Breastfeeding, why...

• Breastfeeding and infant growth
• Complementary feeding and infant growth
• Breastfeeding and overweight

Breastfeeding and infant growth

Kramer MS, Guo T, Platt RW, Shapiro S, Collet JP, Chalmers B, Hodnett E, Sevkovskaya Z, Dzikovich I, Vanilovich I. Breastfeeding and infant growth: biology or bias? Pediatrics 2002;110:343-7

Is prolonged and exclusive breastfeeding (EBF) associated with lower infant weight and length at a later age? This study suggests that it may actually accelerate weight and length gain in the first few months, with no detectable deficit by 12 months. Within a randomised trial conducted in Belarus (see BB 31/32 for details), 17,046 healthy, full-term, singleton breastfed infants weighing more than 2,500 g were followed up at 1, 2, 3, 6, 9, and 12 months for measurements of weight and length. Data were analysed according to randomisation, but also combining the two randomised groups and comparing 1,378 infants weaned in the first month and those breastfed for the full 12 months of follow-up with either 3 months or more (n = 1,271), or 6 months or more (n = 251), of EBF.

In the analysis by random assignment, mean weight was significantly higher in the intervention group (i.e., where training for the BFHI was conducted) by 1 month of age (4,341 vs 4,280 g). The difference increased through 3 months (6,153 vs 6,047 g), declined slowly thereafter, and disappeared by 12 months (10,564 vs 10,571 g). Length followed a similar pattern. In the analysis by type of feeding, infants weaned in the first month were slightly lighter and shorter at birth and their weight-for-age and length-for-age declined by 1 month, but they caught up to the other groups by 6 months and were heavier and longer by 12 months.

Simondon KB et al. Breastfeeding is associated with improved growth in length, but not weight, in rural Senegalese toddlers. Am J Clin Nutr 2001;73:959-67

Some studies have reported that children weaned late show lower height-for-age. Is this explained by their height before weaning or is prolonged breastfeeding the cause of this impaired growth?

This study shows that prolonged breastfeeding actually increased length, and that the negative correlation between height-for-age and duration of breastfeeding is probably due to earlier weaning of healthy, well-nourished children. A cohort of 443 children recruited from dispensaries at 2 months of age was visited in their homes at 6-month intervals when they were approximately 1.5 to 3 years old. Weight, length, arm circumference, and triceps skinfold thickness were measured. Six-month increments were analysed in relation to breastfeeding (breastfed compared with weaned children or breastfeeding duration), and maternal housing. The mean duration of breastfeeding was 24.1 months. At 3 years, height-for-age was greater for those infants who were weaned earlier, but this association disappeared after adjustment for height-for-age in infancy. Length increments were significantly greater in both the second and third years of life in children breastfed for longer duration and tended to be greater in breastfed than in weaned children in the second year of life. In the third year of life, breastfed children had greater length increments than did weaned children in the subgroup with poor housing. Breastfeeding had no significant influence on weight gain.

Complementary feeding and infant growth

Padmadas SS, Hutter I, Willekens F. Weaning initiation patterns and subsequent linear growth progression among children aged 2-4 years in India. Int J Epidemiol 2002 Aug;31(4):855-63

In India, malnutrition is still an important problem and breastmilk should be seen as an essential source of nutrients. About 47% of infants are weaned (i.e., first given complementary foods) at 6 months or beyond, and more than 50% of children under 4 years are stunted. This study used cross sectional data on 6,285 children aged 2-4 years from the National Family Health Survey of 1992-1993 to look at the association between weaning and stunting. Children weaned at age 6 months or later had 57-88% higher likelihood of being stunted compared with those weaned before 6 months. Stunting appeared to be considerably lower for children weaned at age 3 months and showed an upward trend thereafter. The effect persisted after controlling for important demographic, health, social and geographical variables. The effect, however, may be due to bias: the cross sectional nature of the study does not allow to control for weight and length at weaning, as in the longitudinal studies summarised above and below.

WHO Working Group on the Growth Reference Protocol, WHO Task Force on Methods for the Natural Regulation of Fertility. Growth of healthy infants and the timing, type, and frequency of complementary foods. Am J Clin Nutr 2002;76:620-7

There is no evidence of benefit or risk related to growth and the timing of introduction of different types and frequencies of complementary foods at any specific time between 4 and 6 months of age in healthy infants living in environments without major economic constraints and with low rates of illness. This conclusion is drawn from a longitudinal study on breastfeeding and lactational amenorrhea in seven developed countries. Small differences in growth that were statistically significant, but probably not biologically important, were noted among infants in whom complementary foods were introduced at different times. Weight gain was more sensitive to feeding frequencies than were gains in length, but the differences were small. These results, however, may not be valid for populations living in poor environments.

Breastfeeding and overweight

Hediger ML, Overpeck MD, Kuczmarski RJ, Ruan WJ. Association between infant breastfeeding and overweight in young children. JAMA 2001;285:2453-60

If a mother is obese, the child might have a higher probability of obesity as well. Breastfeeding may not be as effective as moderating familial factors, such as dietary habits and physical activity, in preventing children from becoming overweight. The authors draw these conclusions from the study of a sample of 2,685 US-born children between the ages of 3 and 5 years, with height and weight measures, and information on infant feeding. A body mass index (BMI) between the 85th and 94th percentile was considered as overweight and a BMI in the 95th percentile or higher was considered as obesity. After adjusting for potential confounders, there was a 37% lower risk of overweight for ever breastfed children compared with those never breastfed. There was no reduced risk of obesity and there was no clear dose-dependent effect of the duration of full breastfeeding on being overweight or obese, and no threshold effect. The strongest predictor of child obesity was the mother's concurrent weight. The rate of obese children nearly tripled with maternal overweight and more than quadrupled with maternal obesity.

Gillman MW, Rifas-Shiman SL, Camargo CA Jr, et. al. Risk of overweight among adolescents who were breastfed as infants. JAMA 2001;285:2461-7

Infants who are fed breastmilk more than infant formula, or who are breastfed for longer periods, may have a lower risk of being overweight during older childhood and adolescence. This is the result of a study on 8,186 girls and 7,155 boys aged 9 to 14 years. Overweight was defined as in the above study, but in this one, even controlling for the mother’s BMI, breastfed infants were protected against obesity. In the first 6 months of life, 62% of subjects were only or mostly fed breastmilk, and 31% were only or mostly fed infant formula. 48% were breastfed for at least 7 months while 31% were breastfed for 3 months or less. At ages 9 to 14 years, 5% of girls and 9% of boys were overweight. Among those who had been only or mostly fed breastmilk, compared with those only or mostly fed formula, the risk of overweight was 22% lower after adjustment for age, sex, sexual maturity, energy intake, time watching television, physical activity, mother's BMI, and other variables reflecting social, economic, and lifestyle factors. Compared with subjects who had been breastfed for 3 months or less, those who had been breastfed for at least 7 months had a 20% lower risk of overweight.

Armstrong J, Reilly JJ, Child Health Information Team. Breastfeeding and lowering the risk of childhood obesity. Lancet 2002;359:2003-4

In Scotland, breastfeeding may be associated with a reduced risk of obesity in childhood. This hypothesis was tested in 1998 and 1999 in a population-based sample of 32,200 Scottish children studied at age 39-42 months. Obesity was defined as in the above studies. The prevalence of obesity was significantly lower by 30% in breastfed children, and the association persisted after adjustment for socio-economic status, birth weight and sex. Maternal BMI was not controlled for.