The diet of an organism is what it eats, which is largely determined by the perceived palatability of foods. Dietitians are health professionals who specialize in human nutrition, meal planning, economics, and preparation. They are trained to provide safe, evidence-based dietary advice and management to individuals (in health and disease), as well as to institutions. Clinical nutritionists are health professionals who focus more specifically on the role of nutrition in chronic disease, including possible prevention or remediation by addressing nutritional deficiencies before resorting to drugs. While government regulation of the use of this professional title is less universal than for "dietician", the field is supported by many high-level academic programs, up to and including the Doctoral level, and has its own voluntary certification board,professional associations, and peer-reviewed journals, e.g. the American Society for Nutrition and the American Journal of Clinical Nutrition.
A poor diet can have an injurious impact on health, causing deficiency diseases such as scurvy and kwashiorkor health-threatening conditions like obesity and metabolic syndrome and such common chronic systemic diseases as cardiovascular disease,diabetes,and osteoporosis.