Targeted investigations for etiologies of malnutrition are critical for wellness in treating patients with rheumatic disease since nutrition is a cornerstone for health. Dietary intake is a key regulator of the structure and function of gut microbiota, which populate the lumen of the intestine and perform complex host-microorganism interactions that modulate immune response. This chapter discusses the importance of understanding the role of nutrition and the gut microbiome in rheumatic disease risk and modification of inflammatory outcomes.