> In the trial of interest here, mothers elected to breastfeed but varied in their success in expressing milk and, therefore, in the need for supplementary feeding. According to randomisation before breastfeeding commenced, these infants were given one of three supplements: a nutrient enriched preterm formula (PTF), a standard term formula (TF; used in the 1980s for feeding preterm infants) or banked breast milk (BBM; provided by unrelated donors and unfortified).

Since the mothers self-selected breastfeeding, the study makes the assumption that banked breast milk (from a random donor) is equivalent to fresh milk from the mother.

It assumes that the act of suckling on the mother's breast has no bearing on brain development. See recent evidence regard pre-term babies and skin contact: http://handtohold.org/resources/helpful-articles/the-benefit...

Finally, it ignores other (more recent) studies showing how the mother's milk reacts to signals from the baby's saliva (backwash from baby sucked back into breast). https://www.sciencenews.org/blog/growth-curve/backwash-nursi...

(Not saying these links aren't equally or more flawed, but it's avenues of causation ignored.)

Wouldn't a valid study require randomized instruction to mothers about whether to breastfeed? Is that ethical? Compliance is equally tough: breastfeeding can be incredibly difficult for some moms/babies. Further, couldn't the difficulty in breastfeeding also be correlated to the effects -- could children reject breastmilk based on the mother's health or otherwise based on the "quality" of the milk?

Please forgive if I'm asking questions that are well understood -- by no means am I claiming to be knowledgeable in this field. But I do have kids and went through hell with one of them on this, so I'm very interested in the research.