Early infancy
The human body undergoes its most rapid phase of growth during infancy and healthy babies usually double their birthweight in the first six months of life.
Nutritional requirements
The term infant is born with reserves of energy and many nutrients that have been acquired during foetal life, particularly in the third trimester. These contribute to meeting the nutritional needs of the newborn but all the dietary energy and the majority of essential nutrients are supplied by milk;
Fat
- Fat is a rich source of energy (as calories) for the baby and accounts for approximately half of the energy content of breast milk
- Babies energy needs are much greater than adults relative to their body weight, due to the fast rate of growth in early life
- Fat is also the vehicle for the transfer of the fat-soluble vitamins A, D, E &K and other substances such as prostaglandins
- Breast milk also supplies other essential fats: omega-3 and omega-6 fatty acids, docosahexaenoic acid and arachidonic acid, which are vital constituents of brain and neural tissues
Carbohydrate
- Carbohydrate is another major energy source for the baby, providing about 40% of the total energy in breast milk
- The principle carbohydrate in breast milk is lactose
- Breast milk contains significant quantities of other carbohydrates, mainly monosaccharides and oligosaccharides
- The oligosaccharides of breast milk may have a function in the defence against viruses, bacteria or other toxins and in promoting the growth of intestinal flora, including strains with possible probiotic effects, such as bifidobacteria
Protein
- The infant requires protein for growth and the maintenance and repair of body tissues, as well as to make enzymes that control many body functions
- There are two distinct protein components in breast milk; casein and whey. The ratio of casein/whey protein in mature milk is approximately 40:60
- Whey proteins form a soft curd in the stomach that is easily digested
- The whey component in breast milk contains important proteins such as:
- Lactoferrin, which inhibits bacterial growth by making iron unavailable
- Lysozyme, which is an enzyme that inhibits bacteria by disrupting their cell walls
- Alpha-lactalbumin, which helps provide the appropriate balance of essential amino acids in breast milk
- Immunoglobulins, which are antibodies
- Casein protein has coagulating properties, which forms a firmer curd and takes longer to digest in the baby’s stomach
Vitamins
Infants require both fat soluble and water soluble vitamins for a variety of functions:
- Vitamin A: essential for normal growth and development, healthy skin and eyes and also the immune function
- Vitamin D: essential for calcium absorption; deficiency can cause poor bone growth and rickets
- Vitamin E: important in metabolism
- Vitamin K: important for maintaining the normal blood clotting function of the body
- B vitamins: important in energy metabolism and expenditure
- Vitamin C: necessary for normal growth and development. It is needed to form collagen, a protein used to make skin, scar tissue, tendons, ligaments and blood vessels. It is also important for the absorption of iron
Breast milk from well nourished mums provides adequate amounts of all vitamins with the exception of vitamins D and K;
- Vitamin D intake from food is low but is supplemented by synthesis on exposure to adequate sun light in the summer months
- Due to health concerns about sun exposure, few infants are likely to have regular sun exposure
- All women are recommended to take supplements containing 10 µg of vitamin D each day during pregnancy and breastfeeding, which can help prevent deficiency in their infants
- Vitamin K is synthesised by bacteria in the gut. In the UK and ROI, intramuscular or oral supplements are administered in the first few weeks of life by the midwife
Minerals
Infants require minerals that play a variety of roles in the body:
- Calcium: essential for bone growth, muscle contraction, nerve transmission and blood clotting
- Phosphorous: essential for bone growth
- Iron: an important nutrient which has many metabolic functions, including oxygen transport in the red blood cells
- Zinc: essential for growth, development and immune function
The iron content of breast milk is low but is well utilised by the body and the baby also relies on its body stores in the first 4-6 months of life
At around 4 to 6 months, as the body stores start to deplete, the baby has to depend more on the diet for its source of iron
Breast milk: a unique source of nutrition for infants
- The unique composition of breast milk changes according to the nutritional needs of the newborn and, through its non-nutritional components, helps in adaptation to life outside the womb
- Breast milk is the best food for babies and contains all the energy and nutrients they need
- The composition of breast milk is not constant but changes during feeds, according to the time of day and during the course of lactation
- Breast milk contains bioactive non-nutritional substances that provide protection from bacterial and viral infections and may aid growth and development
- The advantages of breastfeeding to mother and baby are numerous and long lasting; in addition to its nutritional benefits, breastfeeding gives a number of non-nutritional advantages to young babies
Current feeding recommendations
- British and Irish Governments recommend exclusive breastfeeding for the first six months (26 weeks) of life
Alternatives to breast milk
- Infant formulas are the only alternatives to breast milk in babies under the age of one year
- Most infant formulas are based on cows’ milk and have been designed to mimic the nutrient composition of breast milk
- In recent years, infant formula composition has evolved from just trying to mimic breast milk to trying to replicate specific biological effect of it, thus providing some of the known benefits of breast milk
- Major advances include the addition of nucleotides and long chain polyunsaturated fatty acids (LCPs) to formulas and, more recently, the improvement of protein quality (in alpha-protein enriched formula)
