Infant colic is a common problem among infants, with between 10-30% of US infants identified as colicky infants. Despite the common experience that is colic, colic is in fact poorly understood. Medically, colic is defined using Wessel’s criteria, perhaps better known as “The Rule of 3s”: crying that last more than 3 hours a day, for more than 3 days a week, for over 3 weeks, although most parents do not seek medical advice for colic. There are also stereotypical behaviors associated with a bout of colic – the infant will pull their legs up as if in pain, there is increased abdominal bloating, passing of gas, face flushing, and a specific, high pitched cry. Colic usually resolves by 4 months, making it difficult to determine if treatments worked, or the colic naturally resolved on its own.
Historically, any number of factors have thought to be play a role in the development of colic ranging from the tired old trope of the refrigerator mother (cold, uncaring mother), to reflux, protein sensitivity, or issues with lactose digestion.
Emerging evidence does suggest that some of the cases of colic may be caused by infant reflux, GERD, or protein sensitivity. However, in a large number of infants, these causative factors can be ruled out. New evidence however, suggests that the factors underlying colic may be quite complex – and definitely non-human. Colic, it seems, may be a behavioral response by infants to differences in the microorganisms living in their GI tracts.
Three studies have investigated the association between infant gastrointestinal microbiome and infant colic, with some very interesting results.
For the first study, Savino et al., (2004) collected fecal samples from 71 infants aged 15-60 days with no prior use of antibiotics or probiotics. There were no differences in the amount of several common aerobic GI bacteria. However, infants with colic were much less likely to have bacteria from the genus Lactobacillus. Those colicky infants that did have Lactobacillus had much smaller colony forming units (a way of quantifying the amount of bacteria in the infant’s GI tract) 1.26 cfu per gram, compared to 2.89 cfu/gram.
In the follow-up study, Savino et al., (2005) investigated these microflora differences in 30 colicky and 26 unaffected controls; all exclusively breastfed. Colic was defined by physician assessment, and fecal samples were collected from each infant. Fecal samples were analyzed for bacterial type – down to the species level. Unlike the prior study, Savino et al., reported no differences in total Lactobacillus colony forming units between the colicky and non-colicky infants. However, at the species level, there were some striking differences.
None of the colicky infants had Lactobacillus acidophilus. No non-colicky (control) infants had Lactobacillus brevis or Lactobacillus lactis lactis. These differences may be tremendously important in influencing infant health and GI function. First, while all Lactobacillus are anaerobic bacteria (they do not require oxygen), a few species are capable of glucose fermentation, producing as byproducts carbon dioxide and ethyl alcohol. The species that produce carbon dioxide and ethyl alcohol? You guessed it: Lactobacillus brevis and Lactobacillus lactis lactis – the very bacteria ONLY present in colicky infants.
Lactobacillus acidophilus (Figure 1), the bacteria not found in colicky infants, is an important contributor to immune function in the GI system, and likely promotes immune activity and the development of oral tolerance to food antigens (reduces risk of reactions to foods). Presence and absence here becomes a perfect storm: the increase in gas and ethyl alcohol producing species and the loss of protective species may increase the risk of GI infection in colicky infants, and may contribute to the gas and distress commonly associated with colic. This may also explain why fecal calprotectin, a hormonal marker of inflammation commonly used as a measure of GI damage, is increased in the stools of infants with colic (Rhoads et al., 2009).
However, these three studies are somewhat limited in their study design – primarily by the use of a single sample per infant. Infant microflora may differ between colicky and non-colicky infants – but how does this process occur?
deWeerth et al., (2013) have some answers. Piggy-backing on an existing study, they identified 12 infants with colic and 12 infant without colic from a larger sample of infants. The infants had similar ages, birth weights, and current weights, but differed in the amount of crying reported by the parents. They then analyzed nine fecal samples collected from day 2 to 4 months postpartum, using DNA measurements to determine the types of bacteria in gut microflora. As found in the earlier studies, there were significant differences in the types of bacteria, especially Lactobacillus. These differences were present in the samples collected at 2 weeks postpartum - colicky babies already had less Bacteroidetes, and more E. coli and Enterobacteria, while non-colicky babies had more Bifidobacteria and Lactobacillus gasseri. Most striking however, was the decreased diversity in bacterial species found on days 14 and 28 in the feces of the future colicky infants - and remember, these samples were collected before the colic emerged.
|Figure 2: Image from deWeerth et al., 2013. The distribution of bacterial groupings in the fecal samples collected from infants at day 14 (before the onset of colic) classified by whether or not the infant developed colic. Each Circle with a letter is a non-colicky infant, each red square with a letter is a colicky infants. There is little overlap in the bacterial groupings of the infants. The paper is open access and you can read it here.|
By 4 months postpartum, there were no differences in the microflora between colicky and non-colicky infants. This is about the time that colic usually resolves, and deWeerth et al., speculate that this shift in the microbiome may be one of the potential mechanisms.
Here is what I want to know : if there are known differences in the GI microflora between colicky and non-colicky infants, what factors contribute to these differences? deWeerth speculates genetics or chance encounters may contribute to these differences. But what is if is something else? What is the differences start with milk? Is it possible that differences in the oligosaccharides in milk may promote the growth of different types of bacteria? Alternatively, may the cfu units in milk differ between women? If the later, could maternal probiotics be a treatment for colic? No one really knows – as far as I can tell, no one has investigated milk composition and microflora differences in the milk or guts (and maybe vaginas?) of mothers who have infants with or without colic. Or, perhaps following the elegant study design of deWeerth, a longitudinal study utilizing maternal and infant microflora measurements of control and colicky infants recruited into the study at birth and followed over the first four months of life. In any event, there are a lot of questions and missing pieces remaining – and milk may be an important one!
Next month: the milk microbiome: or there are bacteria in human milk and that is a good thing.
Rhoads JM1, Fatheree NY, Norori J, Liu Y, Lucke JF, Tyson JE, Ferris MJ. Altered fecal microflora and increased fecal calprotectin in infants with colic. J Pediatr. 2009 Dec;155(6):823-828.e1. doi: 10.1016/j.jpeds.2009.05.012.
Savino F, Bailo E, Oggero R, Tullio V, Roana J, Carlone N, Cuffini AM, Silvestro L. Bacterial counts of intestinal Lactobacillus species in infants with colic. Pediatr Allergy
Immunol. 2005 Feb;16(1):72-5.
Savino F, Cresi F, Pautasso S, Palumeri E, Tullio V, Roana J, Silvestro L, Oggero R. Intestinal microflora in breastfed colicky and non-colicky infants. Acta Paediatr. 2004 Jun;93(6):825-9.
de Weerth C, Fuentes S, Puylaert P, de Vos WM. Intestinal microbiota of infants with colic: development and specific signatures. Pediatrics. 2013 Feb;131(2):e550-8. doi: 10.1542/peds.2012-1449.