Dietary modifications can help to prevent and manage many chronic diseases. The Mediterranean and Dietary Approaches to Stop Hypertension (DASH) diets emphasize consumption of fruits and vegetables while reducing intake of red meat. These diets are supported by well-established evidence for patients with cardiovascular disease and hypertension, respectively. Whole-food, plant-based diets have been shown to result in reduced body weight, lower A1c levels, and decreased insulin resistance in patients with diabetes. Patients with diabetes and hypertension should adhere to a heart-healthy diet, such as the DASH diet. For patients with diabetes and at risk of diabetes, key nutritional recommendations include emphasizing intake of nonstarchy vegetables, minimizing intake of added sugars and refined grains, and choosing whole foods instead of processed foods. The Dietary Guidelines for Americans, 2020-2025 recommend that adults limit sodium intake to less than 2,300 mg/day. Patients with chronic kidney or liver disease should follow sodium restriction and protein intake guidelines. Patients with irritable bowel syndrome should follow a low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) diet with fiber supplementation. For patients with gastrointestinal symptoms, fiber can effectively manage constipation and stool irregularity. Probiotic supplements or foods can be useful for digestive problems.