Nursing frequency and the energy intake from breast milk and supplementary food in a rural Thai population: a longitudinal study.

A group of 60 infants representative of a rural Thai population were studied longitudinally over the first year of life. Their breast milk intake, supplementary food intake and nursing patterns were measured for 2 consecutive days at about 15, 45, 90, 180, 270 and 360 days of age. For the sample as a whole, the estimated peak value for energy intake from breast milk was 529 kcal (2213 kJ) and occurred at 34 days post-partum. Thereafter milk intake declined, with 40% of infants fully weaned by the end of the first year. Supplements were introduced early, with 15% of infants supplemented by 2 weeks and 68% by 6 weeks. Higher levels of supplementation were associated with lower breast milk intake. In addition there was an independent positive effect of nursing patterns (number of breast feeds per day). Interaction terms show that both supplementary feeding and number of feeds have quantitatively different effects at different ages: breast milk intake varies more with level of supplementation in younger infants than in older infants, and varies more with number of feeds in older infants than in younger infants. Higher peak levels of breast milk intake were followed by a steeper decline, and infants who took more breast milk at 15 days were more likely to be fully weaned by their first birthday.