The Study
Influence of Diet on Bioaccessibility of Iron from Dietary Supplements and Medicinal Products—Results of In Vitro Digestion Model and Analytical Determinations
This study is like testing how fast a candy melts in a glass of water — it tells you which candy dissolves faster, but it doesn't tell you if your body can use the sugar from it. Just because iron comes out of a pill in a test tube doesn't mean your body can absorb it.
Analysis score
Maximum 44 for a cross-sectional study.
Where the score came from
Not all iron supplements are equal—what you eat and what kind of iron is in the pill changes how much your body can use.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 58 / 100
Quality score
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes—this means choosing the right iron form and avoiding coffee/dairy with your supplement can make a big difference in how well it works.
- 2Iron sulfate worked best (12.58% released), iron lactate worst (5.25%).
- 3Extended-release pills released 19.31%.
- 4Eating high-calcium foods (like dairy) or drinking coffee/tea cut iron release to as low as 1.92%.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Nutrients
Year
2026
Authors
Piotr Bawiec, Agnieszka Jaworowska, Jan Sawicki, M. Czop, Joanna Tokarczyk, P. Helon, W. Koch
Related Content
Claims (5)
The chemical structure of nutrients in supplements determines how much of the nutrient the body can absorb and use.
Different chemical forms of iron in supplements release different amounts of iron when tested under conditions mimicking the human digestive tract, with iron sulfate releasing the most and iron lactate releasing the least.
Diets high in calcium result in less iron being released during digestion compared to diets low in calcium.
Extended-release iron tablets release more usable iron during digestion than regular iron tablets, and this difference is due to how the tablets are designed.
A diet low in calcium and high in vitamin C results in 7.96% iron bioaccessibility, while a diet high in calcium, low in vitamin C, and rich in polyphenols results in 4.63% iron bioaccessibility when no supplements are taken.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.