Fasting and Vegetarian Diets

An alternative approach to alleviating the symptoms associated with chronic inflammation is elimination of various foods or food components, most often by fasting or a vegetarian diet. Some studies have demonstrated a significant improvement in various objective and subjective measures of disease activity, including number of tender and swollen joints, Ritchie articular index, duration of morning stiffness, erythrocyte sedimentation rate (ESR), C reactive protein (CRP), grip strength and score on health assessment questionnaires, among patients with RA 6 weeks to 2 years after initiating a vegetarian diet. Furthermore, these clinical improvements were accompanied by changes in biochemical and immu-nological parameters consistent with a substantial reduction in inflammatory activity. Other studies, however, have demonstrated no clinical improvement among patients with RA following a vegetarian diet.

Several possible mechanisms have been proposed to explain the impact of elimination diets on clinical symptoms in RA. One possibility is that RA might be the result of hypersensitivity to environmental toxins or specifically to foods or food-related products, resulting in a food allergy of sorts that exacerbates symptoms of RA. However, true food intolerance, involving a systemic humoral immune response against food items, appears to be relatively uncommon among patients with RA. Another possible mechanism that has been proposed includes an alteration in the fatty acid content of the diet. Vegetarian diets contain more linoleic acid, but less AA, EPA, and DHA than omnivorous diets. Therefore, the eicosanoid precursors (AA, EPA, and DHA) must be produced endogenously from linoleic and a-linolenic acid (see Figure 1). It has been hypothesized that if this endogenous production cannot compensate for the absence of AA in the diet, then the precursor of the proinflammatory eicosanoids would be reduced, perhaps explaining the beneficial effect of vegetarian diets in patients with RA. Furthermore, it has also been demonstrated that fasting for 7 days resulted in decreased release of LTB4 from neutrophils, in addition to reductions in morning stiffness, articular index, and ESR, but that this reduction in LTB4 occurred despite an increased AA content of the serum, platelets, and neutrophils. These findings suggest that perhaps fasting may impair a metabolic step of AA conversion.

Other potential mechanisms include the possible effect of a vegetarian diet on antioxidant status, or on other dietary practices frequently associated with vegetarianism. Plant-based foods are naturally high in antioxidant nutrients (vitamin C, vitamin E, and beta-carotene) and low serum antioxidant levels have been associated with an increased risk of developing RA, although the specific mechanism involved remains unknown. Certainly, RA is associated with increased production of reactive oxygen species; these compounds seem to contribute to the inflammatory process, so a diet high in antioxidants could limit damage via their anti-inflammatory properties. While changes in fatty acid composition or antiox-idant status seem to be the most plausible explanations for the potential benefit of adhering to a vegetarian diet, there are other possible mechanisms as well. Fasting, for example, suppresses inflammation and frequently a period of fasting is recommended prior to initiating an elimination or vegetarian diet; it is possible that this fasting period contributes to the reduction in inflammation among patients with RA following a vegetarian diet.

In summary, the notion that food sensitivity reactions contribute significantly to clinical symptoms associated with RA remains controversial. However, it seems that at least a small subgroup of patients with RA may benefit from individualized dietary manipulation involving elimination of specific foods or food components, in combination with other medical therapies. However, fasting and other elimination diets should be used with caution in light of the prevalence of rheumatoid cachexia in this population. Such patients are prone to further loss of cell mass during restrictive diets, and the net effect may be to do more harm than good.

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