Diarrhea described as functional or acute non-infectious involves loose or frequent stools that are not framed around an infectious cause. The biological pattern can involve rapid intestinal transit, altered fluid movement across the intestinal lining, sensitivity to meal composition, osmotic load from poorly tolerated carbohydrates, bile acid irritation, stress-linked motility changes, high-fat meals, artificial sweeteners, emulsifiers, alcohol exposure, dehydration, electrolyte imbalance, and disruption of normal gut microbial fermentation. The intestinal lining controls movement of water, sodium, potassium, chloride, bicarbonate, and nutrients while also maintaining a barrier between the gut lumen and the bloodstream. When transit becomes too fast, water reabsorption may be reduced and stool can become loose. When the gut lining is irritated, epithelial barrier signaling, mucus production, immune activity, prostaglandin activity, leukotriene activity, NF-kB signaling, and oxidative stress can all influence digestive comfort and stool pattern. P53 Nutrition is classified as 100% whole-food plant-based nutrition with no oils, meat, dairy, or toxins. For functional or acute non-infectious diarrhea, the emphasis is on gentle whole plant foods that support hydration, electrolyte balance, soluble fiber intake, microbial fermentation, short-chain fatty acid signaling, epithelial barrier integrity, and inflammatory balance. Foods such as banana, apple, pear, oats, brown rice, sweet potato, carrot, potato, pumpkin, lentils, chickpeas, green beans, spinach, ginger, and green tea provide intact carbohydrates, soluble fiber, resistant starch, potassium, magnesium, vitamin C, folate, carotenoids, flavonoids, catechins, gingerols, and gentle starch structure. Soluble fibers and resistant starches can influence stool form by holding water, supporting microbial metabolism, and contributing to short-chain fatty acid production. Short-chain fatty acids, especially butyrate, acetate, and propionate, are studied for roles in colonocyte energy metabolism, barrier regulation, immune signaling, and intestinal fluid balance. A low-fat whole-food plant pattern also reduces concentrated fat exposure, which may lessen bile-driven irritation and rapid transit in sensitive digestion. This framework supports the biological systems involved in intestinal fluid regulation, epithelial barrier maintenance, microbial balance, motility rhythm, antioxidant defense, and hydration without oils, meat, dairy, or toxin-linked processed foods.