I know there has been a lot of research into the benefits of BF against FF.
By its nature though, surely the only type of research possible would be observational studies. It wouldn't be ethical to force a woman to breastfeed, or to not breastfeed, for research purposes.
So how do the researchers make sure their findings are significant? How do they eliminate all other variables to ensure they are recording only differences caused by the type of milk consumed by a baby?
Some examples of variables might be...a woman prepared to put in the time and commitment to BF might be more inclined to ensure their toddler eats a fresh, organic, balanced diet, which would also have an impact on long term health, or there might be differences in mother's ages, socioeconomic status etc of people more likely to BF or to FF.
Much of the research would be long term studies, and I should imagine that to have large numbers of participants, in order to minimise any variations, would be prohibitively expensive.
I hope I've managed to word this so as not to offend anyone (I know threads on this topic can get quite heated sometimes!) but I'm genuinely interested in how the researchers come up with such strong pro-BF evidence when they have such little control over the participants in their studies.