Soya protein and iron absorption from infant formulas
What it found
In 138 women, iron was absorbed less from soya-based infant formula than from milk-based formula, and vitamin C boosted absorption less from the soya version.
The women also absorbed iron from isolated soya protein better than from soya flour.
What they found
Studies in people
Soya formula vs milk formula
Iron absorption was greater from the milk-based formula than from the soya-based formula. The geometric mean values were 0.083 for milk and 0.044 for soya.
Vitamin C with milk formula
Ascorbic acid increased iron absorption from the milk-based formula in a dose-dependent way. The increase was fivefold at an ascorbic acid to iron ratio of 6 to 1 and over tenfold at 20 to 1.
Vitamin C with soya formula
Ascorbic acid had a less-marked effect on iron absorption from the soya-based formula. There was only a two- to threefold increase at an ascorbic acid to iron ratio of 20 to 1.
Isolated soya protein vs flour
Iron absorption from a drink with 10 g isolated soya protein and 30 mg ascorbic acid was better than from a similar drink with soya-bean flour. The geometric mean values were 0.044 and 0.027.
Heating soya protein
Heating isolated soya protein to 200 degrees for 2 hours before use had no effect on iron availability. With 2.3 g heated protein and 10 mg ascorbic acid, absorption was 0.135 compared with 0.099 for untreated protein.
Citric acid effect
Citric acid had a dose-related but limited enhancing effect on iron absorption from 10 g isolated soya protein. Absorption rose from 0.011 with no citric acid to 0.068 with 4 g citric acid.
What the authors conclude
“It is, therefore, important that the inhibitor(s) of Fe absorption present in soya-bean be identified and removed.”
Also in their conclusions
- They say it is important that the inhibitor or inhibitors of iron absorption present in soya-bean be identified and removed.
- They note that the effects of ascorbic acid in the presence of soya-bean protein are at best modest, even when present in relatively large amounts.
- They distinguish between soya-bean products used in infant formulas, where soya seriously inhibits the absorption of added iron, and soya-bean products used as meat substitutes, where the total amount of iron retained is adequate.
How it was done
The authors wanted to find out why iron is poorly absorbed from soya-based infant formulas and to see what factors might change that.
They gave single drinks of milk-based or soya-based infant formula, or drinks made with isolated soya protein, to 138 Indian women aged 21 to 63. Each woman took part in one experiment only, and iron absorption was measured using a radioactive iron method.
What it can’t tell you
- The study was done in adult women, so the results may not be the same in infants.
- The women took part in one experiment only, so the findings show absorption from single drinks, not long-term iron status.
- The authors found unexplained variation between different studies, suggesting that unidentified manufacturing or preparative differences might affect the results.
The paper
- Title
- Factors influencing the absorption of iron from soya-bean protein products
- Type
- Study
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Derman DP, Ballot D, Bothwell TH, et al (1987). Factors influencing the absorption of iron from soya-bean protein products. The British journal of nutrition. doi:10.1079/bjn19870042Free full textPubMed 3593666DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error