Diet and Immunity

This special issue of Nutrients published in 2019 looked at the relationship between diet and nutrients, and immune function. This article not only outlines the important functions of the immune system but also how it interacts with nutrients across the life course. It is already established that a well-functioning immune system is crucial for survival. The cells that form the immune system must be able to distinguish between host cells and foreign cells, and to identify any harmful non-self-molecules (for example present on pathogens). In addition, these cells should be able to distinguish innocuous particles such as food from these harmful non-self-molecules. This review presents the roles of macronutrients, micronutrients, and the gut microbiome in mediating immunological effects. The immune system can potentially be modulated through dietary means, which has applications in both clinical patients and healthy populations. Nutritional strategies can help reduce or delay the onset of immune-mediated chronic diseases. [NPID: immunity, immune system, diet, nutrients, nutrition, macronutrients, micronutrients, gut microbiome, bacteria]

This 2007 article outlines the importance of adequate vitamins and mineral consumption in the efficient functioning of the immune system. Micronutrient deficiency impairs immune function, and increases the host’s chances of catching infection, giving rise to morbidity and mortality. Infections in turn worsen micronutrient shortages by reducing nutrient intake, increasing losses, and interfering with its utilization. Insufficient levels of micronutrients are particularly seen in people with eating disorders, smokers (both passive and active), individuals with chronic alcohol abuse, the elderly, and during pregnancy and lactation. Antioxidant vitamins and trace elements such as vitamins C, E, selenium, copper, and zinc counteract potential damage caused by reactive oxygen species to cellular tissue and adjust immune cell function. Moreover, adequate consumption of these vitamins and trace elements supports an immune response including the production of proinflammatory cytokines, which helps maintain an effective immune response and prevent an increase in infection risk. Moreover, vitamins A and D play important roles in both cell-mediated and humoral antibody response. Insufficient intake of vitamin A inhibits both natural immunity and adaptive immune responses to infection, resulting in poorer ability to fight pathogens. Vitamin D deficiency is also correlated with greater vulnerability to infections. Overall, not obtaining enough of these vitamins and minerals may lead to suppressed immunity, which increases likelihood of infections and further aggravates malnutrition. [NPID: nutrients, micronutrients, nutrition, malnutrition, vitamins, minerals, immune system, immunity, infection, disease, alcohol, pregnancy, pregnant]

This 2019 paper summarizes the evidence on the extent to which excessive salt consumption could worsen proinflammatory responses, influencing the development of immune-mediated diseases. While the prevalence of autoimmune diseases has risen in Western countries over the past years, the development of this disorder can be attributed to several factors including genetics and the environment. This trend in increasing incidences over the years cannot be associated with genetic background since there was no significant change over that time span. Of the environmental factors, dietary habits (particularly excessive salt) have been implicated in the pathogenesis of autoimmune diseases. While there has been research conducted on several diseases such as rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, and Crohn's disease, many of these studies suggest that salt possesses proinflammatory features. Similar proinflammatory effects were observed in experimental models conducted both in living organisms (in vivo) and outside of living organisms in laboratories (in vitro). However, conflicting data comes from murine models of spontaneous autoimmune polyneuropathy exposed to high salt diets. Based on these results, we need to further analyze the role of cooking salts in the treatment and prevention of autoimmune diseases. We should consider the advantages of restricting salt intake, as well as the changes in metabolites, mediators, and hormones that accompany salt consumption, which can potentially affect autoimmunity. [NPID: immunity, autoimmunity, autoimmune diseases, diet, dietary habits, salts, nutrition, inflammation, genetics, environment, arthritis, lupus, MS, multiple sclerosis, Crohn’s]

This 2016 article outlines the potential roles of various nutrients in protecting the host from pathogenic organisms. The immune system should be able to tolerate its own cells, food particles, and other environmental components. Host immunity is positively influenced by the consumption of many nutrients, micronutrients, and bovine milk. Now there are various studies on how probiotics and prebiotics enhance immunity in the presence of intestinal diseases. While vitamins and minerals also boost immunity, deficiencies in micronutrients often lead to suppressed immune function through modulation of immune responses and adoptive antibody responses. Other dietary variables include essential fatty acids and amino acids, both of which have impacts on immune responses in numerous ways. Glutathione and nucleotides are said to be important components of immunonutrient mixes. Furthermore, this review discusses how interactions between different nutrients can affect host immunity. [NPID: immunity, immune system, nutrients, nutrition, food, micronutrients, milk, probiotics, prebiotics, antibody]

In this 2020 study, a total Western diet was developed for rodents by using the energy and nutrient profiles like a typical Western diet. This total Western diet (TWD) was then given to mice to test the hypothesis that intake would worsen colitis, delay recovery from gut injury, and promote the formation of tumors in the colon. Multiple experiments concluded that mice fed the total Western diet experienced more severe and prolonged colitis when compared with mice fed a standard diet. In addition, these mice grew considerably more tumor cells in the colon, which was attributed to the micronutrient component of the total Western diet. Restoring the calcium and vitamin D concentration to standard levels in fact helped reduce the stimulation of tumor growth induced by the diet. Furthermore, exposing the mice to the TWD caused marked changes in mRNA characteristics in the colon related to inflammation, adaptive immunity, and antigen processing pathways. To summarize, the consumption of this total Western diet exacerbated colitis, slowed recovery from intestinal injury, and increased colon tumor growth, probably through modification of immune-related genes in the colon mucosa. [NPID: immunity, colon, tumors, cancer, western diet, diet, nutrition, colitis, micronutrients, vitamin D, calcium]

While it is well established that consuming too much salt can increase the risk of developing cardiovascular diseases, this 2019 article discusses how excess salt intake may also affect the immune system and influence the chances of autoimmune diseases such as multiple sclerosis (MS). Some evidence suggests that T helper 17 cells (Th17) play a role in the pathogenesis of multiple sclerosis. And there are studies that have demonstrated that excessive intake of salt increases differentiation of these Th17 cells, and thereby induces a phenotype that worsens neuroinflammation. Moreover, the actions of salt can be related to the gut-immune axis - diets rich in salt can modulate intestinal microbiota. The first few human studies indicated a connection between increased MS disease activity with elevated sodium chloride consumption, although more recent studies with larger sample sizes did not reveal any correlation between salt intake and the autoimmune disease. It can be argued that nutritional questionnaires and ordinary analyses of sodium levels in the urine do not absolutely correspond to the actual sodium load. Studies have shown that sodium can be temporarily stored in the body. More sophisticated instruments may be needed to accurately determine internal sodium levels. This review not only summarizes the recent discoveries on the impact of salt on the immune system but points out the potential challenges in investigating dietary salt intake as a risk factor in multiple sclerosis. [NPID: MS, multiple sclerosis, salt, sodium, diet, nutrition, immune system, immunity, autoimmune, inflammation]

Since patients are curious about whether dietary patterns affect the course of inflammatory bowel diseases, the purpose of this 2019 review was to shed light on diet’s influence on gut microbiota composition, gut epithelial barrier function, and the mucosal immune system. Many of these patients are avoiding certain foods that are suspected to aggravate their condition and symptoms. While interest in nutritional interventions is growing among doctors, these interventions are not frequently used in the management of inflammatory bowel diseases. This is due to the lack of scientific evidence from clinical trials. However, several studies have indicated links between diet, gut microbiota, intestinal epithelial integrity, and mucosal immune responses. Damaged gut epithelial barriers and disturbances in gut microbial communities have been observed in sufferers who consume a mainly Western diet, which is low in fruits and vegetables, and high in n-6 poly-unsaturated fatty acids (PUFAs), sugars, and meat. The result is often chronic mucosal inflammation. Experts believe that anti-inflammatory diets may restore this loss in balance. [NPID: diet, immunity, autoimmune diseases, inflammation, IBD, inflammatory bowel disease, immune system, sugars, western diet, meat, fatty acids, fruits, vegetables, gut microbiota, nutrition]