Breastfeeding, why...

• Age of introduction of complementary foods and growth of term, low-birth-weight, breast-fed infants: a randomized intervention study in Honduras
• Effect of breastfeeding on infant and child mortality due to infectious diseases in less developed countries: a pooled analysis
• Protective effect of breastfeeding: an ecologic study of Haemophilus influenzae meningitis and breastfeeding in a Swedish population
• Breast-feeding and alcoholism: the Trotter hypothesis
• Impact of breast feeding on admission for pneumonia during postneonatal period in Brazil: nested case-control study
• Breast feeding and obesity: cross sectional study
• Influence of infant-feeding patterns on early mother-to-child transmission of HIV-1 in Durban, South Africa: a prospective cohort study

Dewey KG, Cohen RJ, Brown KH, Landa Rivera L. Age of introduction of complementary foods and growth of term, low-birth-weight, breast-fed infants: a randomized intervention study in Honduras, American Journal of Clinical Nutrition, 69: 679-686, 1999.

The optimal age at which to introduce complementary foods is a topic of considerable debate. A study on term, low-birth-weight infants in Honduras is a valuable addition to the scientific data necessary to resolve this issue. 128 small-for-date (1500-2500 g) infants who had been exclusively breastfed for 4 months were randomly divided into two groups. The first group continued to breastfeed exclusively (EBF) until the age of 6 months. The second group continued to breastfeed and were fed twice daily complementary food (jarred rice cereal, chicken, fruit, and vegetables) (SF). At 6 months it was found that 1) time spent breastfeeding in the SF group declined by 38 min/24 hr, but increased 11 min/ 24 hr in the EBF group, 2) breast milk intake decreased by 39g/ 24 hr in the SF group, but increased by 28 g/24 hr in the EBF group, 3) there were no significant differences in weight, length or head circumference between the two groups.

The authors concluded that "...from the perspective of infant growth, exclusive breast-feeding for about 6 months can be recommended even among full-term, low-birth-weight babies in a developing country..."

WHO Collobrative Study Team on the Role of Breastfeeding on the Prevention of Infant Mortality. Effect of breastfeeding on infant and child mortality due to infectious diseases in less developed countries: a pooled analysis, The Lancet, 355: 451-455, 2000.

More information is needed to guide policy makers and community health workers about the effect of breastfeeding on infant anf child mortality. This information is especially important in the light of the HIV/AIDS and infant feeding debate. WHO sponsored researchers did a pooled analysis of studies which assessed the effect of not breastfeeding on the risk of death due to infectious diseases. Data from six studies was available, but because of universal breastfeeding in Africa an analysis of the effect of breastfeeding in these countries was not possible. It was done on three countries, Brazil, the Philippines and Pakistan. Acute respiratory infections (ARI) and diarrhea were the leading causes of death from infectious diseases. The results showed that infants less than 2 months of age were 5.8 times less likely to die, and infants 2-3 months of age were 4. 1 times less likely to die if breastfed. Infants 4-5 months were 1.8 times less likely, and infants 6-8 months were 1.4 times less likely to die if breastfed. In the first 6 months of life protection from death from diarrhea was substantially greater than protection from death from ARI. Protection against death from ARI did not decrease with age as it did against death from diarrhea.

The authors suggest that their findings should be used in assessing the impact of withholding breastfeeding in HIV-positive mothers and in shaping policy decisions, especially for families of low socioeconomic status.

Silfverdal SA, Bodin L, Olcén P. Protective effect of breastfeeding: an ecologic study of Haemophilus influenzae meningitis and breastfeeding in a Swedish population, International Journal of Epidemiology, 28: 152-156, 1999.

Previously researchers in Sweden had done a case-control study between 1987 and 1992 in which they found that a long duration of breastfeeding decreased the risk of Haemophilus caused meningitis infection. In the present study they studied the long term effects of exclusive breastfeeding on the rate of meningitis infection over a period of 15 years (1956-1992) at a population level. They found that breastfeeding strongly reduced the risk of contracting meningitis for 5-10 years, but not 15 years and beyond. Over the time span studied the data showed that low breastfeeding rates were followed by increased menigitis rates 5-10 years later. The authors concluded that the results should affect strategies to promote breastfeeding, especially in countries where Haemophilus vaccination is too costly.

Goodwin DW, Gabrielli WF, Penick EC, Nickel EJ, Chhibber S, Knopp J, Jensen P, Schulsinger F. Breast-feeding and alcoholism: the Trotter hypothesis, American Journal of Psychiatry, 156 (4): 650-652, 1999.

A British physician during the American Revolutinary War proposed the theory that early weaning was a factor in alcoholism. 200 hundred years later Danish investigators tested this hypothesis using a large database of 9,182 consecutive deliveries to study the relation between perinatal factors and alcoholism later in life. 200 sons of alcoholics were matched with 107 controls all from the same database. Results showed that 48% of the alcohol dependent men were weaned very early (less than 2 weeks after birth) while only 19% of the non-alcohol dependent men were weaned very early. When other variables like mother or father being alcohol dependent were controlled for, early weaning significantly contributed to the prediction of alcoholism at age 30.

César JA, Victora CG, Barros FC, Santos IS, Flores JA. Impact of breast feeding on admission for pneumonia during postneonatal period in Brazil: nested case-control study, British Medical Journal, 318: 1316-1320, 1999.

Pneumonia is the leading cause of death in children under 5 years old world-wide. Breastfeeding is known to reduce the risk of contracting lower respiratory infections. A study carried out in Brazil was designed to determine to what extent breastfeeding reduces this risk and whether the protection varies with age. 152 infants aged 28-364 days who had been admitted to hospital for pneumonia were matched with 2391 controls. Results showed that infants who were not breastfed were 17 times more likely to be admitted for pneumonia, while infants receiving breast milk and other fluids were 3.8 times more likely. According to age, infants less than three months were 61 times more likely to be admitted, and children older than 3 months 10 times more likely to be admitted for pneumonia if they were not breastfed. Infants who were fed complementary foods were 13.4 times more likely to contract pneumonia. When analyzed by age results showed that infants less than 3 months fed complementary foods were 175 times more likely to be admitted for pneumonia, those 3-6 months were 9.1 times more likely, while infants older than 6 months were less likely to contract pneumonia (relative risk, 0.7).

This study provides more data to support the recommendation that complementary foods should not be introduced before the age of about 6 months.

von Kries R, Koletzko, B, Sauerwald T, von Mutius E, Barnert D, Grunert V, von Voss H. Breast feeding and obesity: cross sectional study, British Medical Journal, 319: 147-150, 1999.

Investigators are increasingly studying the long term effects of breastfeeding. A study of a large group (13,345) of 5-6 year olds in Southern Germany found that exclusive breastfeeding reduced the risk of both obesity and overweight. The obesity rate in children never breastfed was 4.5% as compared with a rate of 2.8% in breastfed children. The effect was seen to be dose-dependent. The prevalence was 3.8% in children breastfed exclusively for 2 months, 2.3% for 3-5 months, and 1.7% for 6-12 months of exclusive breastfeeding. After adjusting for other factors like social class, parental education and current eating habits, breastfeeding remained a significant protective factor against obesity. The authors think that breastfeeding may have a metabolic programming effect in preventing obesity. Since the risk of adult obesity is increased by child obesity, breastfeeding could be an important preventive measure in the effort to reduce cardiovasular and other diseases related to obesity.

Coutsoudis A, Pillay K, Spooner E, Kuhn L, Coovadia HM. Influence of infant-feeding patterns on early mother-to-child transmission of HIV-1 in Durban, South Africa: a prospective cohort study, The Lancet, 354: 471-476, 1999.

Studies have shown that there is a 1 in 7 chance that the HIV virus is transmitted from mother-to-child through breastfeeding. However, there is uncertainty regarding the influence infant feeding patterns have on the mode of transmission. Researchers in South Africa studied the infant feeding patterns of 549 HIV-infected women and their effect on transmission. Results showed that at 3 months 18.8% of never-breastfed infants were estimated to be infected with HIV-1 compared with 21.3% of breastfed infants. Infants who were exclusively breastfed showed an infection rate of 14.6% which was significantly lower than the 24.1% showed by infants receiving mixed feeding. The transmission rate in the exclusively breastfed infants was similar to the 18.8% transmission rate in the never-breastfed infants.

The UNAIDS, UNICEF and WHO recommendations currently encourage mothers infected with HIV to breastfeed exclusively if they chose to breastfeed their infants. Coutsoudis and her colleagues would encourage women who have no safe alternatives to exclusively breastfeed to reduce the chance of transmission.