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Frequently Asked Questions (FAQs)
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USDA Nutrient Database:

Nutrition Resources:

Education Resources:

Note:  Although we have made reasonable efforts to assure the accuracy of linked information, the Nutrient Data Laboratory does not assume responsibility for information obtained beyond this point or for interpretations of our data on other sites.  Please remember to click on the BACK Button on your browser to return to this page.


How do I reference the USDA National Nutrient Database for Standard Reference?

The suggested citation is:

US Department of Agriculture, Agricultural Research Service, Nutrient Data Laboratory. USDA National Nutrient Database for Standard Reference, Release 28. Version Current:  September 2015.  Internet:  /nea/bhnrc/ndl

Note: Release numbers change as new versions are released.

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 Is there a copyright on USDA food composition data?

USDA food composition data is in the public domain, there is no copyright and no permission is needed for its use. We would appreciate it if you would list us as the source of the data and when possible we would like to see the product which uses the data or be notified of its use.

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I multiplied protein, fat and carbohydrate values by 4-9-4 my energy value is different from USDA's. Why?

Calorie values are based on the Atwater system for determining energy values. The factors used in the calculation of energy in the database are given in the food description file of the USDA National Nutrient Database for Standard Reference, Release. The basis and derivation of these factors are described in

Merrill, A.L. and Watt, B.K. 1973. Energy Value of Foods...Basis and Derivation. Agriculture Handbook No. 74. U.S. Government Printing Office. Washington, DC. 105p.

This reference is out of print, but a scanned copy is viewable on our home page.  It may also be available at many university libraries. The Atwater system uses specific energy factors which have been determined for basic food commodities. These specific factors take into account the physiological availability of the energy from these foods. The more general factors of 4-9-4 were developed from the specific calorie factors determined by Professor Atwater and associates. For multi-ingredient foods which are listed by brand name, calorie values generally reflect industry practices of calculating calories from 4-9-4 kcal/g for protein, fat, and carbohydrate, respectively, or from 4-9-4 minus insoluble fiber. The latter method is frequently used for high-fiber foods because insoluble fiber is considered to provide no physiological energy. If the calorie factors are blank or zero for an item in the Database, energy was calculated by recipe from ingredients or was supplied by the manufacturer.

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How is Carbohydrate, by difference determined?

Carbohydrate is determined as the difference between 100 and the sum of the percentages of water, protein, total lipid (fat), ash, and, when present, alcohol. Total carbohydrate values include total dietary fiber.

Total carbohydrate by difference = 100 - [water, protein, total lipid, ash and alcohol in g/100g]

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Why don't the individual fatty acid or the fatty acid classes add up to the total lipid (fat)?

The fatty acids are reported as grams of fatty acid per 100 grams of food. They may not add up to the total lipid value provided in a database because the fat value may include some non-fatty acid material, such as, glycerol, phosphate, sugar or sterol. In the case of vegetable oils that are 100% triglyceride, 95.6% is fatty acid and the remaining 4.4% is glycerol. For other fats, the percent of fatty acid will be even lower. Lipid conversion factors for specific fats define the amount of fatty acid (in grams) per gram of fat. The factor is 0.956 for triglycerides and lower for other fats. The factors used in each section of Agriculture Handbook No. 8 were published in an appendix table.  In addition, the individual fatty acids may not add up to their respective total fatty acid classes (saturated, monounsaturated, and polyunsaturated) and in turn, the sum of the total for each class may not add up to the value for total lipid.  

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 How do I get a copy of Agriculture Handbook No. 8?

The electronic version of Agriculture Handbook No. 8, the USDA National Nutrient Database for Standard Reference can be downloaded from this Home Page. A program allowing you to search the database is also available. Reports giving the content of each item in the Database are  available online. Printed copies of Agriculture Handbook No. 8, Composition of Foods, are no longer available, though copies may be available at libraries in universities with departments of nutrition or food science. Since there is no copyright, you are free to make additional copies.

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What is the status of the USDA Database for the Added Sugars Content of Selected Foods?


In 2012 USDA's Nutrient Data Laboratory (NDL) removed the USDA Database for the Added Sugars Content of Selected Foods from the NDL website due to constant changes in formulations for commercial, multi-ingredient foods, the primary contributor of added sugars to the diet.  Though a reevaluation of these foods, their ingredients and ingredient proportions is integral to our ongoing monitoring program, we are not recalculating added and intrinsic sugars at this point in time.  This is, in part, because brand name market shares and ingredients are changed so rapidly that these estimates are more a temporary cross-section in time than fixed values. No method can analyze for added sugars so their amounts must be extrapolated or supplied by food companies, many of which are not willing to make public such proprietary information.

For these reasons the Added Sugars Table, previously available on this web site, has been withdrawn.

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I'm looking for dietary advice. Can you tell me which foods are best for me to eat?

NDL does not provide any kind of dietary advice. The U.S. Department of Agriculture and the Department of Health and Human Services has prepared Dietary Guidelines for Americans, 2010. We recommend nutrition counseling by a qualified professional. The American Dietetic Association maintains a service to find a Registered Dietitian in your area. Other resources include your local dietetic association, health department or hospital.

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Where can I get information on Dietary Supplements?

The Nutrient Data Laboratory (NDL), in collaboration with the Office of Dietary Supplements, National Institutes of Health (ODS/NIH) and other federal agencies developed a Dietary Supplement Ingredient Database (DSID) to evaluate levels of ingredients in dietary supplement products. ODS/NIH conducts research on dietary supplements and has collected information on vitamins, minerals, and botanicals, which is available on the ODS web site. USDA's Food and Nutrition Information Center has also compiled a number of resources on dietary supplements.

Dietary supplement ingredients were prioritized for analysis based on public exposure, public health significance, research needs, and the availability of validated analytical methods and reference materials. Representative supplement products are identified and sampled using statistical sampling plans. Samples are then analyzed by experienced laboratories and these data are statistically evaluated by ingredient. The third release of DSID (DSID-3) provides analytically derived estimates of levels of vitamins and minerals in adult, children's, and non-prescription prenatal MVMs. The DSID-3 release includes data tables, data application tables to the National Health and Nutrition Examination Survey data, research summaries and online MVM calculators. For the first time, DSID-3 also reports on the estimated relationship of label and analytical values and variability in omega-3 (n-3) polyunsaturated fatty acid supplements (ALA (alpha-linolenic acid), EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid)). DSID predicted estimates are based solely on the labeled level for each product category and the predictions are not brand or supplement specific. For these reasons, the DSID data are appropriate for population studies of nutrient intake, rather than to be applied to content adjustment in individual products.

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Where can I get information on nutrition? logo, provides easy access to all online federal government information on nutrition. This national resource makes obtaining government information on nutrition, healthy eating, physical activity, and food safety, easily accessible in one place for many Americans.  More nutrition information is available in the 2010 Dietary Guidelines,and on the Web site.  USDA's Food and Nutrition Information Center has compiled a wide variety of links to food and nutrition resources on the Internet.  Some of the resources they have developed contain information on food allergies, food, labeling, food safety, dietary guidance, dietary supplements, nutrition and cancer, vegetarian nutrition and many more.   USDA's Center for Nutrition Policy and Promotion also has information on preparing nutritious meals andother nutrition information.   The American Dietetic Association also has a variety of nutrition information on their Web site.

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Do you have a copy of the RDAs on your Web site?

In 1996 the Food and Nutrition Board, Commission on Life Sciences, National Research Council began developing Daily Reference Intakes (DRIs) to replace the Recommended Dietary Allowances (RDAs).  These new DRIs are published by the National Academies Press.  Copies of the RDA and DRI  tables are available on the National Agricultural Library's Food and Nutrition Information Center's Web site


In 1973 the FDA developed the U.S. RDA system to replace the minimum daily requirements which had previously been used for nutrition labeling purposes. The U.S. RDAs were based on the Food and Nutrition Board's RDAs, but were not identical to them. The Daily Values (DV) used on current nutrition labels are based on the U.S. RDAs and can be found in the Code of Federal Regulations, Title 21, Part 101.9.

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What is the difference between calories and kilocalories?

In the U.S., energy in foods is expressed in kilocalories (kcal). The scientific definition of a kilocalorie is the amount of energy needed to raise the temperature of 1 kilogram of water one degree Celsius from 15? to 16? at one atmosphere. The true calorie, sometimes referred to as a "small calorie," is the amount of energy needed to raise the temperature of one gram of water one degree Celsius from 15? to 16? at one atmosphere. A kilocalorie is equal to 1000 calories. While the term "calorie" technically applies to the "small calorie," in common usage, such as in reference to food energy, the term "calorie" is actually a kilocalorie. Internationally, most countries express food energy in kilojoules (kJ). One kcal equals 4.184 kJ. The USDA National Nutrient Database for Standard Reference contains values for both kilocalories and kilojoules.

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 What are omega-3 and omega-6 fatty acids?

These are types of polyunsaturated fatty acids. Linolenic acid, the shortest chain omega-3 fatty acid, and linoleic acid, the shortest chain omega-6 fatty acid, are essential fatty acids. This means they cannot be synthesized by the body from other fatty acids and must be obtained from food. The most common fatty acids of each class are linolenic (18:3), EPA (20:5), DHA (22:6) for omega-3 and linoleic (18:2) and arachidonic (20:4) for omega-6. Some of the food sources of omega-3 fatty acids are fish and shellfish, flaxseed, walnuts, and canola oil. A computer software package, KIM (Keep it Managed) can be downloaded from This software evaluates the balance of omega-3 and omega-6 fatty acids in your diet. A scientific discussion of physiological effects of omega-3 fatty acids can be found on the American Heart Association Web site.

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 Where do I get information on nutrition labeling?

USDA's Food Safety and Inspection Service (FSIS) regulates the labeling of meat and poultry. The Food and Drug Administration (FDA) is responsible for all other foods. Information on labeling is available from FDA's Home Page

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 My son/daughter has a science fair project. How does he/she analyze a food for a particular nutrient?

Methods for determination of nutrients in foods are published in the "Official Methods of Analysis of AOAC International," The 18th edition comes in 2 volumes. If only earlier editions of the publication can be found, some methods such as the titrimetric method for vitamin C, have not changed in many years. There are also other publications which your child's science teacher can recommend. Caution: Many methods of analysis for foods require the use of strong chemicals, use of specialized equipment and adult supervision. Age and experience of the student should be considered when experiments are planned. Younger students may be encouraged to conduct simple experiments which are planned with the teacher's or parent's guidance.

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 Do you have resources for teachers?

ARS's Information Staff has prepared " Science 4 Kids."  which is a series of stories about what scientists do here at the ARS.  They have also prepared the " Whiz Kid" Activity Packet, which is intended for teachers, and is chock-full of fun and clever graphics to introduce agricultural research topics. 

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