Soya-bean protein and iron absorption in women
What it found
Women absorbed less iron from soya-based infant formula than from milk-based formula.
Adding vitamin C boosted iron uptake much more from the milk drink than from the soya drink.
What they found
Studies in people
Less iron from soya formula
Women took in about half as much iron from the plain soya formula as they did from the plain milk formula. The measured values were 0.044 for soya and 0.083 for milk.
Vitamin C helped milk more
Adding vitamin C boosted iron uptake from the milk formula by five to ten times. The same vitamin only doubled or tripled iron uptake from the soya formula.
Refined soya worked better
A drink made with refined soya protein let women absorb more iron than one made with regular soya flour. Both drinks contained the same amount of protein and vitamin C.
Heating made no difference
Baking the soya protein at 200 degrees for 2 hours before mixing it into a drink did not change how much iron the women absorbed.
Citric acid gave a small boost
Adding citric acid to a soya protein drink raised iron uptake slightly. The more citric acid added, up to 4 g, the more iron was taken in, but the effect was modest.
What the authors conclude
- They say it is important to identify and remove whatever blocks iron uptake in soya-bean products used in infant formulas.
- They note that when soya is eaten as a meat substitute rather than in formula, the total iron kept by the body may still be enough because soya naturally contains a lot of iron.
- The authors point out that vitamin C helps far less when soya protein is present compared to when it is absent.
How it was done
Earlier work showed that soya-bean protein can block the body from taking in iron, but scientists did not know exactly why or how to fix it. They wanted to find out what changes might help people absorb more iron from soya products.
They tested 138 adult women who had each had children before. The women drank either milk-based or soya-based infant formulas, or drinks made with isolated soya protein. Iron was tracked using a small amount of radioactive iron over two weeks after each test drink.
What it can’t tell you
- These tests used adult women, so the results might not match what happens in babies who actually drink these formulas.
- The study measured short-term iron uptake from single drinks, which cannot show whether eating soya regularly changes overall iron levels in the body.
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 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error