CrossFit and Paleo: Why cutting gluten out of your diet may set you up for trouble later: the microbial explaination

CrossFit, Paleo and Gluten

Many CrossFit enthusiasts follow the “paleo diet”.  This diet claims, among other things, that gluten is bad for you.  Is gluten “bad” or are some people not able to tolerate it?  Is toleration genetic or aquired?  So far it looks like exposure to gluten during infancy plays a key role in determining whether or not someone will become gluten intolerant.

The human gut maintains large bacterial populations. In fact they outnumber you by about 10 to 1 on a cell to cell level (as in for each of your cells, there are ten bacteria). Each of us is a walking bus. We are designed to be this way. Our bacterial passengers have always been here. Our good health requires passengers who are not hijakers, jerks or even dead weight. The good ones help us digest food, keep us from getting horrible gas and other forms of intestinal distress, may protect us from obesity, defend against pathogens and degrade harmful substances.

Gut Bacteria and health

The dominant bacterial family present in infants, if they are breast fed, are Bifidobacteriaceae. Bottlefed infants also harbor Bifida sp., but not as much. If a breastfed infant is supplemented with formula he or she will experience a rapid loss of bifida sp. Bifida sp. provide many benefits to their human hosts including protection against pathogens, prevention of diarrhea, maturation of the immune system and reduced risk of developing allergies. Breastfed infants may be better able to handle exposures to environmental chemicals too (Shellor et al. 2012).

The bacteria in your gut will also be dependent on what you eat. A change in diet, for example elimination of gluten by a person who does not have celiac disease, may cause a decline in bacterial populations that help digest gluten (Nistal et al. 2012).

A person eating gluten after a period of abstinence may not be able to digest gluten as well if they eat it again, at least not until bacterial populations re-balance. This may lead some people to get gas, cramps etc. and conclude that they have celiac disease, or that gluten is harmful in itself. It has been brought up by some that the intestinal distress suffered by people following a Paleo-type diet who start eating wheat again is all in their heads (some chat board or other). It probably isn’t. But it’s probably not because gluten is inherently bad either.

Shelor, C., Kirk, A., Dasgupta, P., Kroll, M., Campbell, C., & Choudhary, P. (2012). Breastfed Infants Metabolize Perchlorate Environmental Science & Technology, 46 (9), 5151-5159 DOI: 10.1021/es2042806

Nistal, E., Caminero, A., Herrán, A., Arias, L., Vivas, S., de Morales, J., Calleja, S., de Miera, L., Arroyo, P., & Casqueiro, J. (2012). Differences of small intestinal bacteria populations in adults and children with/without celiac disease: Effect of age, gluten diet, and disease Inflammatory Bowel Diseases, 18 (4), 649-656 DOI: 10.1002/ibd.21830


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  1. Minor point, but I don’t believe anybody thinks that bacteria aid in gluten digestion – the suggestion seems to be that the change in diet changes bacterial populations involved in immunity, and celiac is an autoimmune disorder.

    • Hi Michael. Thank you for writing. We not talking about celiac disease and autoimmune disorders. Our point is that people who do not have celiac disease, and stop eating gluten may very well experience a change in intestinal ecology. Same thing with vegetarians who eat meat and then get sick. They may take this as evidence that meat is bad for all people, when they may simply not have the microbial tools, at this point in time, to handle it.

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