I’ve been interested in Secretory IgA (SIgA) ever since I began using stool testing to understand my client’s gut terrain over 14 years ago. In this post, I want to share with you the importance of understanding what your SIgA levels mean for your health and well-being, the impacts low SIgA may be having on you, as well as giving some insight into how I seek to raise SIgA clinically using food and supplements.

What is Secretory IgA?

Secretory IgA (SIgA) is the most abundant immunoglobulin (also known as antibodies) in the body, and it resides in all our liquid secretions. So that means it can be found in the tears in your eyes, the saliva of your oral cavity, your blood, your sweat, your urinary system, your vagina and most importantly, in your gut!

All of these places have Secretory IgA and it plays an important protective role as our first line of defence in immunity. Its job is to block and protect the body from bacterial, viral, and parasitic infections, toxins and food allergens

Therefore, if you are low in SIgA you may experience an array of gut health issues (more on this below). Most treatments start by eradicating the gut of the bad guys with antibiotics, the problem is, it’s also important to look at the terrain of the gut and increase SIgA levels to treat the problem at its source.

The good news is, once you uncover the imbalances in your gut chemistry and ecology, the solution(s) can be rapid and effective.

What Happens When Our Secretory IgA is Low?

People with low SIgA levels are more prone to experiencing gut and digestive health issues as well as a number of wider health concerns. This can include things like IBS, Leaky Gut, food sensitivities, gastrointestinal infections and coeliac disease as well as things like skin conditions, allergies, autoimmune disease, inflammatory conditions, adrenal fatigue and exhaustion.

Because of SIgA’s role of fighting “the bad guys” as part of our immune system, a low SIgA level means our bodies are much less capable of controlling the equilibrium in our gut and digestive systems. This inevitably leads to the overgrowth of bad bacteria and increased levels of toxins causing inflammation and hampering the body’s ability to repair the damage. 

The flow-on effect is we begin to experience any number of secondary symptoms which can cause discomfort, pain, and severely impact our quality of life. A person with low levels of SIgA may have trouble overcoming gut problems or skin conditions, allergies and sensitivities until SIgA levels are corrected. 

Some symptoms which may indicate your Secretory IgA may be low include:

  • Skin problems (acne/eczema)
  • General issues with gut health 
  • Overgrowth of bad bacteria, dysbiosis and potential parasites
  • Low immune system in general 
  • Fatigue and exhaustion
What Happens When Our Secretory IgA is Low graphic depicting food sensitivities, mood issues, thyroid issues, IBS, malsorption of nutrients, inflammatory skin disorders, autoimmune diseases and difficulty losing weight

Common Causes of Low Secretory IgA Levels


One of the most common reasons for low SIgA levels is STRESS! Yes, this humble marker has been shown in numerous studies to be impacted by chronic stress.

Cortisol (one of the main stress hormones) has been shown to actively decrease SIgA levels. Whether mental, emotional or physical stress, all can be key contributors. I find stress is often to blame when someone comes to see me experiencing ongoing problematic gut symptoms, but all their standard tests are clear. 

Diet and Food Sensitivities

Poor dietary choices such as overindulgence in foods that have low nutritional value or a lack of dietary fibre can lead to conditions inside the body that may lower SIgA. Problematic foods or food intolerances may also play a role.

Still, with experience and research, I noticed that when I increased secretory IgA levels, the symptoms of a potential food intolerance were often reduced.

That’s not to say that you don’t have a food intolerance, but if I see you are reacting to EVERYTHING then it’s important to think about the gut and IgA rather than just removing the food alone as the first line of intervention.

We want to heal and seal our gut alongside the removal of trigger foods. It’s with the help of an experienced practitioner that you may be able to find out the root cause of what’s going on and avoid wasting time and money on unnecessary food sensitivity testing. 

Chronic Infections

Chronic infections are also a common cause of SIgA depletion. Assessing for problematic bugs such as Candida, Blastocystis Hominis, H.pylori, C.Diff etc in the stool should be high on the priority list. Some of the above overgrowths are seen as potential pathogens. Some are problematic depending on the levels within the body, and with others, it is more to do with the virulence.


Certain medications have been shown to deplete SIgA levels. Anti-inflammatory medications appear to lower the levels of SIgA, but so can antibiotics because of their depleting effects on bacteria that are beneficial to SIgA.

How Can I Raise My Secretory IgA Levels?

The good news is, you can increase your SIgA through diet, supplementation and lifestyle changes. I always recommend working with an experienced practitioner to do this because there may be multiple compounding factors such as:

  • Are you low in zinc which helps to create IgA?
  • Are you chronically stressed?
  • Have you got a pathogen which could be worsening your symptoms?
  • Do you have dysbiosis and need support with eradicating some of the bad guys while at the same time increasing your SIgA?

Diet and Nutrition

Examining and improving what you eat in your daily diet is a great place to start for anyone looking to increase their SIgA levels. There are generally 4 components I seek to increase in my client’s diets to improve SIgA levels; Zinc, Protein, Fat Soluble Vitamins and Prebiotics.


Increasing Zinc intake has been shown to be a key driver in improving SIgA levels. Even if you currently get your daily recommended intake of 14 mg/day for adult men and 8 mg/day for adult women, there can often be benefits in increasing this to up to 40mg/day, though this should be assessed on a case by case basis by an experienced practitioner.

Improving Zinc intake can be especially important for vegans and vegetarians with some of the most common Zinc-rich foods being meats and seafood. Check out my post on Zinc Deficiency for a breakdown of foods that are rich in Zinc, with plenty of options for vegetarian and vegan readers.

Foods High in Zinc including salmon, seafood-shrimps, beef, yellow cheese, spinach, mushrooms, cocoa, pumpkin seeds, garlic, bean and almonds.


Protein is a key ingredient in the creation of immunoglobulins in the body with SIgA being among them. Studies have proven the link between protein and increases in T-cell-independent sIgA production. To simplify, just like you need bricks to build a home, you need protein to build the antibodies that are crucial in the gut’s immune responses.

Where necessary, increasing protein intake can be among the most important steps in improving SIgA levels. As always it’s important to seek advice from an experienced practitioner for guidance on what “enough” protein looks like for you.

Animal products such as meat, seafood, dairy and eggs are among the most common high-protein sources. For vegans and vegetarians tofu, lentils, chickpeas, quinoa, and nuts are among the many options available as well as protein supplements.

assorted food high in protein including meats, eggs, dairy, nuts and grains

Fat-Soluble Vitamins 

Fat-soluble vitamins (in particular vitamin A and vitamin D) are another key element for raising SIgA levels in the gut. Studies have demonstrated a link between increased intake of fat-soluble vitamins and elevated levels of IgA, IgG, and IgM

Consuming animal fats including beef liver, oily fish and fish oils, dairy and eggs is my go-to for increasing the dietary intake of fat-soluble vitamins with one important caveat; It’s important to preference organic products when sourcing foods that are high in animal fats. This is because like us animals store toxins from their body in their fat. Therefore if the animals have been exposed to excessive toxins and you’re eating an increased amount of that animal’s fat, you inherently will be consuming an increased amount of these toxins yourself.

Again, it is important for vegans and vegetarians to be extra vigilant with vitamin A and D intake. While Vitamin D can be obtained from exposure to sunlight, there are very few vegan-friendly foods that contain it naturally, so supplements may be your best option. Vitamin A is available in sweet potato, kale, spinach and other green leafy vegetables, carrots, rock melon, and black-eyed peas

Foods rich in natural vitamin D including fish, eggs, cheese, milk, butter, mushrooms, canned sardines


Dietary prebiotics like GOS (galacto-oligosaccharides) and FOS (fructo-oligosaccharides) have been shown to increase SIgA levels in the gut as they act as food for “good” bacteria in the intestine and colon. 

GOS and FOS are prebiotics made up of plant sugars linked in chains. GOS can be found in dairy products, beans, and certain root vegetables, while FOS can be found in onion, chicory, garlic, asparagus, banana and artichoke, among many others. While these are natural sources they can also be made in a lab and taken as a supplement, more on that below. 

Probiotic rich foods including dairy, fruits, vegetables, nuts and seeds


My go-to supplements for increasing Secretory IgA are a multistrain clinically relevant dose of probiotics, most typically Saccramyces Boulardi (SB) and Lactobacillus Rhamnosus (LGG). While many probiotics have been linked with increased SIgA levels, I don’t typically recommend self-prescribing probiotics and would advise you to speak to a practitioner to get the correct one for your needs.

Where we are not able to achieve a sufficient intake of the other important elements for increasing SIgA through diet alone I may also advise the supplementation of Zinc, Vitamins, Protein and Glutamine as required for the client’s specific needs.

The biggest take home here is that any supplementation should be curated to suit the individual’s needs, including any secondary symptoms of allergy and atopy. This is key in treating the whole person and not simply relying on increasing SIgA as a fix-all. 

Saccharomyces Boulardii (SB) 

SB is a probiotic yeast often used for the treatment of GI tract disorders. The most important issue with the use of SB in this case is dosage. Evidence shows that some people may need up to 1000mg/day for adults or 500mg/day for children of this supplement to get the benefits of increasing their SIgA levels. Suitability and dosage should be assessed on an individual basis by an experienced practitioner for best results. 

Lactobacillus Rhamnosus GG (LGG) 

LGG is a clinically trialled probiotic that is great for your digestive health. It belongs to the Lactobacillus family, which produces lactic acid and in doing so helps to prevent the survival of potentially harmful bacteria in your digestive tract. Again, suitability and dosage should be assessed on an individual basis by an experienced practitioner for best results. 

Stress Management

Clinically, I see those people that have undergone stress, whether it be from a major life event, chronic stress from work, or family stresses often have low SIgA levels. Evidence suggests that Secretory IgA production can be suppressed by stress and elevated cortisol levels. When the cortisol level is chronically elevated, SIgA production decreases, leading to an inadequate immune response which then, ultimately, increases the risk of infection. 

This also includes perceived stress. Basically, if you think you’re stressed then you are stressed! If you have gut health issues, skin issues or sleep issues it may be based on stress which is in turn affecting your SIgA levels.

Part of my gut strategy is to always be thinking about lifestyle medicine as well as food and supplements. Are you getting enough sleep, are you getting enough physical activity and are you getting enough exposure to sunlight? These types of lifestyle interventions can play a huge role in supporting an increase in SIgA levels in the body. 

lifestyle reminders on colorful sticky notes including slow down, relax, take it easy, keep calm and other motivational reminders

Can I Get My Secretory IgA Levels Tested?

Yes! A practitioner can understand and track your SIgA levels via stool testing to get a quite accurate picture of where you’re at and what might be necessary to improve. The process is quite simple

  1. Seek a referral from a practitioner (I can help here).
  2. We order the test kit to be sent directly to your house with the testing instructions included. You can then run the in-house test at your convenience. You then mail the stool test back to the testing house (don’t worry the express post envelope is included as part of the test kit!
  3. The results will be sent to your practitioner and they will get in touch with you to discuss what happens next.

The best part about being an online nutritionist is that no matter where you live in Australia, as long as I can see your stool test results, I can help you to understand your Secretory IgA levels and improve them where necessary. The testing is simple, cheap and readily available to most people and I promise not embarrassing in the slightest – dealing with poop is part of the job!

It is important to understand that SIgA testing won’t tell us the cause of the problem, it only provides clues to where further investigation is needed. This is why I recommend you work with an experienced practitioner who can begin to investigate the causes behind your low SIgA.

Once we have an accurate understanding of your gut microbiome, we can formulate a plan for increasing your SIgA levels as required as well as any other issues that may present themselves. Typically when we work on increasing your SIgA levels, we find that the common issues you may have been experiencing are reduced or even cleared along the way.

So if you’re concerned about your SIgA levels, would like more information or would like to organise a test, please reach out to me or book a free 15-minute intro chat.

Sonya Reynolds, nutritionist and wellness coach portrait

About Sonya 

Sonya Reynolds is a Sydney-based degree certified Nutritionist and Life Coach with over 16 years of experience. Sonya uses a holistic approach to help her clients achieve their health and wellbeing goals by combining natural nutrition and wellness coaching.

Sonya provides holistic online nutrition and coaching consultation to clients in Sydney and throughout Australia.

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