Whether you're a formula-only feeder or supplementing breastfeeding with formula, experts weigh in to make sure your baby gets all the nutrition they need.

Formula Feeding Baby
Priscilla Gragg

Some women formula-feed their infant because they can't breastfeed, and others simply don't want to nurse. Many moms also choose to supplement breastfeeding with formula. Any of these options can give your baby the proper nutrients they need, as long as you follow a few guidelines. Here, experts weight in on frequently asked questions about formula.

Formula Feeding vs. Breastfeeding

My baby isn't nursing well. Should I switch to formula?

Your baby can have a hard time nursing for many reasons—the shape of your breast or nipples, a slight tongue-tie, or simply disinterest. “Despite being a doctor and working with patients all the time to get babies back on the breast, I wasn’t able to with either of my kids,” says Jessica Grant, M.D., a pediatrician in New York City, who pumped and bottle-fed breast milk for much of their first years. “I tell my patients that a mom’s health and well-being is number one,” says Rachel Barton, a certified pediatric nurse-practitioner in Texas, who switched to formula after having difficulty breastfeeding. “Breastfeeding is great if it works for you. You can always offer the breast first if you still wish to breastfeed and then supplement with pumped milk or formula.”

Is formula good enough for my baby?

There's no reason to feel guilty about switching to formula. Some of the most intelligent, healthy people were bottle-fed as infants, according to Nancy Krebs, M.D., a pediatric gastroenterologist affiliated with the department of pediatrics at the University of Colorado Health Sciences Center. Although they can't pass along the resistance to infection that breast milk does, formulas provide adequate nourishment for a growing baby, since they contain a comparable balance of protein and fat and match the calorie content in mother's milk. And just like breast milk, formula gets about half its calories from fat, which is crucial to brain development. Formulas are also supplemented with various vitamins and minerals, including calcium, iron, and vitamins C, D, and K.

Of course, no infant formula exactly duplicates breast milk. Human milk is incredibly complex, notes William Klish, M.D., head of gastroenterology and nutrition at Texas Children's Hospital in Houston. According to Dr. Klish, "Just being able to identify all of the ingredients in breast milk—there are hundreds—is a challenge. And then we don't know whether all of those substances play an important biological role or if they just happen to be there."

Research shows that formula-fed babies are more likely to be overweight and have lower IQs, right?

Well, like everything, there are lots of factors (and many contradicting studies), and the differences are minuscule, especially on the IQ thing. “The higher rate of obesity, which is different from being overweight, is probably more about overfeeding—you can hold a bottle in a baby’s mouth, but you can’t always shove a breast back in—than the fact that it’s formula instead of breast milk,” says Dr. Grant. Pay attention to your baby’s cues that he’s full. Breastfed babies do have a slightly lower risk of gastrointestinal infections, ear infections, and upper-respiratory infections because they get their mom’s antibodies, but some formulas now contain specific nutrients that try to help build immunity

Are the DHA and ARA supplements being added to formulas healthy for my baby?

Some studies suggest that infants who are breastfed may have slightly better brain and eye function than infants who are formula fed, explains Amy Lynn Stockhausen, M.D., an associate professor of general pediatrics and adolescent medicine at the University of Wisconsin School of Medicine and Public Health, but she adds that the differences are small and the research is not consistent or clear in terms of whether this is surely true, or how it might work. Two long-chain polyunsaturated fatty acids, docosahexaenoic acid (DHA) and arachidonic acid (ARA), found in breast milk are credited in the structure and function of human tissues, immune function, and brain and retinal development during gestation and infancy, according to a study published by the National Institutes of Health. While our bodies do make DHA and ARA, the study says that growing infants cannot maintain necessary levels of these fatty acids without supplementation.

"Formula companies are now adding DHA and ARA to formula in an effort to mimic breast milk, in hopes that it will provide benefit to formula-fed infants similar to breastfed infants," says Dr. Stockhausen. "So far, there is no good research that shows clear benefits from adding DHA or ARA to formula, but it is generally recognized as safe by the Food and Drug Administration (FDA) and does not appear to have harmful side effects. It’s hard to find formulas these days that do not have these compounds added to them because they are so popular in the formula market; while we think they are safe, they may or may not provide any actual benefit."

The Best Types of Formula

I've seen store-brand formulas on the shelves next to the big-name brands, and they're less expensive. Are they just as good?

There are some differences, notes Robert Baker, M.D., co-chief of gastroenterology and nutrition at the Children's Hospital of Buffalo and a member of the American Academy of Pediatrics's committee on nutrition, but the generic formulas are definitely adequate. That's because all formulas sold in the U.S. must comply with minimum health standards set by the FDA. However, unlike brand-name formulas, store brands aren't continually tinkering with their recipes—adding extra ingredients, for example, or making changes to the protein makeup or the ratio of one nutrient to another. And this tweaking, which aims to make formula more like breast milk, may add benefits in terms of baby's growth and development. "But none of the evidence definitively states that the newer formulas are better," says Dr. Baker. So if parents are trying to save money, they can consider using the store brands.

I'm thinking of switching to a low-iron formula because my baby is constipated. Is that a good idea?

Low-iron formulas are no longer commercially available in the United States, and for good reason. Iron deficiency is the number one nutritional deficiency in the country and the most frequent cause of anemia, a serious health condition for a child, so it's important that a baby get enough of this mineral. Some parents think that iron in formula is the cause of their infant's tummy issues, but Dr. Stockhausen says that's not likely. "There is not enough iron in infant formula to be the cause of stomach upset or constipation for most healthy infants, and the risk of iron deficiency with the low-iron formulas was concerning enough concern that the low-iron formulas were taken off the market," she said.

I'm a vegan and would like to give my child a soy formula. Is it just as good as one with cow's milk?

Yes. Soy formulas are nutritionally equivalent to cow milk-based formulas, according to the American Academy of Pediatrics. They recommend using soy formula for term infants with galactosemia, hereditary lactase deficiency, documented immunoglobulin E-associated allergy to cow milk who are not also allergic to soy protein, or parents seeking a vegan- or vegetarian-based diet for their term infant. However, soy protein-based formula is not recommended for preterm infants with a birth weight less than 1800g, prevention of colic, or infants with cow milk protein-induced enterocolitis or enteropathy. In these cases, ask your pediatrician for appropriate formula alternatives.

My baby has stomach problems, like gas or constipation. Should I switch to a "sensitive" or "gentle" formula?

"For babies with gassy tummies, hard or pasty stools, or digestive upset with formula, it may be helpful to try a formula that has the milk proteins partially broken down already, which for some babies can make them easier to digest, says Dr. Stockhausen. "These are often labeled as 'gentle,' and often also contain less lactose than regular formulas. For some babies it may also be useful to look for a formula that contains probiotics, as some recent research suggests that probiotics can be helpful to aid in digestion for fussy infants, and are generally considered safe in this context. If trying a product like this does not help, or if there is forceful vomiting, stools that are watery or that contain blood or mucus, or if Baby is very fussy throughout the day and night, then it’s time to call the doctor."

Organic formula is so expensive, but I worry I’m making a mistake by not buying it.

You’re not at all. “If you feel the need to buy organic and you can afford it, go for it. But all formula has to meet FDA standards, and remember, for something to be labeled organic, only some of the ingredients have to be from organic sources. It doesn’t mean that every ingredient is,” says Barton. The calorie counts (the standard being 19 to 20 calories per ounce) and the ingredients will be pretty identical across the board.

baby drinking out of bottle
Credit: Shutterstock

Making Baby Formula

Is it better to use bottled water when I make formula for my baby?

You may be tempted to buy bottled water to mix with formula, but in general, tap water is safe. In fact, since there aren't clear standards for the filtering process used in bottled water's production, it may not be any better than your local tap water and could be worse, says Dr. Klish. Bottled water also lacks fluoride, important for healthy teeth, so if you use it, ask your doctor about starting Baby on fluoride drops at 6 months.

Whatever kind of water you use, it's best to sterilize it first. "Bring the water to a running boil for one minute and then turn it off," says Dr. Klish. "If you let it boil for too long, concentrated salts and minerals can build up." You can stop sterilizing water once you've introduced your baby to solid food, at 4 to 6 months, since your child's system will be exposed to bacteria in real food.

When preparing formula, be sure not to add more or less water than recommended. If the formula is too diluted, your baby will be undernourished; formula that's too strong can dehydrate your baby. Concentrated liquid formulas should be mixed with an equal amount of water, and powdered formulas require measuring out a specific amount of water. Ready-to-feed formulas, of course, don't require any additional water.

When I know I’m going to be out all day, I bring powdered formula and a bottle of water to prepare bottles, but I worry that the ratios are off.

Even storage containers that hold pre-measured amounts of formula can be tricky to dump and shake into the narrow opening of a bottle, especially when you’re sitting on the bleachers of your older child’s soccer game. If you need something foolproof, Barton loves ready-to-use liquid formula that you can simply pour directly into a bottle or top with a nipple—no stirring required. You can also get single-serve packets of formula (they look like the powdered lemonade flavoring you might add to your own water bottle), which can be pricey per serving but will likely be easier to open and mix while on the go.

Formula Feeding Your Baby

How will I know if my baby is allergic to milk-based formula? He’s spitting up a lot, and his poop reeks.

Spitting up and stinky poop can be completely normal. But if your baby is spitting up very large amounts, it looks forceful (like vomiting), and they aren't gaining weight, you might be dealing with an allergy, significant reflux, or other, more serious issues, such as a blockage. Two other telltale signs of a milk allergy include severe eczema on their face or in the creases behind their elbows and knees or blood in their stool. If you notice any of these symptoms, call your child’s pediatrician.

I want to add in a bottle of formula here and there to give myself a break from nursing, but I’m afraid my baby will stop liking breast milk.

No chance, say our experts. If your baby is used to breast milk, it’s more likely that they’ll reject formula than the other way around, says Dr. Grant. The more common issue is that a baby will start to prefer a bottle to a breast because the liquid comes out faster, with less work, so you may want to start with a slow-flow nipple.

My baby drank half a bottle and fell asleep, and now I’m pouring money down the drain.

Sorry, but that’s probably the right move. Formula spoils quickly, and bacteria can form from your baby’s saliva that’s gotten in from the nipple. Here are the rules to play by: If your baby drinks from it, the bottle should be finished within one hour. After that, toss it. If you make a bottle, and Baby suddenly falls asleep and doesn’t touch it, put it in the refrigerator for up to 24 hours and rewarm it later, using the same one-hour rule once they start drinking.