Food Nutrition

Well-characterized food-matrix reference materials are critical to facilitate compliance with nutritional labeling laws, provide traceability for food exports, improve the accuracy of label information for packaged foods, and contribute to studies of human nutritional status. Enactment of the Infant Formula Act of 1980 and the Nutrition Labeling and Education Act (NLEA) of 1990 resulted in requirements for labeling of processed and packaged foods in the US. Some nutrients (e.g., calories, fat, cholesterol) must be declared on the label, while information about other nutrients can be included at the manufacturer’s discretion. However, all nutrient declarations must be accurate and within thresholds set by the regulatory agency (i.e., U.S. Food and Drug Administration (FDA) or the U.S. Department of Agriculture (USDA)). In support of compliance with these regulations, the CSD has developed a series of food-matrix reference materials characterized for mass fractions of common nutrients. The selection of commodities for reference material development was strongly informed by the AOAC INTERNATIONAL triangle model for classification of foods into groups with similar composition [1]. The AOAC food triangle is based on the relative levels of fat, protein, and carbohydrate in the food, and built on the premise that foods with similar macronutrient profiles will offer similar analytical challenges for determination of micronutrients. Food-matrix reference materials are developed from animal, plant, and mixed-matrix sources to represent common food types with various macronutrient profiles [2, 3]. These reference materials are used by laboratories involved with the characterization of food composition (e.g., food manufacturers and processors, regulators, third-party testing laboratories) to develop and validate new analytical methods, to improve the quality of their analytical measurements, and to support compliance with a number of federal regulations enforced by the FDA and USDA [4].

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Project Areas

Nutritional Elements

The FDA requires the content of sodium, calcium, iron, and potassium be provided on the nutritional label of any processed or packaged food sold in the US. In addition, other elements of nutritional interest, such as magnesium, phosphorus, or zinc, may be declared on nutritional labels to bolster or prove the food label or marketing claim. Prior to analytical measurement, the food sample is most often digested in concentrated acid using a microwave or open beaker technique. The NIST approach for elemental analysis includes the addition of internal standards and determination by inductively coupled plasma with optical emission spectrometry (ICP-OES) or with mass spectrometric detection (ICP-MS) [5].  In addition, NIST uses X-ray fluorescence spectrometry (XRF) and the use of multiple neutron activation analysis techniques, instrumental neutron activation analysis (INAA), radiochemical neutron activation analysis (RNAA), and prompt gamma neutron activation analysis (PGAA), for elemental measurements.  To date, over 35 food-matrix reference materials have been issued with values assigned for nutritional elements. For additional technical information, contact Colleen Bryan Sallee (colleen.bryansallee [at] nist.gov (colleen[dot]bryansallee[at]nist[dot]gov)).

Water-Soluble Vitamins

Declaration of water-soluble vitamin content is not required on nutritional labels, but many are included as optional values to bolster or prove food label or marketing claims. Water-soluble vitamins may be present in foods in a variety of forms, with varying levels of individual vitamers depending on the type of food product. Prior to analytical measurement, vitamins are extracted from the food sample, which may include weak hydrolysis to release protein- or lipid-bound forms. The NIST approach for water-soluble vitamin measurement includes the addition of labeled vitamins as internal standards and determination by liquid chromatography with tandem mass spectrometric detection (LC-MS/MS) [6, 7, 8]. To date, over 15 food-matrix reference materials have been issued with values assigned for water-soluble vitamins. For additional technical information, contact Melissa Phillips (melissa.phillips [at] nist.gov (melissa[dot]phillips[at]nist[dot]gov)).

Fat-Soluble Vitamins and Carotenoids

The FDA requires the content of vitamin D be provided on the nutritional label of any processed or packaged food sold in the US. Declaration of other fat-soluble vitamin content is not required on nutritional labels, but many are included as optional values to bolster or prove food label or marketing claims. Fat-soluble vitamins may be present in foods in a variety of forms, with varying levels of individual vitamers depending on the type of food product. Prior to analytical measurement, vitamins are extracted from the food sample, which may include saponification to release lipid-bound forms and/or esters. The NIST approach for fat-soluble vitamin measurement includes the addition of labeled vitamins or related compounds as internal standards and determination by liquid chromatography with absorbance detection (LC-absorbance), with fluorescence detection (LC-fluorescence), or with tandem mass spectrometric detection (LC-MS/MS). To date, over 15 food-matrix reference materials have been issued with values assigned for fat-soluble vitamins. For additional technical information, contact Kate Rimmer (kate.rimmer [at] nist.gov (kate[dot]rimmer[at]nist[dot]gov)).

Fatty Acids

The FDA requires the content of total fat, calories due to fat, and total saturated and trans fats be provided on the nutritional label of any processed or packaged food sold in the US. In addition, other fatty acids of nutritional interest, such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), often are declared on nutritional labels to bolster or prove the food label or marketing claim. Fatty acids are typically present in plant and animal tissues as triglycerides and/or phospholipids, with varying levels of individual fatty acids depending on the type of food product. Prior to analytical measurement, fat is extracted from the food sample, triglycerides and phospholipids are saponified (hydrolyzed) into their free fatty acid components, then all free fatty acids are converted to fatty acid methyl esters (FAMEs). The NIST approach for fatty acid measurement includes the addition of deuterated fatty acids as internal standards and determination by gas chromatography with flame ionization detection (GC-FID) or with mass spectrometric detection (GC‑MS) [9, 10]. To date, over 20 food-matrix reference materials have been issued with values assigned for fatty acids. For additional technical information, contact Ben Place (benjamin.place [at] nist.gov (benjamin[dot]place[at]nist[dot]gov)).

Cholesterol

The FDA requires the cholesterol content be provided on the nutritional label of any processed or packaged food sold in the US. Cholesterol is present in animal tissues as free cholesterol and also bound in triglycerides. Prior to analytical measurement, cholesterol is extracted from the food sample, cholesterol esters are saponified (hydrolyzed) into free cholesterol, then derivatized. The NIST approach for cholesterol measurement includes the addition of labeled cholesterol as an internal standard and determination by gas chromatography with mass spectrometric detection (GC‑MS) [11, 12]. Currently, 5 food-matrix reference materials have been issued with values assigned for cholesterol. For additional technical information, contact Melissa Phillips (melissa.phillips [at] nist.gov (melissa[dot]phillips[at]nist[dot]gov)).

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Measurement Services

Reference Materials for Food Nutrition

other Food-matrix RMs

QUALITY ASSURANCE PROGRAMS (QAPs)

NIST Quality Assurance Programs (QAPs), such as the Food Nutrition and Safety Laboratory QAP (FNSQAP) and the Dietary Supplements Laboratory QAP (DSQAP), provide opportunities for participants to identify and understand community-wide measurement challenges, improve the accuracy of their measurements, and demonstrate an effort to comply with various regulations. These programs offer the opportunity for laboratories to assess their in-house measurements, and participation in a quality assurance program in conjunction with the use of RMs has been shown to improve the comparability and precision of data over time. For additional information, contact the QAP Teams at QAPHUB [at] nist.gov (QAPHUB[at]nist[dot]gov).

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Key Collaborators

NIST’s mission is to promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life. Stakeholder engagement is critical for development of impactful measurement services, and some long-standing partnerships are described below. To share your measurement services needs or suggest new or upgraded solutions, please contact Melissa Phillips (melissa.phillips [at] nist.gov).

AOAC INTERNATIONAL

Consumer Brands Association (formerly Grocery Manufacturers Association)

National Institutes of Health Office of Dietary Supplements (NIH ODS)

US Food and Drug Administration (FDA)

US Department of Agriculture (USDA)

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Opportunities

• NIST supports the efforts of small and medium-sized manufacturers through the Manufacturing Extension Partnership and MEP-Assisted Technology and Technical Resource (MATTR) Program
• Food Safety Postdoctoral Opportunities at NIST are available in cooperation with the National Academies/National Research Council.

References

[1] Wolf, W.R., Andrews, K.W. Fresenius J Anal Chem 352, 73–76 (1995). https://doi.org/10.1007/BF00322300

[2] Phillips, M.M., Sharpless, K.E., Wise, S.A. Anal Bioanal Chem 405, 4325–4335 (2013). https://doi.org/10.1007/s00216-013-6890-5

[3] Wise, S.A., Phillips, M.M. Anal Bioanal Chem 411, 97–127 (2019). https://doi.org/10.1007/s00216-018-1473-0

[4] Sharpless, K.E., Duewer, D.L., Lippa, K.A., Rukhin, A.L. NIST Special Publication 260-181 Revision 1 (2015). https://doi.org/10.6028/NIST.SP.260-181r1

[5] Winchester, M.R., Butler, T.A., Turk, G.C. Analytical Chemistry 82 (18), 7675-7683 (2010). https://pubs.acs.org/doi/10.1021/ac101471a

[6] Phillips, M.M. Anal Bioanal Chem 407, 2965–2974 (2015). https://doi.org/10.1007/s00216-014-8354-y

[7] Camara, J.E., Lowenthal, M.S., Phinney, K.W. Anal Bioanal Chem 405, 4561–4568 (2013). https://doi.org/10.1007/s00216-013-6733-4

[8] Thomas, J.B., Yen, J.H., Sharpless, K.E. Anal Bioanal Chem 405, 4539–4548 (2013). https://doi.org/10.1007/s00216-013-6891-4

[9] Place, B.J. J AOAC INT 100, 814–819 (2017). https://doi.org/10.5740/jaoacint.16-0356

[10] Sander, L.C., Schantz, M.M., Sharpless, K.E., Wise, S.A. Lipid Technology 21, 7-12 (2009). https://doi.org/10.1002/lite.200800080

[11] AOAC Official Method 996.06; Official Methods of Analysis, 18th ed.; AOAC International, Gaithersburg, MD (2000). http://eoma.aoac.org

[12] Ellerbe, P., Meiselman, S., Sniegoski, L.T., Welch, M.J., White, V.E. Anal Chem 614, 1718–1723 (1989). https://doi.org/10.1021/ac00190a025

Contact

To share your measurement services needs or suggest new or upgraded solutions, please contact Melissa Phillips (melissa.phillips [at] nist.gov (melissa[dot]phillips[at]nist[dot]gov)).