The one thing all these sources agree on — at least they all say so — is that “breast is best,” which leads to much discussion and, at times, debate about breastfeeding. All the while, formula sits quietly on the shelf, relatively unscrutinized. We hear and read a lot about breastfeeding, but little about formula. It’s time to correct that with some straight answers.
What is in formula? Back to top
Most infant formula comes from cow’s milk (the exception is soy formula), but a lot has to happen before it goes from the cow to the can and, ultimately, babies. The short, blunt version is that the manufacturing process literally takes cow’s milk apart and puts it back together again with some components left out and others added.
Cow’s milk is very high in saturated fat, which human babies have trouble digesting, and low in monounsaturates, the main fats in human milk. So the first step is to remove all the fat. The resulting skim milk is heated, then dehydrated if it’s going to be in powdered form. Then new fats, in the form of vegetable oil blends, are added along with proteins, milk sugar (lactose) and a long list of nutrients, vitamins and minerals that are required by federal regulation to approximate their levels in breastmilk.
Cow’s milk has three times as much protein as breastmilk. Calves need this because they grow so quickly, but for human babies it would put too much of a load on the liver and kidneys. Cow’s milk also has a higher proportion of casein to whey — the two kinds of proteins in mammal milks — than breastmilk does. So formula manufacturers must reduce the overall amount of protein and add extra whey to mimic the protein balance found in breastmilk.
Other ingredients prevent the mixture from separating or going bad. Some formulas have thickeners, and specialized formulas for premature babies have enhanced levels of nutrients. Any newly developed formula must meet a number of safety and nutritional standards, including clinical evidence that it is nutritionally adequate to promote normal growth.
What’s not in formula? Back to top
Human milk is a complex substance which, even now, is not fully understood. The list of known breastmilk components not present in formula is too long to go into fully and includes enzymes, hormones, growth factors and substances that fight infection and help develop the immune system.
Simply put, human milk is alive, says James Friel, professor of human nutrition at the University of Manitoba. “Some components are biologically active. They play a role that goes far beyond nutrition,” he explains. “For example, if you put an oxidant stressor — something like cigarette smoke — in breastmilk, it resists the stressor, and breastmilk does this better than formula even though formula contains more antioxidants. That strikes me as odd and I wish I understood it better.” Friel thinks it might one day be possible to add biologically active material to formula, but doesn’t expect to see this any time soon.
One important biologically active component of human milk is a protein called secretory immunoglobulin A (sIgA), which has the ability to bind to foreign substances (including harmful bacteria) so they can be eliminated from the body. It lines the wall of the gut, which is one of the main entry points for infection. Colostrum, the thicker milk that a mother’s body produces in the first few days, is especially high in sIgA.
Formula contains these little fighters as well, although they’re less plentiful and they’re bovine (cow) immunglobulins which are programmed to recognize micro-organisms that cause disease in cattle rather than humans, and operate in the bloodstream rather than the gut. Bottle-fed babies still develop immune systems, obviously, but they miss out on some of the early and long-term protection provided by sIgA.
The most immediate threat from lack of sIgA is during the first weeks of life, when a baby’s gut is vulnerable to infection. Advances in hygiene and sanitation, plus ready access to treatment, have made life-threatening gastrointestinal infections rare in Canadian babies. But they still cause considerable illness and many infant deaths in the developing world, where powdered formula is sometimes mixed with contaminated water.
Another biological capability, present in breastmilk but not formula, is the ability to alter itself. Breastmilk changes, both as the baby grows and during each feeding. Foremilk, which is produced at the start of each feeding, is relatively low in fat. As the baby sucks, the level of fat rises, satisfying him and lulling him into that blissful state a nursing mom loves to see. The fat levels of human milk also change in the baby’s second six months, when his growth rate slows. In recent years new formulas, called follow-up formulas, have been designed to more closely match some of the nutritional needs of an older baby.
How close is formula to breastmilk? Back to top
Both are milks that can sustain fledgling human life, but the similarity ends there. Nutrients in a man-made substance do not work the same way as they do in a naturally occurring substance. As dietitian Cristine Bradley, senior manager of medical affairs for Indiana-based formula maker Mead Johnson, puts it: “Compositionally, I’d call it apples to apples but functionally, it’s apples to oranges in many ways.”
A couple of examples: Iron was added to formula in the 1980s. However, the iron in formula is not nearly as well absorbed as that in breastmilk, so formula must contain considerably more for a baby to get the same amount.
Another example is nucleotides, which are the building blocks of DNA and RNA and help strengthen the immune system. After they were added to formula in the ’90s, Bradley says, the expected immunity benefit was not borne out. “There was some excitement about this for a while, but after inconsistent research findings it was generally agreed that this was not as promising as we first thought.”
What are they doing to improve formula? Back to top
Although formula is still fundamentally different from human milk, several significant improvements have been made in the past 30 years, including fine-tuning to improve the balance of proteins and the blend of fats. Manufacturers have added new varieties, including lactose-free formulas, special formulas for premature and ill babies, and hydrolyzed formulas with predigested protein, for infants with digestion problems.
The most recent innovation is the addition of two long-chain polyunsaturated fatty acids called DHA (docosahexaenoic acid) and ARA (arachidonic acid). Both play a key role in brain development and it has been theorized, though never proven, that the presence of DHA and ARA in breastmilk may explain why breastfed babies score higher than formula-fed babies on toddler mental development tests.
This past winter Canadian babies got their first taste of formula with DHA and ARA (made from algae and fungus, respectively). The question is, will these additives make formula-fed children smarter, as the “A+” in one product’s name implies?
Sheila Innis, a professor of paediatric nutrition at the University of British Columbia, says the clinical research is mixed. “I would be very cautious about making that statement for a healthy full-term baby. In one small study, 18-month-old babies fed formula with DHA and ARA scored higher as a group than babies fed standard formula, but four other larger studies showed no difference. The evidence is much clearer for premature babies, who are born without stores of these and other nutrients.”
What are the risks associated with formula?Back to top
There are risks associated with formula feeding. To help mitigate them, parents need to fully understand them.
Improper mixing: Formula should be mixed exactly according to directions. Some parents have made mistakes, sometimes because of literacy or language problems. Some have over-diluted powdered formula, which can lead to malnutrition, or failed to properly dilute concentrated liquid formula, sometimes in a misguided attempt to increase nutrients. The result can be dehydration and kidney problems.
Contamination: Formula manufacturers say their quality control and product safety are the tightest in the food industry. Still, any man-made food carries the risk of contamination. In recent years there have been several small, isolated outbreaks of serious illness and a few deaths (mostly premature babies or those with immune problems) caused by a bacterium called E. sakazakii which was found to have come from powdered formula. (The outbreaks prompted Health Canada to recommend liquid formula — which is less likely than powder to be contaminated — for bottle-fed babies who are immuno-compromised or in intensive care.)
The take-home message is that powdered infant formula is not a sterile product and must be handled and stored properly. Dawn Walker, a nurse and former executive director of the Canadian Institute of Child Health, says that one of the most common infant feeding questions she hears is, “Can I reheat formula?” “The answer is no,” Walker says. “Once formula has been warmed up for use, if you reheat it, bacteria growth increases exponentially. It’s very risky.”
Illness: Statistically, formula-fed babies are more likely to get colds, ear infections, milk allergies, diarrhea, urinary tract infections and bacterial meningitis. How much more likely? That’s hard to say. Obviously, few babies (formula fed or not) get meningitis, so the risk is very low to begin with. With more common illnesses like ear infections, other factors also increase the risk — such as whether mom smokes or the child is in group daycare. One large study of two- to seven-month-old babies found that the risk of ear infection increased with the proportion of formula in the child’s diet; those fed entirely on formula were twice as likely (13.2 percent) as those who breastfed exclusively (6.8 percent) to have had an ear infection in the past month.
Bottle-fed infants are also at greater risk for becoming overweight; they grow and gain weight more quickly and, on average, are less lean than breastfed babies. One large German study of five- and six-year-olds found a 4.5 percent rate of obesity among those who had been bottle-fed, compared with 2.8 percent for breastfed children. Since it’s mom or dad who decides how much goes in the bottle and when, a formula-fed baby may not learn to read his body’s signals as easily as one who nurses on demand. Stephanie Atkinson, professor of nutrition in paediatrics at McMaster University, comments, “I’m concerned that there may be some kind of metabolic programming going on that may explain the increased rates of obesity in formula-fed children.”
Another concern is that formula-fed children may face an increased risk for developing Type 1 diabetes. Some studies have found a higher incidence in children who were exclusively formula-fed or who were breastfed for less than three months. Other research has found that early exposure to cow’s milk increases the likelihood of developing a type of antibody that can be found in children with diabetes. No clear link has been established, but a major ten-year international study was launched in 2002 to compare the rates of Type 1 diabetes in babies fed standard formula versus those fed hydrolyzed formula.
When you add up all the risk factors, it sounds daunting. However, trying to predict the likelihood that any one child will get any one illness is impossible. Likewise, lower risk is no guarantee; some breastfed babies get ear infections and some bottle-fed babies don’t. And let’s face it: There are a lot of healthy adults walking around who were raised on formula.
If we look at formula as a medical intervention, a way to nourish a baby when breastmilk is not available, it stands up fairly well. The problem is that this substitute became a competitor. And formula simply can’t compete with human milk. Here’s how James Friel views it: “We’ve been making formula for over 100 years and I’ve spent 20 years of my life trying to make formula better. All the people I’ve dealt with in the industry are honest, hard-working and dedicated. In spite of that, we are still unable to make formula that comes very close to human milk and, for me, that’s a disappointment. We try to break human milk down into its components and put it back together again, but it really doesn’t work that way.”
Formula’s greatest achievement may be that, although it still doesn’t really compare to human milk, it has become a reasonably safe substitute that has improved over the years. Perhaps that is all it ever can be.
Soy: Who Needs It?Back to top
About 15 percent of the formula sold in Canada is soy based. Soy formula was developed because many babies had trouble digesting cow’s milk formula. In recent years concerns have been raised because soy formulas contain high levels of isoflavones, a plant-based form of the hormone estrogen. Isoflavones have been found to affect the fertility and sexual development of rats. No clear link has been made to problems in humans, although researchers are paying attention.
According to Stephanie Atkinson, professor of nutrition in paediatrics at McMaster University, the real story about soy formula is that too many parents are using it inappropriately. “Very few infants actually need soy formula,” she says. “Non-breastfed infants who have trouble digesting regular formula would do better on the new hydrolyzed cow’s milk formulas [where the protein is predigested]. But many parents are still switching to soy formula when there is a digestion problem. The only sound indication for soy formula that I can think of would be a non-breastfeeding mother who wants her baby to follow a strict vegan diet.”
* The terms human milk and breastmilk will be used interchangeably, as will formula-fed and bottle-fed.