Nutrient density, or nutrient richness, generally refers to the amount of nutrients provided per calorie of a food or beverage. A nutrient dense food or beverage provides more of and a wider variety of nutrients in relatively fewer calories. The Dietary Guidelines for Americans 2010 recommends focusing on a diet that includes nutrient-dense foods and beverages; that is, those that provide vitamins, minerals, and other substances that may have positive health effects with relatively few calories. Citrus juices have been shown to have higher nutrient density compared to other commonly consumed 100% fruit juices.
A Comparison of Nutrient Density Scores for 100% Fruit Juices (Journal of Food Science. 2007;72:S261-S266.) http://www.ncbi.nlm.nih.gov/pubmed/17995788