Common Questions

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

CDC's Nutrition Report provides separate biochemical indicator data for supplement users and non-users. The biochemical indicator levels for these groups informs scientists about differences in nutritional status due to supplement use. CDC and several other organizations are 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. The report shows us what the levels of nutrition indicators are in people. In some places, the report shows that certain population groups have adequate levels of specific nutrients. This does not necessarily mean that people are eating healthy and balanced diets. Eating food that is fortified and taking dietary supplements can affect an individual's biochemical levels. Differences in biochemical levels between groups do not necessarily suggest health problems. Independent research is needed to determine levels that indicate who is at risk for disease.

How does this report differ from the previous reports?

This report provides comprehensive reference information for biochemical indicators of diet and nutrition measured in the blood and urine of people who took part in the National Health and Nutrition Examination Survey (NHANES). This report covers all the available NHANES data from 1999–2000 to August 2021–August 2023. The first report provided information for 27 biochemical indicators from NHANES 1999–2002; the second report provided information for 58 indicators from NHANES 2003–2006. This report provides information for 131 indicators.

This report presents

• Data on changes in biochemical indicator levels over time
• Stratification by supplement use
• New data for serum and red blood cell folate forms, red blood cell fatty acids, serum trace metals, serum trans-fatty acids, urine caffeine and caffeine metabolite levels in the U.S. population
• Updates on folate; vitamins C, A, E, and D; carotenoids; phytoestrogens; iron; iodine; and selenium 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 diet and nutrition biochemical indicators in the U.S. population and in selected subpopulations. These data will help healthcare providers, scientists, and public health officials assess inadequate or excess nutrition indicators and inform analyses on the relation between biochemical indicators and health outcomes.

In addition, the report can:

• Establish and improve the 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 reproductive age, or the elderly––to other population groups, pointing out differences and areas that need improvement
• Track trends 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
• Dietary intake

The report does not make recommendations about diet. The Dietary Guidelines for Americans provides recommendations about what to eat. Several professional 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 report?

CDC measured the levels of 131 biochemical indicators. 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)
• Iron status indicators (compounds that evaluate the amount of iron stored, transported, and utilized in the body) such as ferritin and soluble transferrin receptor
• Trace elements (dietary minerals that are needed in very small quantities) such as iodine, selenium, zinc, and copper
• Isoflavones and lignans (natural compounds found in certain plant foods that can bind to estrogen receptors)
• Caffeine and caffeine metabolites (natural compounds found in coffee, tea, soft, and energy drinks recognized as central nervous system stimulants)
• Acrylamide hemoglobin adducts (chemical compounds formed when certain starchy foods are cooked at high temperatures and react with hemoglobin)
• Trans fatty acids (unsaturated fats found naturally in some animal products and artificially in partially hydrogenated oils)

What is a biochemical indicator?

Biochemical indicators of diet and nutrition show 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, caffeine) 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 diet and environmental exposure. Blood and urine concentrations reflect the amount of nutrients and dietary compounds actually in the body or passing through the body.

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 or arithmetic means and selected percentiles with confidence intervals for the total population and by supplement use. Data are presented for the total population by age, sex, race, and Hispanic origin.

What methods did CDC use to analyze these biochemical indicators?

CDC used several analytical methods, including chromatographic methods. Chromatographic methods separate the compound of interest from other compounds in blood and urine to measure biochemical indicators.

References for these methods can be found in Appendix C of the 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. An important emphasis in the study is examining the relationship between biochemical indicators and health outcomes.

Some of the other studies first looked at baseline levels before changes in dietary intake recommendations and then evaluated changes in biochemical levels after supplementation or fortification regimens.

In addition, the National Institutes of Health (NIH) sponsors 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 website.

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 website.

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 website.

How can people find out their levels for biochemical indicators?

You can ask your healthcare provider to test 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 Nutrition 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 laboratory to be sure their methods compare closely with those used in this report.

How can I get a copy of the nutrition report?

You can view the entire report or sections of the report online.

How do I find out more about NHANES?

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