The Western diet is characterized by a high intake of saturated and omega-6 fatty acids, reduced omega-3 fat intake, an overuse of salt, and too much refined sugar . Most are aware that this type of eating, if not in moderation, can damage the heart, kidneys, and waistlines; however, it is becoming increasingly clear that the modern diet also damages the immune system. The modern lifestyle is also typified by reduced exposure to microorganisms, increased exposure to pollutions, heightened levels of stress, and a host of other exceptionally well reviewed variables that likely contribute to immune dysfunction . Therefore, while dietary effects on immunity should not be thought of in isolation, herein we focus on the body of evidence detailing the mechanisms for the Western diet’s impact on immune function.In vitro evidence suggest processed, simple sugars also reduce white blood cell phagocytosis and possibly increase inflammatory cytokine markers in the blood [24,25]; of note, the author’s attribute their findings more to the relative glycemic load of meals than the sugars themselves and the most direct study on sugar’s effect on lymphocyte function is now four decades old and thus, repeat investigation employing in vivo and/or modern techniques is required. Meanwhile, the complex carbohydrate fiber (but not starches), such as that found in fruits and vegetable, appear to reduce inflammation in both humans [26–32] and mice . The impacts of artificial sweeteners are less clear; provocative, yet highly limited, evidence implicates saccharin and sucralose as contributors to Crohn’s and Ulcerative Colitis via interference with homeostatic inactivation of digestive proteases [34,35]. However this evidence is only epidemiologic correlation and animal modeling, and lacks direct human investigation. Other studies looking at the effects of sweeteners in cell culture suggest anti-inflammatory effects in the blood [36,37]. Few studies on newer sweeteners have been conducted, yet limited cell-culture evidence on stevioside suggests anti-inflammatory properties while improving phagocytosis and mitogen responses for both T and B cells [38–40]. Potential immune impacts of the newest sweetener, mongroside V, have not been directly investigated. Therefore, definitive commentary on the immune impacts of sweeteners will require further investigation.