Secretory immunoglobulin A (sIgA) deficiency is a less known but a significant aspect of having good immunity and a well-functioning digestive system.

I’ve long been interested in sIgA’s role in health and wellbeing, and would like to shed some light on this subject based on my clinical experience and research. The importance of sIgA for effective immune defence is indicated by the fact that more sIgA is produced than all the other immunoglobulin classes combined. 

Despite the importance of sIgA for health, it’s one of the least well-understood areas of immunology.

What is Secretory Immunoglobulin A (sIgA)?

The body’s mucosal surfaces such as those of the nose, throat, eyes and gastrointestinal tract (GIT) are a large point of entry for various pathogens and thus must be well protected by the body.

The primary antibody/ immune system response to these irritants at the mucosal level is sIgA produced by the B lymphocytes (immune system cells) present in all mucosal linings.

sIgA acts as the ‘first line of defence’ helping to protect against the entrance of foreign substances or organisms into the body such bacteria, viruses, fungi, parasites and food particles (via the damaged gut wall caused by the leaky gut syndrome).

The immune system responds to the protein component (antigens) of these invaders by producing large quantities of specific antibodies, including sIgA. These antibodies bind to the antigens on the surface of an invader (bacteria, for example) and prevent them from multiplying, thus halting the spread of disease in the body.

This mechanism works well when the GIT is healthy and sIgA levels are normal.

The daily production of sIgA is weight and age dependent with the maximum production level being reached at the age of 7-10 which then declines with age, especially after 60 years of age. It’s been calculated that around 60 mg of IgA is produced per kilogram of body weight per day in the average human, mainly in the mucosal surfaces of the body.  These surfaces, which collectively have a surface area in adult humans of around 400 m2, are major sites of vulnerability, given their exposure to the environment.

sIgA production is both beneficially and adversely affected by a number of factors including stress, emotions such as frustration and anger, as well as nutrition, pathogens and inflammation. In particular, chronic and repeated bouts of acute stress suppress sIgA over time compromising the gut and the immune function.

We know from research that even a relatively short-term sIgA deficiency due to acute stress predisposes a person to the development of food intolerances or sensitivities, or to being susceptible to having pathogens in the GIT. When sIgA is low or lacking, absorption of food particles and microbial antigens increases dramatically making the GIT increasingly susceptible to infection.

People with food sensitivities, and especially food intolerances or allergies, have low levels of sIgA making them particularly susceptible to gut damage and increase in immune response reactions. sIgA ‘tags’ food as acceptable or not, so low sIgA leads to increased sensitivity to foods.

Causes of low sIGA

Medical research suggests that sIgA deficiency can be the result of genetics i.e. it’s an inherited disease that is passed from parent to child.

Some people can also have a partial sIgA deficiency which isn’t genetic and is caused by environmental or lifestyle factors such as;

  • Poor diet
  • Nutrient deficiencies
  • Certain drugs (including anti-inflammatories)
  • Viruses and impaired immune function
  • Excessive stress

The good news is that the environmental and lifestyle factors can be reversed by identifying and addressing the cause(s) via better diet, tailored supplements and lifestyle modifications, as discussed below.

Low/ reduced sIgA levels

These are commonly seen in individuals with:

  • Depleted immune system
  • Food intolerances, allergies or sensitivities e.g. present in people who are “reacting to everything”
  • Small intestine bacterial overgrowth (SIBO)
  • Chronic Candida or small intestine fungal overgrowth (SIFO)
  • Coeliac disease
  • Inflammatory bowel diseases – ulcerative colitis, Crohn’s disease
  • Parasitic infections
  • Stress – several studies link stress and negative emotion with low levels of sIgAs. Secretion is adversely affected by stress which is mediated by cortisol produced by the adrenal glands. Therefore low sIgA levels are often present in burnout/ adrenal fatigue/ adrenal exhaustion when cortisol levels are low.

High/ elevated sIgA levels

May reflect the following:

  • An activated immune response to chronic infections including viral infections such as EBV (Epstein–Barr virus), CMV (Cytomegalovirus), HIV, and/ or inflammatory reactions.
  • High level of sIgA may also indicate an infection of the digestive system or inflammatory conditions such as Crohn’s disease or ulcerative colitis.

It’s thought that the initial immune response to the pathogens or inflammation is an elevation in sIgA, followed by its depletion with continued exposure to irritants. Dysregulation of this immune function has also been implicated in autoimmune and chronic inflammatory conditions.

Symptoms of sIgA deficiency

secretory immunoglobulin A structure

Many people with sIgA deficiency are asymptomatic. It’s not understood why some individuals with sIgA deficiency have almost no complaints while others are quite sick.

Those who do have symptoms typically have recurring ear, sinus, or lung infections that may not respond to regular treatment even with antibiotics.

Other problems include multiple food intolerances/ sensitivities or allergies, coeliac disease, asthma, chronic diarrhoea, and autoimmune diseases such as lupus and rheumatoid arthritis.

Since sIgA serves to protect the gut, lower levels can also lead to an increased risk of ‘leaky gut’ (or increased intestinal permeability), dysbiosis or SIBO.

When secretory immunoglobulin A is decreased and is unable to adequately fight invaders attacking the intestinal wall, the gut becomes inflamed and irritated resulting in the integrity of the gut wall becoming weakened, allowing toxins or undigested food particles to enter the body via the blood stream.

These food particles cause the body to react by creating other classes of immunoglobulins, primarily IgG, to protect the blood and tissues. A person with leaky gut may therefore have IgG reactions to many foods which can be detected in blood tests.

Testing

sIgA levels can be tested by performing a blood test measuring serum IgA, salivary or fecal sIgA tests. When measured via the comprehensive diagnostic stool analysis test, the reference range of sIgA is between 51 – 204mg/dL (Genova Lab range). Different labs use different ranges according to the type of test performed.

How to normalise sIgA levels

Conventional medicine doesn’t offer any particular treatment; however, there is much that can be done to balance out sIgA levels by following naturopathic medicine therapies below:

  • Embark on a comprehensive gut treatment to repair and seal the gut wall involving correcting gut flora imbalances, decreasing food sensitivities, decreasing inflammation and restoring gut wall integrity.
  • Eliminate food allergies and intestinal parasites – using medications and/ or anti-parasitic herbs and supplements. In clinical practice a combined approach is often quite effective.
  • Enhance the immune function – using herbs, supplements, lifestyle modifications and stress reduction.
  • Address any existing acute and/or chronic infections anywhere in the body –  by testing the immune function, inflammation levels and other relevant parameters, and then embark on improving them with medications, supplements and herbs, as appropriate.
  • Reduce stress – stress is particularly detrimental to sIgA levels and stressful events contribute to development of adrenal fatigue (exhaustion or burnout), worsen GIT function and food sensitivities in vast majority of people. Lower levels are found in those with excessive cortisol production which correlates with increased stress levels, so decreasing stress will lead to higher sIgA levels.
  • Check for vitamin A deficiency – vitamin A is known for its protective roles against infections. An important part of the protective function is its ability to enhance antibody responses, especially IgA antibody responses in mucosal tissues. Adequate vitamin A from animal sources such as cod liver oil, combined with good quality probiotics, and sIgA support with Sacharomyces boulardii (S. boulardii) probiotic strain (which increases sIgA production) are important steps in restoring immunological health.
  • Helpful supplements and foods include:
  • Use specific probiotics that have been studied to date to increase sIgA levels including:
  • GAPS diet or an elimination diet based on the IgG food sensitivities testing are effective strategies for healing the gut, normalising digestion, addressing nutrient deficiencies and reducing inflammation, among others.

Feel free to post a comment below if you have abnormal levels of secretory immunoglobulin A and would like to exchange ideas on potential natural solutions for this complex issue.

I update this post regularly as new information and studies reveal more about the role and importance of secretory immunoglobulin A for overall health. Consider subscribing to my newsletter to keep up to date (see the right side column of this blog to subscribe).

Please note that the above material is for informational and educational purposes only and is not intended as a substitute for medical advice, diagnosis, or treatment. Consult with your health practitioner or doctor for advice specific to your circumstances.

Best of Health
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Joanna Sochan
Wholistic Health and Lifestyle Therapist
Natural and Lifestyle Therapies for Abundant Health and Wellbeing

sIgA image source: Dolphin Microbiology Group website

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Disclaimer: The above material is for informational and/or educational purposes only. It should not be used to self-diagnose and it is not a substitute for a medical advice, diagnosis, treatment, prescription or recommendation. All viewers of this content, especially those taking prescription or over-the-counter medications, should not make any changes in their health regimen or diet before first consulting a doctor or other qualified health provider with any questions they may have regarding a medical condition or their particular circumstances.

Joanna Sochan is a Natural Therapist and founder of Naturimedica Holistic Wellcare. She has a passion for helping clients transform their lives by becoming healthy and well naturally. Joanna has 12+ years experience in clinical practice and has special interest in solving complex cases, functional medicine testing, gut health, sleep, fatigue and chronic pain. She guides clients through her tailored programs and eCourses as well as helping them individually (mostly online) Australia-wide. View full bio.

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