Mouth ulcers, also called recurrent aphthae or recurrent aphthous stomatitis, are small, painful, shallow lesions that develop on non-keratinized oral mucosa such as the inside of the lips, cheeks, tongue, and soft palate. They are different from cold sores because they occur inside the mouth and are not defined by external blistering. The biological pattern commonly involves localized epithelial injury, mucosal immune activation, inflammatory cytokine signaling, oxidative stress, altered antioxidant status, and reduced resilience of the oral barrier. Episodes may appear after mechanical irritation, acidic food exposure, emotional stress, sleep disruption, oral trauma, or periods of poor nutrient intake. Recurrent aphthae are associated in research literature with immune dysregulation, epithelial barrier fragility, hematinic insufficiency, zinc imbalance, iron status changes, folate status changes, oxidative stress markers, and altered local antioxidant defense in saliva and oral tissue. Nutrients involved in epithelial turnover, collagen formation, redox balance, methylation, immune regulation, and wound repair are especially relevant to mucosal resilience. Vitamin C supports collagen hydroxylation and connective tissue integrity. Folate, vitamin B6, vitamin B1, vitamin B2, and vitamin B3 support cellular energy metabolism, methylation, nucleotide synthesis, and normal epithelial renewal. Iron, zinc, magnesium, copper, and selenium participate in oxygen transport biology, antioxidant enzymes, connective tissue stability, and immune cell function. A whole food plant-based diet can support oral mucosal health by emphasizing vitamin C-rich fruits, mineral-rich legumes and seeds, leafy greens, cruciferous vegetables, and polyphenol-rich foods. Strawberry, orange, kiwi, guava, broccoli, kale, lentils, chickpeas, pumpkin seeds, and sunflower seeds provide a practical nutrient pattern for supporting epithelial repair, antioxidant defense, and immune balance. These foods provide vitamin C, folate, magnesium, zinc, iron, copper, selenium, carotenoids, flavonoids, glucosinolates, and amino acids needed for tissue maintenance. The support strategy focuses on strengthening the mucosal barrier, improving antioxidant capacity, supporting collagen formation, maintaining steady nutrient intake, and reducing irritant exposure from highly processed foods, added sugars, alcohol, smoking-related toxins, and acidic refined products. Fiber-rich legumes and whole plant foods also support gut microbiome signaling, short-chain fatty acid activity, and systemic inflammatory balance. Recurrent aphthae are multifactorial, so the nutritional pattern does not address only one pathway. It supports the overlapping systems involved in epithelial repair, immune regulation, redox control, hydration, and oral tissue resilience.