Quick answer: S100A12 is a calcium-binding alarm protein released mainly by activated neutrophils, a type of white blood cell. A higher stool level is generally read as a sign of neutrophil-driven inflammation in the gut lining, and one study found it rose in active inflammatory bowel disease and bacterial gut infections but stayed low in irritable bowel syndrome. It is a close cousin of calprotectin and has been studied less.
Key takeaways
S100A12 is a protein released by activated white blood cells in the gut.
In studies of children, high stool S100A12 was strongly linked with inflammatory bowel disease.
Evidence in adults is more limited, and the test is usually read alongside calprotectin.
When the gut lining becomes inflamed, neutrophils rush in, and they carry a set of calcium-binding proteins that act as alarm signals. Calprotectin is the best known of these, and I cover it in a separate article. S100A12 is its close cousin. It is made and released mainly by neutrophils, and it can be measured in both stool and blood. Because one study found that it tracked inflammation in the gut lining even more closely than calprotectin, researchers have been interested in whether it adds a sharper view of what is happening in the gut.
This article is educational. It explains what the marker reflects and how researchers connect it to the deeper mechanisms of aging, so you can have a more informed conversation with your own provider.
What does a high S100A12 level in stool mean?
In a 2007 study in Gut, Kaiser and colleagues measured stool S100A12 in 171 consecutive patients and 24 healthy volunteers. Levels were much higher in people with active inflammatory bowel disease than in healthy volunteers or in people with irritable bowel syndrome, and S100A12 was also raised in bacterial gut infections but not in viral ones. Stool S100A12 correlated with the inflammation seen in tissue samples more closely than calprotectin or the other markers studied.
A higher stool S100A12 result is therefore generally read as a sign of neutrophil activity in the gut lining, which can come from an inflammatory bowel condition or from a bacterial infection. In that same study, levels in people with irritable bowel syndrome stayed low, which is why researchers see the marker as a way to separate inflammatory from non-inflammatory gut problems. Blood S100A12 reflects inflammation more broadly, so it is a different measurement from the stool test.
How is S100A12 connected to aging and root causes?
S100A12 belongs to a group of molecules called damage-associated molecular patterns, sometimes called alarmins. In a 2007 review in the Journal of Leukocyte Biology, Foell and colleagues explained that these proteins are found at high concentrations in inflamed tissue, where they recruit more inflammatory cells, and that S100A12 binds to RAGE, the receptor for advanced glycation end products. Advanced glycation end products are sugar-damaged proteins, so this shared receptor places S100A12 at the crossroads of chronic low-grade inflammation, intercellular signaling and nutrient sensing.
That link to blood sugar shows up in people too. In a 2004 study in the Journal of Clinical Endocrinology and Metabolism, Kosaki and colleagues found that plasma S100A12 was more than twice as high in people with type 2 diabetes as in people without it, and that white blood cell count and HbA1c were the factors most strongly tied to the level. Researchers use the word inflammaging for the gradual rise in inflammatory signals with age, and in a 2018 review Ferrucci and Fabbri listed a leakier gut barrier, changes in the microbiome, fat around the middle and immune cell imbalance among its likely sources. S100A12 reflects the neutrophil side of that picture.
Blood vessels are another place where this matters. In a 2015 review in Arteriosclerosis, Thrombosis, and Vascular Biology, Oesterle and Bowman described how mice engineered to make S100A12 in their artery walls developed more calcification in the coronary arteries and aorta and more vulnerable plaque, and they noted that blood S100A12 had predicted future cardiovascular events in a longitudinal population study. One honest caveat is that mice do not naturally make S100A12, so animal research has real limits here.
From a root-cause perspective, I want to know why neutrophils in the gut are active in the first place. Bacterial infections, the balance of the microbiome, gut barrier health, blood sugar regulation, food quality, sleep, ongoing stress and everyday exposures are all worth considering, along with genetics.
What does the research show about S100A12?
Researchers tested stool from 61 children who needed a scope for digestive symptoms. Fecal S100A12 was a median of 55.2 mg/kg in the 31 children found to have inflammatory bowel disease versus 1.1 mg/kg in those without it, and at a cutoff of 10 mg/kg it correctly sorted 97% of both groups, compared with 67% specificity for calprotectin. The study was small and limited to children. (Sidler et al., 2008)
A meta-analysis pooled 7 studies with 712 children and teens. Fecal S100A12 identified inflammatory bowel disease with 95% sensitivity and 97% specificity, with higher specificity than calprotectin. The number of studies was small, and the test is less widely available than calprotectin. (Witarto et al., 2023)
Most of the evidence for S100A12 comes from children, and adult data are more limited.
Related reading
If you would like to explore related topics, my articles on calprotectin, lactoferrin and IL-6 go deeper. You can also see the specialty tests I commonly recommend on my functional labs page.
Common questions about S100A12
How is S100A12 different from calprotectin?
Both belong to the same family of calcium-binding proteins released by neutrophils, and both rise with inflammation in the gut lining. Calprotectin is far more widely used, while one study found that S100A12 tracked gut inflammation in tissue samples even more closely.
Can an infection raise S100A12?
Yes. In one study, stool S100A12 was raised in bacterial gut infections but not in viral ones, so a recent stomach bug is worth keeping in mind when reading a result.
What does RAGE have to do with S100A12?
S100A12 binds to RAGE, the receptor for advanced glycation end products, which are sugar-damaged proteins. That shared receptor is one reason researchers study S100A12 in relation to blood sugar and blood vessel health.
Sources
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before making changes to your diet, exercise, supplements, or medications, especially if you are pregnant, nursing, or managing a health condition.
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