When a baby is straining and turning red and struggling to produce poos like hard rabbit droppings, solving the constipation problem becomes a high priority. Well-meaning people might suggest that the iron in the formula milk may be to blame, and parents sometimes think that switching to a low-iron formula will help. No one wants pellet-like poos, but is iron-fortified formula really the culprit?
No.
Researchers in Britain conducted a randomized, controlled trial of 493 infants who were given either cow’s milk, iron-fortified formula or low-iron formula. Over a period of nine months, they carefully followed any problems the infants had with infections, diarrhoea or constipation. Infants who drank the iron-fortified formula did not have any more constipation (or any more diarrhoea or other infections) than the babies who drank low-iron formula or cow’s milk. Moreover, in a study of 300 children, half of whom were given iron supplements and half of whom were given a placebo or fake medicine, the infants taking the placebos had more constipation than the babies taking the iron. There is just no evidence that iron causes constipation in children.
In case you are now worried that iron might instead cause diarrhoea, a different randomized, controlled trial of 1,655 infants found that iron-fortified formula did not lead to any more diarrhoea than using low-iron formula.
Formula with iron also provides important benefits to babies. Not having enough iron can lead to anaemia (red-blood-cell deficiency). Infants who receive formula fortified with iron have significantly less anaemia than infants who are given low-iron formula or plain cow’s milk. Severe anaemia can even lead to developmental delays or heart failure.
The evidence is fairly conclusive that iron-fortified formula does not give babies constipation, and that without enough iron in their diets, babies face significant health risks. That should be reason enough to make sure that you give your baby formula with full iron until they are one year old. If your baby keeps pooing pellets, talk to your doctor about other possible causes of bowel distress instead of switching the formula.