Nutrient standards are nutrient consumption limits defined by experts for good eating by healthy persons. These guidelines are based on scientific knowledge about the distribution of nutritional needs and dietary variables in the population. They are used by governments to set maximum levels for specific nutrients in food supplies. The first nutrient standard was proposed by the Food and Nutrition Board (FNB) of the National Academy of Sciences in 1946. At that time, there were few data available on the relationship between diet and health. The FNB recommended a daily allowance (DRA) of four essential minerals and vitamins A, B1 (thiamin), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), C (ascorbic acid), D (cholecalciferol), E (alpha-tocopherol), and K (potassium). Since then, more research has been done on nutrition and health. In addition, new methods have been developed to measure certain nutrients in the body called biomarkers. Biomarkers are substances found in the body that show evidence of exposure to environmental factors or the presence of disease. Biomarkers can be used as indicators of how people are doing nutritionally.