."

Value of Observational Studies

Studies such as this one represent a necessary first step toward understanding the relationship between coffee and cancer, said Jian-Min Yuan, MD, PhD, of the University of Pittsburgh and Hillman Cancer Institute.

"A larger scale or experimental study can confirm the results," Yuan told 番茄社区app. "We see something and then develop experimental studies or animal models. This is a typical study for [the research process]."

Additionally, a meta-analysis offers a means to overcome the limitations of small sample size and reduce the inconsistencies among the individual studies.

The studies included in the meta-analysis were observational, and the biological mechanism for the relationship between coffee and cancer is not clear, he continued. However, the observational data allow researchers to develop and explore hypotheses.

"You have to [observe] something before you can do anything else," said Yuan. "That is what makes these studies important. They provide background that's helpful for future studies."

"At the end of the day, if we truly believe there is some sort of true protection [from coffee consumption], the last step is to do a clinical trial, randomizing patients to three cups of coffee [for example] or you give them nothing," he continued. "We follow them for 5 years or a certain number of years to see whether we can confirm the observations."

Search for Biologic Mechanism

Despite numerous studies spanning decades, relationships between coffee and tea consumption with cancer risk, specifically HNC, remain unclear, Lee and co-authors noted in their introduction. Coffee and tea are consumed worldwide and contain bioactive compounds with potential antioxidant, anticancer, and anti-inflammatory effects.

"We have looked at the literature, and we suspect that perhaps bioactive compounds other than caffeine contribute to this potential anticancer effect of coffee and tea," she said. "Polyphenols found in caffeinated and decaffeinated coffee and tea have exhibited anti-oxidative and anticancer properties that contribute to inhibition of angiogenesis, cell proliferation, cell invasion, and metastasis of cancer cells. This bioactive capability of coffee has also been found in lab studies of human cancer cell lines."

A by the International Head and Neck Cancer Epidemiology (INHANCE) consortium included nine case-control studies and showed an inverse association between caffeinated coffee and oral cavity and pharyngeal cancers. The data showed no association between tea consumption and HNC.

Given the increasing global burden of HNC, an updated meta-analysis of INHANCE data might provide more insight into coffee and tea consumption's association with the cancer, including the various subtypes. The new analysis comprised 14 individual-level case-control studies involving 9,548 cases of HNC and a control group of 15,783 individuals. Models developed for the analysis controlled for multiple demographic and behavioral/lifestyle factors, including smoking, alcohol consumption, and dietary intake.

Overall, coffee-drinking status (yes/no) was not associated with the risk of HNC or any of the subtypes. Daily consumption of more than four cups of caffeinated coffee had a modest but statistically significant inverse association with the risk of HNC (OR 0.83, 95% CI 0.69-1.00), as well as larger effects on the risk of oral cavity cancer (OR 0.70, 95% CI 0.55-0.89) and oropharyngeal cancer (OR 0.78, 95% CI 0.61-0.99).

"A dose-response relationship [P<0.01] was observed across increasing levels of daily caffeinated coffee drinking for HNC, oral cavity, oropharyngeal, hypopharyngeal, and laryngeal cancers," the authors stated.

Tea drinkers had a reduced risk of hypopharyngeal cancer as compared with non-drinkers. The data showed a dose-response relationship for daily tea consumption with HNC, hypopharyngeal, and laryngeal cancers (P<0.01).

"Our findings support associations on the protective effects of coffee and tea consumption on HNC risk," the authors concluded. "Further studies should assess the effects of coffee and tea consumption in regions beyond North America and Europe, especially in low- and middle-income countries burdened by HNC, as well as including different coffee and tea types and processing styles, which may further help contribute to an understanding of the mechanisms for the association between coffee and tea consumption and HNC risk."

Lee and colleagues hope to continue the research and extend their investigation into areas such as temperature of the consumed coffee and tea, as well as additives such as cream, sugar, and milk and the way coffee beans are prepared.

"If we can carry out an ideal study, we would like to have more information about the specific types of coffee and especially tea," she said. "We were not able to look into that in the current study."

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