We investigated the relationship between upper gastrointestinal tract cancers (including cancers of the oral cavity, pharynx, larynx, esophagus, and stomach) and consumption of hot tea, iced tea, coffee and carbonated soft drinks in the NIH-AARP Diet and Health Study. We found an inverse association between hot tea intake and pharyngeal cancer risk and a direct association between coffee intake and gastric cardia cancer risk. There were no associations observed between hot tea or coffee consumption and the other cancer sites, or between iced tea or carbonated soft drinks and any of the UGI tract cancers.
The possible preventive effect of tea on cancer has received much attention in recent years.16
Tea polyphenols may act at numerous points of carcinogenesis including cancer cell growth, apoptosis, and metastasis.17
On the other hand, chronic thermal injury from drinking very hot beverages may be a risk factor for carcinogenesis in some UGI sites,7,18,19
and black tea may acquire carcinogenic contaminants, such as benzo[a
]pyrene (BaP) or mycotoxins, when being processed.20,21
We found an inverse association between hot tea intake and pharyngeal cancer. Our results are consistent with a previous case-control study conducted in Southern Brazil, which found pharyngeal cancer risk was significantly decreased by 69% when comparing tea drinkers with non-drinkers.22
On the other hand, another case-control study conducted in India found a significant positive dose-response association between tea drinking and pharyngeal cancer.23
Comparing subjects who drank three, four, or five or more cups per day with those who drank two cups or less per day, a significant increase in risk for pharyngeal cancer was found (relative risks (RRs): 1.1, 1.8, and 2.3, respectively, P
for trend = 0.035). Studies that have analyzed both pharyngeal and oral cavity tumors together have shown no association between hot tea consumption and the risk of these tumors.5,24–26
We found no significant associations between hot tea intake and cancers of the oral cavity or larynx. This is consistent with three previous case-control studies.22,27,28
Since the oral cavity, pharynx and larynx are adjacent, connected structures and have similar squamous epithelium, the associations between hot tea and pharyngeal cancer alone that were found in our and other studies could be due to chance.
We found a suggestion of a protective effect of hot tea drinking for ESCC and no association between hot tea consumption and EADC risk. As noted above, these results probably reflect the combined effects of the tea constituents themselves, tea processing techniques, and thermal injury. A recent review of epidemiological studies evaluating the effects of green tea reported inconsistent findings between case-control and cohort studies of esophageal cancer.29
Three case-control studies found a protective effect for green tea against esophageal cancer.30–32
However, two cohort studies demonstrated positive associations between drinking green tea and mortality from esophageal cancer among men,33,34
and a randomized controlled trial with 400 participants showed no benefit for decaffeinated green tea against precancerous lesions or abnormal cell proliferation. 35
Since black tea may acquire potentially carcinogenic contaminants during processing, attention has also been paid to the association between black tea consumption and esophageal cancer risk.20,21
A recent case-control study conducted in Iran showed no association between the frequency of drinking black tea and ESCC risk.19
However, a hospital-based case-control study in China, including 1,248 ESCC cases and 1,248 controls, reported an inverse association between drinking Congou tea (a grade of Chinese black tea) and ESCC risk.36
In the current study, we didn’t distinguish between the consumption of green, black or herbal tea, and we did not assess the drinking temperature of hot tea. Also, only 16% participants in our cohort drank ≥1cups of hot tea each day, a lower intake than in most Asian populations. These differences may contribute to the heterogeneity of results.
We found no association between hot tea consumption and stomach cancer (both gastric cardia and non-cardia cancers). A meta-analysis of 13 epidemiologic studies found a significant inverse association between green tea consumption and risk of stomach cancer (RR: 0.82, 95% CI: 0.70, 0.96).37
Summary relative risks (95%CI) were 0.73 (0.64, 0.83) for case-control studies and 1.04 (0.93, 1.17) for cohort studies, respectively. A recent case-control study conducted in Italy, including 999 gastric cancer patients and 2,628 controls, also reported black tea consumption was unlikely to be associated with gastric cancer.38
This is the first study to examine the association between iced tea consumption and risk of upper digestive tract cancers. We found no consistent dose-response associations that suggested a link between iced tea intake and upper GI cancer risk.
Similar to hot tea, coffee is drunk at high temperatures and it contains compounds that may reduce UGI tract cancer risk. We found that drinking >3 cups of coffee per day was associated with increased risk of gastric cardia cancer but was not associated with gastric non-cardia cancer risk. Results from the few previous studies of these associations have been null.39,40
Therefore, it is not clear whether the difference we found by anatomic subsite in our study reflects a true difference or the effects of chance. For EADC, we found an inverse association during the last three years of follow-up but no association during the first three years. This difference by follow-up time could reflect chance or it may be that early cancer symptoms might alter coffee intake. We did not find associations between coffee consumption and ESCC or squamous cancers at other sites. Both case-control5,18,22,28,40–46
and cohort studies2–4
have previously explored these associations, but no consistent patterns have emerged.
The association between carbonated soft drinks consumption and UGI tract cancers has received little attention overall, but several reports have evaluated a possible association with esophageal adenocarcinoma. Carbonated beverages have been shown to increase gastric reflux, and thus could be associated with an increased risk of esophageal adenocarcinoma.9
Three previous case-control studies have examined this possibility. One US study showed an inverse association9
but the other two studies, from Australia10
and the US11
, showed no association. In our study we also found no association between carbonated beverage intake and EADC risk.
We also found no association between carbonated soft drinks consumption and risk of gastric cardia or non-cardia cancers. Gastric cardia cancer showed no association with carbonated soft drinks intake in two earlier case-control studies.10,11
The only previous prospective study of carbonated soft drinks and UGI tract cancers was conducted in Japan.47
After 8 years of follow-up of 1,524 men and 1,634 women, no association was found between cola or carbonated drink intake and stomach cancer in men (RR: 0.8, 95%CI: 0.4–1.8), but a significant positive association was found between carbonated drink intake and stomach cancer in women (RR: 3.9, 95%CI: 1.4, 11.1).
The current study has a number of strengths and limitations. It is a large prospective analysis with exposure information collected before cancer diagnosis. Furthermore, we performed lag analysis to examine whether reverse causation affected our results. The associations for UGI tract cancers were examined by anatomic sub-sites and different tumor histology types. To limit confounding, we adjusted our models for most of the major risk factors for UGI tract cancers, including alcohol and cigarette use. Nevertheless, confounding by these or other exposures, such as Helicobacter pylori
infection and esophageal reflux disease, could still affect results. We also lacked information on types of tea consumed (green, black, herbal, etc.) and we did not collect any information on the usual temperature of tea and coffee consumption, which may be an important risk factor for ESCC.7
In addition, we had limited power for several cancer sites because of small case numbers. Finally, because we examined multiple exposures and multiple endpoints, significant associations could be due to chance.
In summary, in this large prospective study that included 1,760 cases of oral, laryngeal, pharyngeal, esophageal and gastric cancers, we observed an inverse association between hot tea intake and pharyngeal cancer, a direct association between coffee intake and gastric cardia cancer and an inverse association between coffee intake and EADC during some follow-up periods.