After an initial period of exclusive milk feeding, in the infants' diet we start introducing other food. Scientific associations recommend not introducing whole cow's milk before the age of 12 months.

In infants younger than 6 months of age who cannot receive breast milk should ingest infant formula and those older than 6 months a follow-up formula. Although differences between both have been reduced along time, follow-up formulas contain a higher amount of protein as well as iron than follow-up formula. The European Society of Pediatric Gastroenterology, Hepatolgy, and Nutrition (ESPGHAN), points out that there are no problems in receiving whole milk after one year.

However during the last years different modified milks for children of under a year have appeared. Differently from the other formulas there is no specific legislation on their composition, what has given rise to big differences in the composition of the "un weaned milk formula". Most of them resemble follow-on formula while in others there are modifications in their fat composition. Some of them decrease the total amount; some of them replace saturated fat with monounsaturated fatty acids or add long chain poly-unsaturated fatty acids.

Do they represent a major advance in toddler feeding? For the greatest part of children whom take a varied diet in sufficient quantity, the use of toddler's milk formula is only a small modification of their diet. But given that a significant number of Spanish pre scholars intake unbalanced diets, the consumption of these types of milks is of great interest.