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  • We reviewed the literature for

    2019-08-11

    We reviewed the literature for other studies of preferred beverage temperature [[16], [17], [18],23,[31], [32], [33], [34], [35], [36], [37], [38], [39], [40]], (Table 4), and found that the mean preferred tea temperature in our study was 1.5 °C higher than any other studied population. It should be noted that the various studies presented in Table 4 use various methodologies to assess temperature and this limits the ability to compare them, and numerous studies concerning beverage temperature do not report descriptive statistics for temperature. Previously, the hottest beverage temperature reported in any geographic location was from Tanzania, with a mean of 70.6 °C [23]. Such hot temperatures could have an important effect on the risk of esophageal cancer in our population. A previous study from Golestan, Iran reported an 8.2-fold increase in ESCC risk for individuals who consume hot tea (>70 °C) versus those who drink warm tea (<65 °C) [18,41]. Interestingly, those who consumed hot tea at >70 °C in Iran included only 5% of the population. In contrast, 85% of the participants in our study preferred their chai at or above 70 °C (Table 4). Only one participant in our study preferred their initial chai drinking temperature less than the “very hot” potentially carcinogenic threshold of 65 °C [21,22]. All participants preferred their initial drinking temperature > 60 °C, which has been shown to be a risk factor for ESCC in a different (±)-Baclofen as evidenced by a prospective cohort study in Iran 41]. This Kenyan experience also contrasts with that reported from non-endemic areas, where mean beverage temperatures are nearly always <65 °C and are often <60 °C (Table 4). The importance of validating a questionnaire in this region rests on the impressive differences between populations. Of note, 12 (12%) of the participants in this study started drinking the chai immediately, at the poured temperature of 80 °C. Thus, the true mean preferred drinking temperature was underestimated in this series. All twelve of these drinkers of extremely hot chai were Kipsigis men. In addition to the starting temperature, there may be additional factors that potentiate the thermal injury potential of Kenyan chai. In our population, all participants preferred chai and drank multiple cups a day with an average of 4.2 (+1.9) cups per day, roughly equivalent to 1260 mL (+570 mL). In Iran, the association with tea and ESCC is dose-dependent with an increase in risk for those who drink more than 3 cups (270 mL) per day [41]. It is not clear what impact the volume of beverage consumed, the quantity that is sipped or swallowed, has on ESCC risk, but higher volumes increase intra-esophageal temperatures in experimental studies [27] and should increase the time that the esophageal mucosa is exposed to potential thermal injury. Studies in experimental animals have demonstrated the potentiating effects of thermal injury by hot liquids on carcinogenic agents in the esophagus. After instilling very hot water (>65 °C) into the esophagus of rats, Li et al. observed an increase in nitrosamine-induced esophageal tumors, and the effect increased with increasing water temperatures [42]. In addition, Tobey et al. demonstrated that exposure of rabbit esophageal epithelium to hot beverages negatively impacted epithelial structure and function [43]. The questionnaire agreement was less strong than the agreement of similar questions and measured tea temperatures in the study of Islami et al. in Iran (weighted kappa values of 0.49 and 0.39) [18]. This difference in the (±)-Baclofen agreement between interview questions and measured temperatures reminds us that questionnaires designed to evaluate associations between hot beverage consumption and clinical outcomes should be validated against measured temperatures for each population. Asking Europeans if they consume “hot beverages” and drawing conclusions about cancer risk is very different than asking East Africans (since the meaning of “hot beverages” probably differs by about 15 °C as we have shown). In addition, systematic reviews of hot beverages and esophageal cancer risk should analyze studies that include measured temperatures of consumption separately from those that report only subjective estimates of relative beverage temperature. As someone drinking “warm” chai in our region would still be consuming very hot (>65 °C) beverages in other regions. The mean serving temperature in many other populations [[44], [45], [46]], is similar to the mean initial temperature of drinking in our population. Our institution is undertaking a case-control trial on the risk factors for ESCC, the validation and information of the questionnaire will help in the understanding of hot chai as a risk factor. A case-control study from Eldoret in Kenya reported an association between hot beverages and ESCC [24]. Although no temperature measurements were included, the controls reported consuming “very hot”, “hot”, and “warm” tea in 7%, 68%, and 25%, respectively, which is quite similar to our distribution of 11%, 64%, and 25%.