Otherindependent cross-checkabstract only checked I-INTA-04 standard review
Does tea block iron from food?
The effect of tea on iron absorption.
Overview
Disler PB et al.. Gut 1975 · PMID 1168162 · DOI 10.1136/gut.16.3.193
Tea taken with meals reduced absorption of plant (non-haem) iron in volunteers.
Does the study support the specific claim? Partly · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Tea and iron absorption
- How was the study done?
Absorption studies in volunteers
- How many people, animals or samples were studied?
Not stated in abstract
- What was actually found?
Tea inhibited non-haem iron absorption
- How large was the observed effect?
Not given in abstract
- What do the results mean in everyday life?
People at risk of iron deficiency may drink tea between rather than with meals
- What are the study's limitations?
Old; short-term
- What does it say about Elawady's specific claim?
Supports a different harm than constipation/reflux
- Do the results apply to Germany and Europe?
High
- What can explicitly not be concluded from this study?
Effects on long-term iron status
Scientific in-depth review
1. Full reference
- Authors
- Disler PB et al.
- Journal
- Gut
- Year
- 1975
- Identifier
- PMID 1168162 DOI 10.1136/gut.16.3.193
- Verification
- verified – PubMed efetch 2026-10-25
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
not stated in abstract
2. Research question
Effect of tea on iron absorption
3. Study design and population
- Study design
- Other – Human iron-absorption studies in volunteers
- Population
Human volunteers
- Country
Not stated in abstract
- Period
Not stated
- Sample size
not stated in abstract
- Inclusion and exclusion criteria
not stated in abstract
4. Methods and endpoints
- Exposure / intervention
Tea taken with iron solutions or meals
- Comparator
Same iron sources without tea
- Endpoints
Iron absorption
- Statistical methods
not stated in abstract
5. Actual results
- Results
Tea inhibited absorption of iron from FeCl3 and FeSO4 solutions, bread, a rice meal with potato and onion soup, and uncooked haemoglobin, with or without ascorbic acid; no inhibition with cooked haemoglobin. Inhibition attributed to insoluble iron tannate complexes.
- Absolute risks
not reported
- Authors' conclusion
Drinking tannin-containing beverages such as tea with meals may contribute to iron deficiency if the diet consists largely of vegetable foods.
6. Strengths
- Direct measurement in humans
- Several food matrices
7. Weaknesses
- Old study
- Sample size not given in abstract
- Short-term absorption, not iron status
8. Risk of bias
- Orienting tool
- none applicable
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- not assessable
- Rationale
Experimental absorption study; details not in abstract.
9. Assessment of the statistical interpretation
Shows reduced non-haem iron absorption per meal; long-term effect on iron status depends on whole diet.
10. Relevance to the specific claim
A correct concern about tea (iron absorption), not raised by Elawady but relevant to fair assessment.
11. Independent contrary findings
Effect mainly relevant for diets low in haem iron and for people at risk of iron deficiency.
12. Transferability to Germany and Europe
High.
13. Overall methodological judgement
Valid, classic evidence that tea with meals lowers non-haem iron absorption.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | not assessable |
| Precision of results | not applicable |
| Directness | indirect |
| Reproducibility | replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Impact at population level in Egypt.