Parents selecting baby formula have their work cut out for them. Supermarkets contain shelves full of choices, with new ones seemingly coming all the time.
There are formulas designed for babies with fussiness or gas, formulas made with organic ingredients, and formulas enriched with omega-3 fatty acids, suggested to enhance vision and brain development. Future formulas may contain the live bacteria found in yogurt.
Such a wide array of options can baffle parents, and many may be tempted to buy brands with recipes rejigged in response to the latest nutritional discoveries. But in fact, child nutrition experts say these new products may not benefit babies as much as their ads suggest -- and that any brand, including less expensive ones, will offer adequate nutrition, although none as good as breast milk. All must meet strict standards set by the Food and Drug Administration.
"There's very little difference, frankly -- they just tweak it a little," says Linda Heller, a registered dietitian and clinical nutrition manager at Childrens Hospital Los Angeles.
Formula makers hint, and some parents hope, that such tweaks will enhance the development and health of a baby.
A developing substitute
The American Academy of Pediatrics recommends that women breastfeed exclusively until babies are 6 months old. Only about one-third of women do so.
The alternative, infant formula, is historically fairly new. Until the Civil War, babies who were not breastfed received milk from cows or donkeys.
Then in 1867, Henri Nestle (a Swiss pharmacist who later founded the Nestle food company) developed an infant formula made with malt, cow's milk, sugar and wheat flour.
It took a while for Nestle's invention to catch on. During the first half of the 20th century, most mothers weren't convinced they needed commercial formula. When not breastfeeding their babies, they made their own concoctions with evaporated milk, water and table sugar or corn syrup.
Commercial formulas begin to gain wide acceptance during the post-World War II baby boom years. Many doctors began to believe that formula was more nutritious than breast milk. By the 1970s, just 25% of babies -- a record low -- were still being breastfed by the time they were discharged from the hospital. (Today, that number is 70%.)
Formula companies keep trying to emulate human milk, but the mixture still differs from the real stuff in key ways. "We know a lot about what's in breast milk, but it's hard to replicate all the ingredients," says Dr. Richard J. Deckelbaum, a professor of pediatric nutrition at Columbia University and chairman of the Institute of Medicine's infant formula safety committee.
Those ingredients include, among other things, living cells, hormones, active enzymes and antibodies that fight infection.
Such differences appear to have real health effects. Studies have found that breastfed babies have lower rates of pneumonia, bronchitis, colds, meningitis, urinary tract infections, asthma, ear infections and possibly sudden infant death syndrome.
Studies also suggest that people who were breastfed are less likely to become overweight or obese and to develop breast cancer, allergies, insulin-dependent diabetes, and chronic intestinal diseases such as Crohn's disease.
And, intriguingly, several large studies have shown that breastfed babies have IQs that are, on average, about six points higher than formula-fed babies.
As they work to close the breast milk-formula gap, manufacturers have been tweaking recipes pretty much since the substance was invented.
In the 1960s, for example, they started adding iron to formula, which led to a significant drop in the incidence of iron-deficiency anemia in bottle-fed babies.
In the 1990s, manufacturers started enriching formula with nucleotides, chemicals present in breast milk that are the building blocks of the body's genetic material, after studies showed that babies fed formula with nucleotides had less diarrhea.
Likewise, different brands have been introduced to meet special needs of some babies. In 1929, for example, manufacturers discovered cow's milk formulas bothered some babies, and introduced soy-based formula.
Later they learned that lactose, a natural sugar in milk, gave some babies colic-like symptoms such as fussiness, gas and diarrhea. And so, in the 1990s, they developed lactose-free formulas.
Manufacturers have also developed formulas for babies with allergies. Made with hydrolyzed protein, they are easier to digest and reduce the likelihood of triggering an allergic reaction. (A 2005 study found that such formula, compared with standard types, may help prevent the development of allergies in babies whose parents suffer from them.)
Formulas for preterm babies have also been developed, because babies born prematurely have different nutritional needs than full-term babies. (They need more protein, fat and calcium, for example.) These formulas "have really helped premature babies achieve better weight gain, bone health, and in some cases allows for earlier discharge from neonatal intensive care units," says Erin Feldman, a registered dietitian and board-certified specialist in pediatric nutrition at Cedars-Sinai Medical Center.
In addition, manufacturers have developed specialized formulas for babies with certain illnesses, such as one for babies with cystic fibrosis.
But for babies born normally, nutrition experts and pediatricians see little to choose between. Brands may be formulated slightly differently -- for example, containing different kinds of proteins and fats -- but the FDA has specifications for minimum amounts of 29 nutrients and maximum amounts for nine of those nutrients.
Manufacturers must analyze each batch of formula to check nutrients and purity. And they must test samples from store shelves to make sure they remain safe during their shelf life.
Manufacturers today are heavily marketing formulas that contain two omega-3 fatty acids, DHA (docosahexaenoic acid) and ARA (arachidonic acid). Sold in Europe for 10 years, these formulas were first introduced in the U.S. in 2002, and have since become increasingly popular.
Scientists have long known that breast milk naturally contains DHA and ARA, and that breastfed babies have higher blood levels of these chemicals than do formula-fed babies. They are important in the development of the brain and visual system, and some nutrition experts have suggested that their presence in breast milk may partly answer why breastfed babies have higher average IQ scores.
However, child nutrition experts also say that these formulas may not make much difference for healthy, full-term babies. "For the preterm baby they are advantageous to improve their brain development and visual acuity. But the research does not indicate there is a big impact on brain development and visual acuity if the baby is full-term," says Heller.
For example, in 2005, Australian researchers conducted an analysis of 14 previous studies of formulas containing DHA and ARA and found that formulas with these chemicals have no effect, positive or negative, on full-term babies' weight, length or head circumference (a measure of normal brain development).
And a report by the Cochrane Collaboration, an organization that evaluates medical evidence, found omega-3 formulas safe, but said there was not much evidence that they provided long-term benefit to the vision or intellectual ability of full-term infants.
The American Academy of Pediatrics neither endorses nor warns against including omega-3s in formula. The FDA, which permits DHA and ARA in formula, notes the mixed evidence and that there have been no published studies of the long-term effect.
Formula manufacturers choose their words carefully, merely noting that DHA and ARA are "compounds found in breast milk that support infant eye and brain development."
The formula frontier
Nutrition experts predict that formulas will continue to evolve. The next likely wave: ones containing probiotics, live bacteria and yeasts found in substances such as yogurt. These organisms are not found in breast milk, but the hope is that they'll help boost the ability of babies to fight infection. Studies suggest that formula lacks some of the infection-fighting components of breast milk, causing higher rates of intestinal upset, infection and diarrhea in formula-fed infants.
In a 2004 study published in the American Journal of Clinical Nutrition, infants and toddlers receiving formula containing two probiotic bacterial strains (Bifidobacterium lactis and Streptococcus thermophilus) experienced less colic-like symptoms, and were prescribed fewer antibiotics, than children who received ordinary formula.
Despite all these advances and future ones no doubt waiting in the wings, nutrition experts believe that formula will never be as good as the complex, poorly understood white fluid that our bodies naturally produce. "Factories," says Deckelbaum, "just don't do as well as the human mammary gland."