Breastfeeding, Gluten Introduction, and Risk of Celiac Disease
A study published yesterday in the journal Pediatrics suggests that later introduction of gluten and breastfeeding beyond 12 months both increase the risk of a child developing celiac disease. These new findings add to the already muddy waters of our current understanding of the role of infant feeding in celiac disease.
Celiac disease is an immune response to gluten, a protein found in wheat, barley, and rye. Celiac is characterized by inflammation and damage to the small intestine, leading to symptoms such as diarrhea and digestive pain. In the U.S., celiac disease is present in about 1 in 141 people, although many of these cases go undiagnosed. Infants that develop celiac disease often have poor growth or weight loss, because intestinal damage compromises nutrient absorption. They also may have chronic diarrhea and a swollen, painful belly.
Celiac can usually be treated with a gluten-free diet, but there isn’t a cure for the disease. Multiple genetic markers have been identified for celiac disease, but many genetically susceptible individuals tolerate gluten and never develop symptoms, leading to speculation about other risk factors, including early childhood nutrition.
This latest study was a large, prospective survey of infant feeding practices and development of celiac disease in Norwegian children. Parents were asked when they first introduced gluten and how long they breastfed their babies. Children that developed celiac disease were tracked through Norway’s national medical system. The study included 324 children with diagnosed celiac disease and 81,843 without celiac. The researchers then looked for patterns in the data that might help to explain why some children developed celiac disease and others did not.
There were two major findings to emerge from this study:
- Children that had not yet tried gluten by 6 months of age were more likely to develop celiac disease.
- Breastfeeding at the time of introduction to gluten did NOT appear to be protective. In fact, breastfeeding for longer than 12 months was associated with an increased risk, although it was borderline significant (P=0.046).
Both of these findings are contradictory to current infant feeding advice in the U.S. The AAP’s Section on Breastfeeding recommends exclusive breastfeeding for about 6 months before introducing solid foods, followed by “continuation of breastfeeding for 1 year or longer as mutually desired by mother and infant.” The same AAP policy goes on to say, “There is a reduction of 52% in the risk of developing celiac disease in infants who were breastfed at the time of gluten exposure.” But this Norwegian study effectively found that following the current advice of the AAP seems to increase a baby’s risk of celiac, not decrease it.
Obviously, we need more information here. And as usual, one study isn’t enough to give us the full picture of what we know and don’t know about this topic.
To understand the evolving hypotheses around celiac disease and infant feeding, we need to go back to Sweden in the mid-1980’s, when the rates of celiac disease in young kids suddenly quadrupled from an incidence of 1 in 1000 births to 4 in 1000 births over just a few years. It was an epidemic, and it appeared to be isolated to Sweden; neighboring countries weren’t affected. What’s more, celiac was showing up in really young kids. The median age of diagnosis during the epidemic was just about a year old. In 1995, celiac disease in Sweden plummeted back to pre-epidemic levels, and the median age of diagnosis increased to 4 years of age.
In 2005, researchers screened more than 7500 Swedish 12-year-olds, born at the height of the epidemic, and found that 3% of them had celiac disease. That number stood in marked contrast to a 1999 study that found 0.5% of Swedish adults had celiac.
During and following Sweden’s celiac epidemic, infant feeding practices went under the microscope. Could they explain the dramatic increase in celiac rates in young children, and the just-as-dramatic declines?
In fact, there were some very big changes in infant feeding during this time, and it is assumed that these drove the epidemic. Prior to 1982, the national recommendation was to introduce gluten to babies between 4 and 6 months of age. At the end of that year, the advice changed to waiting until the 6-month birthday. Breastfeeding rates in Sweden were around 50% at 6 months. “Follow-on” formulas, marketed for older babies, were growing in popularity. These formulas were thickened with wheat flour, and intake of gluten among babies more than doubled during the mid-1980’s. So, during the celiac epidemic, you had a lot of babies suddenly getting a lot of gluten around 6 months of age – much of it coming not from solid foods but from formula.
When the epidemic ended in 1995, infant feeding practices were quite different. The popularity of the follow-on formulas had declined, and gluten intake dropped (probably because of media coverage of the epidemic). Breastfeeding rates had increased gradually over the previous decade, reaching around 75% at 6 months by the mid-1990’s. And the recommendation for gluten introduction changed back; now parents were again advised to begin introducing gluten in small amounts between 4 and 6 months of age. As the epidemic ended, babies were being gradually introduced to gluten, often prior to 6 months and while still breastfeeding.
The Swedish epidemic was a unique opportunity to try to tease apart feeding factors associated with celiac disease, and a retrospective case control study of Swedish kids revealed some patterns from the epidemic. Children that developed celiac, most of them diagnosed before age 2, were less likely to be breastfed during and beyond gluten introduction. They were more likely to eat large amounts of gluten within the first couple of weeks of introduction, and the major source was the formulas with added flour. In this cohort, there was no association between celiac risk and age of gluten introduction.
The story of the Swedish epidemic is really compelling, but it can only tell us so much. For one thing, it was retrospective, so it relied on parents’ memories of how they fed their babies, sometimes years later. That’s particularly problematic when you’re comparing kids with and without a disease with digestive symptoms. Children with celiac probably suffered from diarrhea and failure to thrive during their first years of life, and their parents might thus recall their feeding practices differently from those never affected by the disease. There were also a lot of confounding factors. For example, babies that weren’t breastfed at the time of gluten introduction were more likely to get large doses of gluten in the form of flour-based formula. So was it the lack of breast milk, or was it the bunch of gluten, or was it a combination of these factors? These are things that the researchers tried to model statistically, but there are limitations to this approach. The observations from Sweden were important though, and they compelled researchers to look more closely at these questions.
We now have a decent body of research (reviewed here and here) on early nutrition and celiac disease, but much of it is conflicting. This latest study from Norway only adds to the confusion. Here’s what we know and don’t know so far:
Timing of Gluten Introduction: In addition to the Swedish studies cited above, others have found no association between timing of gluten introduction and celiac. However, the best-designed study of this question (prospective, accurate feeding records, excellent celiac screening) actually did find an effect. Led by Dr. Jill Norris of the University of Colorado, this study found that children introduced to gluten in the first 3 months of life had a 5-fold increased risk of celiac. Those introduced after 7 months also had a marginally increased risk. However, this study only included kids at high-risk for celiac (based on genetic markers or a first-degree relative with the disease), so it might not apply to the general population. But now we can add in the recent findings from Norway that introducing gluten beyond 6 months of age may increase risk. So, different studies have come to different conclusions on this question, but let me simplify: Don’t introduce gluten before 4 months of age (and there are lots of good reasons for this beyond the celiac issue). Waiting too long beyond 6-7 months may increase celiac risk, but more importantly, delaying your baby’s first taste of gluten doesn’t seem to be protective.
Amount of Gluten Fed: The Swedish research indicated that gradual introduction of gluten might be protective against celiac. However, this effect was only observed in kids diagnosed before age 2, so some researchers wonder if large amounts of gluten simply accelerate appearance of symptoms. This question really requires more and better research; retrospective case control studies do a poor job of capturing a detail like the amount of gluten fed. The latest Norwegian study did not attempt to measure gluten amounts so did not help clarify this question. For now, it seems prudent to introduce gluten slowly, as part of a varied diet.
Role of Breastfeeding: Multiple studies (mostly retrospective, case control studies, summarized here) have found that breastfeeding at the time of gluten introduction is associated with lower incidence of celiac. However, several other studies have either found no protection from breastfeeding or even a trend towards greater risk of celiac with more breastfeeding. And the prospective study by Norris, which focused on kids at high risk for celiac, did not find a protective effect of breastfeeding. In fact, the celiac positive kids were breastfed on average for 1.4 additional months compared to those negative for the disease. The latest study from Norway found no protective effect of breastfeeding at the time of gluten introduction, as well as a slightly greater risk of celiac in children breastfed beyond 12 months.
So when it comes to celiac, is breastfeeding helpful or is it harmful? Given the conflicting findings on this question, I suggest some caution in jumping to one or the other conclusion. I don’t find the evidence that breastfeeding is protective all that compelling, but I also have my doubts about this latest finding that it is harmful. For example, I can imagine that babies that are at risk for celiac might exhibit more early feeding issues, such as food sensitivities. Moms of these babies might be more likely to breastfeed longer to try to compensate for a slow start at solids, or they might consciously choose to keep breastfeeding because they’ve heard that it could protect their babies from celiac. All of these factors that go into our decision to breastfeed for 4 or 6 or 12 months are hard to measure and hard to control for in an observational study.
If you’re confused by now, so am I. What we do know is this: Breastfeeding, early influence of nutrition, and celiac disease are all hot research topics at the moment. As new data emerge, hypotheses rapidly evolve – sometimes before we really know what we’re talking about. What we really need are randomized controlled trials. At least two of those are in progress right now (mentioned here and here), so I hope we’ll have more useful data on this topic soon.
In the meantime, I think the best advice is to begin introducing gluten slowly around 6 months, using developmental readiness for solids as your guide. A further preventative measure is to follow the CDC immunization schedule and have your child vaccinated for rotavirus, as childhood rotavirus infections are associated with a greater risk of celiac disease.
UPDATE: The research on gluten introduction and celiac disease continues to evolve. Be sure to read a more recent post from October 2014 about two randomized controlled trials that clarified several of the issues discussed in the post above: New Research on Gluten Introduction to Infants and Risk of Celiac Disease