Toxins in our Favourite Beverages

We all love our coffee and teas don’t we? Some so much that it could be consider a sacred religious routine not to be missed in their daily lives.

However what no coffee or tea company will tell you are the toxins and anti-nutrients?

Yesterday in our Herbal Medicine class, I came across something interesting of note in a reading on the toxicology of comfrey. This article compared the toxicology of the common Tea (Thea sinensis) that we drink with the supposedly ‘poisonous’ plant.

In summary, the caffeine and tannins in tea have been extensively studied and found to be many times more toxic to humans than the small amount of pyrrolizidine alkaloids found in comfrey tea!

Potential Dangers of drinking Tea

  1. Caffeine in tea can cause foetal malformation in animal studies and is cautioned against for pregnant women – not to exceed 2 cups of coffee’s worth of caffeine a day! [1]
  2. Caffeine is also a suspected carcinogen (cancer causing agent). However, the evidence for this is not strong, with many confounding variables. [2]
  3. Caffeine is associated with promoting cancers in animal models but not so much in humans. [3] “Caffeine’s toxicological symptoms vary according to the dose and individual, with psychological side effects generally manifesting at lower dosed-intoxications and more serious side effects occurring in the cardiovascular and muscular tissues with higher doses.” [3]
  4. Tannins in tea may be carcinogenic, inhibit your digestive enzymes required to digest food, inhibit your absorption of minerals from food/supplements and are highly toxic to the liver and kidneys.
Figure 1. Source [7]

However, it seems like there are some benefits to tannins too: they are antioxidant and radical scavenging, anti-cancer, antimicrobial, cardioprotective, anti‐diabetic and anti‐obesity. [4]

And to complicate things further, there are many different types of tannins in the plant world. Some like those found in betel nuts and some herbal teas have been associated with oesophageal cancer [5] whilst many others such as the tannic acids in green tea have been associated with anticancer properties. [6] Tannic acid is also approved as a natural pesticide and food additive. [7]

So… what to do? (sg slang)

As my naturopath mentor likes to say, “Moderation is key.” 

However, in this instance, I would HIGHLY RECOMMEND consuming Teas and Coffees AWAY FROM FOOD.

They are potent anti-nutrients (digestive and absorption inhibitors) and consuming them regularly with your food is like starving yourself of the nutrients in your foods. This might lead to nutritional deficiencies, malnutrition, anaemia and weight loss.

So, you can still enjoy your tea or coffee as a separate ‘meal’ by itself. It is best to do so 30 minutes to an hour BEFORE food or to be safe 3 hours AFTER food as food stays in your stomach for around 3 hours.

And don’t drink too much! 1 cup a day is more than enough. 😉

Happy sippin’


  1. Nehlig, A., & Debry, G. (1994). Potential teratogenic and neurodevelopmental consequences of coffee and caffeine exposure: a review on human and animal dataNeurotoxicology and teratology16(6), 531-543.
  2. Hashibe, M., Galeone, C., Buys, S. S., Gren, L., Boffetta, P., Zhang, Z. F., & La Vecchia, C. (2015). Coffee, tea, caffeine intake, and the risk of cancer in the PLCO cohortBritish journal of cancer113(5), 809–816. doi:10.1038/bjc.2015.276
  3. Willson C. (2018). The clinical toxicology of caffeine: A review and case study. Toxicology reports5, 1140–1152. doi:10.1016/j.toxrep.2018.11.002
  4. Smeriglio, A., Barreca, D., Bellocco, E., & Trombetta, D. (2017). Proanthocyanidins and hydrolysable tannins: occurrence, dietary intake and pharmacological effectsBritish journal of pharmacology174(11), 1244–1262. doi:10.1111/bph.13630
  5. Chung, K. T., Wong, T. Y., Wei, C. I., Huang, Y. W., & Lin, Y. (1998). Tannins and human health: a reviewCritical reviews in food science and nutrition38(6), 421-464.
  6. Chu, X., Guo, Y., Xu, B., Li, W., Lin, Y., Sun, X., … & Zhang, X. (2015). Effects of tannic acid, green tea and red wine on hERG channels expressed in HEK293 cellsPloS one10(12), e0143797.
  7. UNITED STATES ENVIRONMENTAL PROTECTION AGENCY. February 27, 2006. Inert Reassessment -Tannin (CAS Reg. No. 1401-55-4).

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