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Research appearing in the Annals of Rheumatic Diseases (1993;52:503-510) looked at the relationship between the overgrowth of bowel flora in the small intestine (SIBO) and rheumatoid arthritis. There were 25 subjects with a positive rheumatoid factor who were compared to 23 controls; 11 of the control subjects had normal stomach HCl secretion and 12 of them were either achlorhydric or hypochlorhydric (as determined by pentagastrin stimulation). Both the controls and the rheumatoid patients were tested for small intestine bacterial overgrowth. The researchers noticed that a high percentage of the rheumatoid patients had small intestine bacterial overgrowth. Of the subjects with rheumatoid arthritis, 35% of those with normal acid secretion and half of those with hypochlorhydra or achlorhydra had bacterial overgrowth.  None of the controls with normal acid secretion had small intestine bacterial overgrowth. Also, serum rheumatoid factor was higher in rheumatoid patients with bacterial overgrowth.  The authors concluded that small intestinal bacteria overgrowth was found in great frequency in patients with RA and is associated with a high degree of disease activity.

An article appearing in the Scandinavian Journal of Rheumatology (Volume 24, Issue 6, Supplement 101, 1995, Pages 207 – 211) discusses the connection between bowel flora and arthritis. Various bacteria can cause reactive arthritis, and patients with inflammatory bowel disease often suffer from joint inflammation. According to the authors of the article, gut flora produce substances that are implicated in arthritis associated with inflammatory bowel disease. T cells come into contact with these antigens and develop recognition and eventually become involved with joint inflammation. Research has shown vegetarian diets to be beneficial for both inflammatory bowel disease and for arthritis.

A commentary on the benefits of diet therapy on rheumatoid arthritis, appearing in The Lancet (1992;339:68-69) points out the patients benefit from a diet high in raw foods that avoids dairy and grains. The authors point out the absence of RA in prehistory and that the differences between ancient diets and the modern diet include grains, dairy, and cooking. The authors cited a study where 75% of rheumatoid arthritis patients experienced improvement utilizing such a diet. The authors of this article believe that RA is caused by bacterial peptides crossing the intestinal barrier and creating inflammation.