Tea: wait an hour after the meal and you keep the iron

Tea blocks the absorption of iron from plants, and the size of it is not small: in Senegalese mother-child pairs a herbal tea with the meal cut iron absorption by 56 percent in the mothers and by up to 72 percent in the children. Then someone tested the obvious fix. Twelve British women ate the same labelled porridge three times, with water, with tea, and with tea an hour later. Tea with the meal cut absorption from 5.7 to 3.6 percent. Tea an hour later returned it to 5.7. One hour of separation recovers about half of what the tea would have taken, and nobody has to give up tea.

The numbers, per 100 g

What a real portion looks like

• Drinking tea an hour after a meal instead of with it recovered about half the iron the tea would have blocked. — 12 iron-replete non-anaemic women in the United Kingdom, mean age 24.8 (n = 12) Evidence B source
  Iron absorption was 5.7% with water, 3.6% with simultaneous tea and 5.7% with tea one hour later; absorption was significantly higher with the one-hour gap than with simultaneous tea (difference 2.2 percentage points, p = 0.046), about a 50% reduction in the inhibitory effect
• Across fifty-nine trials green tea extract lowered weight, body fat and body mass index, by small amounts. — 59 studies with 3802 participants, from 11286 records screened (n = 3802) Evidence A source
  Body mass, body fat percentage, body mass index and malondialdehyde all fell significantly; the review also reports changes in obesity-related hormones and total antioxidant capacity

What your body absorbs

• Tea taken with a meal cut iron absorption by more than half in mothers and by up to three quarters in their children. — 17 Senegalese mother-child pairs (n = 17 pairs) Evidence B source
  Tea lowered fractional iron absorption by 56% (p<0.05) and 50% (p = 0.077) in mothers and by 65% and 72% (both p<0.0001) in children, for the sulfate and fumarate meals; relative bioavailability of ferrous fumarate in children was 51% and 64% of ferrous sulfate

What it does to your health

• Pooled with cocoa and other flavan-3-ol sources, tea lowered blood pressure most in the people whose pressure was highest. — 109 publications covering 145 randomised trials and 5205 participants, with tea among the intervention sources (n = 5205) Evidence A source
  In people with elevated or hypertensive baseline pressure the office reduction reached 5.9/2.7 mmHg and the 24-hour ambulatory reduction 6.8/5.1 mmHg, against 2.8/2.0 mmHg overall; meta-regression confirmed the size of the reduction was inversely related to baseline pressure

Safety, limits and interactions

• Liver side effects appeared in four of thirty-four green tea extract trials, at roughly double the rate of placebo. — 34 trials identified from 561 titles and 119 full-text articles (n = 34 trials) Evidence A source
  Liver-related adverse events were reported in four trials, involving seven subjects and eight events in the green tea groups against one subject and one event in controls; the summary odds ratio against placebo was 2.1

What people believe that the data does not support

• Green tea lowered blood pressure by about one millimetre of mercury, which is less than a home monitor can detect. — 36 randomised controlled trials in adults (n = 36 trials) Evidence A source
  Systolic pressure -1.08 mmHg (95% CI -1.98 to -0.18, I2 85.0%) and diastolic -1.09 (-1.67 to -0.50, I2 74.0%); stronger in people with systolic pressure at or above 120 at baseline, in those taking under 500 mg a day, in trials of 8 weeks or less, in Asian populations and in women

The bottom line

The health claims are thinner than the culture around them. Green tea lowers blood pressure by about one millimetre of mercury across 36 trials, which is below what a home monitor can detect, and the pooled figure hides trials that disagree strongly with each other. The effect is larger in people who start high, which is the pattern for every blood pressure intervention. Green tea extract supplements are a different product from tea: across 34 trials, liver-related adverse events appeared in four of them, at roughly double the placebo rate. Europe has refused all fourteen health claims filed for tea, starting with the one that says it helps burn fat.

Sources

1. tea-dr-01 · controlled crossover trial with stable isotopes
   Mean fractional iron absorption was found to be significantly higher (2.2%) when tea was administered 1 h postmeal (TM-3) than when tea was administered simultaneously with the meal (TM-2) (P = 0.046).
   Am J Clin Nutr, 2017 · checked 2026-09-22
2. tea-dr-05 · systematic review and dose-response meta-analysis of randomised controlled trials
   Pooled effect sizes indicated that BM, BFP, BMI and MDA significantly reduced following GTE supplementation.
   Br J Nutr, 2024 · checked 2026-09-22
3. tea-dr-02 · randomised factorial stable isotope study
   In mothers, the presence of TK decreased FAFe by 56% (P < 0.05) and 50% (P = 0.077) and in children by 65 and 72% (both, P < 0.0001), in the meals with 58FeSO4 and 57FeFum, respectively.
   Eur J Clin Nutr, 2020 · checked 2026-09-22
4. tea-dr-06 · systematic review and meta-analysis of randomised controlled trials
   Effects were larger with elevated and hypertensive baseline BP or categorical hypertension (office: -5.9 [-10.0, -1.8]/-2.7 [-4.4, -1.0] mmHg, 24 h ABP: -6.8 [-16.3, 2.8]/-5.1 [-12.5, 2.2] mmHg).
   Eur J Prev Cardiol, 2025 · checked 2026-09-22
5. tea-dr-04 · systematic review of randomised controlled trials
   Of these, liver-related adverse events were reported in four trials; these adverse events involved seven subjects (eight events) in the green tea intervention group and one subject (one event) in the control group.
   Eur J Clin Nutr, 2016 · checked 2026-09-22
6. tea-dr-03 · systematic review and dose-response meta-analysis of randomised controlled trials
   Green tea reduced SBP (WMD: -1.08 mmHg; 95% CI: -1.98, -0.18; I2 = 85.0%) and DBP (WMD: -1.09 mmHg; 95% CI: -1.67, -0.50; I2 = 74.0%).
   Blood Press, 2025 · checked 2026-09-22