"Cow's milk protein intolerance is a common problem in young people with chronic fatigue syndrome, and is a treatable contributor to their symptoms."
So said the paper by Peter Rowe and colleagues  who looked prospectively for signs of cow's milk protein intolerance (CMPI) in "55 adolescents and young adults with chronic fatigue syndrome" over the course of 2 years. Defining CMPI using 4 factors: "(1) no evidence of immediate or anaphylactic reactions to milk, (2) at least 2 of the following 3 chronic symptoms: gastroesophageal reflux, early satiety, and epigastric/abdominal pain, (3) improvement in upper gastrointestinal symptoms on a milk protein elimination diet, and (4) at least 2 recurrences of upper gastrointestinal symptoms > 2 hours following open re-exposure to milk protein" researchers set about on this fairly unusual study course to ascertain some preliminary prevalence data and to see what impact such food issues might have on self-reported quality of life.
Nearly a third of their quite small participant group (17/55) hit their thresholds for CMPI and we are told that in comparison to non-CMPI participants, those with milk issues "had significantly worse health-related quality of life at baseline but not at 6 months (after institution of the milk-free diet)." As per that opening quote, prevalence of CMPI might be common in cases of CFS and might play some not insignificant role on quality of life.
Wearing my 'diet and behaviour' hat (see here for example) the Rowe results make for interesting reading. The fact that some of the authors have quite a lot of research standing when it comes to chronic fatigue syndrome (CFS) adds to my interest in these results; specifically with another of their papers in mind on orthostatic intolerance and gastrointestinal (GI) symptoms  for example (orthostatic intolerance = development of symptoms when standing upright, and is thought to be linked to quite a few cases of CFS).
Quality of life (health-related) when applied to CFS is something else that has already been covered on this blog (see here) and the observation that its presentation can be about as bad as it gets for some people in comparison to various other diagnostic labels. Anything therefore that can improve [elements of] such an important measure has to be taken seriously, particularly when it is something as 'treatable' as potentially eliminating milk from ones diet (I say this with no medical or clinical advice given or intended).
But just before anyone decides to embark of a milk-free diet solely on the basis of Rowe results, a bit of a research 'to-do' list to think about in this area: (a) The sample size was quite small and we need to know more with larger sample sizes and perhaps more strenuous research methodologies. (b) The measures used to assess CMPI didn't appear to include anything 'biological'. I know this is still a bit of a grey area in terms of 'intolerance vs' allergy' but I'd like to think that more could be attempted during future study including that related to those bowel symptoms  given previous discussions in this area (see here). (c) Given that this was a study of CFS I think most people would like to know whether CFS symptoms were impacted by a milk-free diet as well as quality of life measures. Again, measuring CFS is not the easiest of tasks given the number of definitions (see here) but it's not impossible. (d) Acknowledging that not all milk is the same (see here and see here) and that protein is but one element of milk, I have to wonder whether it might be worthwhile doing some further study on this too. Given also that institution of a milk-free diet is not without potential complications, the question is once again: is there more science to be done?
But that doesn't mean that the Rowe results are not interesting...
 Rowe PC. et al. Cow's Milk Protein Intolerance in Adolescents and Young Adults with Chronic Fatigue Syndrome. Acta Paediatr. 2016 May 13.
 Sullivan SD. et al. Gastrointestinal symptoms associated with orthostatic intolerance. J Pediatr Gastroenterol Nutr. 2005 Apr;40(4):425-8.
 Frissora CL. & Koch KL. Symptom overlap and comorbidity of irritable bowel syndrome with other conditions. Curr Gastroenterol Rep. 2005 Aug;7(4):264-71.
Rowe, P., Marden, C., Jasion, S., Cranston, E., Flaherty, M., & Kelly, K. (2016). Cow's Milk Protein Intolerance in Adolescents and Young Adults with Chronic Fatigue Syndrome Acta Paediatrica DOI: 10.1111/apa.13476