As a nutrition support pharmacist, you may receive questions about the benefits and potential harms of consuming black tea. Black tea is commonly consumed in amounts of 1-4 cups per day and can interfere with iron absorption in iron-deficient individuals. Furthermore, adding milk to black tea may reduce some of its beneficial cardiovascular effects by potentially binding with and reducing the absorption of flavonoids. The clinical significance of this interaction requires further investigation.
Due to its caffeine content, it's important for mothers to monitor their intake and aim for moderate consumption. During pregnancy, moderate black tea consumption is possibly safe, but caffeine intake should be below 300 mg daily (equivalent to approximately 3 cups). Excessive black tea intake while lactating can affect iron metabolism and folic acid bioavailability. Adverse effects of black tea include diuresis, gastric irritation, and insomnia.
A recent study conducted in the United Kingdom found that drinking at least 2 cups of black tea daily can have a modest reduction in the overall risk of death, especially from heart disease or stroke. The study followed nearly 500,000 adults for about 11 years and took into account lifestyle and genetic factors. It was discovered that drinking more than 2-3 cups of tea per day did not provide additional benefits. Interestingly, these findings differ from previous research that mainly focused on green tea in Asian countries. Black tea, which is more popular in Europe and the US, also seems to offer similar benefits. Green tea and black tea come from the same plant (Camellia sinensis) but are prepared differently. Green tea contains a compound called epigallocatechin gallate (EGCG), known for its health benefits, while black tea, being fermented, is rich in theaflavins, which are believed to have positive effects on heart health and may help prevent cancer.
REFERENCES
-
Merhav H, Amitai Y, Palti H, Godfrey S. Tea drinking and microcytic anemia in infants. Am J Clin Nutr. 1985 Jun;41(6):1210-3. Available at: https://www.sciencedirect.com/science/article/abs/pii/S0002916523348846?via%3Dihub
Temme EH, Van Hoydonck PG. Tea consumption and iron status. Eur J Clin Nutr. 2002 May;56(5):379-86. Available at: https://www.nature.com/articles/1601309
Hertog MG, Sweetnam PM, Fehily AM, Elwood PC, Kromhout D. Antioxidant flavonols and ischemic heart disease in a Welsh population of men: the Caerphilly Study. Am J Clin Nutr. 1997 May;65(5):1489-94. Available at: https://www.sciencedirect.com/science/article/pii/S0002916523177768?via%3Dihub
Lorenz M, Jochmann N, von Krosigk A, Martus P, Baumann G, Stangl K, Stangl V. Addition of milk prevents vascular protective effects of tea. Eur Heart J. 2007 Jan;28(2):219-23. Available at: https://academic.oup.com/eurheartj/article/28/2/219/2887513?login=false
Ahmad AF, Rich L, Koch H, Croft KD, Ferruzzi MG, Kay CD, Hodgson JM, Ward NC. Effect of adding milk to black tea on vascular function in healthy men and women: a randomised controlled crossover trial. Food Funct. 2018 Dec 13;9(12):6307-6314. Available at: https://pubmed.ncbi.nlm.nih.gov/30411751
Leenen R, Roodenburg AJ, Tijburg LB, Wiseman SA. A single dose of tea with or without milk increases plasma antioxidant activity in humans. Eur J Clin Nutr. 2000 Jan;54(1):87-92. Available at: https://www.nature.com/articles/1600900
Savitz DA, Chan RL, Herring AH, Howards PP, Hartmann KE. Caffeine and miscarriage risk. Epidemiology. 2008 Jan;19(1):55-62. Available at: https://journals.lww.com/epidem/Fulltext/2008/01000/Caffeine_and_Miscarriage_Risk.10.aspx
Nehlig A, Debry G. Consequences on the newborn of chronic maternal consumption of coffee during gestation and lactation: a review. J Am Coll Nutr. 1994 Feb;13(1):6-21. Available at: https://pubmed.ncbi.nlm.nih.gov/8157856
Inoue-Choi M, Ramirez Y, Cornelis MC, Berrington de González A, Freedman ND, Loftfield E. Tea Consumption and All-Cause and Cause-Specific Mortality in the UK Biobank : A Prospective Cohort Study. Ann Intern Med. 2022 Sep;175(9):1201-1211. Available at: https://www.acpjournals.org/doi/10.7326/M22-0041