The Scoop - September 2012

The Role of the National Health and Nutrition Examination Survey

The National Health and Nutrition Examination Survey (NHANES) is a major program of the National Center for Health Statistics (NCHS). NCHS is part of the Centers for Disease Control and Prevention (CDC) and has the responsibility for collecting and summarizing health information about our country. Begun in the 1960s, NHANES assesses the health and diet of American adults and children and tracks changes over time. Using a combination of interviews and physical examinations, the survey collects information from about 5,000 people every year. Data from NHANES are important to public health programs and policies. For example, NHANES data have been used to develop growth charts, determine vitamin and mineral fortification of foods, uncover the problem of lead exposure, and track the amount of obesity in the United States, to name just a few. The National Institutes of Health (NIH) Office of Dietary Supplements (ODS) funds the collection of data from survey participants as the basis for research, including the study described below. For more information, visit NHANES.

Do dietary supplements help children get adequate amounts of vitamins and minerals?

Many children fail to get enough calcium and vitamin D, even when using dietary supplements. This was one of the findings published recently in the Journal of Pediatrics when researchers analyzed 4 years of data for more than 7,000 children who participated in NHANES. The analysis, led by Dr. Regan Bailey from ODS, was undertaken to determine whether dietary supplements help “fill the gaps” in children’s diets or whether they contribute to excessive intakes of some vitamins and minerals. With the exception of calcium and vitamin D, children age 2--8 years had adequate intakes of all vitamins and minerals whether or not they used supplements. Many older children had trouble getting enough of several important nutrients including magnesium and vitamins A, C, and E from food and beverages alone. But the use of supplements significantly increased intakes of all of these nutrients. Use of supplements also increased the likelihood that children (particularly those age 2--8) would get excessive amounts of some vitamins and minerals, although it is not known whether this causes any harm.

Information about food, nutrition, and how it affects our health is everywhere. You probably have heard, for example, that many Americans eat too much fat or too much salt, and some do not get enough of certain vitamins and minerals.

But how do scientists learn what people actually eat and whether they take any vitamins, minerals, or other dietary supplements? You might be surprised to learn that thousands of people in the United States volunteer to take part in an ongoing federal government survey that collects this information. It is called the National Health and Nutrition Examination Survey or NHANES (see "The Role of the National Health and Nutrition Examination Survey" to the left).

About 5,000 people in the United States participate in NHANES each year. Participants answer questions about their health, disease history, and diet; undergo a health examination; and provide blood and urine samples for measurements and tests. These volunteers, both male and female, range in age from infants to older adults and come from diverse racial and ethnic backgrounds. They are selected from neighborhoods across the country, with each volunteer representing approximately 60,000 other residents. Together, NHANES participants provide a snapshot of the health and diet of the U.S. population.

Findings from NHANES are used for many purposes. For example, scientists are able to learn the amounts of vitamins and minerals people get from the foods they eat, from fortified foods (containing added nutrients), and from dietary supplements. This type of information helps doctors, researchers, and policymakers identify such things as nutrient intakes linked with good health and whether there is a need to change vitamin and mineral fortification regulations for the U.S. food supply. NHANES data have helped scientists learn the extent to which the fortification of breads, cereals, and other grains with folic acid has increased Americans’ intake of this nutrient. Getting enough folic acid is crucial for women before they become pregnant because it helps reduce the risk of spina bifida and other birth defects that occur very early in pregnancy----often before a woman knows she is pregnant.

NHANES researchers also found that about one-half of adults and one-third of children in the U.S. take dietary supplements. Use of supplements is highest among non-Hispanic whites, older adults, and those with more than a high school education. And scientists recently examined how the use of dietary supplements by children affects their intakes of many important nutrients (see "Do dietary supplements help children get adequate amounts of vitamins and minerals?" to the left). NHANES also has started to explore the reasons why people take dietary supplements.

So if you see one of the NHANES mobile exam centers in your city or somewhere in the country, you will know that the information collected there will help to improve the health of the U.S. population and prevent future health problems.