Classification of adverse reactions to foods. (From: Turnbull JL, et al. Aliment Pharmacol Ther 2015; 41: 3–25. The diagnosis and management of food allergy and food intolerances).

Classification of adverse reactions to foods. (From: Turnbull JL, et al. Aliment Pharmacol Ther 2015; 41: 3–25.

Around 20% of people in developed societies have adverse reactions to particular foods, and some have outright food intolerances, defined as undesirable non-allergic reactions that do not involve a direct immune response. The most common food ‘sensitivities’ in the modern world are to gluten, lactose, fructose, milk and eggs, but there are a plethora of other candidates (see Figure).

Food intolerances also have a significant role in ME/CFS. Sensitivity to foodstuffs is one of the possible “immune, gastro-intestinal & genitourinary impairments” used for diagnosis (see the 2011 ICC definition), and many individual patients say that they benefit from avoiding certain foods. Gluten is a good example, and we know from emails and phone calls to ME Research UK that excluding gluten from the diet improves some patients’ symptoms. These symptoms not only include gut discomfort (abdominal pain, bloating etc.) as might be expected but more systemic manifestations such as brain fog, headache, joint and muscle pain. Now, a new report in the August 2016 issue of Acta Pediatrica (read more) suggests that milk protein may also be contributing to symptoms, at least in some ME/CFS patients.

The very active group led by Prof Peter Rowe at Johns Hopkins University School of Medicine in Baltimore has been conducting a two-year cohort study of physical findings and outcomes in young people with ME/CFS. One of the beauties of a programme of research is that unexpected observations can be followed up, and the group had noticed that a number of their patients had symptoms and signs consistent with a delayed reaction to milk protein.

Lactose is one of the constituents of milk that can contribute to intolerances (Cohen cartoons

Lactose is one of the constituents of milk that can contribute to intolerance (Cohen cartoons

To test whether milk intolerance might be a factor in the maintenance of illness, they designed a sub-study to examine overall quality of life (including fatigue, sleep and activity limitations caused by physical health problems) before and after a 6-month period of dietary milk protein restriction. Intolerance to milk protein is diagnosed on clinical grounds alone because no validated laboratory tests exist as yet, so the team performed an initial dietary trial. Of 55 young ME/CFS patients,  17 (31%) were found to be milk-protein intolerant. In the testing phase of the study, a clinically important improvement in the frequency and severity of symptoms was reported by some participants once milk protein was eliminated from their diet. These patients were then put on a milk-free diet for 6 months, and their quality of life was compared at the start and end of the study with that of patients who could tolerate milk protein.

At the start of the study, health-related quality of life was significantly worse in patients who were milk protein intolerant than in those who were not. However, six months after the milk-free diet, quality of life had improved to a greater degree in the patients with milk protein intolerance, and there was no longer a difference in quality of life between the two groups. Also, milk-intolerant patients on the milk-free diet had improvements in upper gastrointestinal and systemic symptoms, and these improvements occurred within two weeks of starting the diet. Of course, as this was not a randomised trial, it’s not possible to say that these effects were due to the milk-free diet alone. The evidence is certainly suggestive, however, and it may be that a milk-free diet could have a significant positive effect in some ME/CFS patients.

For the authors, the importance of the results is that almost a third of adolescents and young adults with ME/CFS “had evidence of treatable milk protein intolerance”, a higher proportion than expected given the evidence that the prevalence of ‘true’ reactions to food may be quite small in the general population (read more). Crucially, most of the study patients who benefitted from a milk-free diet  had previously been unaware of the contribution of milk to their symptoms, probably because of the time delay between consumption and symptoms (unlike in true food allergy where symptoms develop far more rapidly). The authors point out that for patients with ME/CFS the situation can be clarified by a two-week trial of a milk-free diet. While stopping or reducing milk consumption is not the ‘answer’ to ME/CFS, it’s worth being aware that the symptoms of ME/CFS may be exacerbated in some people by milk, a common foodstuff. If patients’ experience of avoiding gluten is anything to go by (read more), the effects of a milk-free diet for a short period could be both surprising and welcome.

Drinking milk in Germany in 1932 (German Federal Archive; Bundesarchiv, Bild)

Youngsters drinking milk in Germany in 1932 (German Federal Archive; Bundesarchiv, Bild)