Does Your Diet While Breast-Feeding Affect Your Kid?

Advice for parents
April 11 2013 12:40 PM

A Dairy Dilemma

Can changing your diet calm your breast-feeding baby?

Newborn being examined by a pediatrician.
Is this baby crying because of cow's milk?

Photo by Suzanne Plunkett/Reuters

When my son was 6 weeks old, he would cry and cry and cry and cry. Even though I knew, of course, that babies did this—crying is their M.O.—the fact that nothing I did remedied my son’s shrieks and that I couldn’t identify a cause made the scientist in me crazy. There has to be something logical going on here, I would tell myself. Something I can fix.

Several Google searches later, I decided that his wails were my fault: My son, I surmised, was allergic to cow’s milk, and my smoothies and more-than-occasional ice cream indulgences were probably infiltrating my milk and making his tummy hurt. I gave up dairy for a few weeks to see if it would help. And to this day, I have no idea if it did. Sometimes it seemed to; other times it didn’t. Eventually, a piece of pizza called to me, I ate it, my son did OK, and I gave up on my theory.

Advertisement

Parenting forums are teeming with moms discussing their babies’ so-called dairy and soy “sensitivities” (one mom helpfully recommends gummy bears, oreos, and potato chips as dairy-free snacks), and many of my friends swear that after giving up certain foods, their unhappy babies turned into cooers overnight. But anecdotal reports are one thing; what does science have to say? The research on this issue is complex, but the consensus is that, most of the time, a baby’s crying—even when incessant—isn’t caused or exacerbated by what you or he is eating. Babies cry, and it sucks, but it’s normal. Moreover, mothers who give up foods while breast-feeding can put themselves or their children at risk for nutritional deficiencies. That said, a small percentage of babies are indeed allergic to food proteins—somewhere between 2 to 8 percent are allergic to cow’s milk, but among babies who have only ever been fed breast milk, the risk is only about 0.5 percent; an infant’s risk of being allergic to soy is estimated at 0.7 percent—and these babies, who usually have other warning signs in addition to crying a lot, do fare better after dietary changes.

Food allergies and intolerances are notoriously difficult to diagnose in young kids. (An allergy is not the same thing as an intolerance: The former usually involves an immune-mediated reaction, whereas an intolerance can involve different physiological responses, not usually immune.) Some children do not respond to skin prick tests when they are allergic, while others who aren’t allergic do. Blood antibody tests (which look for evidence that the body is primed to react to certain proteins) aren’t always useful either, in part because some food intolerances don’t involve antibodies.

In general, immunologists and allergists believe that the best way to diagnose mild food allergies is through double-blind, placebo-controlled oral food challenges, in which children are exposed to suspected food allergens and to “fake” allergens at alternating times, without knowing which is which, while being closely monitored for symptoms. Diagnosing allergies this way helps to identify the high percentage of kids who seem allergic but really aren’t. When Dutch researchers gave food challenges to 116 infants and toddlers who were suspected of having cow’s milk allergies in a study published in February 2013, they found that only 40 of the kids, or about one-third, were truly allergic. To further complicate things, childhood allergies are often short-lived, so tests aren’t always consistent. (This is true of cow’s milk allergies, which most children outgrow by age 3.)

And true food allergy or intolerance “symptoms” involve far more than just crying. “If a baby really does have an allergy to something that was in the mother's milk, there would be a broad spectrum of symptoms,” explains Jane Heinig, director of the Human Lactation Center at the University of California–Davis. These include breaking out in hives or an eczema-like rash, having mucusy or bloody diarrhea, coughing and/or vomiting. So if your baby is crying and spitting up a bit after a meal, but nothing else, there’s probably no allergy or intolerance. (If you do see these symptoms, then yes, your baby could be allergic, and you should take her to a physician to help identify the triggers. Or she could be lactose intolerant, but this problem is, again, rare in children under the age of 2.)    

If food allergies are so rare in babies, why do so many breast-feeding moms cut out foods? Well, for one thing, the foods you eat can give little Lena gas, just like they give you gas, and this can make her grumpy. One survey-based study found that nursing mothers who reported eating cabbage, broccoli, cow’s milk, onions, or chocolate were more likely to also report irritability and crying in their infants. But a little gas doesn’t mean you should limit your diet. Breast-feeding moms need lots of nutrients, and it’s harder to get them on restricted diets, especially if mothers have eliminated nutrient-rich food groups like dairy. Plus, “being exposed to different foods is a really good thing for a baby,” in part because it helps introduce and prime them to like important flavors, says Diane Spatz, director of the lactation program at the Children's Hospital of Philadelphia—and this achievement is probably worth more than a few smelly farts.

There is, however, some research suggesting that a limited diet could make difficult babies easier—hence my warning that the research literature is complex. In a randomized, controlled clinical trial from 2005, Australian researchers told a group of 47 nursing moms with colicky 3-to-9-week-old babies to stop eating cow’s milk, eggs, peanuts, tree nuts, wheat, soy, and fish for seven days. They told a second group of 43 nursing moms to specifically eat these foods. Both groups were told that they were testing the effectiveness of diets that had previously been shown to improve colic. All the moms kept detailed journals of when and how long their babies cried or fussed during the first two days and the last two days of the trial, and the researchers decided that the intervention would be deemed effective if it reduced the infants’ crying or fussiness by at least 25 percent. At the end, they found that nearly three-quarters of the babies of moms who cut out the foods achieved this benchmark, but only a little more than one-third of the babies of the free-eating moms did.

Yet there are other aspects of the study to keep in mind. Like the fact that one-third of the babies in the free-eating group cried or fussed significantly less at the end of the trial. This is probably because they passed their fussy “peak,” which often happens right around six weeks of age, the average age of the infants in this trial. Colic (and general fussiness) resolves on its own, which makes it difficult to confirm cause and effect when interventions seem to work. If you cut out dairy on Tuesday and your baby cries less on Friday, is it because of what you’re not eating, or is it because your baby is naturally becoming more agreeable? Another issue with the study is that it was not blinded: The moms knew what they were eating, and those who might have heard from friends that dietary restriction can reduce crying might have subconsciously evaluated their babies’ behavior differently at the end of the trial. (The free-eating moms may have had similar ascertainment biases if, for instance, they had preconceived notions that their “diet” wasn’t going to work.)

The other thing that’s interesting about the trial is that there was no significant difference in how well the two groups of moms thought the interventions worked. More than one-half of the moms in both groups said that their diets reduced their babies’ crying or fussing. This finding helps to illustrate just how tough it can be for people—and especially desperate, exhausted moms who really need things to get better—to objectively assess whether interventions work. People often feel better or report improvements based on the very fact that they are being treated, even if the pill or regimen doesn’t really do anything. This powerful phenomenon is known as the placebo effect, and some scientists believe it is, over time, getting stronger.

It’s likely, then, that many nursing mothers give up foods without needing to—yet many will swear that it helps, in part because of the tricks our brains play on us when we attempt to evaluate interventions we desperately hope will work. That said, for the small percentage of babies who suffer from food allergies or intolerances, yes, cutting out the trigger foods as a breastfeeding mom may help. And, really, if it seems to help, “if a mother is still eating a well-balanced diet, and she's thinking that her baby has less colic when she eats X rather than Y, then go ahead,” says Michael Kramer, scientific director of the Institute of Human Development, Child and Youth Health at McGill University. Believe me, if ditching dairy had turned my son into a cooing machine—or even if it didn’t but I truly believed it did—I sure as hell would have kept doing it. But if you’re really missing that yogurt you gave up three weeks ago and your baby never had serious gastrointestinal or allergic symptoms anyway, consider allowing yourself to indulge again. Sometimes, as moms, we blame ourselves or our choices for things that, well, just are. Babies cry—it’s a fact of life and it’s one that is probably not our fault.

Melinda Wenner Moyer is a science writer based in Cold Spring, N.Y., and is DoubleX’s parenting advice columnist. Follow her on Twitter.