Advanced Dietary Analyses

The Advanced Dietary Analyses course contains 6 modules:

Module 17. Estimate Prevalence of Supplement Use and Examine Relationships Using Supplement Data
Module 18. Model Usual Intake Using Dietary Recall Data
Module 19. Evaluate the Effects of Covariates on Usual Dietary Intakes
Module 20. Estimate Population-Level Distributions of Usual Dietary Intake
Module 21. Examine the Relationship Between Usual Dietary Intake and Some Outcome Measure
Module 22. Examine Usual Total Nutrient Intake from Supplements and Diet

These six modules describe techniques for estimating usual intake of dietary and supplement intake, how dietary intakes vary among individuals, and how individual intakes relate to other factors.

Most modules in this course distinguish between two types of dietary constituents depending upon the frequency with which they are consumed by most individuals. Those that are consumed on a daily or almost daily basis, such as nutrients like calcium, are referred to as “ubiquitously consumed” dietary constituents. Some food groups, such as total grains, are also ubiquitously consumed. Dietary constituents that are consumed on a less frequent basis, such as most foods and some food groups (e.g., dark green vegetables) and some nutrients, are referred to as “episodically consumed”.

Many of the statistical methods used in this course are advanced, and may require consultation with a statistician. The course begins with a description of analyses using the categorical-level dietary supplement data, which is presented first because the statistical techniques are relatively straightforward (Module 17). It then describes a unified approach to estimate usual dietary intakes of both ubiquitously-consumed and episodically-consumed dietary constituents from 24-hour recall data (Module 18). The unified approach can be used for a variety of applications that are described in subsequent modules: evaluating the effects of covariates on usual dietary intakes (Module 19), estimating population-level distributions of usual food and nutrient intake (Module 20), examining the relationship between usual dietary intake and health outcomes (Module 21), and examining total nutrient intake from food and dietary supplements (Module 22).

The material presented in the Advanced Dietary Analyses Web Tutorial Course was developed for NHANES 2003-2006, which obtained two 24-hour recalls on the participants and collected dietary supplement data in the household interview. Data from NHANES 2003-2004 is used in the examples given in the course.

The course is aimed at specific issues surrounding usual dietary intake analysis. If you are interested in learning more about the basics of estimating distributions and examining relationships among variables in NHANES, please see the section on “NHANES Analysis” course on the Continuous NHANES Web Tutorial Home page.

Users of this tutorial are expected to have a command of the material presented in the Basic Dietary Analysis Course.

If you are an experienced analyst who only needs specific information to help you complete an analysis on your own, you can choose topics of interest from the navigation bar to the left, or from the Tutorial A-Z Index. You may also go to the Sample Code and Datasets page to download and modify sample programs and datasets for your own use.

Sample Code

Abbreviated SAS and SUDAAN code is presented throughout the course for the sole purpose of demonstration and explanation. The abbreviated code does not comprise a complete SAS or SUDAAN program that can be readily submitted for a computer run. If you need the complete SAS or SUDAAN program, please consult the Download Sample Code and Dataset links listed under the tasks in the respective module.

Before you get started

• Check out the NHANES Dietary Web Tutorial Roadmap section to orient yourself to the tutorial’s content
• Read the Introduction section to find answers to frequently asked questions about NHANES dietary data and this tutorial.
• Browse through the Logistics section to learn about the web layouts and templates used in the tutorial and find out the basic knowledge and skills you’ll need to use the tutorial.
• Go to Technical & Software Requirements for information about what’s required to view the tutorials correctly and run the sample programs properly. This section also is the place to go if you need help with technical problems.
• Learn about the tutorial's Learning Objectives