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Base foodLow concern
Black Tea
In plain words
The short version
Rich in tannins, which bind iron in the same meal and lower how much of it the body takes up.
Why it's green
It's widely considered safe at the amounts used in food, so we mark it green. The Safety section below has the details.
Safety profile
Tea polyphenols bind non-haem iron — the form found in plants, grains and fortified foods — into complexes the gut cannot absorb. The effect is large and well documented, and it applies to the meal the tea is drunk with, not to the diet as a whole. Vitamin C eaten at the same time counteracts a good part of it.
The detail
The leaves of Camellia sinensis, oxidised before drying. Its astringency comes from tannins, the same compounds responsible for the iron effect.
Both timing and strength matter: the effect grows with the amount of polyphenols in the cup, and in a small controlled trial, drinking tea one hour after the meal roughly halved its effect on that meal's iron. Coffee also lowers iron absorption. In one study, coffee drunk an hour before a meal had no effect on that meal's iron, but coffee drunk an hour after the meal lowered it as much as coffee taken with the meal.
Sources
- Hurrell RF, Reddy M, Cook JD. Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages. Br J Nutr 1999;81:289–295 — British Journal of Nutrition (Cambridge University Press), 1999. The effect is large and well documented; it depends on polyphenol dose
- Disler PB et al. The effect of tea on iron absorption. Gut 1975;16:193–200 (doi:10.1136/gut.16.3.193; PMID 1168162) — Gut (BMJ) — abstract via US National Library of Medicine, 1975. Tannins bind non-haem iron into complexes the gut cannot absorb
- Ahmad Fuzi SF et al. A 1-h time interval between a meal containing iron and consumption of tea attenuates the inhibitory effects on iron absorption. Am J Clin Nutr 2017;106:1413–1421 (doi:10.3945/ajcn.117.161364; PMID 29046302) — American Journal of Clinical Nutrition — abstract via US National Library of Medicine, 2017. Timing: tea 1 h after a meal roughly halves the effect
- Siegenberg D et al. Ascorbic acid prevents the dose-dependent inhibitory effects of polyphenols and phytates on nonheme-iron absorption. Am J Clin Nutr 1991;53:537–541 (doi:10.1093/ajcn/53.2.537; PMID 1989423) — American Journal of Clinical Nutrition — abstract via US National Library of Medicine, 1991. Vitamin C eaten at the same time counteracts the effect
Checked against these sources on .
Educational information only. Not medical, dietary or veterinary advice. Spotted an error? Tell us.