Why your low Secretory IgA (SIgA) levels are causing immune and digestive issues

SIgA Image

Mucosal surfaces cover a large part of our body. The digestive tract, nose, mouth and throat are prime examples where this mucosal layer plays a critical role in supporting our health.

Our digestive systems role is essentially to let good things into the body such as nutrients and prevent bad things from getting into the body such as toxins and undigested food substances from the GI tract.

The goal of preventing unwanted substances from getting in the body is achieved through a combination of innate and acquired immunity.

The innate immunity includes things such as mucus, cytokines and lactoferrin, whereas the acquired related more to the production of antibodies.

SIgA is the most abundant and primary antibody response at the mucosal level. The B-cells within the mucosa are activated upon the presence of pathogens and allergens and thus produce SIgA in response. Ultimately SIgA is crucial in preventing the overgrowth of problematic bugs within the digestive tract. Low levels seen in stool testing is commonly associated with the presence of dysbiosis and infection, more about this later in the article.

SIgA insufficiency as tested using a stool sample is incredibly common. I believe this is both a major cause of chronic digestive complaints and a result of an imbalanced microbiome. Therefore, establishing if low SIgA is causing other digestive issues or it is a result of these other digestive issues is an important part of the journey in establishing cause and effect.

What happens if I have low SIgA levels?

Low SIgA levels generally have an increased risk of food sensitivities, inflammatory bowel disease (IBD), Irritable Bowel Syndrome (IBS), intestinal permeability, autoimmunity, coeliac disease and gastrointestinal infections.

This is one of the key reasons why I think that money spent on food sensitivity testing, without adequate investigation into the underlying reason you may have developed more food sensitivities can be a waste of money and time. It may help fight the fire, perhaps even give a window of opportunity to address other underlying causes, but it may not be dealing with what is causing the fire in the first place.

Because of the lowered levels of SIgA in many people, we are becoming less able to adequately fight invaders getting into the gut lining. The lining then becomes inflamed and the tight junctions that ordinarily keep toxins and undigested food particles out breakdown. This causes havoc in the body because now toxins and undigested substances get a free ticket into the blood stream, causing inflammatory and immune reactions that often drive symptoms systemically throughout the body.

As part of our free Functional Medicine Health Score Assessment, you can assess your nutrition and lifestyle as well as symptoms associated to many systems and imbalances in the body, including that of intestinal permeability. We prioritise order risk areas and provide free educational material to help guide you with areas you may want to improve upon to improve your overall health score and lower your symptom risk scores.

What causes low SIgA levels?

There are many potential causes behind low SIgA levels in the gut. Below are some of what I feel are the most common:

Mental / Emotional / Physical stress

Cortisol one of the main stress hormones has been shown to decrease SIgA levels. Lowering stress and introducing stress reduction habits and techniques is crucial in the long-term management of SIgA levels. One study demonstrated the effects of just our thoughts on SIgA levels, showing that just by thinking negative / vindictive thoughts, this actually had a lowering effect on SIgA levels.

You should not underestimate the impact of thoughts and emotions on immunity and digestive health. We have noticed over years of experience, working with hundreds of digestive health clients that in most cases, there is a stress/emotional component to their symptoms. Whether it is an underlying cause or simply something that further exacerbates the symptoms or changes nutrition and lifestyle behaviours that impact digestive health is person dependant.

We have seen phenomenal results by including our associated clinicians who offer mindfulness therapy, clinical hypnotherapy, life coaching and general talking therapies to support our clients as we assist them through the underlying physiological imbalances.

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 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 others it is more to do with the virulence.

Also, an interesting point to note is that some of these “infections” are opportunistic by nature. Meaning, they often come about when SIgA levels reduce. Therefore, it is not uncommon to see the development of candida and blastocystis hominis in SIgA compromised clients. Therefore, you can argue that by supporting and addressing low SIgA levels, this may actually be the best possible treatment for such opportunistic bugs. Without addressing low SIgA and the causes of low SIgA, the risk is very high of that these opportunistic bugs return within just a few weeks or months of running an antimicrobial protocol. This can leave someone very frustrated as their symptoms re-emerge and they feel they are back to square one.


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

Poor dietary choices

Calorie rich, but nutrient devoid foods do little to support our immune system and, in some cases, interfere with appropriate immune responses within the body. Certain nutrients are very helpful in supporting healthy SIgA levels such as Vitamin D, Vitamin A, Zinc and Glutathione.

A good intake of dietary fibre and phytonutrients can also play a role in supporting a heathy gut microbiome. This can help to develop beneficial bacteria that promote good SIgA levels.

Problematic foods

Chronic food sensitivities can be a major contributor to low levels of SIgA. It is debatable whether they are the initial trigger, but once they develop something should be done to remove these foods even if only temporarily, such as the use of a well structured elimination diet. In some cases though a decent food sensitivity test may well bring some long-term benefit and some short-term symptomatic relief.

What can I do to raise my SIgA levels?

Raising SIgA, first requires investigation into the above areas that have just been outlined. Below are some specific tips to help you address low SIgA levels.

Increase Consumption of Polyphenols – Check out our article on phytonutrients for more details on the general benefits of these compounds. Specifically, adding in foods such as green tea, cacao, pomegranate, grapeseed & medicinal mushrooms have been shown to support SIgA.

Saccharomyces Boulardii – This competitive yeast that has been shown to raise SIgA levels, whilst also being very effective against traveller’s diarrhoea and combating Clostridium Difficile and Candida overgrowths.

Beta Glucans – Beta glucans have been shown to help stabilise SIgA in children with chronic respiratory issues. Beta glucan is a type of soluble fibre that is found in foods such as oats, mushrooms like reishi, miatake and shiitaki, rice as well as seaweed.

Colostrum – An immunoglobulin secreted in the early stages of breast-feeding. Again this has been shown to stimulate SIgA levels. Colostrum is useful with those that take part in a high level of physical activity, however, if you have issues with tolerating dairy this may need to be avoided.

Cayenne pepper – This substance has the ability to stimulate the B cells into increased manufacturing of SIgA. However it should be said many people react negatively to cayenne pepper, thus use with caution.

Bone Broth / Gelatine – Bone broth and specifically the gelatine it provides is said to be supportive of SIgA levels in the gut. As well as the gelatine bone broth also provides an array of nutrients that can help optimise digestive health.

Support Fat Soluble Vitamins – Focus on Vitamin D through increased exposure to the sun or appropriate supplementation as well as vitamin A from foods or supplementation in the active form, Retinyl palmitate. Vitamin A is needed for the transport of SIgA over the mucosal lining.

Get Tested – If you only have low SIgA without any other information, you are going to need to broaden your assessment to help uncover potential underlying issues. Our team of Functional Medicine Practitioners will be able to help facilitate this.

Nutrition Improvements – If your diet leaves a lot to be desired, you may want to work with a nutritionist that specialises in digestive health.

Stress Management – Last but not least. Look over your current stressors or perceived levels of stress. If you have numerous underlying stressors, perhaps past traumatic events that are still affecting you now, you may need to go deeper to address the impact that stress and emotions are having on your physiology, including immune function, like SIgA.

How can I test my SIgA levels?

SIgA is commonly tested in saliva and the stool. Blood IgA levels can also be tested, however it is worth noting that these are independent of each other, thus blood IgA may not be a good indicator or SIgA levels in the stool or mouth and likewise saliva SIgA may not indicate what is going on deep inside the digestive system or the blood.

With recurrent or chronic digestive issues, it is always worth assessing SIgA as a stool test. We use several stool testing labs to assess one’s microbiome and gut health. Part of that assessment is that of Secretory IgA as an important GI Health marker alongside 50-100 other markers that give a broad overview of microbiome balance, digestion and absorption, inflammation and immune function, infections, overgrowths, intestinal permeability and more.

We have a team of nutritionists and functional medicine clinicians, some of which are digestive health specialists, who work frequently with clients who have IBS and the symptoms associated with this such as bloating, distension, variable stools, constipation, loose stools, reflux etc.

If you are keen to work on a one-to-one basis with a member of our team, you can complete the enquiry form below.

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