Two epidemiological studies were published this past year looking at large populations and assessing potential correlations between tea consumption and reduced risk for certain diseases, most notably nonmelanoma skin cancer (NMSC), and diabetes mellitus. Both studies showed statistically significant, dose dependent relationships between drinking tea/caffeine and reduced incidence of NMSC, and type 2 diabetes mellitus (Chen et al., 2019; Oh et al., 2019).
These studies both looked at middle age, Asian populations, adding to previous data-sets showing people of European descent that consume more caffeine (from either tea and/or coffee) may be at less risk for nonmelanoma skin cancer (NMSC) than those who drink less or no caffeine.
Caffeine Appears to Reduce Risk of Skin Cancer:
Oh et al. (2019) discussed the results of their analysis, pointing to the experimental research that explains the physiological protection provided by caffeine against skin cancer cell proliferation and how it matches other epidemiological data; they explain in detail:
Experimental studies have provided evidence of an in vitro proapoptotic effect of caffeine on keratinocytes. Previous experimental studies have reported that caffeine has the ability to induce apoptosis in UV-damaged keratinocytes and prevent UV-induced carcinogenesis in animals. This photoprotective effect of caffeine has also been seen in cultured human keratinocytes. Caffeine inhibits the UV B-induced formation of thymidine dimers and may enhance apoptosis of precancerous cells through p53-dependent and p53-independent biologic pathways. One of these proapoptotic pathways mediated by caffeine includes the inhibition of the protein ATR serine/threonine kinase (previously known as ataxia telangiectasia and Rad3 related), which has preferential binding to UV-damaged DNA to obstruct premature chromatin condensation. Our finding of a protective association of coffee and caffeine intake with basal cell carcinoma (BCC) is consistent with all previous prospective studies in Australia, United States, and Europe that have examined the association between caffeinated coffee and risk of BCC. Conversely, decaffeinated coffee has not found to be associated with risk of BCC. (p. 399)
In other words, repeated studies have shown, in both laboratories, and in real-world analysis of large populations, that caffeine intake is significantly correlated with reduced risk of basal cell carcinoma and squamous cell carcinoma.
Caffeine Appears to Reduce Risk of Type 2 Diabetes Mellitus:
Chen et al. (2019) looked at a large Chinese population (> 12,000) and analyzed their tea-consumption, looking at potential relationships between tea-consumption and reduced risk of type 2 diabetes mellitus. They found statistically significant and step-wise relationships between daily tea drinking and reduced incidence of type 2 diabetes. This matches results from a number of other studies published in the last few years (Chen et al., 2019; Ding et al., 2019; Fu et al., 2017).
In introducing their research, they look at previous studies which provide similar and related results:
The predominant bioactive substance contained in tea, for example, catechin, caffeine, thearubigins and polyphenols, have been suggested to have anti-diabetic effects in diabetic mice. In addition, researches reported that tea consumption could prevent the development of obesity, T2DM and cancer. In recent years, population-based studies about association between tea consumption and diabetes have received significant attention. A survey conducted in Poland showed that tea consumption was negatively correlated with central obesity and fasting plasma glucose(FPG) in adults. The Singapore Chinese Health Study aged 45-74 years reported that consuming >=1 cup of black tea/d had a potential 14% reduction in risk of type 2 diabetes [RR: 0.86 (0.74, 1.00)] compared with non-consumers, and reported no association with green tea. Nevertheless, studies in Japan found that oolong tea may increase the risk of T2DM in Japanese women adults, but there was no correlation of green tea and black tea with the risk of diabetes. A cross-sectional study conducted in a community-based specialized care center in Pakistan observed that higher consumption of tea was independently associated with uncontrolled T2D, as OR: 1.5(95%CI: 1.0–2.2). In short, inconsistent results have been reported in different subjects, it seems to be prudent for tea drinkers to acquire effective prevention. (Chen et al., 2019, p. 2)
And in looking at their results, which clearly show a relationship between drinking tea and reduced occurrence of type 2 diabetes, they also note how these results match other results:
Our result is in accordance with a meta-analysis in which drinking more than three cups of tea/day was associated with a lower risk of T2DM. Additionally, Jing et al. also found that consuming > 4 cups/day may reduce the risk of T2DM by approximately 20% (RR: 0·80; 95%CI: 0.70, 0.93). Furthermore, experimental studies have discovered that several bioactive components, including catechins, gallic acid, polysaccharides and epigallocatechin-3-gallate within tea show antioxidant activity and improve insulin sensitivity. The polysaccharides extracted from fully fermented black tea and dark tea contain a higher percentage of low molecular weight portions (antioxidants) than those extracted from green tea and oolong tea, resulting in more benefits to T2DM. (Chen et al., 2019, p. 6)
All of this research, along with the other studies we have highlighted on our website that have been completed over the last couple of decades, consistently and repeatedly suggests that drinking caffeine, and particularly caffeine from tea (any type), provides potential protective benefits from a variety of common diseases.
For more research on tea, look to our Tea Research page where we host a collection of valuable research on the subject of our favorite beverage.
For our current curated selection of very high quality tea, check out our online store and/or contact us at 408-724-9999 to speak with Dr. Brown about the teas in-stock.
Bibliography:
Chen, G., Chen, R., Chen, D., Ye, H., Hu, B., Zeng, X., & Liu, Z. (2019). Tea Polysaccharides as Potential Therapeutic Options for Metabolic Diseases. Journal of Agricultural and Food Chemistry, 67(19), 5350–5360. https://doi.org/10.1021/acs.jafc.8b05338
Chen, Y., Li, W., Qiu, S., Vladmir, C., Xu, X., Wang, X., Nian, X., Chen, Q., Wang, Q., Tu, P., Zhang, L., Yan, S., Li, K., Chen, J., Wu, H., Wang, X., Wang, X., Liu, J., Cai, M., … Sun, Z. (2019). Tea consumption and risk of diabetes in the Chinese population: A multi-centre, cross-sectional study. British Journal of Nutrition, 1–9. https://doi.org/10.1017/S000711451900299X
Ding, Q., Zheng, W., Zhang, B., Chen, X., Zhang, J., Pang, X., Zhang, Y., Jia, D., Pei, S., Dong, Y., & Ma, B. (2019). Comparison of hypoglycemic effects of ripened pu-erh tea and raw pu-erh tea in streptozotocin-induced diabetic rats. RSC Advances, 9(6), 2967–2977. https://doi.org/10.1039/C8RA09259A
Fu, Q.-Y., Li, Q.-S., Lin, X.-M., Qiao, R.-Y., Yang, R., Li, X.-M., Dong, Z.-B., Xiang, L.-P., Zheng, X.-Q., Lu, J.-L., Yuan, C.-B., Ye, J.-H., & Liang, Y.-R. (2017). Antidiabetic Effects of Tea. Molecules, 22(5), 849. https://doi.org/10.3390/molecules22050849
Lin, H.-C., Lee, C.-T., Yen, Y.-Y., Chu, C.-L., Hsieh, Y.-P., Yang, C.-S., & Lan, S.-J. (2019). Systematic review and meta-analysis of anti-hyperglycaemic effects of Pu-erh tea. International Journal of Food Science & Technology, 54(2), 516–525. https://doi.org/10.1111/ijfs.13966
Oh, C. C., Jin, A., Yuan, J.-M., & Koh, W.-P. (2019). Coffee, tea, caffeine, and risk of nonmelanoma skin cancer in a Chinese population: The Singapore Chinese Health Study. Journal of the American Academy of Dermatology, 81(2), 395–402. https://doi.org/10.1016/j.jaad.2019.01.084
Saeed, M., Naveed, M., Arif, M., Kakar, M. U., Manzoor, R., Abd El-Hack, M. E., Alagawany, M., Tiwari, R., Khandia, R., Munjal, A., Karthik, K., Dhama, K., Iqbal, H. M. N., Dadar, M., & Sun, C. (2017). Green tea ( Camellia sinensis ) and l -theanine: Medicinal values and beneficial applications in humans—A comprehensive review. Biomedicine & Pharmacotherapy, 95, 1260–1275. https://doi.org/10.1016/j.biopha.2017.09.024