Great Ingredients in the Recipe for Breast Milk

The Breastfeeding Book: Everything You Need to Know About Nursing Your Child
by Martha Sears, R. N., William Sears, M. D.

(Page 8 of 9)

Each species of mammal makes a unique kind of milk that can satisfy all the nutritional requirements of its offspring at the beginning of life. This milk, like blood, has specific qualities that ensure the survival of the young in its particular environment. This principle is known as biological specificity. Mother seals, for example, make a high-fat milk because baby seals need lots of body fat to survive in cold water. Since brain development is crucial to the survival of humans, human milk is high in nutrients for rapid brain growth.

No matter what animal it comes from, milk contains the basic nutritional elements of fats, proteins, carbohydrates, vitamins, and minerals. Let's look at each one of these nutrients in human milk and compare them to the same nutrients in formula or cow's milk so you can further appreciate how your milk is custom-made to meet the needs of your baby.

Fabulous Fats

Human milk is richer in the essential fatty acids needed for optimal human brain growth. Formula and cow's milk, on the other hand, are deficient in certain omega-3 fatty acids, especially DHA. Not only do breastfeeding babies get the right kind of fats, they get the right amount. The fat content of your milk changes during a feeding, at various times during the day, and at various stages as your baby grows, according to the energy needs of your baby. At the start of a feeding, your foremilk is low in fat. As the feeding progresses, the fat steadily increases until baby gets the “cream,” the higher-fat hindmilk. After baby gets sufficient hindmilk, baby stops eating and radiates that contented look. During growth spurts, your baby nurses more frequently and because of the shorter intervals between feedings, he receives milk with a higher fat content that supplies the energy he needs to grow.

Not only does baby get the right kind of fat in just the right amount, but most of the fat in breast milk is absorbed, so baby gets healthier fats with less waste. Breast milk contains an enzyme called lipase that helps digest fat, so more energy is available to the baby and less fat is eliminated in the stools. Formula and cow's milk do not contain this enzyme, and the baby's intestines - the body's food judge - can't digest all of the fat in formula and cow's milk by themselves. So the excess fat passes into the stools, giving them an unpleasant odor - unlike the acceptable milder odor of breast milk stools.

Specific Proteins

Remember the curds and whey in the nursery rhyme “Little Miss Muffet”? Curds and whey are the two types of milk protein. The whey is the easy-to-digest liquid portion, and the curd is the casein protein that forms a rubbery, harder-to-digest lump. Breast milk contains a much higher whey-to-casein ratio than most formulas and cow's milk do, so it's easier to digest. (Note that whey is the preferred protein for competitive body builders.) Breast milk's amino acids (the components of protein) supply the specific nutrients that babies need to build healthy brains and bodies, and research has shown that the amino acid taurine, which is present in much larger amounts in human milk than in cow's milk or formula, is especially important to brain growth. Breast-milk protein is almost completely absorbed, so there is less waste and less strain on the digestive system. The excess protein in formula and cow's milk, on the other hand, creates extra work for the intestines and kidneys, a phenomenon known as metabolic overload.

Sweeter Sugars

How sweet it is! Taste infant formula and compare it with the sweeter taste of breast milk. Human milk contains more lactose than formula does, and it is not only sweeter but better suited for brain growth. Lactose is an intestines-friendly sugar for babies. In infant formulas, some or all of the sugar comes from highly processed table sugar or corn syrup.

More Usable Vitamins and Minerals

No factory can make minerals and vitamins as well as mom can. On paper the vitamin-and-mineral profile of breast milk and formula may look the same - or it might even seem that formula contains more of some nutrients - but charts and comparisons can be deceiving. Mommy-made nutrients are better because of their high bioavailability, which means more of the vitamins and minerals that are in human milk get absorbed by the baby. What counts is not how much of a nutrient is listed on the Nutrition Facts label on a can but how much of that nutrient is absorbed through the intestines into the bloodstream. What counts is how much is available to the body - thus the term bioavailability.

The three important minerals calcium, phosphorus, and iron are present in breast milk at lower levels than they are in formula, but in breast milk these minerals are present in forms that have high bioavailability. For example, 50 to 75 percent of breast-milk iron is absorbed by the baby. With formula, as little as 4 percent of the iron is absorbed into baby's bloodstream. To make up for the low bioavailability of factory-added vitamins and minerals, formula manufacturers raise the concentrations. Sounds reasonable: if only half gets absorbed by the body, put twice as much into the can. This nutrient manipulation may, however, have a metabolic price.

Baby's immature intestines must dispose of the excess, and the unabsorbed minerals (especially iron) can upset the ecology of the gut, interfering with the growth of healthful bacteria and allowing harmful bacteria to flourish. This is another reason formula-fed infants have harder, unpleasant-smelling stools.

To enhance the bioavailability of nutrients, breast milk contains facilitators - substances that enhance the absorption of other nutrients; for example, vitamin C in human milk increases the absorption of iron. Zinc absorption is also enhanced by other factors in human milk. In an interesting experiment, researchers added equal amounts of iron and zinc to samples of human milk, formula, and cow's milk and fed them to human volunteers. More of the nutrients in the human-milk sample got into the bloodstream than in the formula and cow's milk. In essence, breast milk puts nutrients where they belong - in baby's blood, not in baby's stools.

Other Good Things Too Numerous to Mention

Each year scientists discover more and more health-promoting substances in human milk that can only be mommy-made, not man-made. The late Dr. Frank Oski, world-renowned pediatrician, former professor of pediatrics at Johns Hopkins School of Medicine, and our friend, was a longtime advocate of the importance of breastfeeding. He once told us, “When researching the difference between human milk and formula, I discovered that there are over four hundred nutrients in breast milk that aren't in formula.” As always, mother knows best.

© 2000 by Martha Sears, R.N., and William Sears, M.D.

About the Author

Martha Sears is a registered nurse, childbirth educator, and breastfeeding consultant.

William Sears, M.D., received his pediatric training at Harvard Medical School's Children's Hospital and Toronto's Hospital for Sick Children. He has practiced as a pediatrician for more than thirty years.