Nutrition is a major environmental influence on human health. Epidemiological and interventional studies suggest a pathophysiological or therapeutic role, respectively, for nutrition in inflammatory rheumatic diseases (IRDs). Nevertheless, the associations between nutrition and IRDs are often weak and inconsistent, and the available clinical trials on nutrition are methodologically flawed. Experimental evidence is accumulating that micronutrients in the diet may influence intestinal and systemic immune responses via complex interactions involving the gut microbiota. Micronutrients may, therefore, contribute to the pathogenesis of inflammatory diseases. No interventions targeting these interactions for diagnostic, prophylactic, or therapeutic purposes have been developed to date. Moreover, the relevance to human disease of experimental results obtained in animals or in vitro is unclear. Novel high-throughput technologies (-omics) may prove useful for a systems biology approach to these results that takes the complexity of the interactions into account. Concomitant cohort studies combining clinical and laboratory data collected over time may provide new impetus to research into the connections between nutrition and IRDs.