|Food and Nutrition Bulletin Volume 04, Number 4, 1982 (UNU, 1982, 85 pages)|
Tin Tin Oo and Khin Maung Naing
Nutrition Research Division, Department of Medical Research, Rangoon, Burma
Studies of the output of breast-milk are extremely difficult to undertake because of interference with let down reflex by emotional factors and problems of measuring throughout the day and night (1). The objectives in this study were (a) to compare three different methods to determine potential milk output; (b) to determine the output of breast-milk by Burmese mothers; (c) to compare the 12-hour milk volumes produced in the day multiplied by two, and the actual 24-hour output as well as infant's intake, and (d) to assess the consumption of breast-milk by infants during the night.
MATERIALS AND METHODS
The first study involved ten low-income, apparently healthy mothers, 18 to 35 years of age and without regard to parity, with their infants. Ail the women had been lactating for one to four months. They were admitted to the clinical investigation rooms of the Department of Medical Research for four consecutive days. Three methods for measuring 12-hour breast-milk output were compared on each of the ten women.
1. Method to determine infant intake of breast-milk. After the breasts had been emptied and the time was recorded, the infants sucked for 10 to 15 minutes at about three-hour intervals during the first two days, and their weights before and after feeding were taken. A thick diaper was put on the infants so as not to lose any urine or stool voided during the feeding.
2. Method to measure mothers' potential milk output vs. infants' intake. During the same two days, the following measurements were also made for each mother: (a) While the mother was nursing her infant, the milk that dripped from the opposite breast was collected; (b) the milk left in the breast after the child had suckled for more than 10 minutes was expressed by hand The dripped breast-milk and residual milk together were weighed at each three-hour interval within the 12-hour period from 9 a.m. to 9 p.m.
3. Manual expression method. For the remaining two consecutive days, milk was manually expressed and weighed at about three-hour intervals for 12 hours. The total amount of milk collected within 12 hours was multiplied by two to obtain the 24-hour milk production, as in method one.
A second study was carried out with a different group of women. Twenty-two mothers from the low socio-economic group, 18 to 30 years of age, without regard to parity, who had been lactating for one to six months, were admitted to the clinical investigation unit for 24 hours. The potential method was used to measure the milk volume during the day and at night, and the first method described above was used to give the actual 24-hour milk intake.
The milk output of the first group of mothers, determined by the three different methods, is shown in table 1. There was no statistical difference in the mean values on each of two days using either method one or the manual expression method. The output measured by the potential method, however, was significantly higher than that determined by measuring the milk intake of the child (p < 0.001), indicating that the infants did not fully extract the breast-milk contents. The results of comparison of milk output and milk intake 112 hours x 2) versus actual 24-hour volume in 22 mothers with their infants are shown in figure 1. The regression line and correlation coefficient (r = 0.799, p < 0.001) of 12 x 2 and actual 24-hour milk intake and milk output are given.
TABLE 1. Milk Output of Ten Burmese Mothers Determined by Different Methods
Milk Output, ml/24 hr (mean + SE)
|First day||Second day||Mean|
|Manual expression||742 ± 52||816 ± 56||779 ± 50|
|Measured intake||684 ± 74||690 ± 74||687 ± 74|
|Potential||820 ± 67||824 ± 63||822 ± 64|
Statistic., using Student's t-test for related sample: Measured intake, first day vs.. second day, NS. Manual expression first day vs, second day, NS, Potential vs., measured intake, P < 0.001. Using Student's t-test for unrelated sample: Potential vs. manual expression, NS.. Manual expression vs. measured intake alone, NS.
Figure 2 shows the results on actual 24-hour production and actual 24-hour intake, including the milk consumed during the night. All the infants under study consumed milk during the night in amounts ranging from 100 to 240 ml. They were fed between two and four times during the night. The frequency and duration of feeding and the body weight of the infant are related to the amount of milk consumed.
From the present study there was a significant difference between values determined by measuring infant intake and those obtained by the method of measuring the mothers' potential output. Potential volume was 822 ml, and con. gumption value was 687 ml. This difference could account for about 100 kcal. If the milk intake of the child is taken as the milk output of mothers, then the milk output of the Burmese mothers studied was lower than the figure of 850 ml assumed by the FAO/WHO Expert Committee on Calorie Requirements. If 850 mil were taken for the purpose of calculating the requirement of lactation and in the assessment of the nutritional adequacy of breast-milk, an over-estimate would be obtained.
Rao studied the lactation performance of some poor South Indian mothers and found that the quantity of milk yield ranged between 530 and 730 ml during the first year and between 400 and 480 ml in the second year (2). Hanafy and Morsey 13) reported an average milk output of 840 ml among Egyptian mothers during the first six months of lactation. Maximum production in New Guinean, Indian, and Egyptian mothers is thus below the figure of 850 ml generally accepted for European or American women (4).
The average potential milk output determined by the potential method in Burmese mothers of a low socioeconomic group at the peak period of milk production (1 to 4 months) was 855 ml/day; the average milk output from the first to the seventh month of lactation was 779 ml/day; and for all stages from 1 to 12 months, the average figure was 821 ml/day (5). Breast-milk production at 12 to 18 months was 523 ml; at 18 to 24 months it was 458 ml; and at 24 to 30 months it was 382 ml (unpublished data, Department of Medical Research, Rangoon, Burma).
Tin Tin Oo and Khin Maung Naing (5) have reported that, even though breast-milk alone is not sufficient for the nutrient needs of infants beyond four months, it still plays an important role in the maintenance of nutritional status of infants for up to one year. At one year breast-milk provides 50 per cent of the protein and 50 per cent of the calorie needs of infants. At two years, breast-milk provides about 25 per cent of the protein requirement and 26 per cent of the calorie requirements of the children. Milk protein with a high biological value is a good supplement to the predominantly rice-based weaning diet of Asian children.
Reliable and accurate determination of milk consumed daily can be ascertained by measuring the 12-hour intake. A procedure of personal interview and the mother's weighing of the child and filling in the form is not recommended among the poorly educated social class in Burma.
Where infants sleep with mothers and consume breast milk during the night, it is essential to know the amount of milk consumed at night. All 22 Burmese infants studied sucked a minimum of two times during the night (between 9 p.m. and 6 a.m.), and each period of sucking lasted five to ten minutes. In the present study, 151 ml of breast-milk was consumed during the night out of the total daily intake of 521 ml. No references could be found showing the actual milk intake at night except for one study by Omololu (personal communication to Jelliffe, quoted in reference 6). He stated that the significance of night feedings can be seen in traditional families in West Nigeria, where about one-third of the total intake is at night, locally defined as from 8 p.m. to 6 a.m.
1. D.B. Jelliffe, 'World Trends in Infant Feeding," Amer. J. Clin. Nutr., 29: 1227 (1976).
2. S. Rao, M.C. Swaminathan, S. Swarup, and V.N. Patwardhan, "Protein Malnutrition in South India," Bull.. Wld. Hlth. Org, 20: 603 (1959).
3. M.M. Hanafy and M.R.A. Morsey, "Maternal Nutrition and Lactation Performance," J. Trop.. Pediat Environ. Child Hlth, 18: 187 11972).
4. World Health Organization, Nutrition in Pregnancy and Lactation, report of a WHO Expert Committee, WHO technical Report Series No. 302 (WHO Geneva, 1965), pp. 24-30.
5. Tin Tin Oo and Khin Maung Naing, "The Pattern of Breast-Feeding and Its Nutritional Adequacy in Rural Communities," Proceedings of a research seminar organized by the Department of Medical Research, Rangoon, Burma, 8 Sept. 1979, pp. 4-19.
6. D.B. Jelliffe and E.F.P. Jelliffe Human Milk in the Modern World [Oxford University Press Oxford, New York, Toronto 1978).