What is Secretory immunoglobulin A (sIgA)?

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

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.

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 – 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, according to the Genova Diagnostics lab.

SIgA production is both beneficially and adversely affected by a number of factors including stress, emotions such as frustration and anger, 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 that even a relatively short-term sIgA deficiency due to acute stress predisposes a person to the development of food allergies or sensitivities, or to being susceptible to having pathogens in the GIT. When sIgA is lacking, absorption of food particles and microbial antigens increases dramatically making the GIT increasingly susceptible to infection.

It’s known that people with food sensitivities – and especially food allergies – have low levels of sIgA making them particularly susceptible to gut damage and increase in immune response reactions, as sIgA ‘tags’ food as acceptable, so low sIgA leads to increased sensitivity to foods.

Low / reduced sIgA levels

Are commonly seen in individuals with:

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

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

Despite the importance of sIgA for health, it’s one of the least well-understood areas of immunology. 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 diets, nutrient deficiencies, certain drugs (including anti-inflammatories), viruses, impaired immune function and 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.

Symptoms of sIgA deficiency

Many people with sIgA deficiency are asymptomatic. It’s not understood why some individuals with sIgA deficiency have almost no complaints while sIgA structureothers 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 allergies or sensitivities, 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 sIgA 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.


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 suggestions below:

  • Embark on a comprehensive gut treatment to repair and seal the gut wall involving correcting gut flora imbalances, 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 – test the immune function, inflammation levels and other relevant parameters, and then embark on eradicating 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 allergies/ 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 through 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:
  • GAPS diet is highly indicated and effective 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 sIgA 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 sIgA for overall health. Consider subscribing to my blog updates below to keep up to date.

Good health and blessings
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Joanna Sochan
Holistic Health and Lifestyle Therapist
Natural and Lifestyle Solutions for Chronic Diseases

sIgA image source: Dolphin Microbiology Group website

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Joanna Sochan is a Natural Therapist and founder of Naturimedica Holistic Health & Wellness. She has a passion for helping her clients transform their lives by becoming healthy and well naturally. Joanna is a fatigue, sleep and gut health expert helping tired, stressed or unwell individuals to regain their energy, sleep better and be happier, more relaxed and calm. Joanna practices in Sydney and Lake Macquarie, Australia and also conducts online consultations for clients Australia-wide. View full bio.