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Canker sores may be related to a vitamin D deficiency

Canker sores may be related to a vitamin D deficiencyAround 25 percent of adults have had canker sores, also referred to as recurrent aphthous stomatitis (RAS). The condition is characterized by painful, superficial sores, and we don’t know all that much about what causes it or how to treat it. However, according to a meta-analysis that is published in Frontiers in Nutrition, a possible cause may be low blood levels of vitamin D, a nutrient with a key role in oral health and immune defense.

Canker sores, or recurrent aphthous stomatitis (RAS), is a condition that can affect everyone, primarily adults. In severe cases, these painful mouth ulcers can impair quality of life and disrupt oral functions such as eating, swallowing, and even speaking. It is theorized that unwanted immune reactions to a triggering factor are involved. The condition is linked to oral traumas, other diseases, side effects from medicine, celiac disease, and food allergies. Viruses and stress may also be involved. Studies of vitamin and mineral deficiencies (e.g., folic acid, other B vitamins, and iron) have been made but with conflicting results. However, in recent years there has been increasing focus on vitamin D.
The researchers behind the new meta-analysis found 14 relevant studies by trawling databases like PubMed, Scopus, Embase, and others. The studies include 1,468 people from Europe, the Middle East, and India, and 721 participants were RAS patients while 747 served as controls. The scientists compared blood levels of vitamin D with the risk of developing recurrent aphthous stomatitis and found a significant relation between low blood levels of vitamin D and an increased risk of RAS.
The scientists say that their meta-analysis supports a recent study in which it was seen that vitamin D supplementation of vitamin D-deficient RAS patients significantly reduced the number of RAS cases, the number of mouth ulcers, and the duration of outbreaks.

  • RAS (Recurrent Aphthous Stomatitis) is also known as canker sores.

How does vitamin D protect against RAS?

Vitamin D is considered a steroid hormone and most cells in the body have vitamin D receptors. We still don’t know all that much about how vitamin D works in relation to RAS, but it commonly known that the nutrient plays a role in the innate immune defense that handles infections and tissue damage and the adaptive immune defense that is more specialized, makes antibodies, and has a “memory”. In addition, vitamin D helps regulate inflammatory processed via cytokines and other inflammation markers. The scientists behind the new meta-analysis believe that vitamin D’s primary effect on RAS is related to its role in immune regulation. They mention that there is a link between vitamin D and autoimmune diseases like Sjögrens syndrome, lupus erythematosus, and rheumatoid arthritis.

Clinical forms of RAS

Minor RAS that affects around 80 percent of patients and is characterized by one or several mild aphthous ulcers (< 10 mm) surrounded by a red halo. The wounds heal within a week without scarring

Major RAS is more serious and typically involves few large deep-tissue ulcers (> 10 mm in size). It may take several weeks for the ulcers to heal, and they leave scars.

Herpetiform aphthous stomatitis is characterized by recurrent crops of multiple small ulcers (< 10 mm in size) in the floor of the mouth or the underside of the tongue. The ulcers may coalesce to form large ulcers that resemble herpes, but it is not a virus.


Sadeq Ali Al-Maweri et al. Vitamin D deficiency and risk of recurrent aphthous stomatitis: updated meta-analysis with trial sequential analysis. Frontiers in Nutrition 2023

Bjarne Klausen. AFTER: det bør du vide. Tandlægebladet 2017

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