MAKING NUTRIENT-RICH FOOD CHOICES FIRST: KEY TO A HEALTHFUL DIET
Volume 78, Number 5 September/October 2007
NUTRIENT DENSITY: RENEWED INTEREST IN A LONG-STANDING CONCEPT
The advice to “choose your calories by the company they keep” is a long-standing dietary principle (10). Yet, only recently has this concept of nutrient density served as the cornerstone of dietary guidance, such as the 2005 Dietary Guidelines for Americans (4) and USDA’s MyPyramid (12). The 2005 Dietary Guidelines recommends consuming a variety of nutrient-dense foods within and among the basic food groups to help ensure that nutrient needs are met while maintaining calorie needs (4). The Dietary Guidelines also provides examples of nutrient-dense foods – fruits and dark green and orange vegetables; fat-free and low-fat milk and milk products such as yogurt and cheese; lean meats, poultry, fish, and legumes; and regular and whole-grain products – within the DASH (Dietary Approaches to Stop Hypertension) and USDA food group patterns (4). USDA’s MyPyramid, which translates the Dietary Guidelines into practical advice for consumers, conveys the importance of nutrient density with the recommendation, “Get the most nutrition out of your calories” (12).
Support for the concept of nutrient density is widespread (4,9-17). In addition to the Dietary Guidelines (4) and MyPyramid (12), the 2005 Dietary Guidelines Advisory Committee called for the development of a science-based definition of nutrient density (15). The Institute of Medicine, Food and Nutrition Board’s Dietary Reference Intake: Applications in Dietary Planning proposed using nutrient density to plan diets for groups (16). The U.S. Food and Drug Administration (FDA) expressed interest in using a nutrient density approach instead of the 10% nutrient contribution requirement for health claims (17). The American Dietetic Association, in a recent practice paper, urges health professionals to use the current concept of nutrient density to provide guidance to their clients and to consumers to help them build healthier diets (11). Also, a scientific symposium held in Washington D.C. in 2004 and supported by the Nutrient Rich Foods Coalition explored approaches toward creating a nutrient density index or score for individual foods and beverages as an educational tool to help consumers choose foods that are naturally nutrient-rich first and less nutrient-dense foods as calories allow (9).
Nutrient density is a long-standing dietary principle and a cornerstone of the 2005 Dietary Guidelines for Americans and MyPyramid. Efforts are underway to develop a scientifically valid definition for nutrient density and a scientific score to identify the most nutrient-rich foods and beverages.
Despite the recent attention on nutrient density, a scientifically agreed upon definition of nutrient density or nutrient-dense foods has yet to be established (11). The 2005 Dietary Guidelines defines nutrient-dense foods on a nutrient to calorie basis: “Nutrient-dense foods are those foods that provide substantial amounts of vitamins and minerals (micronutrients) and relatively few calories. Foods that are low in nutrient density are foods that supply calories but relatively small amounts of micronutrients, sometimes none at all”(4). The 2005 Dietary Guidelines Advisory Committee, after a comprehensive review of the current literature on diet and health, called for more research to develop a scientifically valid definition for nutrient density and to determine what criteria are necessary for foods to meet this definition (15). In response to the Dietary Guidelines Advisory Committee’s call-to-action, the Nutrient Rich Foods Coalition has been working with leading researchers to develop and validate a scientifically-based definition and score that indicates the nutrient density of individual foods and beverages.
DEVELOPING A NUTRIENT DENSITY SCORE: A WORK IN PROGRESS
An agreed upon scientifically valid nutrient density score or index that could be objectively applied to individual foods and beverages could help consumers identify and select nutrient-dense foods within food groups, while permitting some flexibility in discretionary calories (11). That is, this nutrient density score could help people implement the Dietary Guidelines to meet their nutrient needs within energy requirements and control calorie intake for weight management.
In Europe, nutrient profiling – the science of ranking foods based on their nutrient composition – is fast becoming the basis for food labeling, regulation of health claims, and marketing and advertising to children. Other potential applications of the nutrient density approach include use in development of nutrition policy, such as decisions about nutrient standards for foods available in schools.
With respect to food labeling, both internationally and domestically, there has been a proliferation of symbols or icons on food labels based on differing “nutrient profiling” criteria that are intended to help consumers choose healthier diets (18,19). For example, the United Kingdom's (U.K.) Food Standards Agency has introduced a “traffic light” food label that indicates the level of fat, saturated fat, sugar, and salt in a food or beverage with the color green (low), yellow/amber (medium), or red (high) (19). Likewise in the U.S. and Canada, various food manufacturers and health professional organizations have adopted on-package food symbols that highlight healthful food choices (18,19).
However, different criteria are used to determine whether or not a specific food can carry a “health logo.” Some criteria include the presence of health-promoting vitamins and minerals. Other criteria such as that used to develop the U.K.’s “traffic light” food label, focus on the absence of nutrients such as fat, sugar, or sodium (18). Lack of standardized criteria to define the nutritional quality of food and beverages and failure to consider the whole nutrient package can result in consumer confusion and misinformation (18).
Over the years, several attempts have been made to define the quality of individual foods on a nutrient density basis (9-11,13,20). As many as eight such schemes, some dating back to the 1980’s, have been identified by the American Dietetic Association (11). Nutrient profiles can be based on desirable nutrients only, undesirable nutrients only, or a combination of both. The basis for calculation can be 100g, 100kcal, or RACC values (reference amounts customarily consumed) as defined by the FDA.
The Nutrient Rich Foods Coalition – a partnership of scientific researchers, communications experts, and agricultural commodity groups – has developed a comprehensive Live Well! tool kit for health professionals and a web site (www.nutrientrichfoods.org) to help Americans improve the nutritional quality of their diets.
The Naturally Nutrient Rich (NNR) score, a nutrient to calorie ratio focusing on beneficial nutrients only, was introduced in a 2005 article in the American Journal of Clinical Nutrition (13). The NNR is a mean of percent Daily Values (DVs) for a number of nutrients, including fiber (13). The nutrients are protein, vitamin A, vitamin C, calcium, iron, zinc, folate, thiamin, riboflavin, vitamin D, vitamin E, monounsaturated fatty acids, and potassium (13). Overall, scores have been shown to rank from 2 (soda) to 1,000 (spinach). In an evidence-based background paper on point-of-purchase nutrition programs, the NNR score was singled out by the Dietitians of Canada as an objective index to help consumers compare food products within and across food groups (18).
Since the NNR score is a nutrients-to-calories ratio, foods with higher energy density are typically awarded lower scores. The score does not specifically address the foods’ content of fat, saturated fat, trans fats, total sugars, or sodium (13). However, many current nutrient profiles include these nutrients. The intent of nutrient profiling should be to focus on beneficial nutrients, not just calories or nutrients to avoid. This approach will better characterize food and beverages based on their full nutrient packages.
To date, there is no consensus regarding the best approach to assess nutrient dense foods and to determine a nutrient density score (11). The American Dietetic Association suggests that before a scientifically valid definition of nutrient-dense foods can be established, a number of questions need to be answered. Furthermore, research needs to verify whether a nutrient density approach is feasible, economical, culturally sensitive, and usable by health professionals and consumers (11). Also, research needs to identify the best way to validate nutrient density scores and nutrient density education materials (11).
The American Dietetic Association has published a paper on the role of nutrient density in nutrition guidance (11). The paper outlines questions related to defining and assessing nutrient-dense foods that should be considered in the development of a system to help put nutrient density into practice. For example, should nutrient density include beneficial/protective nutrients only, or both beneficial and less desirable nutrients? Although the Dietary Guidelines defines nutrient-dense foods as those that are low in fat and have no added sugar, foods such as some milk products (e.g., low-fat chocolate milk, fruit-flavored low-fat yogurt) and some cereals that have small amounts of added sugars are recognized as being nutrient-dense (4). It is suggested that the Dietary Guidelines’ description of nutrient-dense foods be revisited (11).
The nutrient-rich foods approach to a healthy diet emphasizes enjoying nutrient-rich foods first within each food group identified in MyPyramid and selecting less nutrient-rich options as calories allow. This approach focuses on a full range of nutrients in foods – as opposed to just nutrients to avoid.
Some other questions related to specific nutrients in the definition of nutrient density are whether to consider beneficial/protective food components not considered to be nutrients (e.g., dietary fiber, carotenoids) (11). Also, should nutrients used to assess nutrient density differ for each food group? Should nutrient density be adjusted for different consumption patterns (e.g., lacto-ovo-vegetarian diets, ethnic diets) or expressed differently for naturally nutrient-dense foods vs. fortified nutrient-dense foods?
Other questions relate to how nutrient density should be expressed (e.g., nutrients per calorie, nutrients per gram, or nutrients per standard intake) and how nutrient-dense foods can be identified (i.e., nutrient-dense or not, or use of a score that rates foods on a continuum) (11). A scoring system indicating gradations of nutrient-dense foods within each food group would be less likely to lead to good and bad food categories (11). Another question concerns how to score foods that are energy-dense and nutrient-dense (e.g., dried fruits, nuts, non-lean meats, whole milk) (11). For example, foods such as whole milk and whole milk yogurt may still be considered nutrient-dense despite the availability of their lower-calorie counterparts (11). Clearly, a number of questions related to defining and assessing nutrient-dense foods and beverages need to be resolved (11).
COMMUNICATING THE CONCEPT OF NUTRIENT-RICH FOOD CHOICES FIRST
Although a scientifically valid definition of nutrient density and a consistent method of assessing the nutrient density of individual foods and beverages remain works in progress, the scientific community recognizes the immediate need to effectively communicate a way to help consumers get more nutrition from the calories they consume (9-11,13,14).
The nutrient-rich approach emphasizes enjoying nutrient-rich foods first within the basic food groups identified in MyPyramid (12) and selecting less nutrient-rich options as calorie recommendations allow. To show people how to build and enjoy a healthier diet that delivers the most nutrition per calorie and follow the Dietary Guidelines (4) and MyPyramid (12), the Nutrient Rich Foods Coalition has developed the Live Well! Enjoy Nutrient-Rich Foods tool kit (14) and a new web site (www.nutrientrichfoods.org). The tool kit, designed to help health professionals educate consumers about how to follow recommendations of the 2005 Dietary Guidelines (4) and MyPyramid (12), contains a Leader Guide, reproducible handouts, and a MyPyramid poster (14). The Leader Guide outlines nutrient density scientific research and provides a framework for teaching consumers how to follow MyPyramid (12) by choosing nutrient-rich foods. The guide also includes ideas for using the materials in a variety of settings and highlights findings from market research conducted with consumers and Registered Dietitians. The reproducible handouts include practical tips to help health professionals work with clients to build more nutrient-dense diets based on the Dietary Guidelines and MyPyramid (14). The Nutrient Rich Foods Coalition web site provides nutrient-rich menus, recipe ideas, tips, grocery shopping lists, and information on nutrient-rich options in each food group. The information on this web site is based on nutrition guidelines for MyPyramid (12).
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