USDA's Food Guide: Updating the Research Base to Reflect Changes in Food Consumption Patterns - Statistical Data Included

Family Economics and Nutrition Review, Wntr, 2001 by Kristin L. Marcoe

The Food Guide Pyramid was based on a food guide developed in the early 1980's by the U.S. Department of Agriculture (USDA). This food guide was developed to meet specific nutritional goals and was based on food consumption patterns of Americans (1,3) and food composition data. While the original food guide used the 1980 Recommended Dietary Allowances (RDA) to set nutritional goals for food energy, protein, vitamins, and minerals, the 1980 edition of the Dietary Guidelines for Americans was used to provide nutritional goals for fat and added sugars. The 1989 RDA and the 1985 and 1990 editions of the Dietary Guidelines for Americans were used in subsequent research that described the food guide (4).

In developing the food guide, the USDA used food intakes from the Nationwide Food Consumption Survey (NFCS 1977-78, Spring 1977) for all individuals to identify patterns of actual intake within food groups and subgroups (3). These food-group and subgroup "composites" are important parts of the research base supporting the food guide. For each food group or subgroup, USDA developed a composite that reflected, on a percentage basis, Americans' use of individual foods within that group. For example, in 1977 the deep-yellow vegetable composite was 79.5 percent carrots, 10.6 percent sweet potatoes, and 10.0 percent winter squash. Composites were developed for each of the following food groups or subgroups: Meat, poultry, fish; dark-green leafy vegetable; deep-yellow vegetable; starchy vegetable; legume; other vegetable; fruit; whole grains; and enriched grains. These composites were used to provide documentation that the recommended food-selection patterns, in terms of numbers of servings for each food group and subgroup, would meet nutritional goals.

Nutrient profiles for each composite were calculated by using the forms of the food items that were lowest in fat and added sugars. This reflected the philosophical goals that the food guide be realistic and allow maximum flexibility for users to select specific sources of fats and sugars within their diet.

The objective of the research described here was to determine whether the diet pattern of the Food Guide Pyramid continues to meet nutritional goals. Effects of changes in Americans' food selections between 1977 and 1991 on the nutrient profiles of food group composites were assessed.

Procedures for Updating the Composites

The NFCS 1977-78 composites for each food group and subgroup were updated by using data from the Continuing Survey of Food Intakes by Individuals (CSFII) 1989-91. Foods reported in the CSFII 1989-91 as consumed by 11,488 individuals 2 years old and older were used, and sample weights were applied to provide estimates that were representative of the population. USDA's Center for Nutrition Policy and Promotion developed a Food Guide Servings Data Base that was used to convert grams of foods reported as consumed in the CSFII 1989-91 into numbers of food guide servings.

Composites for each Pyramid food group (e.g., meat, poultry, fish) or subgroup (e.g., dark-green leafy vegetable) were developed based on consumption of food items (e.g., cooked broccoli) as reported in the CSFII 1989-91. For example, all food codes that were consumed and that contained cooked broccoli were grouped together in a "cooked broccoli item group." A composite was then constructed of these item groups and weighted by the number of servings of each that were reported by all individuals. One food code was selected to represent each food-item group in each of the composites, and nutrient values of these food codes were used to calculate the nutrient profile of a composite serving.

The original composites, developed by using NFCS 1977-78 data, were then compared with the updated composites. Both the percentages of each food-item group in the composites and the nutrient profiles of the composites were compared. Nutrient data from 1991 were used for the calculation of both the original and updated composites' nutrient profiles. The nutrient values per serving of each food group or subgroup for the original composites (4) and the updated composites (2) have been published.

To determine whether the food guide patterns based on updated composites continued to meet nutritional goals, the Food Guide Pyramid diet pattern for 1,600 calories was calculated and e nutrient totals were then compared with the current nutritional goals for the food guide, including the 1989 RDA. Results were also compared with the 1,600-calorie pattern based on the 1977-78 composites to examine trends over time.

Results

Changes occurred between 1977 and 1991 in the percentages of specific food items consumed within the food groups and subgroups, thus altering the nutrient profiles of several composites. The amounts of zinc, vitamin [B.sub.12], and iron in the meat, poultry, fish composite decreased due to the smaller amounts of beef and liver consumed in 1991 (44 percent) compared with 1977 (52 percent) (fig. 1). The amount of zinc dropped from 1.27 to 1.10 mg per ounce; vitamin [B.sub.12], from 1.4 to 0.6 mcg per ounce; and iron, from 0.62 to 0.54 mg per ounce.