Encyclopedia of Food & Culture | Lactation

LACTATION. Lactation refers to the ability of mammals, warm-blooded, backboned animals, to nourish their young with milk produced by the mammary glands. Many other distinguishing features separate mammals into families that include over four thousand species. The milk of each species is specifically engineered for the growth and developmental needs of that species. In fact studies of the characteristics of the milk can predict the growth rate of both body and brain and the developmental maturity of the offspring at birth. It is also possible to predict the feeding patterns that vary from the whale, which feeds its young every three to four days and has extremely high-fat milk (50 percent), to the human, who initially feeds the infant every two to three hours and has low-protein, low-fat milk (3.4 percent). Some of the world's finest scientists have turned their attention to human lactation and have not only deciphered the micronutrients of human milk but have studied the nutrient needs of the human infant, especially as they pertain to brain development and physical growth. Research also has explained the physiology of human lactation.

Historically, in times of wealth and prosperity, women of higher socioeconomic levels have sought substitute feedings for their infants to "free" themselves of the burden of breast-feeding. Dogma and ritual have developed in different cultures of the world around nursing. It is significant that the Qur'an states that women should nurse their infants for two years. In the Old Testament, the Book of Psalms refers to the value of mother's milk. Pope John Paul II stated that the women of the world should provide their milk for their infants.

When bottle-feeding became more available for the average mother due to the discovery of sterilization, followed by the availability of prepared formulas, the trend toward bottle-feeding increased from 1930 to 1950. Well-educated women led the march to the bottle because they wanted to raise their infants by the book, with scientific information. In the second half of the twentieth century, these same educated women sought a different mode of childbirth in which the mother was prepared and in control. Concomitant with this, well-educated women began looking at breast-feeding as the most appropriate course for their infants.

In 1978 a bipartisan congressional committee charged with the responsibility of designing a health plan for the United States established the year 1990 as the target date for accomplishing several health goals. In addition to statements regarding decreasing hypertension, obesity, and smoking, the committee stated that 75 percent of women should leave the hospital breast-feeding and at least 35 percent should still be breast-feeding at six months. Many of the goals were not accomplished, and in 1990 they were rewritten with a target date of 2000. In 2000 they were rewritten for 2010, aiming at 75 percent of mothers initiating breast-feeding, 50 percent continuing for six months, and 25 percent continuing for a full year. The World Health Organization Code for Infant Feeding was developed in 1981, and the most industrialized countries of the world endorsed this policy, which supported breast-feeding and rejected the promotion of artificial feedings and advertisement of these feedings to the public. The United States did not sign until 1994. The Institute of Medicine, through the Subcommittee on Nutrition during Lactation, confirmed the position that all women, under ordinary circumstances, should breast-feed their infants and further stated that breast-feeding was ideal, even if the mother's diet was not perfect. The American Academy of Pediatrics, joined by the American College of Obstetrics and Gynecology, stated in 1997 that infants should be exclusively breast-fed for five to six months. They further stated that breast-feeding should continue as weaning foods are added through the first year of life and then for as long thereafter as the mother and the infant choose

Significance of Breast-Feeding to Health

Why have all of these important groups spoken out so strongly in favor of breast-feeding? The knowledge that human milk is for the human infant has been accepted for centuries. In the late twentieth century, however, considerable scientific investigation established unequivocally that breast-feeding is associated with a reduced incidence of infection in the infant, including reduced incidences of gastrointestinal, upper and lower respiratory, ear, and urinary tract infections. Immunologic data have shown reduced incidences of childhood-onset cancers, especially lymphoma and acute lymphocytic leukemia. Crohn's disease, celiac disease, and childhood-onset diabetes also are reduced when infants are breast-fed for at least four months. Probably the most dramatic information published in multiple articles is the relationship between breast-feeding and infant development. A study by Niles Newton compared the developmental progress of breast-fed and bottle-fed three-year-olds. Alan Lucas, Ruth Morley, T. J. Cole, and others reported a multisite study that compared premature babies given their mother's milk by feeding tube with infants given premature-infant formula. The group studied them at eighteen months and followed them until seven and a half to eight years of age. The study showed an 8.5-point difference when the data were adjusted for socioeconomic status and education of the mother. The eighteen-year study by L. John Horwood and David M. Fergusson in New Zealand showed a measurable difference at eighteen years of age in school outcomes and behaviors related to whether or not the children were breast-fed in infancy. Although these studies have been criticized for design flaws, many scientists accept their findings. These results are in addition to the compelling psychologic benefit to the mother and the infant in their relationship during breast-feeding.

Facilitating the Decision to Breast-Feed

A mother needs an opportunity to make an informed decision about how to feed her infant. If a mother comes to pregnancy without any information on this process, it is the health care provider's responsibility to see that she is well informed about the benefits of breast-feeding for her baby, for herself, and for society so she can make a decision that will be optimal.

The economic benefit of breast-feeding. A simple calculation of the cost of buying formula does not reflect completely the monetary benefits of breast-feeding. It costs between $60 and $80 a month to purchase infant formula, $700 to $1,000 for the first year of life. Careful studies in controlled populations, such as in health maintenance organizations, have demonstrated in multiple reports that infants who are not breast-fed have an increased number of illnesses, visits to the doctor, prescription medications, and hospitalizations compared with their breast-fed counterparts. The estimate per infant of the health care costs not to breast-feed is between $600 and $1,000 per year. This estimate does not include the reduction in the onset of chronic illnesses that may last a lifetime, such as diabetes, Crohn's disease, and allergies.

Benefits to the mother. The benefits of breast-feeding to the mother are often ignored. Women who breast-feed return to their prepregnant, physiologic states more rapidly. The uterus involutes, the postpartum blood loss is reduced, and the woman returns to her physiologic weight as well. Among other possible benefits are reduced incidences of long-term obesity, breast cancer, ovarian cancer, and most remarkably long-term osteoporosis. Although breast-feeding is not a contraceptive, it significantly affects the fertility in the childbearing years by suppressing ovulation.

Establishing lactation. Critical information about the mother's potential for a good milk supply is obtained during pregnancy. When the obstetrician does the early examination of the breasts in the first trimester, the breasts should be evaluated with respect to their potential for producing milk. Unusually small, unusually large, asym-metric, or tubular-shaped breasts may pose a problem. Prior surgery of the breast should be discussed. Lumpectomies and augmentation mammoplasty are not contraindications. Reduction mammoplasty, however, may pose a problem if the integrity of the ducts was interrupted. The obstetrician should also evaluate the breasts' responses to the hormones of pregnancy, the degree of increase in size of the breasts, and changes in the areola and nipple. The obstetrician should discuss with the mother her intentions to breast-feed and address any questions she may have. The mother should be encouraged to attend breast-feeding preparation classes, which are commonly available at hospitals with maternity services and at local mothers' groups.

The breast prepares for lactation during pregnancy by enhancing the ductal system and developing lacteal cells that will produce the milk. From about sixteen weeks in gestation on, the breast is capable of making milk if the fetus is delivered. During pregnancy the placenta produces a prolactin-inhibiting hormone (PIH) that blocks the breast from responding to the abundant prolactin of pregnancy. Once the placenta is delivered, the PIH drops, and the breast responds to the hormones oxytocin and prolactin.

The key response of the breast following delivery is called the ejection or letdown reflex, prompted by two major hormones, oxytocin and prolactin. Oxytocin causes myoepithelial cells to contract. Thus when the baby stimulates the breast by suckling, a message is sent via the peripheral nervous system to the mother's brain and pituitary to release oxytocin, which in turn causes the myoepithelial cells that surround the alveoli and the ductal system to contract, ejecting the milk from the ducts. Suckling at the breast also stimulates the release of prolactin, the hormone that stimulates the lacteal cells to produce milk. Prolactin is not released unless the breast is stimulated. Oxytocin, however, may be released when the mother sees her baby or hears her baby cry or as a result of other stimulating sensory pathways.

It is recommended that the infant be put to breast as soon after delivery as is possible. The infant has been sucking and swallowing in utero, consuming considerable amniotic fluid, from about fourteen weeks gestation on, so he or she is ready to begin breast-feeding.

To put the infant to breast, the infant is held with his or her abdomen against the mother's and the infant looking directly at the breast. The mother supports the breast with her hand, keeping her fingers behind the areola and gently compressing it. The mother strokes the center of the infant's lower lip with the nipple. This stimulates the infant to open his or her mouth, extend his or her tongue, and draw the nipple and the areola into his or her mouth. The baby's tongue compresses the elongated nipple and areola against his or her hard palate. The peristaltic motion of the tongue stimulates the letdown reflex, and milk is released and swallowed. Infants should be fed when hungry, which is eight to twelve times a day initially. No other food or drink is necessary during exclusive breast-feeding for up to six months.

See also Baby Food; Dairy Products; Milk, Human.

Ruth A. Lawrence