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breast milk

Alternative Names 
human milk

A woman's body produces breast milk after the birth of an infant. After delivery of the baby, changes in hormonal patterns of the mother change rapidly. This triggers the release of hormones that cause the body to produce breast milk.

How does the nutrient affect the body? 
Breast milk is the best source of nutrition for an infant. Breast milk can provide all or nearly all the nutrition an infant needs during the first 6 to 12 months of life. Both the Dieticians Association of Australia and the National Health And Medical Research Council support breast-feeding for the first 4 to 6 months of life. They also support breast-feeding supplemented by weaning foods for at least 12 months. The first Dietary Guidance for Children and Adolescents is "Encourage and support breastfeeding"!

During the first few days after birth, a woman's body produces a fluid called colostrum. Colostrum is high in protein, zinc and other minerals. It contains less fat, carbohydrates and kilojoules than breast milk. Between the third and sixth day after birth, colostrum changes to a "transitional" form of breast milk. During this time, the amount of protein and immune factors in the milk gradually decrease while fat, lactose, and kilojoules in the milk increase. By the tenth day after birth, the mother produces mature breast milk. Colostrum and human milk are rich in antibodies and have anti-infective factors. These help protect the newborn infant from viruses and bacteria that the infant was exposed to in the birth canal. They help to protect the infant's immature gut from infection. Breast milk promotes the growth of bacteria that all humans normally have in the digestive tract. Breast milk contains immune factors to help an infant fight infection and help prevent the infant from developing possible food allergies.

Breast milk from most women has the same nutrients. There could be small differences, based on what a woman eats and how her body produces breast milk. If the mother eats a poor diet, this can decrease both the amount of milk produced and the nutrients found in the milk. Women who are breast-feeding should consume an extra 2000 kilojoules per day above their maintenance kilojoules. This helps to make sure the mother is able to provide the infant with the quality and quantity of milk needed. Milk content can also change from one time of the day to another, and from the beginning of a breast-feeding session to the end of a session. The nutrients in breast milk also change from the early months of infancy to the later months of infancy. These changes match the changing nutritional needs of the growing infant.

The proteins in human breast milk are mostly whey and casein. Cow's milk contains more casein, and human breast milk contains more whey. Whey is more easily tolerated by an infant's digestive system.

The fat in human breast milk is easily absorbed by an infant's digestive system. An enzyme called lipoprotein lipase helps an infant absorb the fat in breast milk. A mother's breast milk contains essential fats. It also contains cholesterol. Both are needed by infants to make tissues of the nervous system. The amount of fat in breast milk rises significantly at the end of a breast-feeding session. This may be nature's way of making an infant feel full and stop feeding.

Breast milk contains large amounts of lactose, which is a carbohydrate. Lactose is used in tissues of the brain and spinal cord, and it provides the infant with energy. Bacteria in the infant's intestines feed on lactose and produce B vitamins. Lactose may also help the infant absorb essential nutrients such as calcium, phosphorous and magnesium.

Human breast milk contains only a small amount of iron, but the iron in breast milk is easily absorbed. Fifty percent (50%) of the iron in human breast milk is absorbed compared with only 4 to 10% of the iron in cow's milk or commercial infant formulas.

Breast milk contains all the vitamins an infant needs for good health. The actual amount of each vitamin can vary, depending on a woman's diet and genetic make-up.

Reviewer: eknowhow Medical Review Panel
Editor: Dr John Hearne
Last Updated: 16/09/2004
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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