Attempts were first made to commercially produce infant milk formulas in the late 1800's. Unfortunately, no one knew what the make up of breast milk was at the time, and inappropriate formulas were produced. This combined with many unhygienic practises at the time, often lead to the poor health and death of many babies.
By the mid 1900's, techniques in cleanliness and sterilisation were commonplace, making formula feeding safer. Also formulas were starting to be manufactured, to be more in line with the composition of breast milk. However, it has only been in the last few decades that the complexity of breast milk has been truly realised, and formulas have been modified in ways to try and closely resemble breast milk. For example, it is now known that human milk has a finely balanced combination of amino acids (or the 'building blocks' of protein). This combination is unique to human milk when compared to the milk of all other animals (including cows). Therefore it is not only important for commercial formulas to have a certain amount of protein in their milk, but to balance the different amino acids, (such as glutamic acid and taurine), so that the baby is able to digest and absorb fats in their intestines in the first few weeks of life.
Soy based milks were first introduced into western society the early 1900's. (It is thought they were used to limited degree in some Asian countries prior to this.) Soy based formulas were usually used as an alternative for babies who were thought to be intolerant of cow's milk, but up until the 1990's their use has been very limited. Before the 1960's soy flour (which is high in carbohydrates) was used to make the formula. Babies drinking this early formula often had
diarrhoea and colic. By the mid 1960's the carbohydrate was replaced by a soybean protein, which made the milk more digestible.