Maternal nutritional status and milk volume. Is there a cause-effect relationship?

Studies on human lactation were examined in order to gather some answers about questions concerning the effect of maternal food intake, size, fatness and economic status on milk production. Up to date, evidence in the literature is insufficient to permit definitive answers, but a general conclusion can be drawn: milk volume varies little among mothers with largely variable energy intakes, sizes and economic status. There is a great need for more controlled studies focusing on the relationship between maternal energy balance and milk output. Although many studies have separately addressed the nutritional changes in mothers throughout lactation (1-8) and milk consumption by infants (9-17), very few have correlated maternal nutritional conditions and the volume of milk consumed. This report will consider investigations published from 1975 and on, combining data on maternal nutritional status and milk production in the same individual. The rationale is that around 1975 more accurate and standardized methodology began to be used in related studies. Milk output is estimated by the summary of the differences of body weights of infants obtained before and after each milking episode during 24 hours. Before 1975 the balances used for such a purpose had very poor precision, and this interfered seriously on the inter and intra-personal variability of the measurements. Electronic scales made available after that year gave enough reliability to the procedure. This report is comprised of studies from birth to four months postpartum, when energy supplementation is less common, and quantitatively less important. Nutritional status of the mothers will be analyzed on the basis of four categorizing variables: social and economic status, anthropometry, food intake and body composition.