BREASTFEEDING AND ITS NUTRITIONAL CONTENT

 Breastfeeding, or nursing, is the process by which human breast milk is fed to a child. Breast milk may be from the breast, or may be expressed by hand or pumped and fed to the infant. The World Health Organization (WHO) recommends that breastfeeding begin within the first hour of a baby's life and continue as often and as much as the baby wants. Health organizations, including the WHO, recommend breastfeeding exclusively for six months. This means that no other foods or drinks, other than vitamin D, are typically given. WHO recommends exclusive breastfeeding for the first 6 months of life, followed by continued breastfeeding with appropriate complementary foods for up to 2 years and beyond. Of the 135 million babies born every year, only 42% are breastfed within the first hour of life, only 38% of mothers practice exclusive breastfeeding during the first six months, and 58% of mothers continue breastfeeding up to the age of two years and beyond.

Breastfeeding has a number of benefits to both mother and baby that infant formula lacks. Increased breastfeeding to near-universal levels in low and medium income countries could prevent approximately 820,000 deaths of children under the age of five annually. Breastfeeding decreases the risk of respiratory tract infections, ear infections, sudden infant death syndrome (SIDS), and diarrhea for the baby, both in developing and developed countries.  Other benefits have been proposed to include lower risks of asthma, food allergies, and diabetes. Breastfeeding may also improve cognitive development and decrease the risk of obesity in adulthood.

Benefits for the mother include less blood loss following delivery, better contraction of the uterus, and a decreased risk of postpartum depression. Breastfeeding delays the return of menstruation, and in very specific circumstances, fertility, a phenomenon known as lactational amenorrhea.[  Long-term benefits for the mother include decreased risk of breast cancer, cardiovascular disease, diabetes, metabolic syndrome, and rheumatoid arthritis.  Breastfeeding is less expensive than infant formula, but its impact on mothers' ability to earn an income is not usually factored into calculations comparing the two feeding methods.

Feedings may last as long as 30–45 minutes each as milk supply develops and the infant learns the Suck-Swallow-Breathe pattern.  However, as milk supply increases and the infant becomes more efficient at feeding, the duration of feeds may shorten.  Older children may feed less often. When direct breastfeeding is not possible, expressing or pumping to empty the breasts can help mothers avoid plugged milk ducts and breast infection, maintain their milk supply, resolve engorgement, and provide milk to be fed to their infant at a later time. Medical conditions that do not allow breastfeeding are rare. Mothers who take certain recreational drugs should not breastfeed, however, most medications are compatible with breastfeeding. Current evidence indicates that it is unlikely that COVID-19 can be transmitted through breast milk. Smoking tobacco and consuming limited amounts of alcohol and/or coffee are not reasons to avoid breastfeeding.

The pattern of intended nutrient content in breast milk is relatively consistent. Breastmilk is made from nutrients in the mother's bloodstream and bodily stores. It has an optimal balance of fat, sugar, water, and protein that is needed for a baby's age appropriate growth and development. That being said, a variety of factors can influence the nutritional makeup of breastmilk, including gestational age, age of infant, maternal age, maternal smoking, and nutritional needs of the infant.: 10–14 

The first type of milk produced is called colostrum. The volume of colostrum produced during each feeding is appropriate for the size of the newborn stomach and is sufficient, calorically, for feeding a newborn during the first few days of life.: 27–34  Produced during pregnancy and the first days after childbirth, colostrum is rich in protein and Vitamins A, B12 and K, which supports infants' growth, brain development, vision, immune systems, red blood cells, and clotting cascade. The breast milk also has long-chain polyunsaturated fatty acids which help with normal retinal and neural development.The caloric content of colostrum is about 54 Calories/100mL. The second type of milk is transitional milk, which is produced during the transition from colostrum to mature breast milk. As the breast milk matures over the course to several weeks, the protein content of the milk decreases on average.: 10–14  The caloric content of breastmilk is reflective of the caloric requirements of the infant, increasing steadily after 12 months.: 10–14  The caloric content of breastmilk in the first 12 months of breastfeeding is approximated to be 58-72 Calories/100mL. Comparatively, the caloric content after 48 months is approximately 83-129 Calories/100mL.

When a mother has her full milk supply and is feeding her infant, the first milk to be expressed is called the foremilk. Foremilk is typically thinner and less rich in calories. The hindmilk that follows is rich in calories and fat.

If the mother is not herself deficient in vitamins, breast milk normally supplies her baby's needs, with the exception of Vitamin D. The CDC, National Health Service (UK), Canadian Paediatric Society, the American Academy of Pediatrics, and the American Academy of Family Physicians all agree that breast milk alone does not provide infants with an adequate amount of Vitamin D, thus they advise parents to supplement their infants with 400 IU Vitamin D daily. Providing this quantity of Vitamin D to breastfeeding infants has been shown to reduce rates of Vitamin D insufficiency (defined as 25‐OH vitamin D < 50 nmol/L). However, there was insufficient evidence in the most recent Cochrane Review, to determine if this quantity reduced rates of Vitamin D deficiency (defined as 25‐OH vitamin D < 30 nmol/L) or rickets. Term infants typically do not need iron supplementation. Delaying clamping of the cord at birth for at least one minute improves the infants' iron status for the first year.: 50–51 When complementary (solid) foods are introduced at about 6 months of age, parents should make sure to choose iron-rich foods to help maintain their children's iron stores.