Breast milk is a dynamic fluid that changes over time. Our research goal is to determine what changes, over what period and why. Past studies have had difficulty refining the data to the level of an individual breastfeeding mother. Older studies looked at pooled breast milk samples and did not take into account the variations in diet (17,18). Some also included very small samples (eg Hall et al. 1979 studied 3 women). In addition, variability in breast milk composition was often due to different laboratory methods used for the analyzes, including a) direct energy quantification by combustion in a bomb calorimetry and b) calculated energy estimates using water energy multiplication factors for macronutrients such as protein, fat and carbohydrates . The methods used to measure protein also ranged from a) direct quantification of the actual protein content and b) quantification of the nitrogen alone, which does not take into account the presence of nitrogen in non-protein compounds. This has made it difficult to extract reliable data from many early studies. The gold standard for milk collection involves sampling the same individual over a 24-hour period when evaluating milk (19, 20), and many studies have shown that mature milk remains relatively similar in composition with subtle changes during lactation (19, 20). 21, 22). The mother’s diet has a major influence on the composition of breast milk for some nutrients (10,11,12). Breast milk varies significantly from mother to mother. We ask that mothers collect milk 24 hours a day and not just one moment.