Breast Milk Composition Versus Nutritional Requirements of Infants

Infants should be exclusively breastfed during the first months of life with continued breastfeeding after timely introduction of complementary feeding. Along with providing an adequate nutrient supply to the infant for normal growth and development, breastfeeding is also found to have many other advantages such as reduced risk of infections and long-term benefits such as reduced risk of type-II diabetes, obesity, high blood pressure and better performance on intelligence tests.

But after the first few months of lactation, say, after the third month, is breastfeeding enough to meet the nutritional requirements of the fast-growing baby? What changes in the composition of breast milk occur during and after this period? Does formula-milk compare to it?

To answer the questions researcher, V. Grote along with co-workers conducted a study for the European Childhood Obesity Project which was published under the title ‘Breast milk composition and infant nutrient intakes during the first 12 months of life’. It aimed at quantifying breast milk intake and breast milk nutrient content.

The Study:

One hundred and seventy-four Italian breast-fed infants and their mothers were chosen for the study. Healthy infants born after uncomplicated pregnancies were chosen from maternity hospitals in the first 8 weeks of life. Children who had been given formula milk for more than 10% of all feedings or were given more than 3 bottles per week were excluded from the study. Mothers were instructed not to include any complementary food in the diets of the babies before the age of 4 completed months. Data on the course of pregnancy, medical history, socio-economic status and pre-pregnancy Body Mass Index (BMI) of the mothers were also considered in the study.

For the breast milk samples, 30 lactating mothers with child ages one (T1), two(T2), three(T3) and six(T6) months were selected. Over 3 days milk samples were collected from the first feeding in the morning after the mother got up. Mothers were instructed to manually express 10 ml of milk from the breast the infant was fed on, both at the beginning (foremilk) and at the end of each feed(hindmilk). The milk samples were then analyzed for the content of protein, non-protein nitrogen(NPN), total digestible carbohydrates, lactose, glucose, galactose, fatty-acid and lipid composition.

The quantity of milk intake by the infants was assessed over a period of 3 days by weighing the baby before and after each breastfeeding with the baby lying on an electronic scale.

The results we got:

The quantity of each nutrient in the milk samples was determined. The contents of protein, NPN and galactose decreased significantly between 1 and 6 months of lactation. The protein content decreased at first from month 1 to month 4, but after that, it increased to more than two times from month 4 to month 12. None of the other measured parameters changed significantly, although there was a trend towards decreasing fat and energy.

Age and pre-pregnancy BMI of mothers also had an influence on the milk composition. Some fatty acids were higher in younger mothers, while some other were higher in older mothers. Furthermore, energy, fat, protein and galactose content was higher in mothers with higher BMI. However, these differences were insignificant.

Free galactose made up a small fraction of carbohydrates in human milk and significantly decreased over time. Much higher concentrations of galactose are found in formula milk; however, this carbohydrate has no biological importance in human milk.

The percentage of fat increased at first from month 1 to month 3 after which it decreased quite significantly. The type and amount of fat consumed by mothers also influenced the fat composition of the milk. A diet rich in saturated or unsaturated fatty acids was reflected in the breast milk.

What we can conclude from this:

The gradual decrease in the percentage of fats and carbohydrates and the energy derived from these point in one direction – the contribution of complementary diet in meeting the nutritional requirement of the infant. With the increase in the percentage of protein from 4 to 12 months, 70% of the infants receive more protein than the acceptable limit. Since higher protein intakes may lead to a higher risk of obesity at school age, the excessive introduction of protein sources during complementary feeding should be avoided.

With the gradual decrease in the percentage of fat in the milk, more regular consumption of ocean fish and seafood should be encouraged by the mothers as it would increase the mono and polyunsaturated fatty acid content of the milk and hence its supply to the infant. These fatty acids are required for the normal visual and cognitive development of the infant. **Mothers should consult their physicians before taking any decision after reading this article.