Researchers from the Medical University of Lodz in Poland found the strongest associations with recurrent aphthous stomatitis (RAS) and atrophic glossitis, suggesting persistent or unexplained oral symptoms could warrant closer investigation of nutritional status.
“The mouth may reveal systemic deficiency before broader signs become obvious,” the researchers wrote in the review, which was published last week in Nutrients.
B12 leads the evidence
The review covered research on nutrient deficiencies and oral conditions, focusing mainly on studies published between 2015 and 2026.
Vitamin B12 was the most documented vitamin, while iron, folate and zinc also appeared frequently. Evidence for vitamins A, C and D was less consistent.
For RAS, commonly known as recurrent mouth ulcers, systematic reviews and meta-analyses found that people with the condition were more likely than controls to have lower levels of vitamin B12, ferritin, folate, iron, and hemoglobin.
Atrophic glossitis, which can leave the tongue smooth, red and painful, was also repeatedly associated with iron, B12 and folate deficiencies.
Some studies reported improvements in recurrent mouth ulcers after nutrient deficiencies were corrected, although findings varied across nutrients. Evidence for zinc, for example, was mixed, with several studies identifying low zinc levels as a potential risk factor for RAS, while others found no significant differences compared with controls.
Looking beyond hemoglobin
The review highlighted evidence that oral changes may occur before abnormalities are picked up through standard blood tests.
“Normal hemoglobin alone does not exclude a nutritional contribution, and more targeted testing may still be warranted when the phenotype is suggestive,” the researchers wrote.
The authors recommended assessing iron status, B12 and folate in people with persistent or unexplained oral symptoms, with zinc and other markers considered where appropriate.
Burning mouth symptoms were also associated with deficiencies in iron, B12, folate and zinc in some studies. However, the condition can have several other causes, including dry mouth, candidiasis, endocrine disorders and nerve-related problems.
Supplementation evidence remains mixed
While some of the research suggested that correcting deficiencies may improve oral symptoms, the evidence did not support broad supplementation for oral health.
Vitamin B12, folate and iron replacement was associated with improvements in RAS in some deficient patients, while zinc supplementation showed benefits in some studies of recurring ulcers and burning mouth symptoms.
The authors instead emphasized identifying a confirmed deficiency and its underlying cause, which could include low dietary intake, malabsorption, gastrointestinal disease, gastric surgery or medication use.
The findings also raise questions about which patients are most likely to benefit from supplementation and whether consistently correcting deficiencies translates into improvements in oral health.
The authors cautioned that much of the evidence reviewed was observational, and differences in study populations, diagnostic criteria and definitions of deficiency limited the conclusions that could be drawn.
“Nutritional deficiency may be causal in some patients, contributory in others, and incidental in still others,” the researchers wrote.
The review was funded by the Medical University of Lodz. The authors declared no conflicts of interest.
Source: Nutrients, https://doi.org/10.3390/nu18172818, “How Nutrient Deficiencies Impact the Oral Mucosa and How to Manage Them: A Narrative Review.” Authors: Starzyńska, P., et al.
