Clinical Nutrition is the use of food and nutritional supplementation to bring about the proper balance of nutrients in the body in order to treat and prevent illness. Humans have certain nutritional requirements, both in terms of a daily minimum caloric intake and daily requirements of micronutrients, such as vitamins and minerals, as well as fiber, etc. In the United States and other developed countries, caloric intake is usually, though not always, adequate, and typically it is excessive. Unfortunately, even here in the U.S., with all the food we consume, we often see diets that are unhealthy, nutritionally poor, and deficient in key nutrients. Most nutrients can and should be obtained in the diet, with supplementation generally playing a secondary role, though supplementation of targeted nutrients can be very effective at treating specific ailments. The healthiest diet for each patient can vary slightly, depending on food allergies and other factors, but there are some general guidelines that can be very helpful in promoting health and preventing disease. A healthy diet is truly the foundation for good health and longevity.