Does tea break a fast?

What to keep out of your cup

Sugar is the obvious one. Milk is less obvious: it has lactose and protein, and protein raises insulin as well as sugar does. In a Swedish study, milk and whey produced far smaller rises in blood sugar than white bread, yet whey released 90% more insulin ². A splash in your tea adds a little; a latte-sized amount ends the fast.

• Fine: black, green, white and oolong tea, and herbal infusions such as mint, rooibos or chamomile.
• Breaks the fast: sugar, honey, syrups, sweetened iced tea and bubble tea.
• Grey zone: a small splash of milk (see milk in coffee) and zero-calorie sweeteners (see diet soda).

How much caffeine is fine?

Tea usually has less caffeine than coffee, which makes it a good afternoon drink. Up to 400 mg of caffeine a day, about four 240 ml (8 oz) cups of filter coffee, is considered safe for healthy adults ³; if you're pregnant or breastfeeding, keep it under 200 mg ^4,5. Herbal infusions have none.

Tea counts towards your fluids

You don't need to worry that caffeinated drinks dry you out. In habitual coffee drinkers, four cups a day kept them as well hydrated as the same amount of water ⁶. Keep some water nearby as well.

Sources

1. Holt SH, Miller JC, Petocz P. An insulin index of foods: the insulin demand generated by 1000-kJ portions of common foods. Am J Clin Nutr. 1997;66(5):1264-76. doi.org/10.1093/ajcn/66.5.1264
2. Nilsson M, Stenberg M, Frid AH, et al. Glycemia and insulinemia in healthy subjects after lactose-equivalent meals of milk and other food proteins: the role of plasma amino acids and incretins. Am J Clin Nutr. 2004;80(5):1246-53. doi.org/10.1093/ajcn/80.5.1246
3. Wikoff D, Welsh BT, Henderson R, et al. Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children. Food Chem Toxicol. 2017;109(Pt 1):585-648. doi.org/10.1016/j.fct.2017.04.002
4. ACOG Committee Opinion No. 462: Moderate caffeine consumption during pregnancy. Obstet Gynecol. 2010;116(2 Pt 1):467-468. doi.org/10.1097/AOG.0b013e3181eeb2a1
5. EFSA NDA Panel. Scientific Opinion on the safety of caffeine. EFSA J. 2015;13(5):4102. doi.org/10.2903/j.efsa.2015.4102
6. Killer SC, Blannin AK, Jeukendrup AE. No evidence of dehydration with moderate daily coffee intake: a counterbalanced cross-over study in a free-living population. PLoS One. 2014;9(1):e84154. doi.org/10.1371/journal.pone.0084154