Nutrient density and dairy foods: the USDA Dietary Guidelines Advisory Committee has expressed concern that many Americans are consuming excess calories, but not meeting nutritional requirements. A look at some of the advantages and challenges in the development of the concept and possible labeling of nutrient-dense foods is provided

Prepared Foods, August, 2008 by Susan Zaripheh, Greg Miller

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In 2005, the USDA Dietary Guidelines Advisory Committee (DGAC) expressed concern that many Americans are consuming excess calories, but they are not meeting their nutrient requirements. The DGAC recommended that individuals "consume a variety of nutrient-dense foods and beverages within and among the basic food groups, while choosing foods that limit the intake of saturated and trans fats, cholesterol, added sugars, salt and alcohol." Additionally, the DGAC recognized that a standardized, science-based definition of nutrient density is needed.

As discussed below, before such a standardized definition can be created, the key elements of a nutrient profiling index need to be objectively determined and validated against key health measures. Once established, this profile could be implemented on food labels, or by other means, to assist individuals in successfully following the 2005 Dietary Guidelines for Americans (DGA). This index also may help guide nutrition policy (e.g., nutrition standards for foods offered in schools).

Nutrient Density and Energy Density

In the absence of agreed-upon standards, several definitions of nutrient density have been offered. Unlike energy (or calorie) density, which refers to the number of calories per gram in a given food, nutrient density refers to the ratio of nutrients (grams) to calories (Kcal). The DGAC defines nutrient-dense foods as those foods that provide substantial amounts of vitamins and minerals (micronutrients) and relatively few calories. Others suggest including macronutrients or bioactives in the definition of nutrient density. While the concept of looking at foods in terms of energy density was previously popular among nutritionists, they now recognize that accounting for caloric intake alone is insufficient to build healthy diets. Instead, nutritionists now recognize the importance of selecting the highest quality foods (e.g., nutrient-dense foods) within each food group, without exceeding an individual's daily caloric intake.

The concept of nutrient density is relevant to all individuals--particularly, those who are attempting to lose weight, because as caloric intake is reduced, it becomes more difficult to meet nutrient requirements. This makes the selection of high nutrient-quality foods within an individual's calorie requirements even more critical. For example, when focusing on caloric intake only when making a beverage choice, one might select an 8oz diet soda (0Kcal) over a glass of low-fat milk (105Kcal), as it is lower in calories. On the other hand, if one were to also consider the nutrients delivered by a beverage, he or she would recognize that milk provides nine essential nutrients.

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This nutrient-density concept is even more critical, because most Americans are overweight and undernourished. Typically, commodity foods are nutrient-dense food choices. Nutrient-dense foods include brightly colored fruits and vegetables, whole grains, low-fat and fat-free milk, cheese and yogurt; and lean meat, poultry, fish, eggs, beans and nuts. Further, when making food choices, the Food Guide Pyramid food groups can be used as guidance to help select foods with a surfeit of healthy nutrients for minimal calories (see www.mypyramid.gov/downloads/ miniposter.pdf).

Scientific Support for the Concept

Numerous public health and governmental organizations support the nutrient-density approach. The DGA's, in addition to the Institute of Medicine's Food and Nutrition Board's "Dietary Reference Intake: Applications in Dietary Planning Report" suggests that nutrient density be used to plan diets. Further, the American Dietetic Association, the American Diabetes Association, MyPyramid and the American Heart Association all support the nutrient-density approach to selecting a healthy diet. The FDA recently held a hearing to discuss the use of front-of-pack labels that would help consumers identify the healthier, more nutrient-dense foods, within and across food groups. Moreover, the E. U. has recently determined that nutrient profiles will be the formal basis for regulating future nutrition and health claims. In the near future, only foods with favorable nutrient profiles will be allowed to assert nutrition and health claims in Europe.

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Given the heightened interest domestically and abroad, a nutrient profiling system that can be easily incorporated into existing food labels and that can be adjusted for use by government regulatory agencies would be greatly beneficial. Consuming foods of the highest nutrient quality from all food groups within daily energy requirements is critical to the normal growth and development of children; for the health promotion of all age groups; and to the reduced risk of chronic diseases, such as obesity and diabetes.

Scientifically Valid Definitions

According to Dr. Adam Drewnowski, the key elements of a nutrient profiling system include: selection of index nutrients; selection of reference amounts (e.g., 100Kcal, 2,000Kcal, 100g or reference amount customarily consumed, RACC); and finally, validation of the nutrient index against an objective measure of a healthy diet (e.g., Healthy Eating Index, HEI) or health outcome. A science-based definition of nutrient density requires the development of a nutrient-density index that will allow consistent scoring of all foods. Statistical and/or quantitative methods should be applied, as possible, to objectively develop this nutrient profiling index.