There is a stubborn myth about the development of the intestine that appears in almost every online discussion about the start of solid foods. It is the myth that infants up to about 6 months old have a “virgin” or “open” intestine. I’ve received so many emails, Facebook posts, and comments about the virgin gut in recent years that I thought it was finally time to take a look at science – and its lack – behind this myth.
I wrote in earlier my book and in my blog about the controversy about when to introduce solid foods to a baby. Some health organizations recommend 6 months of exclusive breastfeeding, while others recommend offering solids between 4 and 6 months, following the baby’s willingness as the ultimate guide. Based on my analysis of the latest science, I believe that the second approach is more evidence-based and helps parents focus on their baby’s unique development rather than the calendar. I also think it’s okay to wait up to 6 months if you prefer.
However, when I discuss this science, someone gives me lectures on the development of the infant bowel and usually sends me a link KellyMom’s page on the subjectThis urges parents not to offer solids 6 months ago. The following is stated:
“In addition, from birth to between four and six months old, babies have what is often called a baby “Open bowel, “This means that the spaces between the cells of the small intestine make it easy for intact macromolecules, including whole proteins and pathogens, to get straight into the bloodstream. This is ideal for your breast-fed baby, since useful antibodies in breast milk can get directly into the baby’s bloodstream, but it also means that large proteins are made other Food (which can predispose the baby to allergies) and disease-causing pathogens can also get through. “
Wow that does sounds scary! I can see how this “open gut” idea would worry parents approaching the transition to solid foods. But here’s the thing: there are no references to support these statements, and with all my reading of the research literature on solids readiness, I haven’t come across the science that supports this concern. But somehow, this idea of the open intestine keeps popping up in online discussions, including a verdict for parents who offer solids 6 months ago and non-evidence-based suggestions on how to “heal” a baby’s intestine. All of this only serves to increase parents’ fear, which is the last thing each of us needs.
It’s time to get to the bottom of this. Let’s look at some science …
What do we mean when we speak of an “open” or “closed” bowel? How do we measure it?
The Lining the small intestine plays a crucial role in nutrient absorption and immune protection. Food and bacteria from the environment enter the GI tract, and the lining of this tract separates it from the body’s bloodstream. It is important that this is food selectively about taking in the good things and keeping out the less desirable elements as this interface is one of a child’s functions most important obstacles for infection (1).
The intestinal mucosa consists of a single layer of epithelial cells called enterocytes, arranged in many deep folds, which serve to enlarge the surface for the absorption of nutrients. Nutrients are absorbed through the intestinal enterocytes and into the bloodstream.
The rooms between The enterocytes are connected by protein complexes, the most important of which are referred to as tight transitions, Despite their name, these transitions are never a complete seal and let some particles pass while excluding others, mainly due to their size and charge (2).
Researchers use the term intestinal permeability to describe how easily particles can enter the lining of the intestine into the bloodstream. Bowel permeability is tested in research settings by giving an individual an oral dose of two sugars, usually mannitol and lactulose (not to be confused with lactose, the main sugar found naturally in milk). Mannitol is the smaller of the two (molecular weight 182) and is absorbed by pores in the intestinal enterocytes. Lactulose is too large to fit through these pores (molecular weight 342), but part of it sneaks through the tight connections to get into the bloodstream. Once in the blood, neither lactulose nor mannitol are metabolized further; They are only filtered by the kidneys and excreted in the urine. So if you give a person (including a baby) a dose of these two sugars and collect their urine, you can measure how much of each has been absorbed into the small intestine. The results are usually expressed as a ratio of lactulose to mannitol (L / M), with higher values representing greater intestinal permeability and lower values representing lower intestinal permeability or a “closed intestine” (3,4).
Does intestinal permeability change in infancy?
Yes, but the timeline differs from KellyMom’s description.
The sugar absorption test was used to measure the process and timing of intestinal obstruction in infants. Contrary to KellyMom’s claim that this critical process takes place between 4 and 6 months, studies show that the most important bowel obstruction actually takes place in the newborn period. For example, a study determined intestinal permeability in 72 healthy newborns on days 1, 7 and 30 of life and found that the greatest decrease occurred within this first week of life (5).
Does it affect intestinal permeability whether an infant is breastfed or fed the formula? Maybe a little, but the difference doesn’t last long. The study shown in the graph above did not show a difference in intestinal permeability in exclusively breastfed and formula-fed babies on day 1 or day 30. On day 7, intestinal permeability was slightly lower in breastfed infants compared to infants with the formula, suggesting this indicates that feeding can slow intestinal obstruction (5). It is possible that this contributes to the increased incidence of GI diseases in infants who are fed the formula. But this difference is also temporary. By a month and FurthermoreThere is no difference in intestinal permeability between breastfed or formula-fed infants (6).
Premature babies have greater intestinal permeability at birth, but values similar to those of premature babies 3-6 days of life,7 The process of intestinal obstruction is delayed if premature babies are only fed IV and not via the gastrointestinal tract (orally or by tube), and at least partially breast milk feeding Instead of only feeding with the formula, the intestinal obstruction in these at-risk babies is improved (8,9).
What about later in childhood? Studies on this question show a very gradual (if any) decrease in intestinal permeability in the first few years of life. No door to close the bowel is slammed on the 6-month birthday. In the following graphic I have plotted the intestinal permeability by age two studies (10,11).
Another study (3) set a reference value for normal intestinal permeability, as measured by the sugar absorption test (lactulose / mannitol) in healthy children, as 0.033 (average of 30 children with an average age of 5 years), and you can see that most babies in Die The graphic above actually reached this degree of intestinal obstruction by 3 months. The reference value for intestinal permeability in adults determined in the same study was only slightly lower at 0.027.
In other words, when it comes to solid food readiness, bowel obstruction is probably irrelevant. It happens long before today’s parents offer banana or oatmeal bites.
KellyMom also claims that a child’s “open gut” allows breast milk antibodies to get straight into the bloodstream. That actually does not happen in human infants – except could be in the first days of life if the intestinal permeability is really high (and the evidence on this point is not clear). Instead, human babies get maternal antibodies (IgG) into their bloodstream when they cross the placenta during pregnancy. This includes IgG developed by the mother in response to an infection or immunization, and for this reason maternal immunization for pertussis and flu during pregnancy is so effective in protecting babies from post-infection infections. This differs from many other animal species in which IgG cannot cross the placenta and is instead passed on to the baby via milk (especially colostrum) after birth (12, 13).
The main type of antibody in breast milk is secretory IgA, which coats mucosal surfaces like the lining of the GI tract and can thus protect against infections. However, IgA cannot be absorbed by the blood in human babies. This article on The Scientific Parent explains how this works in humans: Passive Immunity 101: Does Breast Milk Protect My Baby From Illness?
What is important for intestinal readiness for solid foods?
When infants start eating solid foods, they switch from the relatively simple diet with easily digestible breast milk and / or formula to a more complex diet with a variety of foods (with milk still being an important one). These foods require more digestive work, which means greater activity by a number of digestive enzymes. In addition, the kidneys have to work a little harder to eliminate metabolites from these foods. How do we know that infants at 4 months of age have the ability to adapt to a more complex diet?
“The data available suggest that both renal and gastrointestinal functions are mature enough to metabolize nutritional supplements at 4 months of age. Regarding gastrointestinal function, it is known that exposure to solids and the transition from a high-fat to a high-carbohydrate diet are associated with hormonal reactions (e.g. insulin, adrenal hormones) that lead to an adaptation of the digestive functions to the Naturally lead the ingested food by increasing the ripening rate of some enzymatic functions and / or activities. Therefore, the maturation of the gastrointestinal tract is largely determined by the food consumed. “ (14)
This is a recurring theme in nutritional biology – only through exposure to some type of food can the GI tract actually digest efficiently. This is one reason why the transition to solids can give you some interesting diapers, from very messy to very tight, as the GI tract adapts to the digestion of these new foods. This is a good reason to gradually start introducing new foods in small quantities, but it is not a good reason not to feed them at all.
If a baby’s GI tract were really too immature to cope with solids for 4 months, we would also expect babies who start eating solid foods at this age to develop more GI disorders and food allergies. However, this is not what we are seeing. Most studies show no difference in the risk of GI infection, regardless of whether babies start between 4 and 6 months or after 6 months (15-17) with solids.
When it comes to the risk of food allergies, recent research suggests that the introduction of solids, including common allergens, can actually reduce the risk of food allergies between about 4 and 6 months. (I will give more details in this post with many references.) A. study The study just published found that babies who started eating solid foods after 4 or 5 months were significantly less at risk of eczema than babies who were exclusively breastfed for 6 months (18). (Infant eczema is often associated with later development of allergies (19).) The development of a baby’s digestive and immune systems is an interwoven process, and exposure to food proteins over the 4-6 month period appears to help direct the immune system towards food tolerance rather than on their reactivity.
None of this means that you have to rush your baby to eat solid foods. It just means that you can cut the open gut from your list of things to worry about. Anytime in the 4 to 6 month range is a good time to offer your baby solid foods, following the signs of your baby’s willingness to develop and your baby’s interest in eating solids as a guide.
I came across this video while looking for pictures to accompany this post. It’s a little off the topic, but it made me laugh a little because I don’t think I could ever call M’s belly “virgin,” whatever that means. And I don’t think that’s a bad thing. (Please be assured that M and our dog appreciate each other’s licking ritual.)
Corrections (5/6/16): The information on IgG passed from mother to fetus during pregnancy has been updated to emphasize that this IgG can develop in response to infection and immunization of the mother. The previous version only focused on immunization. I also deleted a paragraph about “leaky gut syndrome” as the cause and potential target for cures for autoimmune diseases. Readers’ responses showed that the paragraph distracts from the rest of the post, and I thought it wasn’t relevant to this post about infants. In general, there is a lot of pseudoscience in leaky gut information, especially if it comes from people trying to sell remedies. (See Here. Here, and Here for more information.) However, it is an active research area and can be one of the things that mediate the development of autoimmune diseases. If or not This information will ultimately lead to advances in the prevention or treatment of this disease.
- Battersby, A.J. & Gibbons, D.L. The immune system of the intestinal mucosa in the newborn period. Pediatr. Allergy Immunol. 24 414-421 (2013).
- Odenwald, M.A. & Turner, J.R. Bowel Permeability Defects: Is It Time To Treat? Clin. Gastroenterol. Hepatol. Out. Clin. Prakt. Jam. Gastroenterol. Assoc. 11 1075-1083 (2013).
- van Elburg, R.M. et al. Repeatability of the sugar absorption test using lactulose and mannitol to measure intestinal permeability for sugar. J. Pediatr. Gastroenterol. Nutr. 20 184-188 (1995).
- Corpeleijn, W.E., van Elburg, R.M., Kema, I.P. & van Goudoever, J.B. Assessment of intestinal permeability in (premature) newborns using sugar absorption tests. Methods Mol. Biol. Clifton NJ 763, 95-104 (2011).
- Catassi, C., Bonucci, A., Coppa, G.V., Carlucci, A. & Giorgi, P.L. Changes in intestinal permeability during the first month: effects of natural versus artificial feeding. J. Pediatr. Gastroenterol. Nutr. 21 383-386 (1995).
- Colomé, G. et al. Intestinal permeability in different feeding in infancy. Acta Pediatrician. 96 69-72 (2007).
- Van Elburg, R.M., Fetter, W.P.F., Bunkers, C.M. & Heymans, H.S.A. Intestinal permeability in relation to birth weight and gestational and postnatal age. Arc. Dis. Child.-Fetal Neonatal Ed. 88 F52 – F55 (2003).
- Rouwet, E.V. et al. Intestinal permeability and carrier-mediated monosaccharide absorption in premature infants during the early postnatal period. Pediatr. Res. 51 64-70 (2002).
- Taylor, S.N., Basile, L.A., Ebeling, M. & Wagner, C.L. Intestinal permeability in premature babies by feeding type: breast milk versus formula. Breastfeeding. Med. 4, 11-15 (2009).
- Kalach, N., Rocchiccioli, F., Boissieu, D., Benhamou, P.-H. & Dupont, C. Intestinal Permeability in Children: Variation with Age and Reliability in Diagnosing Cow’s Milk Allergy. Acta Pediatrician. 90, 499-504 (2001).
- Noone, C., Menzies, I.S., Banatvala, J.E. & Scopes, J.W. intestinal permeability and lactose hydrolysis in human rotaviral gastroenteritis, evaluated at the same time by non-invasive differential sugar permeation. EUR. J. Clin. Invest. 16 217-225 (1986).
- Van de Perre, P. Transfer of Antibodies through Breast Milk. vaccine 21 3374-3376 (2003).
- Udall, J.N. & Walker, W.A. The physiological and pathological basis for the transport of macromolecules through the intestinal tract. J. Pediatr. Gastroenterol. Nutr. 1, 295-301 (1982).
- Agostoni, C. et al. Complementary feeding: A comment from the ESPGHAN Nutrition Committee. J. Pediatr. Gastroenterol. Nutr. 46 99-110 (2008).
- Cohen, R.J., Brown, K.H., Dewey, K.G., Canahuati, J. & Landa Rivera, L. Effects of age of the introduction of supplements on breast milk intake, total energy intake and growth: a randomized intervention study in Honduras. The lancet 344 288-293 (1994).
- Dewey, K.G., Cohen, R.J., Brown, K.H. & Rivera, L.L. Age of food supplement introduction and growth of low birth weight breastfed infants: a randomized intervention study in Honduras. At the. J. Clin. Nutr. 69, 679-686 (1999).
- Quigley, M.A., Kelly, Y.J. & Sacker, A. Infant feeding, solid foods and hospitalization in the first 8 months after birth. Arc. Dis. Child. 94 148-150 (2009).
- Turati, F. et al. Early discontinuation is beneficial to prevent the appearance of eczema in young children. allergy (2016). doi: 10.1111 / all.12864
- Dharmage, S.C. et al. Atopic dermatitis and the atopic march again. allergy 69, 17-27 (2014).
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