The safety of commercially prepared formula is also ensured by the agency's nutrient requirements and by strict quality control procedures that require manufacturers to analyze each batch of formula for required nutrients, to test samples for stability during the shelf life of the product, to code containers to identify the batch, and to make all records available to FDA investigators.

The composition of infant formula is similar to breast milk, but it isn't a perfect match, because the exact chemical makeup of breast milk is still unknown.

Human milk is very complex, and scientists are still trying to unravel and understand what makes it such a good source of nutrition for rapidly growing and developing infants. However, John C. Wallingford, Ph.D., an infant nutrition specialist with FDA's Center for Food Safety and Applied Nutrition, notes that "infant formula is increasingly close to breast milk."

More than half the calories in breast milk come from fat, and the same is true for today's infant formulas. This may be alarming to many American adults watching their intake of fat and cholesterol, especially when sources of saturated fats, such as coconut oil, are used in formulas. (In adults, high intakes of saturated fats tend to increase blood cholesterol levels more than other fats or oils.) But the low-fat diet recommended for adults doesn't apply to infants.

"Infants have a very high energy requirement, and they have a restricted volume of food that they can digest," says Wallingford. "The only way to get the energy density of a food up is to have a high amount of fat."

While greater knowledge about human milk has helped scientists improve infant formula, it has become "increasingly apparent that infant formula can never duplicate human milk," write John D. Benson, Ph.D, and Mark L. Masor, Ph.D., in the March 1994 issue of Endocrine Regulations. "Human milk contains living cells, hormones, active enzymes, immunoglobulins and compounds with unique structures that cannot be replicated in infant formula."

Benson and Masor, both of whom are pediatric nutrition researchers at infant formula manufacturer Abbott Laboratories, believe creating formula that duplicates human milk is impossible. "A better goal is to match the performance of the breastfed infant," they write. Performance is measured by the infant's growth, absorption of nutrients, gastrointestinal tolerance, and reactions in blood.

Wallingford agrees, explaining that while FDA's regulations on what goes into infant formula are to ensure there are enough nutrients, "that's just a starting point. What's really important is how infants thrive."

Cow's milk contains a different type of protein than breast milk. This is good for calves, but human infants can have difficulty digesting it. Bottle-fed infants tend to be fatter than breast-fed infants, but not necessarily healthier.

Breast-fed babies have fewer illnesses because human milk transfers to the infant a mother's antibodies to disease. About 80 percent of the cells in breast milk are macrophages, cells that kill bacteria, fungi and viruses. Breast-fed babies are protected, in varying degrees, from a number of illnesses, including pneumonia, botulism, bronchitis, staphylococcal infections, influenza, ear infections, and German measles. Furthermore, mothers produce antibodies to whatever disease is present in their environment, making their milk custom-designed to fight the diseases their babies are exposed to as well.

A breast-fed baby's digestive tract contains large amounts of Lactobacillus bifidus, beneficial bacteria that prevent the growth of harmful organisms. Human milk straight from the breast is always sterile, never contaminated by polluted water or dirty bottles, which can also lead to diarrhea in the infant.

Human milk contains at least 100 ingredients not found in formula. No babies are allergic to their mother's milk, although they may have a reaction to something the mother eats. If she eliminates it from her diet, the problem resolves itself.

Sucking at the breast promotes good jaw development as well. It's harder work to get milk out of a breast than a bottle, and the exercise strengthens the jaws and encourages the growth of straight, healthy teeth. The baby at the breast also can control the flow of milk by sucking and stopping. With a bottle, the baby must constantly suck or react to the pressure of the nipple placed in the mouth.

Nursing may have psychological benefits for the infant as well, creating an early attachment between mother and child. At birth, infants see only 12 to 15 inches, the distance between a nursing baby and its mother's face. Studies have found that infants as young as 1 week prefer the smell of their own mother's milk. When nursing pads soaked with breast milk are placed in their cribs, they turn their faces toward the one that smells familiar.

Many psychologists believe the nursing baby enjoys a sense of security from the warmth and presence of the mother, especially when there is skin-to-skin contact during feeding. Parents of bottle-fed babies may be tempted to prop bottles in the baby's mouth, with no human contact during feeding. But a nursing mother must cuddle her infant closely many times during the day. Nursing becomes more than a way to feed a baby; it's a source of warmth and comfort.

A nursing mother is forced to get needed rest. She must sit down, put her feet up, and relax every few hours to nurse. Nursing at night is easy as well. No one has to stumble to the refrigerator for a bottle and warm it while the baby cries. If she's lying down, a mother can doze while she nurses.

Nursing is also nature's contraceptive--although not a very reliable one. Frequent nursing suppresses ovulation, making it less likely for a nursing mother to menstruate, ovulate, or get pregnant. There are no guarantees, however. Mothers who don't want more children right away should use contraception even while nursing. Women who are breast-feeding can use barrier methods of birth control, such as condoms and diaphragms. Hormone-containing methods are not first choice. These include injections (such as Depo-Provera), implants (such as Norplant), and birth control pills. A woman who breast-feeds should consult her doctor about which type of contraception is appropriate for her until the baby is weaned.

Breast-feeding is economical also. Even though a nursing mother works up a big appetite and consumes extra calories, the extra food for her is less expensive than buying formula for the baby. Nursing saves money while providing the best nourishment possible.

Most common illnesses, such as colds, flu, skin infections, or diarrhea, cannot be passed through breast milk. In fact, if a mother has an illness, her breast milk will contain antibodies to it that will help protect her baby from those same illnesses.

A few viruses can pass through breast milk, however. HIV, the virus that causes AIDS, is one of them. Women who are HIV positive should not breast-feed.

A few other illnesses--such as herpes, hepatitis, and beta streptococcus infections--can also be transmitted through breast milk. But that doesn't always mean a mother with those diseases shouldn't breast-feed, Lawrence says.

"Each case must be evaluated on an individual basis with the woman's doctor," she says.

Breast cancer is not passed through breast milk. Women who have had breast cancer can usually breast-feed from the unaffected breast. Studies have shown, however, that breast-feeding a child reduces a woman's chance of developing breast cancer later.

Silicone breast implants usually do not interfere with a woman's ability to nurse, but if the implants leak, there is some concern that the silicone may harm the baby. Some small studies have suggested a link between breast-feeding with implants and later development of problems with the child's esophagus. Further studies are needed in this area. But if a woman with implants wants to breast-feed, she should first discuss the potential benefits and risks with her child's doctor.

Women who plan to go back to work soon after birth will have to plan carefully if they want to breast-feed. If her job allows, a new mother can pump her breast milk several times during the day and refrigerate or freeze it for the baby to take in a bottle later. Some women alternate nursing at night and on weekends with daytime bottles of formula.

In either case, a nursing mother is physically tied to her baby more than a bottle-feeding mother. The baby needs her for nourishment, and she needs to nurse regularly to avoid getting uncomfortably full breasts. But instead of feeling it's a chore, nursing mothers often cite this close relationship as one of the greatest joys of nursing.

If a woman is unsure whether she wants to nurse, she can try it for a few weeks and switch if she doesn't like it. It's very difficult to switch to breast-feeding after bottle-feeding is begun.

If she plans to breast-feed, a new mother should learn as much as possible about it before the baby is born. Obstetricians, pediatricians, childbirth instructors, nurses, and midwives can all offer information about nursing. But perhaps the best ongoing support for a nursing mother is someone who has successfully nursed a baby.

La Leche League, an international support organization for nursing mothers, has chapters in many cities that meet regularly to discuss breast-feeding problems and offer support.

Most La Leche League chapters allow women to come to a few meetings without charge. League leaders offer advice by phone as well. To find a convenient La Leche League chapter, call (1-800) LA-LECHE.

Symptoms that may indicate an adverse reaction to cow's milk protein include vomiting, diarrhea, abdominal pain, and rash. With lactose intolerance, the most common symptoms are excessive gas, abdominal distension and pain, and diarrhea. Since some of the symptoms overlap, a stool test may be necessary to determine the culprit. Usually, lactose intolerance will produce acidic stools that contain glucose. If the protein is the problem, stools will be nonacidic and have flecks of blood.

The main alternative to cow's milk formula is soy formula.

The carbohydrates in most soy formulas are sucrose and corn syrup, which are easily digested and absorbed by infants. However, soy is not as good a protein source as cow's milk. Also, babies don't absorb some minerals, such as calcium, as efficiently from soy formulas. Therefore, according to the American Academy of Pediatrics, "Healthy full-term infants should be given soy formula only when medically necessary."

For a child who can't tolerate cow's milk protein, William J. Klish, M.D., chairman of the American Academy of Pediatrics Committee on Nutrition recommends the use of hydrolyzed-protein formula. Although hydrolyzed-protein formulas are made from cow's milk, the protein has been broken up into its component parts. Essentially, it's been predigested, which decreases the likelihood of an allergic reaction.

"There should not be a low-iron formula on the market for the average child because a low-iron formula is a nutritionally deficient formula," says Klish. "It doesn't provide enough iron to maintain proper blood cell counts or proper hemoglobin." (Hemoglobin is a blood protein that carries oxygen from the lungs to the tissues, and carbon dioxide from the tissues to the lungs.)

In addition, studies have shown that school children who had good iron status as infants because they were fed iron-fortified formula performed better on standardized developmental tests than children with poor iron status. However, Wallingford says that "FDA has permitted marketing of low-iron formulas because some pediatricians prefer to use them, with the caveat that the physician would be monitoring iron status and prescribing iron supplements when appropriate."

Why is there low-iron formula on the market? "In the past there have been a lot of symptoms that have been attributed to iron, including abdominal discomfort, constipation, diarrhea, colic, and irritability," says Klish. "Also there was some concern about too much iron interfering with the immune system. All of those concerns and questions have been laid to rest with appropriate studies."

Another reason for originally producing low-iron formulas was that human milk contains low amounts of iron--less than a milligram per liter. However, it is now understood that an infant absorbs virtually 100 percent of the iron from human milk, but considerably less from infant formula.

The following tips can help foster successful nursing:

• Get an early start: Nursing should begin within an hour after delivery if possible, when the infant is awake and the sucking instinct is strong. Even though the mother won't be producing milk yet, her breasts contain colostrum, a thin fluid that contains antibodies to disease.

• Proper positioning: The baby's mouth should be wide open, with the nipple as far back into his or her mouth as possible. This minimizes soreness for the mother. A nurse, midwife, or other knowledgeable person can help her find a comfortable nursing position.

• Nurse on demand: Newborns need to nurse frequently, at least every two hours, and not on any strict schedule. This will stimulate the mother's breasts to produce plenty of milk. Later, the baby can settle into a more predictable routine. But because breast milk is more easily digested than formula, breast-fed babies often eat more frequently than bottle-fed babies.

• No supplements: Nursing babies don't need sugar water or formula supplements. These may interfere with their appetite for nursing, which can lead to a diminished milk supply. The more the baby nurses, the more milk the mother will produce.

• Delay artificial nipples: It's best to wait a week or two before introducing a pacifier, so that the baby doesn't get confused. Artificial nipples require a different sucking action than real ones. Sucking at a bottle could also confuse some babies in the early days. They, too, are learning how to breast-feed.

• Air dry: In the early postpartum period or until her nipples toughen, the mother should air dry them after each nursing to prevent them from cracking, which can lead to infection. If her nipples do crack, the mother can coat them with breast milk or other natural moisturizers to help them heal. Vitamin E oil and lanolin are commonly used, although some babies may have allergic reactions to them. Proper positioning at the breast can help prevent sore nipples. If the mother's very sore, the baby may not have the nipple far enough back in his or her mouth.

• Watch for infection: Symptoms of breast infection include fever and painful lumps and redness in the breast. These require immediate medical attention.

• Expect engorgement: A new mother usually produces lots of milk, making her breasts big, hard and painful for a few days. To relieve this engorgement, she should feed the baby frequently and on demand until her body adjusts and produces only what the baby needs. In the meantime, the mother can take over-the-counter pain relievers, apply warm, wet compresses to her breasts, and take warm baths to relieve the pain.

• Eat right, get rest: To produce plenty of good milk, the nursing mother needs a balanced diet that includes 500 extra calories a day and six to eight glasses of fluid. She should also rest as much as possible to prevent breast infections, which are aggravated by fatigue. 

Medicines and Nursing Mothers

Most medications have not been tested in nursing women, so no one knows exactly how a given drug will affect a breast-fed child. Since very few problems have been reported, however, most over-the-counter and prescription drugs, taken in moderation and only when necessary, are considered safe.

Even mothers who must take daily medication for conditions such as epilepsy, diabetes, or high blood pressure can usually breast-feed. They should first check with the child's pediatrician, however. To minimize the baby's exposure, the mother can take the drug just after nursing or before the child sleeps.

In the January 1994 issue of Pediatrics, the American Academy of Pediatrics included the following in a list of drugs that are usually compatible with breast-feeding:

• acetaminophen
• many antibiotics
• anti-epileptics (although one, Primidone, should be given with caution)
• most antihistamines
• alcohol in moderation (large amounts of alcohol can cause drowsiness, weakness, and abnormal weight gain in an infant)
• most antihypertensives
• aspirin (should be used with caution)
• caffeine (moderate amounts in drinks or food)
• codeine
• decongestants
• ibuprofen
• insulin
• quinine
• thyroid medications 

Some drugs can be taken by a nursing mother if she stops breast-feeding for a few days or weeks. She can pump her milk and discard it during this time to keep up her supply, while the baby drinks previously frozen milk or formula.

Radioactive drugs used for some diagnostic tests like Gallium-69, Iodine-125, Iodine-131, or Technetium-99m can be taken if the woman stops nursing temporarily.

Drugs that should never be taken while breast-feeding include:

• Bromocriptine (Parlodel): A drug for Parkinson's disease, it also decreases a woman's milk supply.
• Most Chemotherapy Drugs for Cancer: Since they kill cells in the mother's body, they may harm the baby as well.
• Ergotamine (for migraine headaches): Causes vomiting, diarrhea, convulsions in infants.
• Lithium (for manic-depressive illness): Excreted in human milk.
• Methotrexate (for arthritis): Can suppress the baby's immune system.

Drugs of Abuse: Some drugs, such as cocaine and PCP, can intoxicate the baby. Others, such as amphetamines, heroin and marijuana, can cause a variety of symptoms, including irritability, poor sleeping patterns, tremors, and vomiting. Babies become addicted to these drugs.

Tobacco Smoke: Nursing mothers should avoid smoking. Nicotine can cause vomiting, diarrhea and restlessness for the baby, as well as decreased milk production for the mother. Maternal smoking or passive smoke may increase the risk of sudden infant death syndrome and may increase respiratory and ear infections.

"There aren't any rules about when to stop breast-feeding," says Ruth Lawrence, M.D., professor of pediatrics and obstetrics at the University of Rochester School of Medicine in Rochester, N.Y., and spokeswoman for the academy. "As long as the baby is eating age-appropriate solid foods, a mother may nurse a couple of years if she wishes. A baby needs breast milk for the first year of life, and then as long as desired after that."

Formula, however, should not be continued after the first birthday. That's the time to introduce milk. For all babies the milk, however, should be whole milk. Low-fat and skim milk do not have enough fat and calories to supply the nutritional needs of a 1-year-old, explains John Udall, chief of nutrition and gastroenterology at Children's Hospital of New Orleans. At that age, "the child is growing so quickly, and the fat is so important for brain and central nervous system development," he says. "The recommendation that our daily intake of fat should compose less than 30 percent of our caloric intake does not apply to children under 2 years of age."

New on the market are special toddler formulas that claim to be better than milk. The formulas are good nutritionally, says Udall, but they're not necessary. "A well-balanced diet with milk and juices would be just as good in a healthy, normally active, normally growing child," says Udall.

William Klish, chairman of the American Academy of Pediatrics Committee on Nutrition, says that if a child needs to take a vitamin supplement, the toddler formula, fortified with a full range of vitamins and minerals, including iron, can serve that purpose. In addition, the toddler formulas don't need refrigeration, making them a convenient choice for snacks away from home.

--I.S.

Publication No. (FDA) 97-2309