Immune Modulation & Nutrition

The immune system has the primary function of fighting harmful elements that enter the body from the outside and adverse changes that occur inside the body [1]. This blog post will determine how the immune system works and what impact nutrition has on immune modulation, as well as how the gut microbiome is influenced by nutrition and interacts with the immune system.

Traditionally, the immune system has two branches; innate and acquired (or adaptive) immunity.

Although the innate immune system, including the skin barrier and mucosal cells, is important for when the body comes up against infectious challenges, it is  recognised for regulating inflammatory diseases.

There are three levels of defence against pathogens, beginning with the physiological barrier. This includes the epithelial mucus barrier in organ systems including the gut, maintained by beneficial gut bacteria. The beneficial bacteria present in other areas of the body also contribute to the first line of defence, alongside physical barriers such as skin [2].

Within minutes of exposure to pathogens, the innate immune system begins producing a protective inflammatory response through specific immune cells and signalling molecules. The acquired immune system will usually follow an innate response with a much more refined regulation of specific T- and B-cells fighting the pathogens with the input of antibodies.

Antibodies are beneficial for fighting infections when the patient has already been exposed to the given infectious agent. It is important to note that the integration of innate and acquired immunity provides the most efficient host defence [2].

Nutrition and immunity

There are complex interrelationships between nutrient metabolism and the immune system. Hormonal signalling, which is affected by nutrient intake, causes the proliferation of some immune cells. Therefore, nutrient deprivation can be detrimental to the function and provision of immune cells [3]. Furthermore, the gut microbes enable synthesis of nutrients from our food, adding to the complexity of how nutrition and immunity react [3].

Immune cells may be more sensitive to the status of certain nutrients, and the optimal intake of these nutrients can contribute to maintaining immunological balance. Vitamins D, E, Zinc and Omega 3 fatty acids, amongst other food components such as polyphenols, prebiotics and probiotics, are reported to have clinical relevance for immune function [4].

Importantly, appropriate, adequate nutrition and a balanced diet is necessary for all cells, including immune cells, to function properly. Energy and nutrient requirements increase when the immune system is activated. The best nutritional approach for the immune system would be to allow the immune system to respond effectively and resolve rapidly to avoid chronic inflammation [5].

Approximately 70% of the body’s immune cells are found in the gut associated lymphoid tissue (GALT). When ingesting food, our body is exposed to food proteins, potential pathogens. The GALT has sensing and response functions and together with the gut microbiome, signals the wider systemic immune system to recruit immune cells. Dietary and nutritional interventions can be recommended to modulate gut health and to support the immune system, which may result in reduced inflammation in the gut. As an example, the Mediterranean diet is recommended for its high dietary polyphenol content to reduce chronic systemic inflammation in people with non-communicable diseases [5].

Gut microbiome and immune modulation

It is dynamic factors between the gut microbiome and the external environment, such as nutrition, that shapes mucosal and systemic immunity. The immune system constantly interacts with the mucosal barrier and the gut microbiome to maintain homeostasis and modulate immunity.

An impaired interaction between the gut microbiome and the mucosal barrier is associated with disease and pathogenic infection. For example, a disturbed gut barrier is a risk for infection and inflammation [6]. As mentioned above, most of the immune cells are found in the GALT cells in the gut and any infection or inflammation could impair its function.

Probiotics and prebiotics for immunity

Probiotics are live bacteria that have a benefit on the host. The benefits of probiotics have been shown to be extensive. Specific strains of probiotics interact with intestinal epithelial cells or immune cells once administered and regulate the production of immune markers and cytokines.

Another way that probiotics can assist with immune modulation is that they can inhibit the growth of pathogenic bacteria [7]. Some probiotic bacteria produce short chain fatty acids (SCFAs) as a result of carbohydrate fermentation. SCFAs are fuel for colonic enterocytes and stimulate the intestinal epithelium to promote the production of the mucosal barrier.

Prebiotics increase beneficial bacteria in the gastrointestinal (GI) tract because they are non-digestible compounds that feed good bacteria. Similarly, the increase in beneficial bacteria caused by prebiotics inhibits growth of pathogenic bacteria [8]. Bimuno GOS has been shown to reduce the adhesion of pathogens to gut cells, suggesting a positive effect on the innate immune system [8].

Research has demonstrated the immune modulatory effect of Bimuno Galactooligosaccharides (GOS) prebiotic supplements where a daily dose led to an increase in beneficial bacteria in the GI tract and a reduction in less beneficial bacteria [9].

It was also shown to improve natural killer cell activity and phagocytosis of E.coli, as well as  increase anti-inflammatory cytokines and  decrease secretion of proinflammatory cytokines [9]. This research was conducted in healthy elderly adults, which is of particular importance as ageing causes changes to the gut microbiome, particularly levels of bifidobacteria, a health positive genus of gut bacteria.

Further research has verified that a daily dose of Bimuno GOS for 10 weeks in a healthy elderly population significantly increased levels of bifidobacteria. An improvement in natural killer cells and cytokines production was seen again. It is not fully understood how bifidobacteria have a positive effect on health, but it could be through its barrier function and the reduction in inflammation [10].

In overweight adults with metabolic syndrome, Bimuno GOS improved some metabolic markers such as plasma triglycerides, as well as reduced plasma insulin levels. In this cohort, calprotectin, a marker of intestinal inflammation, was lowered significantly compared to placebo. Additionally, a marker of mucosal immunity, secretory IgA, was increased with Bimuno GOS supplementation [11]. The importance of these data for patients is that people with metabolic syndrome are at higher risk to negative health outcomes, therefore, it is of benefit to improve immune modulation and metabolic markers, particularly that this was achieved independently to other lifestyle changes [11].

With the approach of winter, the chances of infection increases and recommending that clients or patients eat for their gut microbiome could be beneficial for their immune system. A varied diet with fruits, vegetables, whole grains, beans and pulses will provide a variety of fibre sources to feed the gut microbes, as well as the all too important micronutrients mentioned previously. Probiotic and prebiotic supplements can be recommended, but a food first approach should be initially considered.


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