Health Secrets Steeping in Your Teacup

Short takes

• Epidemiological studies show that tea drinkers have better health outcomes;

• Randomized controlled studies (more powerful) show the following:

  • Black tea drinkers with diabetes had better cardiometabolic outcomes;

  • Green tea drinkers improved their cholesterol values and blood pressure.

• There are additional impacts of thyme tea on dysmenorrhea (period cramps), and probable benefits of green tea for cognition, and prevention of cancer recurrence;

• Avoid drinking tea that is too hot (130-140 F); it has been associated with esophageal and gastric cancer;

• Choose looseleaf tea to avoid microplastics from the tea bags: even some paper bags have plastic components. Avoid drinking through plastic lids. And don’t (must I mention it) microwave water in styrofoam. Aarghhh.

• For coffee drinkers, a recent association study shows 12% less all-cause mortality, and 30% (!!) less cardiovascular mortality, only for morning coffee drinkers (Wang, 2025).

Favorite finds

• I have no affiliate links, nor am I associated with these companies;

• The company Longeviteas got me started on this post, because they list studies on their website;

•  Rishi Teas and Botanicals is my favorite source for organic tea, though I avoid their flavored teas (even “natural flavors” are sometimes not extracted from plants, and I prefer to avoid this); I am also happy with my purchase of organic bancha tea from Tealyra.

• For chai spices, I highly recommend Anjali's Cup. We combine their spices with either black or green tea in the morning, then switch to caffeine-free rooibos tea in the evening. Having the spices separate from the tea lets you perfect your own cup - adjust the sweetness to your taste and add your choice of nut or dairy milk.

• The type of green tea with the most epicatechins, which are thought to cause the beneficial health effects, is “bancha.” The one with the least caffeine is “kukicha.” The most common is “sencha,” so shop carefully! (Now you are officially a “green tea connoisseur.” 🍵 )

Deep Dive

The topic of tea is a good entry point to quickly review the kinds of studies used to draw these conclusions. The weakest type, in my view, is the study of general biological mechanisms. While a substance can have an effect on something in a petri dish, that is very far from guaranteeing it will have that effect on you.

Next would be epidemiological, or association studies. These examine large groups of people, asking about their tea consumption and medical conditions. The problem is that it’s hard to determine from these studies what represents a causal relationship versus an association for other reasons. One clue can be the dose-response relationship – if higher tea consumption correlates with better health outcomes, that could more strongly suggest that tea is the factor making the difference.

My favorite type of study is the randomized controlled trial. Take 200 people, assign 100 of them to drink tea and give the other 100 a placebo they can't distinguish from tea. Then after a few months or years, compare the health outcomes between the groups.

Health Effects of Tea

In this newsletter, I have focused primarily on randomized controlled studies. I am also including research showing dose-response relationships that suggests black tea helps with increased longevity, coronary artery disease, strokes, and type 2 diabetes in diabetic patients (Yi).

Green tea reduces blood pressure after 12 weeks of consumption (Liu). While the effect is modest, maintained over decades it could account for the benefits observed in epidemiological studies. Many of these studies involve participants drinking 3 cups of green tea daily. Bancha tea may be the best option, as it has high levels of epicatechins but also fairly low caffeine. Also it can be steeped at least twice.

Consuming 3 cups of green tea daily for 14 weeks modestly improves cholesterol levels (reducing total cholesterol while slightly increasing HDL) and enhances glucose regulation in mildly diabetic individuals (Yazdanpanah). Consuming even more green tea provides additional benefits, even up to >10 cups a day (Pang). However, there is a risk of excess fluoride accumulation with excess tea drinking. Levels can be measured in the bloodstream.

The hope is that a longer time frame leads to meaningful protection, which would explain the patterns seen in epidemiological studies. An alternative approach is using extracts, such as green tea extract. Research on extracts tends to be more prolific as it can lead to licensable products, and researchers can rely on precise dosing, making experiments more comparable. However, this newsletter is not about supplements.

Some Lesser Known Effects

In a study of teenage girls in Ethiopia, drinking thyme tea appeared to reduce primary dysmenorrhea (period cramps) by almost 60%. This case-control study compared girls with and without cramps, finding that those without cramps were significantly more likely to drink thyme tea at least once a day - a traditional medicinal beverage in Ethiopia (Zeru). Conversely, girls with cramps were more likely to consume coffee. Those without cramps also tended to eat regular meals and more vegetables. While this highlights the challenges of such research, it offers a promising and harmless intervention worth exploring.

Drinking tea enhances the benefits of exercise for cancer patients (Hu). While tea consumption alone shows limited effect, and exercise independently provides clear benefits, the combination of tea and exercise offers additional advantages.

Green tea consumption may reduce dementia risk (Jiang) in daily tea drinkers. This conclusion stems from a review of cohort studies, where researchers tracked the tea drinking habits of participants and health outcomes over years. Across multiple studies, the risk reduction ranged from 20-40%, with more pronounced benefits in higher-risk individuals. Though not based on randomized controlled trials, these findings are encouraging.

Conclusion

This research has truly inspired me to embrace bancha green tea as a daily ritual! The evidence suggests that even a single daily cup can help protect cognitive function while supporting heart and metabolic health. It's remarkable how such a simple change could yield such meaningful benefits.

Not a fan of green tea? No worries - black tea offers its own array of health benefits, and also consider morning coffee. The key is finding what you enjoy and making it part of your daily routine. Here's to your health - one cup at a time!

REFERENCES

Jiang N, Ma J, Wang Q, Xu Y, Wei B. Tea intake or consumption and the risk of dementia: a meta-analysis of prospective cohort studies. PeerJ. 2023.

Liu G, Mi XN, Zheng XX, Xu YL, Lu J, Huang XH. Effects of tea intake on blood pressure: a meta-analysis of randomised controlled trials. Br J Nutr. 2014.

Pang J, Zhang Z, Zheng TZ, Bassig BA, Mao C, Liu X, Zhu Y, Shi K, Ge J, Yang YJ, Dejia-Huang, Bai M, Peng Y. Green tea consumption and risk of cardiovascular and ischemic related diseases: A meta-analysis. Int J Cardiol. 2016.

Wang X, Ma H, Sun Q, Li J, Heianza Y, Van Dam RM, Hu FB, Rimm E, Manson JE, Qi L. Coffee drinking timing and mortality in US adults. Eur Heart J. 2025.

Yazdanpanah Z, Salehi-Abargouei A, Mozaffari Z, Hemayati R. The effect of green tea (Camellia sinensis) on lipid profiles and renal function in people with type 2 diabetes and nephropathy: a randomized controlled clinical trial. Front Nutr. 2023.

Yi M, Wu X, Zhuang W, Xia L, Chen Y, Zhao R, Wan Q, Du L, Zhou Y. Tea Consumption and Health Outcomes: Umbrella Review of Meta-Analyses of Observational Studies in Humans. Mol Nutr Food Res. 2019 .

Zeru AB, Muluneh MA. Thyme Tea and Primary Dysmenorrhea Among Young Female Students. Adolesc Health Med Ther. 2020.