NUTRIENT WHY BREAST IS BEST
MOTHER'S MILK: IDEAL
NUTRITION FOR HUMAN BABIES
milk, right? Mammals make it (humans are mammals) and babies drink
it. There's more to the story than that. Each species of mammal
makes a unique kind of milk, which meets all the nutritional
requirements of its offspring at the beginning of life. Each
species' milk has specific qualities that insure the survival of the
young in a particular environment. This principle is known as the
biological specificity of milk. 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 provides 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,
comparing them to the same nutrients in formula or cow milk, so you
can further appreciate how your milk is custom-made to meet the
needs of your baby.
Unique nutrition for unique humans. As hormones levels change
in the days after birth, the mother's body starts to make more
plentiful amounts of milk. Colostrum gradually changes into mature
milk--the stuff babies have been thriving on for thousands of years.
Milk's basic ingredients are fat, proteins, lactose, vitamins,
minerals, and water. This is true of milk from all kinds of mammals.
Yet, the proportions of these ingredients differ, as do the kinds of
protein and fat. This is what makes each species' milk uniquely
suited to its young. It's also why cow's milk and cow's milk-based
formulas are not the ideal food for human infants.
HIGH QUALITY PROTEIN
Protein is a prime example of how human milk is unique nutrition for
human babies. Human milk is low in protein, at least when compared
with the milk of other species, especially cow's milk. This isn't a
nutritional deficiency; there are good reasons for this. Human
infants are designed to grow slowly. While it's important for humans
to develop strong bodies, even more important is brain development
and the learning of social skills. The experiences that shape the
brain come from close contact between mother and baby when baby is
held and carried. If human infants doubled their birth weight in
less than 50 days the way baby calves do, and then continued
growing, how could their mothers carry them and talk to them and
keep them close? Baby cows need to learn where to find the best
grass in the meadow; baby humans need to learn how to work with
others so that everyone's needs get met.
Though the protein content of human milk is generally low, the types
of amino acids that make up these proteins are important. One
particular amino acid, taurine, is found in large amounts in human
milk. Studies show that taurine has an important role in the
development of the brain and the eyes. The body can't convert other
kinds of amino acids into taurine, so its presence in human milk is
significant--so significant that some formula manufacturers have
begun adding it to artificial baby milks.
If you let milk stand out of the refrigerator and sour, you will see
that milk proteins fall into two categories, curds and whey.
(Remember Miss Muffet?) The curd portion, the casein proteins, are
the white clots; the liquid is the whey. Cow's milk is mostly casein
protein, which forms a rubbery, hard-to-digest curd in babies'
tummies. Human milk has more whey than curd, and the curds that are
formed are softer and more quickly digested. Breastfed babies get
hungry sooner than babies who are formula-fed because human milk
proteins are digested so efficiently. It doesn't take as much energy
to digest human milk as it does to digest formula. Frequent feedings
also ensure that human babies get lots of attention from their
There's another reason why babies digest human milk so quickly: the
fat in human milk comes with an enzyme, lipase, that breaks the fat
down into smaller globules so this important nutrient can be better
absorbed into the bloodstream. Fat is a valuable source of energy
for babies, so the presence of lipase makes the fat in human milk
more available. This is one of the reasons human milk is so good for
premature babies, who need lots of energy to grow but whose
digestive systems are very immature.
A changing nutrient for changing needs. The fat content of
human milk changes constantly. Typically, fat levels are low at the
beginning of a feeding and high at the end. Babies nurse eagerly to
get the low-fat, thirst-quenching foremilk, then slow down and
linger over the high-fat dessert at the end of their meal. Babies
who nurse again soon after the end of the last feeding get more
high-fat milk, so babies who breastfeed more frequently during a
growth spurt get more calories. Longer intervals between feedings
bring down the fat content of the milk stored in the breast. This
nutritional fact of human milk is one of the many reasons why the
rigid 3 to 4 hour scheduled style of feeding is biologically
Smarter fats. The special kind of fat in human milk is important to
brain development. As newborn babies grow, the nerves are covered
with a substance called myelin which helps the nerves transmit
messages to other nerves throughout the brain and body. To develop
high-quality myelin, the body needs certain types of fatty acids--linoleic
and linolenic--which are found in large amounts in human milk.
VITAMINS AND MINERALS
The vitamins and minerals listed on the formula can are no match for
those in the milk made by mom, even if milligram by milligram
comparisons suggest otherwise. When formula researchers want to know
how much of a particular vitamin or mineral babies need each day,
they look first at how much of that nutrient is present in human
milk and how much milk a baby of a given age takes in a day. But
just doing the math doesn't tell the whole story. More important
than the amounts of nutrients in the milk is the amount that is
available for the infant to use, a nutrient principle called
bioavailability. The bioavailability of a nutrient is influenced by
many factors, including its chemical form and the presence of other
The three important minerals calcium, phosphorus, and iron are
present in breastmilk at lower levels than in formula, but in
breastmilk these minerals are present in forms that have high
bioavailability. For example, 50 to 75 percent of the iron in
breastmilk is absorbed by the baby. With formula, as little as four
percent of the iron is absorbed into baby's bloodstream. To make up
for the low bioavailability of factory-added vitamins and minerals,
formula manufactures raise the concentrations. Sounds reasonable,
right? If only half gets absorbed by the body, put twice as much
into the can. Yet, this nutrient manipulation may have a metabolic
Baby's immature intestines are required to dispose of the excess.
Meanwhile, the excess 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, more unpleasant
To enhance the bioavailability of nutrients, breastmilk 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'd milk, and fed them to adult volunteers. More of
the nutrients in the human-milk sample got into the bloodstream
compared to the formula and cow's milk. In essence, breastmilk puts
nutrients where they belong - in baby's blood, not in baby's bowels.
HORMONES AND ENZYMES
Every year medical journal articles describe more valuable
substances discovered in human milk. Scientists are only beginning
to write the story on other factors in human milk that may be
important to baby's growth and development. For example, other
enzymes besides lipase are available to aid infant digestion.
Epidermal growth factor, present in human milk in significant
amounts, may promote the development of tissues in the digestive
tract and elsewhere. Other hormones in milk may influence a baby's
metabolism, growth, and physiology. The effects may be subtle, but
they may also have far-reaching implications. Being breastfed has
advantages that reach into adulthood. Science is only beginning to
learn what these benefits are.
© Copyright 2006 AskDrSears.com.
All Rights Reserved. Used by permission.
Dr. William and Martha Sears