Various gastrointestinal and neurological problems that are common in people with ME/CFS are surprisingly similar to the symptoms of “D-lactic acidosis”. This condition arises from bacterial fermentation of carbohydrates in the gastrointestinal tract, leading to increased lactic acid levels in the blood. Could there be an overgrowth of Gram-positive anaerobic lactic acid bacteria in the guts of ME/CFS patients too?
Scientists at the University of Melbourne in Australia examined the faeces of 108 ME/CFS patients and 177 healthy controls for the presence of the most common of the 500 different bacterial species that inhabit the human gut. Their paper in the journal In Vivo reported significantly increased levels of aerobic Gram-positive intestinal bacteria in the ME/CFS group than the controls, particularly Enterococcus and Streptococcus species which are the most common aerobic bacteria in humans. Moreover, the organisms found in the patients produced significantly more lactic acid than those from the healthy subjects (p<0.01), indicating that acidosis was at least a possibility in ME/CFS. The researchers postulate that increased colonisation by Enterococcus and Streptococcus could heighten intestinal permeability, assisting the absorption of D -lactic acid into the bloodstream. Increased gut permeability might also aid the release of endotoxins from the bacteria themselves, leading to inflammation, immune activation and oxidative stress, which are prominent features in a large subset of ME/CFS patients.
While the cause of the increased colonisation remains unclear, the researchers point out that eradication of all bacteria is not the answer; indigenous bowel microflora have both positive and negative impacts on health, and the balance of “good” to “bad” bacteria is important. And their next experimental step is to measure D- and L-lactic acid accumulation in the biofluids of ME/CFS patients to confirm whether D-lactic acidosis really is a factor. If so, existing interventions, such as short-course antibiotics, alkalinising agents, a low carbohydrate diet or dietary glucose restriction might prove to be useful.
Reference: Increased D-lactic acid intestinal bacteria in patients with chronic fatigue syndrome. Sheedy JR et al. In Vivo 2009 Jul-Aug; 23(4): 621-8.