Dietary Assessment Primer

Learn More about Biomarkers

A number of dietary [glossary term:] biomarkers are present in blood, urine, adipose tissue, or hair. Some, such as serum calcium, are tightly controlled metabolically and are poor reflections of dietary intake or nutritional status. These are of little interest for dietary assessment. Other biomarkers reflect nutritional status (for example, beta-carotene). These are classified by the relationship between dietary intake and the corresponding presence of the biomarker.

Those termed [glossary term:] recovery biomarkers exhibit a direct relationship between absolute intake and tissue values. These can be used as reference measures to assess and correct for error (e.g., [glossary term:] underreporting) in self-report dietary data. Only a few recovery biomarkers are known. These include [glossary term:] doubly labeled water (DLW), a biomarker that measures average energy expenditure over a two-week period and is used as a marker of energy intake for weight stable individuals, and 24-hour urinary nitrogen, sodium, and potassium, which are used as recovery biomarkers for protein, sodium and potassium intakes, respectively.

Another classification of biomarkers, termed [glossary term:] concentration biomarkers, correlate with intake, but because they are affected by metabolism or personal characteristics (such as smoking status or obesity), they cannot be used as measures of absolute intake or for assessing error of self-reported intakes in [glossary term:] validation studies. They can be useful, however, for assessing the relationship between tissue concentrations and health [glossary term:] outcomes or other [glossary term:] dependent variables.

Recently, a newer classification of biomarkers, termed [glossary term:] predictive biomarkers, has been proposed. These biomarkers are sensitive, stable, time-dependent, and show a dose-response relationship with intakes. Although they may be affected by personal characteristics, the relation with diet outweighs those factors. Predictive biomarkers may help to identify reporting errors. Examples of predictive biomarkers are 24-hour urinary fructose and sucrose.

In certain situations, biomarkers that are not recovery or predictive biomarkers can be highly informative for assessing nutrient status. For example, the geographic region in which sources of selenium are grown affects the nutrient content of foods. It is therefore difficult to estimate selenium intakes using only self-report dietary data.

For More Information

Bingham SA. Biomarkers in nutritional epidemiology. Public Health Nutr 2002 Dec;5(6A):821-7. Review. [View Abstract]

Bingham SA. Urine nitrogen as a biomarker for the validation of dietary protein intake. J Nutr 2003 Mar;133 Suppl 3:921S-924S. Review. [View Abstract]

Potischman N, Freudenheim JL. Biomarkers of nutritional exposure and nutritional status: an overview. J Nutr 2003 Mar;133 Suppl 3:873S-874S. [Look up in PubMed]

Tasevska N, Midthune D, Potischman N, Subar AF, Cross AJ, Bingham SA, Schatzkin A, Kipnis V. Use of the predictive sugars biomarker to evaluate self-reported total sugars intake in the Observing Protein and Energy Nutrition (OPEN) study. Cancer Epidemiol Biomarkers Prev 2011 Mar;20(3):490-500. Erratum in: Cancer Epidemiol Biomarkers Prev. 2011 Dec;20(12):2646. [View Abstract]