Dietary intake methodology I. USDA surveys and supporting research.

Nationwide food consumption and dietary surveys have been conducted about every 10 yr by the U.S. Department of Agriculture (USDA) since the mid-1930s to fulfill responsibilities for monitoring dietary patterns among the nation's population. Survey findings have implications for policies and programs related to food production and marketing, food safety, food assistance, and nutrition education. Until 1965, these surveys measured household food consumption only, but subsequent surveys were expanded to include food intakes by individuals in the sample households. Since 1985, small-scale continuing surveys of food intakes by individuals have been conducted during the years between the large decennial surveys. The 1-d recall was used in the first dietary intake survey. Then, to capture day-to-day variation in diets, 3 d of intake data, 1-d recall and 2-d records, were collected in 1977-1978, 1987-1988, and 1989. Prior to the 1977-1978 dietary intake survey, USDA embarked upon an intensive program of extramural research that was designed to improve methodologies for surveying individuals' dietary intakes. Since 1975, many major investigations have been completed and results have been incorporated in current survey procedures. Studies included testing of varied recall and diary methods, approaches for validating survey data, debriefings of survey respondents and interviewers, intersurvey comparisons, and testing of panel approaches with in-person, telephone, and mail contacts.

Dietary intake methodology. II. USDA's Nutrient Data Base for Nationwide Dietary Intake Surveys.

The U.S. Department of Agriculture's (USDA) Nutrient Data Base for Nationwide Dietary Intake Surveys is specifically organized and maintained to analyze data from nationwide dietary surveys within the federal government's National Nutrition Monitoring System. These surveys include the Nationwide Food Consumption Survey and the Continuing Survey of Food Intakes by Individuals conducted by USDA, and the National Health and Nutrition Examination Survey conducted by the Department of Health and Human Services (DHHS). Each public release of the data base covers one or more specific surveys. The data base contains data for energy and 28 components for over 5000 food items. Data are based on the latest information from USDAs National Nutrient Data Bank, the computer-based system used to update USDAs standard reference on food composition, Agriculture Handbook No. 8. An automated system is also used to update the survey nutrient data base with new information released from the Nutrient Data Bank. This system includes three supplementary data sets (primary nutrient data set, recipe file, and table of nutrient retention factors) and a computer program for calculating nutrient content of mixed food items based on nutrient content of their ingredients. Updates are performed at the beginning of new surveys to incorporate the most up-to-date nutrient values.

Diets of American women, in 1985.

Compared with 1977, women in 1985 consumed more skim and lowfat milk; soft drinks; mixtures that were mainly meat, poultry and fish; and grain products. They consumed less whole milk, less meat (as nonmixtures) and fewer eggs. In 1985, the mean percent of calories from fat was similar for both low- and high-income women. High-income women ate less meat, eggs and whole milk than did low-income women, but they ate more cheese, cream and milk desserts, baked goods, table fats and salad dressings. Regardless of income, mean intakes by women were below the Recommended Dietary Allowances for six nutrients: vitamin B-6, folacin, calcium, iron, magnesium and zinc. Both snacking and eating away from home increased between 1977 and 1985.

Collection of food intake data: an evaluation of methods.

Using USDA's recently completed methodological survey designed to evaluate longitudinal measures of food intake, the authors assessed nine methods for measuring dietary status. Methods evaluated included various combinations of prospective and retrospective recording of daily intake; personal, telephone, and mail- and telephone-assisted reporting; semistructured and open-ended recording documents; and number and spacing of days for recording intakes. Results from tabular and regression analyses indicated that the most effective and least costly methods for assessing mean intakes for groups of individuals were those using telephone and/or personal contact and collecting 24-hour recalls for several selected nonconsecutive days during the survey period. More specifically, it was concluded that the method including an initial personal interview for 24-hour recall followed by three telephone interviews for 24-hour recalls over a 1-year period and the method including four telephone interviews for 24-hour recalls for a 1-year period provided food energy intake data comparable with the data collected with other methods and with less effort or cost. Additional analyses were recommended to determine the numbers of days required to obtain estimates of usual intake for individuals and for diet components other than food energy.

Food supply studies and consumption survey statistics on fat in United States diets.

Studies of the fat content of food available for consumption per capita in the United States (food supply) and the average food intakes of individuals collected in the United States Department of Agriculture Nationwide Food Consumption Surveys (1909 to 1979) are reviewed to show levels and trends in the consumption of fat.