Clinical nutrition examines the relationship between diet and health. "Let thy food be thy medicine and medicine be thy food" wrote Hippocrates fifteen centuries ago.

Understanding the impact of our food choices, what we eat and drink is perhaps the most important step we can take along the road to achieving optimal health. N.D.s may recommend special diets, and may include nutritional supplements such as vitamins, minerals and enzymes, in the therapy they formulate after analyzing each person's individual needs.