Recommended daily allowances (RDAs) are defined as the levels of intake of essential nutrients that the Food and Nutrition Board judges to be adequate to meet the known nutrient needs of most healthy persons.

The best way to get the daily requirement of essential vitamins is to eat a balanced diet that contains a variety of foods from the food guide pyramid.

Specific recommendations for each vitamin depend on age, gender, and other factors (such as pregnancy). The U.S. Department of Agriculture has a PDF file that lists these recommendations.