Common Questions

Common questions

Are some population groups at a higher risk for nutrient deficiencies?

The type of nutrient deficiency may differ by population group. For example, children and women of childbearing age are at increased risk for iron deficiency, and older persons have an increased risk for vitamin B6 or B12 deficiency. Males are at increased risk for vitamin C deficiency, and females have an increased risk for iron and vitamin B6 deficiency. Non-Hispanic blacks and Mexican Americans are at increased risk for vitamin B6 and vitamin D deficiency, and non-Hispanic whites have an increased risk for vitamin C deficiency.

Have nutrient levels changed over time?

No. NHANES data from 1999 through 2006 indicate nutrient levels and rates of deficiency in the U.S. population have not changed.

Does the report include information on the use of vitamin supplements?

CDC's Nutrition Report does not provide separate data on users of vitamin supplements. Data in this report include persons who used vitamin supplements and those who did not. Knowing about the use and non-use of vitamin supplements and role they play in nutrition is valuable information. CDC and several other agencies and organizations are currently researching the impact of vitamin supplements on an individual's nutrition status. The NIH Office of Dietary Supplements gives information on the use and safety of dietary supplements for all age groups.

What does the report tell us about the state of our nation's health?

The report does not rate the state of our nation's health. It evaluates the state of our nation's nutrition status by measuring biochemical indicators. The report shows us what the levels of nutrition indicators actually are in people. In some places the report shows that certain population groups have adequate biochemical levels of specific nutrients. This does not necessarily mean that people are eating healthy and balanced diets. Food fortification and taking dietary supplements can affect biochemical levels. Differences in biochemical levels between groups do not necessarily suggest health problems. Independent research is needed to determine levels that indicate risk for disease.

How does the second report differ from the first report?

Both reports give comprehensive reference information for biochemical indicators of diet and nutrition measured in blood and urine of people who took part in the National Health and Nutrition Examination Survey (NHANES). The first report gave information for 27 biochemical indicators from NHANES 1999–2002; the second report has information for 58 indicators from NHANES 2003–2006. The second report also presents first-time data on:

• Changes in biochemical indicator levels over time
• Prevalence information for deficiency or excess
• Fatty acid levels and acrylamide exposure in the U.S. population, and
• Updates on folate, vitamin D, iron, and iodine status

How can the report be used to help public health?

This report's primary objective is to inform public health scientists and policy makers about the levels of biochemical indicators of diet and nutrition in the U.S. population and in selected subpopulations. These data will help healthcare providers, scientists, and public health officials assess inadequate or excess intake and inform analyses on the relation between biochemical indicators and health outcomes.

In addition, the report can:

• Establish and improve on existing population reference levels used to determine whether a person or a group has an unusually high or low concentration of a diet-and-nutrition biochemical indicator.
• Compare the nutrition status of population groups−like minorities, children, women of childbearing age, or the elderly−to other population groups, pointing out differences and areas needing improvement.
• Track trends over time in the population's biochemical indicator concentrations.
• Assess the effectiveness of public health efforts to improve the diet and nutrition status of the U.S. population.
• Guide research to perform in-depth analyses of the NHANES data for future nutrition and human health studies.

What information does the report not include?

The report does not cover nutrition status factors such as

• Body measurements like height and weight,
• Clinical signs of nutrition deficiency or excess, and
• Dietary intake.

The report does not make recommendations about diet. The Dietary Guidelines for Americans provide recommendations about what to eat, and several associations offer guidelines on nutrition-related risk factors that influence health outcomes.

Lastly because of the NHANES survey design, the report does not give information by state.

What biochemical indicators are included in this second report?

CDC measured levels of 58 biochemical indicators for the second nutrition report. Some of these indicators include:

• Water-soluble vitamins (compounds that can dissolve in water) such as folate, vitamins B6, B12, and C
• Fat-soluble vitamins and nutrients (compounds that can dissolve in fat) such as vitamins A, E, and D, carotenoids, and fatty acids (saturated, monounsaturated, and polyunsaturated)
• Trace elements (dietary minerals that are needed in very small quantities) such as iron-status indicators and iodine
• Isoflavones and lignans
• Acrylamide hemoglobin adducts

Access the Executive Summary for a full list of indicators in the Second Nutrition Report.

What is a biochemical indicator?

Biochemical indicators of diet and nutrition indicate the nutrition status of a person. For this report, a biochemical indicator means a nutrient (e.g., vitamin, fatty acid, trace element), a metabolite (e.g., homocysteine, methylmalonic acid), or a dietary indicator with potential health relevance (e.g., isoflavone, lignan) that can be measured in blood or urine.

Although most biochemical indicators presented in this report enter the human body from foods or supplements, the body itself produces some indicators in response to dietary intake or environmental exposure. Blood and urine concentrations reflect the amount of nutrients and dietary compounds actually in the body or passing through the body from all these sources.

What do these levels of biochemical indicators in people's bodies mean?

Blood and urine levels of biochemical indicators can help assess if the U.S. population is getting enough of certain nutrients. These measurements indicate total intakes from foods (some fortified with micronutrients) and from dietary supplements that contain vitamins and minerals. Blood or urine levels of biochemical indicators can also be influenced by factors other than diet, such as various diseases or environmental exposures. More research is needed to determine levels that indicate risk for disease.

What statistical information is in the report?

The nutrition report presents descriptive statistics about the distribution of blood and urine levels of biochemical indicators in the U.S. population. Statistics include geometric means and selected percentiles with confidence intervals. Data are presented for the total population and by age, sex, and race/ethnicity.

What methods did CDC use to analyze these biochemical indicators?

CDC used several analytical methods involving mostly chromatographic methods that separate the compound of interest from other compounds in blood and urine to measure biochemical indicators for this report.

References for these methods can be found in Appendix D of the Second Nutrition Report.

Is CDC involved in other studies to determine the relationship between biochemical indicators and health outcomes?

Each year, CDC collaborates with other federal agencies, academic institutions, governments, and other organizations on studies of diet and nutrition. Examining the relationship between biochemical indicators and health outcomes is a focus.

Some of the other studies include determining baseline levels before changes in dietary intake recommendations and evaluating changes in biochemical levels as a result of supplementation or fortification regimens.

In addition, the National Institutes of Health (NIH) sponsor research that addresses nutrition status, its relationship to chronic and infectious diseases, and its interactions with the environment or genes. For more information, visit the NIH Web site.

The Agricultural Research Service (ARS) of the U.S. Department of Agriculture (USDA) is conducting research in human nutrition and food safety. For more information, visit the USDA Web site.

The Center for Food Safety and Applied Nutrition (CFSAN) at the Food and Drug Administration (FDA) provides consumer information on nutrition and health, food labeling, food safety, and dietary supplements. For more information, visit the FDA Web site.

How can people find out their levels for biochemical indicators?

Ask your healthcare provider to request tests for some of the biochemical indicators listed in the report: folate, vitamin B12, homocysteine, 25-hydroxyvitamin D, and iron-status indicators. However, analyses for most indicators in the Second Report are not widely available. Regardless of the availability of the test, laboratories may use different methods for measuring the indicators. Different methods may result in different method-specific reference ranges.

Consequently, to apply the results in this report, health science professionals should check with their particular laboratory to be sure their methods compare closely with those used in this report.

How can I get a copy of the second nutrition report?

You can view the entire report or section of the report online. You may order a printed copy of the report by sending an email to ncehdls@cdc.gov or by contacting CDC at 1-800-CDC-INFO (800-232-4636) or cdcinfo@cdc.gov.

How do I find out more about NHANES?

Visit the CDC NHANES Web site or download the CDC Factsheets for more information about NHANES.