Does black tea break a fast?

A 240 ml (8 fl oz) cup of black tea brewed in water has about 2 kcal, no sugar and no protein. USDA data put it at 1 kcal per 100 ml. That makes plain black tea safe for all four goals this site uses to sort answers: weight loss, blood sugar, autophagy and gut rest. Nothing in the cup needs digesting, and nothing in it raises blood glucose.

Milk is what moves tea out of the safe column. A tablespoon (15 ml) of milk adds about 6 to 9 kcal, so a 2-tablespoon splash adds about 12 to 18 kcal. For weight loss that is a grey area, under the common 50-calorie rule of thumb, which is not an official limit. Milk protein breaks a fast for autophagy and gut rest. A level teaspoon of sugar is about 16 kcal. That is a grey area for weight loss, and the sugar breaks a fast for blood sugar, autophagy and gut rest. A milky, sweet chai latte breaks a fast for both reasons.

A cup of black tea has about 47 mg of caffeine, under half the roughly 107 mg in a 250 ml filter coffee. Oolong tea has a little less, at about 16 mg per 100 ml, or about 38 mg a cup. For healthy adults, up to 400 mg of caffeine a day spread through the day raises no safety concerns. That is about eight cups of black tea. Caffeine's half-life averages about four hours, so a cup late in the day can still affect your sleep.

Some people need more care with tea during a fast. If you are pregnant or breastfeeding, keep caffeine to 200 mg a day or less, about four cups of black tea. Talk to a doctor before fasting at all. If you take levothyroxine, take it as prescribed, on an empty stomach 30 to 60 minutes before breakfast and before any tea or coffee. A squeeze of fresh lemon is fine, since a wedge adds about 1 kcal.