Choosing the right baby formula
When it comes to feeding babies, breast is undeniably best. But for parents who decide to or must switch their babies to formula many different types are now available, with almost as many differing opinions about their merits. Most health professionals agree with the World Health Organization’s 1996 statement endorsing the benefits of breast feeding as “the sole mode of nutrition for infants up to six months of age.” But they argue about how long weaned infants should stay on formula, the best formula to use, whether it should be enriched with iron, and when to use substitutes instead of cow’s milk formula.
Many differences between breast milk and formula
Human breast milk is a complex biochemical fluid well suited to human infants. It contains the right blend of fat, sugars and protein (with whey and casein protein in a 60:40 ratio). Its fat content provides about 50 per cent of the baby’s energy needs (calories), and lactose is its primary carbohydrate. It’s the perfect baby food for the first six months of life. (Recent studies suggest that starting complementary foods before the age of six months does not enhance infant growth, and may even undermine nutritional wellbeing.) Besides specific nutrients, breast milk also contains anti-infective agents — antibodies and white blood cells that ward off infection.
Breast milk is “on tap” at the right temperature, requires no addition of (possibly unclean) water, no mixing, warming or night trips to the fridge. In addition to nutritional and anti-infective advantages, breastfed babies allegedly have stronger teeth and better facial structure than bottlefeds because of the way their tiny jaws must work to get food. Those genetically prone to allergies are less likely to develop them if breastfed for a prolonged period (nine months or so).
Furthermore, breastfeeding is a dynamic relationship. As breastfeds tend to feed more frequently than bottlefeds, they often spend more time interacting with their mothers, and some pediatricians believe that the extra intimacy and stimulation enhances mental development. The knowledge that she’s providing the best possible food for her newborn can give the mother profound satisfaction. Also, a nursing mother often regains her normal weight more quickly after delivery because a suckling baby may consume 500 or more calories a day.
Formula cannot completely mimic breast milk
Since human milk is considered the best reference standard, formula manufacturers try to develop products that match it as closely as possible in composition and “performance.” The “performance” of formula is measured by assessing infant growth, nutrient absorption and gastrointestinal tolerance. Commercially prepared formulas are regulated by the federal Health Protection Branch, which designates how much protein, fat, carbohydrate, vitamins and minerals they should contain. Most standard baby formulas are based on cow’s-milk, and manufacturers try to mimic breast milk by such means as:
* diluting the high protein content of cow’s milk;
* adding lactose to raise its concentration;
* replacing the poorly absorbed butterfat of cow’s milk with more easily absorbed vegetable oils.
Yet, despite their best efforts, formula manufacturers have not yet managed to duplicate the complex properties of human milk. Components in breast milk that cannot be replicated in infant formula, include hormones, enzymes, antiviral agents (such as immunoglobins) and antibacterial factors (e.g., lactoferrin), among others.
Confusing array of infant formulas
A quick inspection of today’s pharmacies will reveal a confusing diversity of commercially-prepared baby formulas. The three main categories of formula suitable for most full-term infants are classified according to their protein sources. They contain either cow’s milk protein, hydrolyzed (predigested) milk protein or soy protein. Numerous variations of these three types have been specially designed to manage specific infant feeding problems, such as a cow’s milk intolerance or allergy. Among the much-debated points about baby formula are its optimal iron and fatty acid content, when to replace regular cow’s milk formula by alternative forms, for how long (until what age) to continue formula-feeding and when to introduce fresh cow’s milk.
Meeting the iron needs of young infants
Iron is essential for making hemoglobin — the compound in red blood cells that carries oxygen around the body. Healthy, full-term babies are born with enough iron to see them through the first four to six months of life. However, within the first year of birth, an infant must triple its body weight and double its total iron content, creating a high demand. From the age of six months on infants need extra iron — usually obtained by starting them on varied solid foods.
Infants aged five to 12 months need 7 mg of iron/day; children aged one to three years need 6 mg/day, and those aged 4 to 12 years require 8 mg daily. A lack of iron can lead to iron-deficiency anemia, with red blood cells short of hemoglobin. Most at risk of anemia are: premature and low birthweight babies (because of low iron stores at birth, and their rapid postnatal growth); infants prone to infections; those born into low-socioeconomic backgrounds; infants on vegetarian diets or diets low in vitamin C and those with an iron-poor diet. After 18 months of age the risk of iron-deficiency anemia declines, as the diet becomes more varied and growth rates diminish.
Concerns about iron-deficiency anemia were fuelled by studies suggesting that infants with this disorder score lower on mental and motor function tests than those with adequate iron status, and that the effects may be permanent. A recent Costa Rican study concluded that lower mental test scores persisted in those with iron-deficiency despite extended oral iron therapy. “However,” comments one family practitioner, “these studies were done mainly on infants from poverty-stricken backgrounds and may not apply to all children.”
Should infants be given iron-enriched formula?
The debate about feeding healthy, full-term infants iron-fortified foods focuses mainly on reducing risks of iron-deficiency anemia. Full-term babies are born with ample iron stores, largely used up during the first four to six months after birth. Breast milk, although not rich in iron, contains it in a more “bioavailable” form than cow’s milk, and exclusive breastfeeding for the first six months generally provides enough. By the time breastfed babies are six months old, their iron stores are depleted and they need an additional source–usually provided by starting them on solid foods such as iron-fortified cereal, meats and vegetables.
The experts agree that infants need extra iron after the age of six months. But they disagree about the necessity for all bottlefed babies to have iron-enriched formula at an earlier age. The Canadian Paediatric Society now recommends iron-forti-fied
The chief benefits of breast milk
* Always sterile and ready to serve, at the right temperature;
* No mixing needed — no risk of contamination from unclean water; portable and affordable;
* Easily digestible;
* Biochemical blend right for human babies — nutrients more bioavailable (absorbable) than those in formula;
* Protein content lower than formula so less burden on infant kidneys; amino acid composition well balanced for human brain and nerve development;
* Less allergy-provoking than cow’s milk;
* Rich in valuable polyunsaturated fats — increased fat content at the end of a feed may provide a “satiety” signal that prevents infant overfeeding;
* Contains all necessary minerals present in more “bioavailable” form than formula;
* Contains more vitamin C (but may be low in vitamin D);
* Laxative effects help to clear bowels quickly;
* Contains growth and transfer factors that promote infant metabolism;
* High lactoferrin content favours growth of Lactobacilli bacteria in the infant gut which oust harmful diarrhea-causing microorganisms;
* Contains antiviral agents, white blood cells and immunoglobulins (antibodies) — that help fight infection. formula from birth for all full-term infants who are not breastfed, in order to offset the risk of iron deficiency. However, some experts argue that it’s unnecessary to start bottlefeds on iron-fortified formula until they really need the extra iron — around the age of four to six months. Wouldn’t it make more sense to start babies off on standard formula, and switch them to a high-iron product when they really need more iron?
“The reason why the Canadian Paediatric Society decided against this policy was on a public health basis,” explains one University of Toronto expert in pediatric nutrition. “We didn’t feel confident that parents would switch from a low-iron to a higher iron product when needed, at about four months. And because we know of no risks from starting infants on iron-fortified formula early, we decided to err on the side of caution. However, it would be quite acceptable to use standard non-iron-fortified formula for the first four to six months in a healthy full-term infant, and switch after that.”
Another aspect of the iron-enrichment debate hinges on the finding that bacteria in the stools of infants given iron-fortified formula might increase risks of gastroenteritis (diarrhea)–an allegation some say is unsupported by scientific evidence. Since abdominal discomfort, constipation, diarrhea and colic have also been attributed to supplemental iron, some physicians prefer to recommend regular formula rather than iron-fortified types.
“In deciding what advice to give parents about infant feeding,” comments one expert in family medicine, “we try to weigh up the extent to which official recommendations and consensus statements (from specialist groups) are supported by evidence-based information–that is by results from well designed, peer-reviewed studies.” The optimal amount of iron to put in baby formula has not yet been established. Formulas in North America contain more iron than those in other countries such as Britain and France. In Canada, standard, unfortified infant formulas contain 1.5 to 3.0 mg of iron per litre, and iron-fortified forms have 7 to 13 mg of iron per litre. All soy protein, hydrolyzed protein and lactose-free formulas are iron-fortified.
Should formulas be enriched with fatty acids?
The latest controversy about formula involves its fatty acid composition compared to that in breast milk, and possible effects on infant brains. The omega-3 fatty acids commonly found in fish oils are being investigated for their impact on the development of the brain, nervous system and vision. One fatty acid in particular, docasahexanoic acid (DHA), appears to enhance function in the infant brain, eye and other nerve tissue. An Australian study compared early brain development using a visual acuity test in three groups of healthy, full-term infants: one group was fed standard formula, another was given DHA-fortified formula, and the third was breastfed. The breastfed infants and those given DHA-fortified formula showed twice as much brain activity in the visual area as those fed ordinary formula. However, a 1996 Canadian study found no differences in visual acuity or memory responses in breastfed infants versus those given formula not fortified with DHA.
Nonetheless, formulas in Europe and Japan are now fortified with DHA, but not those in North America or Australia. Should Canada be fortifying its formulas with DHA? One nutritional specialist at Toronto’s Hospital for Sick Children thinks not. “There’s no definite proof it’s beneficial, nor that it’s safe.”
When to consider special formulas
Standard cow’s milk formulas are inappropriate for some infants. Adverse reactions, such as vomiting, diarrhea, abdominal pain and a rash in response to cow’s milk may suggest a switch. The choices available include:
Lactose-free formulas. These are useful for infants with “lactose intolerance” — intolerant to the lactose (sugar) in cow’s milk, shown by symptoms such as excessive gas, abdominal bloating and diarrhea. Since the symptoms of lactose intolerance can mimic those of a milk allergy, tests may be done to distinguish the two. With a milk protein allergy, the baby may develop eczema (a scaly rash), hives (red skin wheals), flushing, swollen lips and other symptoms. For a lactose-intolerant baby with no signs of milk protein allergy, a lactose-free, milk protein formula will serve. Lactose-free formulas include soy-protein and hydrolyzed casein formulas. For a baby who is milk-allergic as well as lactose-intolerant, special hydrolysate formula may be advised. However, consult a physician about feeding infants any specialty formula.
Formulas based on soy protein are the principal alternative to cow’s milk formula, but are not suitable for premature babies. Soy formulas are lactose-free and good for infants with lactose intolerance, milk allergy and galactosemia (an inherited inability to metabolize the milk sugar, galactose.) The carbohydrates used in most soy formulas are sucrose and corn syrup, easily digestible by infants. But soy formula may not be the right choice for infants allergic to milk protein because of the possibility of cross-reactivity — an allergic reaction to proteins in both soy and cow’s milk. A soy protein allergy might be suspected if the infant’s symptoms (such as hives, diarrhea and wheezing) are not relieved within a few days of switching from cow’s milk to soy formula.
Hydrolyzed-protein formulas are suitable for babies with a cow’s milk protein intolerance or allergy, and as “specialty” formulas for severe feeding problems. Although hydrolyzed protein formulas are made from cow’s milk, the milk protein is first broken into its component amino acids–basically “predigested” — decreasing the likelihood of allergic reactions to cow’s milk proteins. However, these formulas are expensive and many physicians suggest trying other forms first.
Specialty “transitional” or “next step” formulas for older infants, relatively new on the market, are designed for six to 12-month olds who have started on solids. They contain higher levels of protein, calcium and iron than regular formula, but less than cow’s milk, and are designed for a gentle, gradual switch from formula to cow’s milk.. Many physicians consider them unnecessary. One pediatric nutritionist is “not convinced” that nutritional differences in “follow-on” formulas produce any measurable advantages. Consult a physician before switching to this kind of specialty formula.
Some suggest delayed feeding of fresh cow’s milk
The best time to start infants on fresh cow’s milk is yet another much-argued issue. Many family physicians and pediatricians continue to suggest that breastfed babies who are weaned after six months or so be started on fresh cow’s milk. Others promote a delay in the introduction of unmodified cow’s milk until infants are nine months to a year old. The Canadian Pediatric Society recommends that infants under 9 to 12 months old should not be fed “unmodified” cow’s milk because of its lower content of vitamin C, essential fatty acids and trace minerals, and because, although cow’s milk contains about the same amount of iron as human milk, it’s in a less absorbable form. In addition, unmodified cow’s milk has high levels of potassium, calcium, phosphorus and magnesium, which can overburden infant kidneys. Infants under six months of age who are given unmodified cow’s milk may have small blood losses in the intestines, and some develop milk protein allergies. For such reasons, some experts now suggest a delay in feeding infants fresh cow’s milk. Others disagree.
Watching for and managing cow’s milk allergy
Cow’s milk allergies (to specific proteins such as whey and casein) affect an estimated 1 to 3 per cent of North American children under three years old, and as many as 7 per cent of those in allergy-prone families. Symptoms of cow’s milk allergy include vomiting, diarrhea, swollen lips and tongue, asthmatic wheezing, breathing difficulties, eczema and hives — often appearing within an hour or two of ingesting cow’s milk. Those with a severe milk allergy can develop symptoms within minutes of ingesting even small amounts of cow’s milk protein. Milk sensitivity often wanes around 18 months of age, as the immune system matures.
To delay or mute a milk allergy, many pediatricians promote prolonged breast feeding (for at least 9 months), avoidance of milk products by the lactating mother, and use of cow’s milk substitutes when weaning. In the past, infants allergic to cow’s milk were switched to soy formula; however, recent studies find that some infants allergic to cow’s milk also develop a soy allergy. Nonetheless, soy remains a cheap and popular substitute. Alternatives include casein hydrolysates (made by heat-treating cow’s milk to break down bovine proteins into less allergy-provoking fractions) — often well tolerated, although rather bitter-tasting and expensive. Newer, reportedly better-tasting products include whey hydrolysates. Allergists stress that these substitutes may not be entirely safe for milk-allergic children: “hypoallergenic” does not mean “nonallergenic.” On rare occasions, severe reactions to hypoallergenic formula have been documented in infants with cow’s milk allergy.
Key messages and tips
* The Canadian Paediatric Society recommends exclusive breastfeeding for the first six months of life.
* Full-term infants have enough iron reserves for the first four to six months of life.
* Some authorities recommend that full-term, bottlefed infants be given iron-fortified formula from birth — others disagree.
* Iron- and vitamin-C-containing foods should be fed from six months of age.
* According to some experts, fresh (unmodified) cow’s milk is best withheld until nine to 12 months of age.
Bottle feeding tips
* Follow formula preparation instructions exactly. Don’t add extra powder to make a stronger feed. If it’s too concentrated, the baby may become dehydrated because the mixture is too rich. Adding extra water means that the baby won’t get enough essential nutrients.
* Never add sugar or food (e.g., cereal) to a baby’s bottle.
* Don’t put baby to bed with a bottle as prolonged sucking on a bottle of formula, milk or juice bathes the upper teeth in a carbohydrate-rich fluid and can produce dental decay.
* Never prop a baby to feed alone, in case of choking.
* Keep made-up bottles of formula refrigerated.
* Never heat bottles in the microwave; the heat can be uneven and lead to scalding from hot spots in the milk.
* Never re-use leftover formula — bacteria levels could have risen.
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