Recurrent Aphthous Mouth Ulcers — supplement protocol
Recurrent aphthous stomatitis (RAS) — common canker sores — has one of the cleanest "find-the-deficiency" supplement stories. A meaningful subset of patients have iron, B12, folate, or zinc deficiency, and correcting these reduces or eliminates recurrence. Volkov 2009 trial: 1000 mcg/day vitamin B12 reduced ulcer frequency and duration in patients regardless of baseline B12 levels. Beyond deficiency correction, supplements offer modest adjunctive symptom relief; behavioural triggers (sodium lauryl sulfate toothpaste, mechanical trauma, specific food triggers, stress) often drive flares.
The supplement stack — find and correct the deficiency
Vitamin B12 (methylcobalamin or hydroxocobalamin)
1000 mcg/day sublingual methylcobalamin for 6 months (test/correct any deficiency first)
Volkov 2009 RCT: B12 1000 mcg sublingual reduced ulcer frequency, duration, and pain regardless of baseline B12 status. This is a striking finding — even patients with normal serum B12 levels appeared to benefit, suggesting a B12-dependent mechanism in mucosal healing distinct from classical deficiency. Test serum B12 and MMA; supplement at 1000 mcg/day for at least 6 months for full effect. Sublingual or oral form works for most people; IM if absorption-impaired.
Iron (if ferritin low) — bisglycinate or sulfate
25–65 mg elemental iron daily; recheck ferritin at 3 months; target ferritin >30 ng/mL
Iron deficiency (even without anaemia) is associated with RAS in multiple case-control studies. Ferritin is the cleanest screen. Treat to ferritin >30 ng/mL (some sources advocate higher targets in symptomatic patients). Iron bisglycinate is better-tolerated than ferrous sulfate. Take alternate days for better absorption (Stoffel 2017). Don't supplement iron without testing — over-supplementation has risks.
Folate (methylfolate or folic acid)
400–800 mcg/day for 6 months if low or low-normal serum folate
Folate deficiency is associated with RAS. Test red-cell folate (more reliable than serum). Methylfolate is preferred in MTHFR-pathway concerns. Treat alongside B12 (high-dose folate can mask B12 deficiency anaemia).
Zinc (if intake low)
15–30 mg/day with food for 8–12 weeks
Small RCTs suggest zinc reduces ulcer frequency in RAS, particularly in zinc-deficient subgroups. Modest signal. Pair with 1–2 mg copper if zinc >25 mg/day chronically. Avoid >40 mg/day chronic supplementation.
L-Lysine (during outbreaks)
1 g three times daily at first sign; continue through resolution
Limited evidence for RAS specifically; better-evidenced for HSV cold sores. Some patients use lysine for RAS based on adjacent biology; modest signal at best. Worth a trial if uncomplicated.
Honey (medical-grade or pure local honey) — topical
Small dab applied 3–4 times daily on ulcer
El-Haddad 2014 trial: topical honey reduced ulcer size and pain vs placebo. Mechanism: antimicrobial, anti-inflammatory, mucosal protection. Cheap, low-risk, modest symptomatic benefit.
The trigger-identification layer
- SLS-containing toothpaste — sodium lauryl sulfate is implicated in RAS flares in susceptible individuals; switch to SLS-free toothpaste (Sensodyne Pronamel, Biotene, Tom's of Maine) for 6–8 weeks as a trial. Cleanest behavioural intervention.
- Mechanical trauma — cheek-biting, sharp dental edges, ill-fitting dentures. See dentist for evaluation of sharp restorations or orthodontic edges.
- Food triggers — citrus, tomato, chocolate, pineapple, salty/spicy foods in susceptible patients. Elimination + reintroduction trial over 2–4 weeks.
- Coeliac disease screen — tTG-IgA + total IgA on usual gluten-containing diet; up to 5% of RAS patients have undiagnosed coeliac disease.
- Behçet's disease screen — if oral + genital ulcers + uveitis: rheumatology referral.
- HIV / immune compromise — RAS that has dramatically changed character (more frequent, larger, atypical) in immunocompromised patients warrants reassessment.
- Stress management — RAS often clusters with stress; addressing sleep, exercise, mindfulness sometimes reduces frequency.
What to skip
- Megadose vitamin C as "immune boost" — no RAS-specific evidence; can be locally irritating.
- Probiotic-only protocols — mixed and modest evidence; not a primary intervention.
- Tea tree oil topically — local toxicity reports; not appropriate for oral mucosa.
- Whole liquorice (vs DGL) — pseudohyperaldosteronism risk.
- Self-prescribed corticosteroid mouthwashes — appropriate as a medical intervention but not a supplement-aisle decision; oral medicine or dental management.