The Role of Nutrition in Immunity
Written by: Dr Tom Shurlock for and on behalf of GWF Nutrition Limited.
Copyright GWF Nutrition Limited April 2020 - Not for reproduction.
Immunity is a complex system, inter-related with the hormonal physiology of the body, metabolic systems and individual organ function, whose function is to protect the body against any invasion of “alien” components. In some instances, the body mis-recognises food, airborne or injected (bite, sting) protein – usually quaternary structure – as a pathogen, giving rise to allergy. Intolerance is a different issue, usually the deficiency of a digestive enzyme, leading to gut dysfunction; whilst the response of the body’s defence mechanism may show some similarities it is a separate response.
The body has a tiered response; barrier, innate and acquired immunity, with increasingly tailored responses through the process.
The main barrier to invasion is the skin, a physical boundary of impervious cells; however, where more vulnerable surfaces – lungs, gastrointestinal tract, urinogenital system, all of which can be exposed to external factors – are exposed, there are mucoid barriers which trap pathogens and help expel them from the body. The gut, for example, has a layer of lipoproteins, similar to those found in cell membranes, sandwiched between mucosal layers. By denying pathogen adhesion, whilst still allowing nutrient transfer, the gut barrier is one of the main defence mechanisms.
Within the barrier function are further defences; antibacterial lysosome in saliva and stomach acid are examples, as are antimicrobial defensins in the lungs and sebaceous secretions in the skin. Within the papillary layer of the dermis, sebaceous glands open at the juncture of the hair shaft under the epidermis. This allows the generation of sebum to coat the growing hair follicle, but also to permeate between the two dermal layers and out onto the skin’s surface. Sebum is reported to be consist of triglycerides (≈41%), wax esters (≈26%), squalene (≈12%), and free fatty acids (≈16%); squalene is a triterpene and precursor of sterol and cholesterol. Sebum waterproofs the skin and coat, forming a physical barrier to the wet, and emulsifies sweat, aiding thermoregulation by promoting evaporation. There are reports that sebum has antimicrobial, antifungal and acaricidal properties. Bioactives can interact with sebum, alter its makeup and pass through the hydrophobic layer. They are also implicated in supporting natural mechanisms that mediate skin health. The presence of omega-3 fatty acids, terpenes (essential oils), curcumin and associated antioxidants all play a role in the generation and secretion of sebum, supporting the barrier function.
Figure 1. Cross section of skin.
It is the role of innate immunity where nutritional support has its most specific role. The immune system operates through the lymphatic system, which has specific nodes throughout the body. The gut, probably being the most challenged organ in the body, is a major immunological structure. Within the gut wall in the small intestine are cells known as Peyers Patches (Gut Associated Lymphoid Tissue – GALT) which are linked to the lymph system. As such they have direct impact on the immune defence system through the generation of macrophages and other components called mucosa associated lymphoid tissue (MALT). Macrophage is a type of white blood cell whose function is to engulf foreign material that gets into the body and is non-specific. Before the body starts manufacturing antibodies to invasive material, macrophages are providing basic defence. GALT & MALT are also involved in combatting other invasive particles including cancer cells and allergenic particles.
Although there are several mechanisms involved, the body’s response to a perceived threat follows several steps. The first response is the generation of inflammatory factors. This Increases blood supply to the site and increases capillary permeability, allowing large molecules, soluble mediators, to enter the site, including leucocyte migration into surrounding tissue. There is also a release of mediators from leucocytes. These can be a variety of products such as leukotrienes, cytokines, superoxide (free radicals), histamine and matrix proteases (MMP) depending nature, site and type of stimulus. For example, specific actions of Vitamin D on leucocytes can activate phagosomes and macrophage cells, and Ig and B and T cell production through its degradation to 1,25(OD) – calcitriol. Also involved is the release of cytokines, and pro-inflammatory suppressants (for more details, see Knowledge Base, Vitamin D in Animal Health). The function of B and T cells is also integral in acquired immunity.
Figure 2 Generalised representation of innate immunity.
Depending on the action, the blanket response will cover a range of effects. Phagocytes, as the name implies, will devour microbial invaders, within which further action resulting in antibody production. Other cytokines can both remove damaged material (such as TNF-α) and also initiate cell regeneration, through the suppression of oxidative damage (IL1-β). Subsequently, anti-inflammatory cues moderate the preceding actions, Inflammatory ring fencing of the damage is removed, and waste/damaged material eliminated.
This action, although described via the GALT, is followed through all defence mechanisms across the body. From the injection of digestive enzymes from a tick bite to a viral lung infection, the broad mechanism is the same. In fact, one of the reasons coronavirus can be so dangerous is that, in some people, it activates an over-production of inflammatory factors that can damage lung tissue – mimicking an autoimmune response. Equally, over-reaction to allergens results in massive inflammatory cytokine release which can result in adverse conditions, such as organ shutdown.
The third line of defence is acquired immunity. This involves activated leukocytes and the generation of “memory” of specific response. Because acquired immunity is dependent on the initial innate response, there is little direct influence from nutrition – apart from general wellbeing supporting the immune system – which has a primary impact on innate immunity.
Although there are a number of applications of different “therapies” – topical, inhalation (a major route of turmeric bioactives in Eastern folk medicine), injection – the main route of immune function support is via the gastrointestinal tract, and it is through the food we eat that benefits can occur. Obviously, a well-fed individual is better equipped to fight infection, but specific supplementation can support the immune system through moderation of the inflammatory/oxidative cycles, support of immune mechanisms as well as more specific macrophage stimulation and t- & b- cell (acquired immunity) activation. Even the microbiome has an impact on both immunity and allergy; the increase in fibre fermenting microbes has an effect of helping desensitise the body to foodborne allergens but also, through its end products can regulate the transition of GALT/MALT activators through the tight junctions between the cells of the gut wall.
Fig. 3. Microbial products and nutrients pass through the intestinal wall and regulate the development and acitivities of the immune system by maintaining a balance between immunosuppressive Treg cells and proinflammatory Th17 cells. If the microbiota composition changes and dysbiosis results, this balance may be disrupted and animals may become predisposed to developing inflammatory and allergic diseases.
Immune Aid has been formulated to address a broad approach to supporting the immune & defence systems both in response to a direct challenge, but also to ensure it is in an optimal state.
Immune Aid contains nutracines and bioactives that both support different aspects of the immune response but also provides additional aid to those inflammatory/oxidative mechanisms that are central to the response to any situation that is “not quite right” from a metabolic point of view. As importantly, Immune Aid is based on the Oatinol delivery system, to ensure those active ingredients are actually absorbed and “presented” to the relevant systems. The molecules involved are generally absorbed across the gut by interstitial mechanisms (between cells, rather than through them), and there are ingredients to facilitate this. For example, β-glucans, an oligosaccharide that also acts as a prebiotic can improve tight junction transfer and can also interact with MALT to activate anti-inflammatory factors and macrophages (please knowledge Base: Beta Glucans – What do they do? For more details).
There are a range of antioxidative factors in Immune Aid. Oxidative processes are intrinsically linked with inflammatory factors, and it is probably this interplay that leads to inflammatory damage and oxidative degeneration of cellular components. Coupled with bioactives that support natural anti-inflammatory cues, these nutracines provide the best help to modulate the response to many immune/allergenic inputs.
There are specific supports to the innate immune system; Vitamin D and its action in macrophage activation, the inclusion of prebiotics (as oligosaccharides) adjusting the microbiome, as well as the direct effect of β-glucans on MALT. Furthermore, the presence of toxin binders removes some components that may stress the defence mechanisms if they were absorbed.
The more recognisable nutrients – omega fatty acids, protein and, specifically, glutamic acid & MSM - also support the inflammatory cycle, but also supply the materials to help regeneration of damaged tissues. This aids the post inflammation/infection phase, as the situation returns to normal.
Whether there is an immune challenge, allergic response, or parasitic challenge (fleas, ticks, worms), the overall approach to supporting inherent defence mechanisms is a multifunctional approach.