Secretory IgA (sIgA): What Low and High Levels Can Tell You About Gut Health

Secretory immunoglobulin A, usually shortened to secretory IgA or sIgA, is one of the most important parts of the immune defence system protecting the surfaces of the digestive tract. But sIgA does much more than simply fight infections.

It works at the interface between your immune system, intestinal lining and gut microbiome, helping your body manage the microbes, food particles and other substances it encounters every day. For this reason, sIgA is sometimes measured as part of comprehensive stool testing. When the result is unusually low or high, it can provide a useful clue that something within the gut environment deserves further investigation.

However, an abnormal sIgA result is a red flag, not a diagnosis. Low sIgA does not automatically mean poor immunity, and high sIgA does not necessarily mean that you have an infection or inflammatory condition. The result needs to be interpreted alongside your symptoms, health history and other gut markers.

The more useful question is not simply: “How can I increase or decrease my sIgA?” It is: “Why might my sIgA be abnormal, and what does the rest of my health picture tell us?”

That is where we begin to connect the dots.

Article update: First published in 2015, this article has been substantially reviewed and updated in 2026 to reflect current research and my evolving clinical understanding of secretory IgA, mucosal immunity and gut health. It now includes expanded information on interpreting low and high faecal sIgA, laboratory testing, the gut microbiome, intestinal barrier function, stress and practical support.

Quick Answer: What Is Secretory IgA?

Secretory IgA is an antibody found predominantly in the secretions that protect the body’s mucosal surfaces, including the digestive, respiratory and genitourinary tracts, as well as saliva and breast milk. In the gut, sIgA forms part of the body’s mucosal immune system, the specialised immune defence that operates along the intestinal lining. Its functions include helping to:

• Bind potentially harmful microbes and toxins
• Prevent some microorganisms from attaching to and penetrating the intestinal lining
• Trap antigens and microbes within the mucus layer so they can be removed
• Regulate interactions between the immune system and the gut microbiome
• Support immune tolerance and intestinal homeostasis

This process is sometimes described as immune exclusion: the immune system helps contain potentially problematic material before it crosses the intestinal barrier and provokes a larger inflammatory response. Modern research therefore gives us a much more sophisticated picture of sIgA than simply describing it as the gut’s “first line of defence.” It also helps us live successfully with the enormous microbial community inside the gut.

What Does sIgA Actually Do in the Gut?

The intestinal lining has a difficult job. It needs to allow nutrients and other useful substances to pass through while keeping potentially harmful microbes, toxins and antigens where they belong. At the same time, the immune system must avoid mounting unnecessary inflammatory responses against harmless food components and the many microorganisms that normally live in the digestive tract. sIgA helps maintain this balance.

It interacts with bacteria and other antigens within the intestinal lumen and mucus layer, helping limit direct contact between microbes and the epithelial cells lining the intestine. Research also shows that IgA helps shape the composition, location and behaviour of the intestinal microbiota. This relationship works in both directions:

The gut microbiome helps influence IgA production, while IgA helps regulate the microbiome. This is why I prefer to think about sIgA as part of a much larger mucosal ecosystem rather than as an isolated immune marker. Healthy mucosal immunity depends on an ecosystem, not one laboratory marker. sIgA works alongside:

• The mucus layer: This provides a physical and biochemical barrier between intestinal microbes and the cells lining the gut.
• The intestinal epithelium: These tightly connected cells control what crosses from the gut into the body.
• The gut microbiome: Resident microorganisms communicate continuously with both the intestinal lining and immune system.
• The mucosal immune system: Immune cells and signalling molecules determine when to tolerate, contain or respond to what the gut encounters.

These systems influence one another constantly. When we find an abnormal sIgA result, therefore, we should not immediately ask which supplement will “fix” it. We need to consider what may be happening within this wider intestinal environment.

The terrain matters.

By “the terrain”, I mean the wider environment in which the gut and immune system are functioning: the microbiome, mucus layer, intestinal barrier, nutritional status, inflammation, nervous system and other factors that influence mucosal health. Rather than focusing on one organism or laboratory marker in isolation, we look at the conditions surrounding it and how those different pieces interact.

Serum IgA, Salivary sIgA and Faecal sIgA Are Not the Same Test

This distinction is particularly important because the term IgA is often used as though every IgA measurement tells us the same thing. It does not. IgA can be measured in blood as well as in mucosal secretions such as saliva and stool. These measurements provide different information and should not be used interchangeably.

Understanding Different IgA Measurements

Measurement	What it reflects	Common use	Important limitation
Serum IgA	IgA circulating in the blood	Conventional medical assessment of immune function, including investigation of IgA deficiency	Does not directly measure intestinal sIgA
Salivary sIgA	IgA secreted at oral/upper mucosal surfaces	Frequently used in research examining stress, exercise and mucosal immunity	Cannot be assumed to represent faecal sIgA
Faecal sIgA	Secretory IgA recovered from intestinal contents	Used in some comprehensive stool tests to assess aspects of intestinal mucosal immune activity	Must be interpreted using the laboratory’s own method and reference range

This distinction becomes particularly important when reading research. For example, much of the research examining the relationship between stress and sIgA measures salivary sIgA. Those findings can help us understand mucosal immune physiology, but we should not automatically assume that the same numerical changes occur in faecal sIgA.

Is Low Faecal sIgA the Same as IgA Deficiency?

No. This is an important distinction.

Selective IgA deficiency is a recognised medical immunodeficiency diagnosed using serum IgA in the blood, together with other immunological criteria. It is not diagnosed from a low faecal sIgA result. International consensus defines selective IgA deficiency in people over four years of age as serum IgA below 7 mg/dL (0.07 g/L) with normal levels of IgG and IgM after other causes have been excluded.

IgG and IgM are other major classes of antibodies (immunoglobulins). IgG is the most abundant antibody in the blood and provides an important part of longer-term immune protection, while IgM is often produced early in an immune response. Measuring these alongside IgA helps clinicians determine whether an abnormal result is isolated to IgA or forms part of a broader immune problem.

People with selective IgA deficiency may experience recurrent respiratory or gastrointestinal infections, allergies or autoimmune conditions, although some people have few or no symptoms. A low faecal sIgA result therefore should not be interpreted as evidence that you have selective IgA deficiency.

If your health history suggests a broader immune deficiency, this requires appropriate medical investigation rather than interpretation of a stool result alone.

Understanding Your Faecal sIgA Test Result

Faecal sIgA is included in a number of comprehensive stool tests used in functional and integrative healthcare. One of the most common questions I have received over the years is: “My sIgA is 400… 800… 2,500… what does that mean?”

The number alone is not enough. Before interpreting a result, we need to know:

1. Which laboratory performed the test?
2. What units did the laboratory use?
3. What reference range appears on that particular report?
4. What other gut markers were abnormal?
5. What symptoms and health history accompany the result?

This is especially important because laboratories use different testing methods, units and reference intervals.

Examples of Faecal sIgA Reference Ranges

Laboratory / Test	Example Reference Range	Units
Genova Diagnostics: GI Effects	≤2,040	mcg/mL
Diagnostic Solutions Laboratory: GI-MAP	510–2,010	µg/g
NutriPath Pathology	510–2,040	ng/mL

Genova’s current GI Effects reporting also graphically displays approximately 680–2,040 mcg/mL within its reference distribution. Diagnostic Solutions currently reports 510–2,010 µg/g for GI-MAP. The NutriPath range above is from current laboratory reporting.

Why You Shouldn’t Compare Your Number With Someone Else’s

Notice something interesting about the table. The Diagnostic Solutions and NutriPath ranges look remarkably similar numerically: 510–2,010 versus 510–2,040. But one is expressed as µg/g and the other as ng/mL. Those numbers therefore cannot simply be compared as though they represent the same measurement. The same problem occurs when people compare current results with older stool tests. Laboratory methods, reporting units and reference ranges can change over time.

Important: Always interpret your sIgA result using the reference range provided by the laboratory that performed your test. Results from different laboratories should not be directly compared.

So What Does the Number Actually Tell Us?

This is where sIgA becomes clinically useful. I don’t regard an abnormal faecal sIgA result as less important simply because it cannot diagnose a particular disease. Quite the opposite.

When sIgA is clearly outside the laboratory reference range, I regard it as a red flag that something within the mucosal immune environment may deserve further investigation. The result may lead us to look more closely at:

• The microbiome
• Gastrointestinal infections or parasites
• Inflammatory and intestinal barrier markers
• Nutritional status
• Stress and nervous system influences
• Medications
• Symptoms, health history and other stool test findings

The aim is not to diagnose from the sIgA number. It is to ask: What else is happening here? A low or high sIgA result can take on very different significance depending on what appears alongside it.

What Does Low sIgA Mean?

A low faecal sIgA result suggests that mucosal immune activity or secretory defence may be reduced at the time of testing. Because sIgA helps limit contact between microbes, antigens and the intestinal lining, persistently low levels may leave one part of the gut’s protective system less effective. However, a low result does not tell us why this has happened. This is where we need to look beyond the number.

Low sIgA may occur alongside or prompt us to investigate factors such as:

• Altered gut microbiome or dysbiosis
• Gastrointestinal infections or persistent microbial challenges
• Nutritional inadequacy
• Prolonged physiological or psychological stress
• Disturbances in the intestinal barrier
• Medications that influence immune or inflammatory activity
• Wider immune dysfunction in appropriate clinical circumstances.

Because the microbiome and IgA influence one another, low sIgA and an unhealthy gut environment can potentially reinforce each other rather than fitting neatly into a single cause-and-effect sequence.

Does Low sIgA Mean Your Immunity Is Low?

Not necessarily. It is tempting to translate a low result into “low immunity”, but the immune system is far too complex for this. Faecal sIgA tells us about one aspect of intestinal mucosal immunity. It does not measure the strength of your entire immune system. However, when a low result occurs alongside recurrent gastrointestinal infections, persistent dysbiosis, nutritional deficiencies or other relevant findings, reduced mucosal immune resilience becomes more clinically meaningful. This distinction can be particularly useful with gastrointestinal infections and parasites.

sIgA and Giardia

Giardia (Giardia lamblia), an infection is quite often seen in practice, is a good example of why both the organism and the host environment matter. An effective mucosal immune response, including IgA activity, contributes to the body’s defence against intestinal pathogens. If someone has persistent or recurrent infection together with low sIgA and other signs of disturbed gut health, I would want to consider not only: “What organism is present?” but also: “How well is this person’s gut environment able to respond to it?”

A low sIgA result does not diagnose Giardia, nor does it prove that low sIgA caused the infection. The immune response to Giardia can also vary with the stage and circumstances of infection. But clinically, the combination can provide another clue that the host’s mucosal defences and wider gut terrain deserve attention.

This is an important distinction. Treating an infection is one part of the picture. Supporting the environment in which normal microbial and immune regulation can recover may be another.

What Does High sIgA Mean?

High sIgA deserves just as much attention as low sIgA. An elevated result may indicate that the mucosal immune system is more actively responding to something within the gut environment. Possible reasons to investigate include:

• Increased exposure to microbial or dietary antigens
• Gastrointestinal infection or pathogen exposure
• Dysbiosis or altered microbial ecology
• Intestinal inflammation
• Other forms of ongoing mucosal immune stimulation

Again, the result does not identify the cause. A high sIgA result cannot tell us which microorganism is involved, whether someone has inflammatory bowel disease or increased intestinal permeability, or whether a particular food is causing symptoms. It tells us that we may need to look further.

This is why I do not think of sIgA as a marker where higher is always better. Healthy mucosal immunity depends on an appropriate and regulated response. Too little activity may leave mucosal defences less effective, while increased activity may indicate that the immune system is responding to a challenge.

The goal is balance, not simply a higher number.

Low or High sIgA: What Should We Investigate?

An abnormal result becomes much more useful when we connect it with other information.

Finding or clinical context	Why it may matter	What sIgA cannot tell us
Dysbiosis / altered microbiome	IgA and the microbiome regulate one another	Which microorganisms are responsible
Gastrointestinal infection	Pathogens can stimulate mucosal immune responses	Which infection is present
Parasites, including Giardia	Mucosal immunity contributes to defence against intestinal parasites	Whether a parasite is present or causing symptoms
Fungal/yeast imbalance	IgA participates in host-microbial interactions, including fungal ecology	Whether Candida or SIFO is present
Intestinal barrier dysfunction	sIgA forms part of the wider mucosal barrier system	Whether intestinal permeability is increased
Coeliac disease	IgA responses are important in coeliac disease and its conventional testing	Whether someone has coeliac disease
IBD / intestinal inflammation	Inflammation can alter the mucosal immune environment	Whether Crohn’s disease or ulcerative colitis is present
Stress	Nervous, endocrine and immune signalling can influence mucosal immunity	Whether cortisol is “high” or “low”
Nutritional inadequacy	Normal immune and epithelial function require adequate nutritional resources	Which nutrients are deficient

This is also why other markers on a comprehensive stool test matter.

For example, when significant intestinal inflammation is suspected, faecal calprotectin is a much more established marker of intestinal inflammation than sIgA. Likewise, suspected coeliac disease, parasites or other gastrointestinal disorders require the appropriate investigations. sIgA can contribute context, but should not be asked to perform a diagnostic job better suited to another test.

sIgA, Intestinal Permeability and the Gut Barrier

sIgA is closely connected with intestinal barrier function, but the relationship is more complex than the old idea that: low sIgA = leaky gut. The intestinal barrier is not a single wall. It is a coordinated defence system involving:

• The gut microbiome
• The mucus layer
• Secretory antibodies such as sIgA
• Intestinal epithelial cells and their tight junctions
• Antimicrobial substances
• Immune cells and signalling molecules

sIgA contributes to this defence by binding microbes and antigens and helping limit their contact with and penetration through the intestinal epithelium. It can also trap material within mucus and facilitate its removal.

Can Low sIgA Contribute to Increased Intestinal Permeability?

Potentially, but it is better to think of low sIgA as one possible weakness within the wider mucosal defence system rather than a direct cause of increased intestinal permeability. If sIgA-mediated immune exclusion is reduced, microbes and antigens may have greater opportunity to interact with the epithelial surface. What happens next also depends on factors such as dysbiosis, inflammation, mucus integrity and tight-junction function.

Research in IgA deficiency supports the broader principle that impaired IgA-mediated mucosal defence can alter microbial containment and antigen handling. But a low faecal sIgA result does not prove someone has a “leaky gut.”

What About High sIgA?

High sIgA can also occur alongside barrier and microbiome disturbances. Greater exposure to microbial or other antigens may stimulate mucosal immune activity, so an inflamed, infected or dysbiotic gut environment may sometimes be accompanied by elevated rather than depleted sIgA. This reinforces an important point: neither low nor high sIgA diagnoses intestinal permeability. Instead, the result can help us decide whether the wider gut environment deserves further investigation.

Stress, the Nervous System and sIgA

Stress belongs in this article, but our understanding of the relationship between stress and sIgA has changed considerably over time. The digestive tract is in constant communication with the nervous, endocrine and immune systems through the gut-brain axis. Stress-related signalling through the autonomic nervous system, hypothalamic-pituitary-adrenal (HPA) axis and other pathways can therefore influence intestinal immune function. Research examining intestinal sIgA supports this biological connection, although much of the mechanistic evidence comes from animal studies.

However, the relationship is not as simple as: more stress → more cortisol → lower sIgA.

Acute and Prolonged Stress Can Behave Differently

Much of the human stress research has measured salivary rather than faecal sIgA, so we need to be careful not to treat the two measurements as interchangeable. Nevertheless, this research demonstrates something important about mucosal immunity: timing matters.

A 2024 meta-analysis of 1,025 adults found that acute psychological stress produced a temporary increase in salivary sIgA, peaking shortly after the stressor before returning towards baseline. Earlier research has also distinguished between immediate responses to stress, which may increase salivary sIgA, and delayed or prolonged stress responses, which may be associated with lower secretion. So, sIgA is better understood as part of a dynamic stress-response system rather than a simple marker of “high” or “low” cortisol.

Why Stress Still Matters for Gut Health

Although we cannot use a stool sIgA result to diagnose stress or adrenal function, prolonged stress can influence digestive function, gut motility, microbial ecology, immune signalling, sleep and intestinal barrier function. This is why stress regulation remains an important part of supporting gut health. The nervous system is part of the terrain in which the gut and immune system operate. Supporting nervous system regulation can therefore help create better conditions for digestive, microbial and immune functions to work together.

How Can We Support Healthy sIgA and Mucosal Immunity?

If your sIgA result is outside the laboratory reference range, it can be tempting to search for a supplement that will raise or lower the number. A more useful approach is to identify what may be contributing to the imbalance and support the wider mucosal environment. The following five steps provide a practical way to approach this.

Step 1: Investigate and Address the Underlying Drivers

The first question is not: “What can I take for my sIgA?” It is: “Why might my sIgA be abnormal?” Depending on your symptoms, health history and other test findings, this may involve investigating:

• Dysbiosis or significant changes in the gut microbiome
• Bacterial, parasitic or other gastrointestinal infections
• Intestinal inflammation
• Digestive dysfunction
• Intestinal barrier disturbances
• Nutritional inadequacies
• Medication effects
• Prolonged stress and other lifestyle influences

The significance of an abnormal sIgA result depends on what appears alongside it. A detected pathogen, for example, presents a different clinical picture from an isolated abnormal sIgA result, while elevated calprotectin warrants appropriate investigation for intestinal inflammation.

Treat what you find, rather than treating the sIgA number in isolation.

Step 2: Feed and Support the Gut Ecosystem

What we eat helps shape the microbial environment in which mucosal immunity operates. A varied, minimally processed diet containing plenty of plant foods provides different fibres and other compounds that can be used by gut microorganisms. Of particular interest are soluble and fermentable fibres. Many of these fibres are fermented by gut bacteria to produce short-chain fatty acids such as acetate, propionate and butyrate. These microbial metabolites communicate with intestinal and immune cells and help support the mucus layer and intestinal barrier.

Human research suggests that some prebiotic fibres can influence sIgA. In one controlled study, 12 weeks of galactooligosaccharides increased bifidobacteria and faecal sIgA in overweight adults. Other prebiotic studies have not produced the same response, reminding us that different fibres can have different effects. Useful food sources of soluble and fermentable fibres include:

• Oats and barley
• Beans and legumes
• Vegetables
• Fruit
• Nuts and seeds
• Resistant starch from foods such as cooked and cooled potatoes or rice
• Prebiotic-rich foods such as onions, garlic, leeks and asparagus

The goal is not to find the one “best” fibre for sIgA. It is to feed a diverse microbial ecosystem. For people with significant bloating, IBS or other digestive problems, fibre may need to be increased gradually according to individual tolerance. Fermented foods can also contribute useful microorganisms and fermentation products where they are well tolerated, although they should not be presented as a direct treatment for abnormal sIgA.

Explore our gut health and the microbiome support article: How to Improve Gut Health Naturally: Why 30 Plant Foods Per Week Changes Everything.

Step 3: Build the Nutritional Foundations for Mucosal Immunity

Normal immune function and intestinal repair require adequate nutritional resources. This is especially important in people who have progressively restricted their diets because of digestive symptoms or suspected food reactions. Removing more and more foods can sometimes reduce the very nutritional diversity needed to support recovery.

Protein

Adequate protein provides amino acids needed for immune proteins, enzymes, tissue repair and continuous renewal of the intestinal lining. Before adding an extensive supplement programme, it is worth asking a very basic question: Is the person eating enough nourishing food and adequate protein?

Vitamin A

Vitamin A has an important role in mucosal immunity, epithelial integrity and the regulation of intestinal IgA responses. I generally prefer to obtain vitamin A from food wherever possible. Sources include liver, eggs, dairy foods and oily fish, while colourful vegetables provide carotenoids that the body can convert to vitamin A. Cod liver oil is another concentrated source of preformed vitamin A, but amounts vary between products and more is not necessarily better. Preformed vitamin A can accumulate in the body, so total intake and individual circumstances matter.

Read more: Vitamin A: What You Must Know About This Vital Nutrient.

Zinc and Vitamin C

Zinc supports innate and adaptive immunity, tissue repair and intestinal barrier function, while vitamin C contributes to normal immune-cell function and antioxidant defence. Neither is a specific treatment for low sIgA. The aim is to ensure adequate intake and correct deficiency where it exists.

Read more: Natural Antibiotics and Immune Support.

Step 4: Consider Targeted Gut Support Where Appropriate

Once the foundations and likely drivers have been considered, some people may benefit from more targeted gut support. This should be guided by the individual pattern rather than assuming that everyone with abnormal sIgA needs the same probiotic or supplement.

Probiotics: Which One, for Whom and Why?

Our understanding of probiotics has changed considerably. The old question was often: “Should I take a probiotic?” A better question is: “Which strain or combination is appropriate for what we are trying to achieve?”

Probiotic effects can be strain-specific, and response may also depend on the person’s existing microbiome, diet and health status. For example, Bifidobacterium animalis subsp. lactis BB-12 is one of the better researched probiotic strains, and human research has found that it can influence immune responses, including faecal sIgA in some populations. Other probiotic and synbiotic interventions have produced different results.

The emerging message is therefore not: “Everyone with low sIgA needs probiotics.” It is: Use probiotics purposefully, with attention to the strain, the person and the clinical objective.”

Saccharomyces boulardii

Saccharomyces boulardii is a beneficial yeast rather than a bacterium and has been used extensively in gastrointestinal health. Experimental research suggests that S. boulardii can influence intestinal immune responses, including IgA responses, but human evidence showing that it directly normalisesphospho abnormal faecal sIgA remains limited. Its value may therefore be broader than simply increasing sIgA.

Glutamine

Glutamine is an important fuel and metabolic substrate for intestinal cells and has a role in maintaining intestinal barrier integrity. It is commonly used clinically where intestinal permeability and mucosal integrity are concerns. Human trial evidence is mixed, with a recent meta-analysis finding no significant overall improvement in intestinal permeability, although some subgroups appeared to benefit. I therefore regard glutamine as a potential gut-barrier support tool where clinically appropriate, rather than a proven treatment for low sIgA.

Phosphatidylcholine

Phosphatidylcholine is an important component of cell membranes and the protective mucus layer of the gastrointestinal tract.It contributes to the intestinal surface barrier and may therefore have a role in targeted mucosal support. Its relevance here is not as a treatment for abnormal sIgA, but as another example of how mucosal health depends on more than antibodies alone.

Step 5: Support the Wider Terrain

The intestinal immune system does not operate independently from the rest of the body. Stress, sleep, circadian rhythms, movement and nutrition all influence the environment in which digestion and immune regulation occur. The aim is not to use lifestyle strategies to manipulate sIgA directly, but to support the whole person and the conditions in which healthy mucosal immunity operates.

Stress and Nervous System Regulation

Reducing prolonged physiological load and supporting nervous system regulation can form part of the wider gut-health foundation. Regular outdoor time, relaxation practices, breathing exercises, enjoyable movement, social connection and adequate recovery can all help support this wider terrain.

Sleep and Circadian Health

Immune function follows biological rhythms, and salivary sIgA itself shows circadian variation. Regular sleep-wake timing, morning outdoor light, daylight exposure during the day and reducing excessive bright light at night help reinforce healthy circadian signals. These habits are not an “sIgA treatment”. They help provide the biological conditions in which immune, metabolic, digestive and hormonal systems can coordinate effectively.

Regular Movement

Regular physical activity supports metabolic, immune and digestive health. Very intense or prolonged exercise can temporarily alter mucosal immune markers, including salivary sIgA, so more is not automatically better. For most people, regular movement balanced with adequate recovery is the more useful foundation.

The Bigger Picture

Supporting healthy sIgA is not about assembling a long list of immune supplements. It is about asking:

• What is disturbing the gut environment?
• What foundations are missing?
• Is targeted support actually warranted?

This reflects the approach I use throughout Naturimedica: See the Whole Person. Build Strong Foundations. Live Well.

When we understand the whole picture, an abnormal marker such as sIgA can become a meaningful place to begin investigating rather than a number to chase.

When Does an Abnormal sIgA Result Need Further Investigation?

An abnormal sIgA result does not usually provide a diagnosis by itself, but symptoms and other findings may indicate that further medical investigation is appropriate. Seek appropriate medical assessment if you have symptoms such as:

• Persistent or severe diarrhoea
• Blood in the stool
• Unexplained weight loss
• Persistent fever
• Significant or worsening abdominal pain
• Recurrent or unusual infections
• Evidence of significant intestinal inflammation
• Symptoms suggesting coeliac disease or inflammatory bowel disease

A significantly elevated faecal calprotectin, for example, requires appropriate interpretation because it is an established marker of intestinal inflammation. Suspected coeliac disease requires validated coeliac testing, while suspected selective IgA deficiency requires blood-based immune assessment.

The role of sIgA is to add another piece to the picture, not replace the appropriate diagnostic test.

Key Takeaways

• Secretory IgA is an important part of intestinal mucosal immunity, helping regulate interactions between microbes, antigens, the intestinal barrier and immune system.
• Both low and high faecal sIgA can provide useful clues, but neither identifies the underlying cause by itself.
• An abnormal sIgA result is a red flag, not a diagnosis. Interpret it alongside symptoms, health history and other gut markers.
• Supporting healthy sIgA means supporting the wider mucosal ecosystem, including the microbiome, mucus layer, intestinal barrier, nutrition and nervous system.
• The aim is not simply to change the number. Investigate likely drivers, build strong foundations and use targeted interventions where appropriate.

Frequently Asked Questions

Continue Exploring Gut Health

If your sIgA result is abnormal, the most useful next step is often to understand the wider gut environment rather than focusing on one marker. Start here: Gut Health & the Microbiome Guide.

Related articles:

• Leaky Gut and Intestinal Permeability
• The Gut-Brain Connection
• Parasites and Gut Health
• Top 7 Natural “Antibiotics” for Immune Support
• Vitamin A: What You Must Know About This Vital Nutrient

If you need individual help making sense of symptoms, health history and testing, online naturopathic consultations are available Australia-wide. Explore our wholistic, systems-based approach to care: The Naturimedica Way.

If you don’t live in Australia, you’re warmly invited to explore the many educational resources available on this website, including articles, health guides and free downloads, which have been created to help people better understand their health and make informed decisions wherever they may live.

A Note About Older Comments

Please note: Some comments and responses below date back many years and reflect the information and terminology available at the time. For current information about sIgA, please refer to the updated article above.

I hope you found this article both informative and practical, and that it has encouraged you to look at the gut function and sIgA trough a broader clinical lens.

Best of Health

Joanna Sochan
Wholistic Health and Lifestyle Therapist
Integrative health support combining clinical evidence, systems-based thinking and traditional naturopathic wisdom for lasting health and wellbeing

References & Further Reading

1. Abbasi F, Haghighat Lari MM, Khosravi GR, et al. A systematic review and meta-analysis of clinical trials on the effects of glutamine supplementation on gut permeability in adults. Amino Acids. 2024;56:60. doi:10.1007/s00726-024-03420-7. PubMed
2. Cassani B, Villablanca EJ, De Calisto J, Wang S, Mora JR. Vitamin A and immune regulation: role of retinoic acid in gut-associated dendritic cell education, immune protection and tolerance. Molecular Aspects of Medicine. 2012;33(1):63–76. doi:10.1016/j.mam.2011.11.001. PubMed
3. Catanzaro JR, Strauss JD, Bielecka A, et al. IgA-deficient humans exhibit gut microbiota dysbiosis despite secretion of compensatory IgM. Scientific Reports. 2019;9:13574. doi:10.1038/s41598-019-49923-2. PubMed
4. Dajti E, Frazzoni L, Iascone V, et al. Diagnostic performance of faecal calprotectin in distinguishing inflammatory bowel disease from irritable bowel syndrome in adults: systematic review with meta-analysis. Alimentary Pharmacology & Therapeutics. 2023;58(11–12):1120–1131. doi:10.1111/apt.17754. PubMed
5. Diagnostic Solutions Laboratory. GI-MAP Advanced Practice Series: Opportunistic Bacteria. Diagnostics Solutions Laboratory
6. Doron I, Kusakabe T, Iliev ID. Immunoglobulins at the interface of the gut mycobiota and anti-fungal immunity. Seminars in Immunology. 2023;67:101757. doi:10.1016/j.smim.2023.101757. PubMed
7. Ehehalt R, Braun A, Karner M, Füllekrug J, Stremmel W. Phosphatidylcholine as a constituent in the colonic mucosal barrier: physiological and clinical relevance. Biochimica et Biophysica Acta. 2010;1801(9):983–993. doi:10.1016/j.bbalip.2010.05.014. PubMed
8. Genova Diagnostics. GI Effects Comprehensive Profile: Inflammation and Immunology/Fecal Secretory IgA. Genova Diagnostics GI Effects
9. Jahn HU, Ullrich R, Schneider T, et al. Immunological and trophical effects of Saccharomyces boulardii on the small intestine in healthy human volunteers. Digestion. 1996;57(2):95–104. doi:10.1159/000201320. PubMed
10. Kabeerdoss J, Devi RS, Mary RR, et al. Effect of yoghurt containing Bifidobacterium lactis Bb12 on faecal excretion of secretory immunoglobulin A and human beta-defensin 2 in healthy adult volunteers. Nutrition Journal. 2011;10:138. doi:10.1186/1475-2891-10-138. PubMed
11. Killeen RB, Joseph NI. Selective IgA Deficiency. StatPearls. Updated 2026. PubMed
12. Mantis NJ, Rol N, Corthésy B. Secretory IgA’s complex roles in immunity and mucosal homeostasis in the gut. Mucosal Immunology. 2011;4(6):603–611. doi:10.1038/mi.2011.41. PubMed
13. NutriPath Pathology. Secretory IgA, Faecal. NutriPath laboratory report sample
14. Pabst O, Slack E. IgA and the intestinal microbiota: the importance of being specific. Mucosal Immunology. 2020;13(1):12–21. doi:10.1038/s41385-019-0227-4. PubMed
15. Pietrzak B, Tomela K, Olejnik-Schmidt A, Mackiewicz A, Schmidt M. Secretory IgA in intestinal mucosal secretions as an adaptive barrier against microbial cells. International Journal of Molecular Sciences. 2020;21(23):9254. doi:10.3390/ijms21239254. PubMed
16. Rodríguez OL, Hagel I, González Y, et al. Secretory IgA antibody responses in Venezuelan children infected with Giardia duodenalis. Journal of Tropical Pediatrics. 2004;50(2):68–72. doi:10.1093/tropej/50.2.68. PubMed
17. Rubio-Tapia A, Hill ID, Semrad C, et al. American College of Gastroenterology Guidelines Update: Diagnosis and Management of Celiac Disease. American Journal of Gastroenterology. 2023;118(1):59–76. doi:10.14309/ajg.0000000000002075. PubMed
18. Seizer L, Stasielowicz L, Löchner J. Timing matters: A meta-analysis on the dynamic effect of stress on salivary immunoglobulin. Brain, Behavior, and Immunity. 2024;119:734–740. doi:10.1016/j.bbi.2024.04.039. PubMed
19. Vulevic J, Juric A, Tzortzis G, Gibson GR. A mixture of trans-galactooligosaccharides reduces markers of metabolic syndrome and modulates the faecal microbiota and immune function of overweight adults. Journal of Nutrition. 2013;143(3):324–331. doi:10.3945/jn.112.166132. The Journal of Nutrition Journal

Disclaimer: This content is for informational and educational purposes only and is not intended to diagnose, treat, cure, or prevent any disease. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making any changes to your health regimen, particularly if you are taking prescription or over-the-counter medications or have a medical condition.

Bio: Joanna Sochan is a Wholistic Natural Therapist and founder of Naturimedica Wholistic Wellcare. She has over 15 years of clinical experience working with complex health presentations, with a focus on gut health, food sensitivities, women’s hormone health (including perimenopause and menopause), metabolic health, weight regulation, and circadian biology. She works with clients Australia-wide and online, and also develops therapeutic programs, eCourses, and educational resources designed to support long-term, sustainable wellbeing. View full bio.