When it comes to our overall health and wellbeing, the health of our gut plays a crucial role. Within this complex ecosystem lies a powerful defender called secretory IgA (sIgA). Secretory IgA is an essential component of our immune system, and the health of our gut can influence the status of this important protective chemical.
Understanding Secretory IgA
Secretory IgA is a type of immunoglobulin, or antibody, that is specifically designed to protect the mucosal surfaces of the body, including the gastrointestinal tract, respiratory system, and genitourinary tract. It is the most abundant antibody found in human secretions such as saliva, tears, and breast milk. Secretory IgA acts as the first line of defence against potential pathogens and toxins that enter the body through contact with these mucosal surfaces.
Guardian of the Gut and Immunity
In the context of gut health, secretory IgA plays a pivotal role. It acts as a barrier, preventing harmful substances from crossing the gut lining and entering the bloodstream. When the delicate balance of gut bacteria is disrupted, a condition known as dysbiosis may occur, leading to a compromised gut barrier function (leaky gut). Secretory IgA helps to maintain our gut barrier integrity by binding to harmful microorganisms, toxins, and antigens and preventing their opportunities to attach and invade. Additionally, secretory IgA promotes the clearance of these bound pathogens and toxins through the process of mucosal immune exclusion.
Secretory IgA also plays an important role in promoting our immune tolerance (the ability of our immune system to not overreact to substances). It achieves this by regulating the immune response to harmless substances like food antigens and commensal (friendly) bacteria. By keeping unnecessary immune reactions under control, secretory IgA has a role in preventing the damage that can be caused by chronic inflammation in the gut. The ability of our immune system to control immune tolerance is particularly crucial as it prevents the development of autoimmune conditions and allergic reactions triggered by an overactive immune response.
Influencing Our Gut Microbiota Living Conditions
Secretory IgA also exerts a profound influence on the composition and diversity of the gut microbiota. Secretory IgA helps maintain a healthy balance of beneficial bacteria by creating an environment they can thrive, whilst simultaneously creating a hostile living place for pathogenic organisms. By fostering diverse and supported gut microbiota, secretory IgA supports optimal digestion, nutrient absorption, and overall gut health.
Factors Affecting Secretory IgA Levels
There are a number of factors that can influence secretory IgA levels. Poor sleep, poor nutrition, frequent history of antibiotic use and some medications and medical conditions play a role in degrading our secretory IgA status. One of the biggest factors, by far, is stress!
Chronic stress is one of the fastest ways to destroy secretory IgA. Numerous studies have demonstrated this link over a number of years. Including a 1983 study in the Lancet and a 2004 study on dental school students and a 2004 study on medical school students that showed that higher stress levels and workloads correlated with depletions to our secretory IgA status.
Another 2015 study showed that higher perceived psychosocial stress also negatively impacted secretory IgA levels. This close connection between our gut, immunity and stress levels serves to explain why when we’re under chronic stress conditions, we are far more susceptible to picking up a cold, flu or infection.
Can We Improve Secretory IgA levels?
Keeping the gastrointestinal tract in tip-top shape is one of the most effective ways to ensure our secretory IgA levels are maintained. There are a range of ways this can be approached with diet and natural medicines.
Saccharomyces Boulardii (SB): This beneficial prebiotic and probiotic yeast is one of the most effective ways to specifically boost secretory IgA levels. The unique actions of SB serve to improve the mucosal layers that line our gut which allows our beneficial microbiota communities to thrive and multiply.
Vitamin A: This often overlooked fat-soluble vitamin plays an important role in gut-mediated immunity. It can help our gut immune system to be more tolerant of food triggers and nourishes the mucus layer within the gut that’s important for microbiota and secretory IgA production.
Medicinal Mushrooms: The upregulation of secretory IgA is one mechanism that’s being explored as a possible explanation for the immune benefits we see with medicinal mushroom species like Reishii and Shiitake mushrooms. This is just one of the many ways medicinal mushroom species serve to support immune function.
Partially Hydrolysed Guar Gum (PHGG): Our intestinal bacteria use PHGG as a food source, and as a byproduct, they produce the short-chain fatty acid butyric acid. Butyric acid helps to promote secretory IgA production, and this is how soluble fibres like PHGG can have a beneficial effect on immunity both within and outside of their gut-regulating benefits.
Zinc & Selenium: These are two important minerals involved as co-factors in many pathways of our body and they play a role in supporting our immunity. Studies have shown that people with low secretory IgA are often deficient in zinc and selenium and that supplementation may help improve SIgA.
Secretory IgA and the The Gut-Brain Connection.
Secretory IgA plays a crucial role in maintaining gut health and supporting overall immunity and wellbeing. It acts as a frontline defender, protecting the mucosal surfaces of the body and promoting a healthy gut barrier. By regulating the immune response, influencing the gut microbiota, and enhancing immune tolerance, secretory IgA contributes significantly to optimal immune function which may offer protective benefits against inflammatory triggers that can place us at risk of neuroinflammation.
The gut and the brain are intricately connected through the network of nerves lining the gastrointestinal tract. If our gut is better equipped to defend us from pathogenic invaders and allergic triggers through the action of secretory IgA, it can have a positive impact on our brain health as well. Studies have shown that disruptions in the gut microbiota and increased intestinal permeability, often referred to as "leaky gut," can contribute to systemic inflammation and neuroinflammation. Neuroinflammation has been linked to various neurological conditions, including depression, anxiety, and cognitive decline. By promoting a robust gut barrier, modulating immune responses, and shaping the gut microbiota, secretory IgA actively participates in the gut-brain axis, supporting both gut health and brain health.
.
.
.
.
.
REFERENCES
Jemmott JB 3rd, et al. Academic stress, power motivation, and decrease in secretion rate of salivary secretory immunoglobulin A. Lancet. 1983 Jun 25;1(8339):1400-2.
Ng V, et al. Stressful life events of dental students and salivary immunoglobulin A. Int J Immunopathol Pharmacol. 2004 May-Aug;17(2 Suppl):49-56.
Otsuki T, et al. Secretory IgA in saliva and academic stress. Int J Immunopathol Pharmacol. 2004 May-Aug;17(2 Suppl):45-8.
Engeland CG, et al. Psychological distress and salivary secretory immunity. Brain Behav Immun. 2016 Feb;52:11-17.
Qamar A, et al. Saccharomyces boulardii stimulates intestinal immunoglobulin a immune response to Clostridium difficile toxin A in mice. Infect Immun 2001;69(4):2762–5.
McFarland LV. Systematic review and meta-analysis of saccharomyces boulardii in adult patients. World J Gastroenterol; 2010 May 14;16(18):2202–22.
Buts JP, et al. Stimulation of secretory IgA and secretory component of immunoglobulins in small intestine of rats treated withSaccharomyces boulardii. Digest Dis Sci 1990:35:251–256.
Ash M. Vitamin A: The Key to a tolerant immune system? Clin Ed. 2010 August.
Macpherson AJ, Slack E. The functional interactions of commensal bacteria with intestinal secretory IgA. Curr Opin Gastroenterol. 2007 Nov;23(6):673-8.
Fan X, et al. Vitamin A Deficiency Impairs Mucin Expression and Suppresses the Mucosal Immune Function of the Respiratory Tract in Chicks. PLoS One. 2015 Sep 30;10(9):e0139131.
Dai X, et al. Consuming Lentinula edodes (Shiitake) Mushrooms Daily Improves Human Immunity: A Randomized Dietary Intervention in Healthy Young Adults. J Am Coll Nutr. 2015;34(6):478-87.
Kubota A, et al. Reishi mushroom Ganoderma lucidum Modulates IgA production and alpha-defensin expression in the rat small intestine. J Ethnopharmacol. 2018 Mar 25;214:240-243.
Sakai S, et al. Continuous partially hydrolyzed guar gum intake reduces cold-like symptoms: a randomized, placebo-controlled, double-blinded trial in healthy adults. Eur Rev Med Pharmacol Sci. 2022 Jul;26(14):5154-5163.
Abu Jamra SR, et al. Proposal to Screen for Zinc and Selenium in Patients with IgA Deficiency. Nutrients. 2023 Apr 29;15(9):2145.