What constitutes a representative human milk sample?

Picciano MF., J Pediatr Gastroenterol Nutr. 1984 Mar;3(2):280-3.

Without due consideration of proper sampling procedures, it is not possible to obtain valid data on the normal composition of human milk. It is well known that the milk excreted by an individual woman exhibits wide biological variations. For example, fat concentrations are reported to double during the course of a single feeding (1). Planned strategies are therefore necessary to obtain a representative sample. Recognition of the magnitude of variation in composition prompted early investigators to recommend collection of the total 24-h production at each stage of lactation as the appropriate sampling technique (2,3). While this may be ideal, it is seldom possible without interfering with the normal lactation process. A compromise approach must therefore be taken. The exact method chosen depends on a number of factors, the most important being the objective of the study. There is no substitute for a preliminary investigation to determine how best to sample human milk for the particular constituent to be measured. In this paper, known patterns of variation will be discussed to assist investigators in planning their own preliminary studies.