Editorial Feature

A Guide to the Units Used in Nutrition Analysis

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For over 125 years, the United States Department of Agriculture (USDA) has maintained a nationally recognized system of measurements by which food composition analyses can refer to. This article will provide a general overview of the history behind national nutrition analysis programs, the previous methods by which federal officials generated nutrition analysis units, as well as how the recent amendments made by the United States Food and Drug Administration (FDA) have changed the way in which the nutrition labeling of foods and dietary supplements is being conducted.

Early Nutrition Analysis Guidelines

In 1997, the National Food and Nutrient Analysis Program (NFNAP) was introduced by the Nutrient Data Laboratory (NDL) in cooperation with the National Institutes of Health (NIH), the Centers for Disease Control (CDC) and the Food and Drug Administration (FDA) in the United States. The NFNAP represents a dynamic and nationally representative food analysis program in the United States that aims to maintain the highest quality and quantity of data on food products.

Since the NFNAP was originally introduced in 1997, its five primary aims have remained the same. These aims include the identification of both Key Foods and appropriate nutrients that can be used for sampling and analysis purposes, evaluation of current data to confirm quality of food and nutrient samples, implementation of probability-based sampling survey of food items, analysis of sampled food that is conducted under standards that have been developed and approved by the United States Department of Agriculture (USDA) and finally the generation and integration of newly generated data into USDA food composition databases.

Current Methods for Nutrition Labelling

There are three classes of nutrients that can be present and analyzed in any food sample. Class I nutrients include any vitamins, minerals, protein, dietary fiber or potassium contents that have been added in fortified or fabricated foods. Upon random selection and analysis by the FDA, the content of Class I nutrients in any given food sample must be equivalent to what was originally stated in the food product’s nutrition label.

Class II nutrients include any vitamins, minerals, protein, carbohydrate, dietary fiber, potassium, as well as both polyunsaturated and monounsaturated fats that naturally exist within a food sample. The Third Group of nutrients that are identified on any nutrition label include calories, sugars, total fat, saturate fat, cholesterol and sodium present in a food product.

Once a food sample has undergone a full content analysis, the nutrition label values must be calculated. To calculate the nutrient content of a food product, the mean of all values obtained during the nutrient analysis is used to represent the mean nutrient content for that product. Food manufacturers must also calculate the standard deviation for each nutrient value, and subsequently use both the mean and standard deviation values to determine a “per 100 grams” basis that reflects the service size required for the specific food product of interest.

Both Daily Reference Values (DRVs) and Reference Daily Intakes (RDIs) are also determined to assist the consumer in interpreting the nutrient values of their food products. More specifically, DRVs provide the consumer with information on the total fat, saturated fat, cholesterol, total carbohydrate, dietary fiber, sodium, potassium and protein levels for adults and children that are older than four years of age.

Comparatively, RDIs provide children under the age of four, as well as women who are pregnant and/or lactating with information on the vitamins, minerals and protein levels present in the food product. To reduce any confusion among consumers with the differences that can exist between DRVs and RDIs, Daily Value (DV) estimates integrate both DRV and RDI information into a single term. DVs are typically calculated according to an estimated daily caloric intake of 2,000 calories.

Recent Updates on Nutrient Conversion Units

In 2016, the U.S. FDA issued an amendment for the current regulations on how folate, niacin, vitamin A, vitamin D, and vitamin E contents were measured on nutrition labels. Previously, the values of vitamins A, D, and E were measured as international units (IUs), whereas the units of measurement for niacin and folate were previously milligrams (mg) and micrograms (mcg), respectively.

The 2016 announcement by the U.S. FDA declared that vitamins A and D must now be measured using mcg units, whereas vitamin E should be measured using mg alpha-tocopherol or mg. Additionally, niacin should now be measured in mg Niacin Equivalents (mg NE) and folate will be measured in mcg dietary folate equivalents (mcg DFE).

These updated guidelines by the FDA are aimed at providing manufacturers with a better understanding of how they can abide by relevant labeling requirements.


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Benedette Cuffari

Written by

Benedette Cuffari

After completing her Bachelor of Science in Toxicology with two minors in Spanish and Chemistry in 2016, Benedette continued her studies to complete her Master of Science in Toxicology in May of 2018. During graduate school, Benedette investigated the dermatotoxicity of mechlorethamine and bendamustine, which are two nitrogen mustard alkylating agents that are currently used in anticancer therapy.


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