Mouth Ulcers

Often a sign of what's missing, not just local irritation

Recurrent aphthous stomatitis, the medical name for ordinary recurring mouth ulcers or canker sores, affects up to a quarter of people at some point. While local trauma and stress are common triggers, a genuine nutritional or gut connection shows up often enough to be worth checking. One controlled study found blood tests revealed a deficiency in vitamin B12, folate, or iron in 56.2% of adults with recurrent ulcers, compared with just 7% of people without them.

Source: Recurrent Aphthous Stomatitis: A Review

A trial that put this to the test directly

Researchers ran a randomised, double-blind, placebo-controlled trial in 58 adults who had recurrent mouth ulcers for at least a year. Daily sublingual vitamin B12 for 6 months significantly reduced how often ulcers came back and how much they hurt, and this held true regardless of whether a person's B12 level had started out low or normal. That last detail matters. It suggests B12 may help some people with recurrent ulcers even without a diagnosed deficiency showing up on a standard blood test.

Source: Effectiveness of vitamin B12 in treating recurrent aphthous stomatitis: A randomized, double-blind, placebo-controlled trial

Why this often traces back to the gut

Nutrient absorption happens in the gut, which is why conditions that damage or inflame the gut lining show up here so often. Recurrent mouth ulcers appear more frequently in people with coeliac disease, Crohn's disease, and ulcerative colitis, largely because these conditions interfere with absorbing B12, folate, iron, and zinc in the first place. A metagenomic study of people with severe, recurrent mouth ulcers found genuine gut bacterial dysbiosis compared with healthy people, and found that thalidomide, a drug sometimes used for severe cases, partly works by correcting that same gut imbalance alongside calming the immune system.

Source: A metagenome-wide association study of the gut microbiota in recurrent aphthous ulcer and regulation by thalidomide

What this means for you

Most single mouth ulcers heal on their own within one to two weeks, but ulcers that are unusually large, don't heal within three weeks, or keep recurring frequently are worth a doctor's assessment, since they can be a sign of an underlying nutritional or digestive condition worth investigating properly. Given how often a deficiency shows up alongside recurrent ulcers, it's reasonable to ask a doctor for a blood test covering B12, folate, iron, and zinc rather than only treating the ulcers themselves. A varied, plant-rich diet, alongside treating any underlying gut condition, supports the broader absorption and microbial balance this research ties to fewer flare-ups. That's the same idea behind GutLab, everyday gut health starts with regularly feeding the microbiome a broad range of plant-rich ingredients.