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Frequently Asked Questions (FAQ)

Many answers to your questions can be found by clicking on the Dietary Supplement Ingredient Database (DSID) web links to access various parts of the website. Responses to FAQs are below.

Background
1. What is the DSID-3 and what data and data formats are provided?
2. Why was the DSID developed?
3. How are the content and claims of dietary supplements regulated?
4. How were dietary supplements categories and ingredients selected for the DSID?
5. How can the DSID predicted values be used in nutrition studies?
6. What is the difference between the DSID and the Dietary Supplement Label Database (DSLD)?
DSID Content and Applications
7. Why are alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) reported for omega-3 fatty acid dietary supplement?
8. Is there an ingredient calculator for omega-3 fatty acid dietary supplements?
9. Why are there 2 children's MVM calculators?
10. How were non-prescription prenatal multivitamin/mineral (MVMs) defined for selection in the DSID?
11. Why are ingredients reported in different units, such as milligrams (mg), micrograms (mcg, µg), or International Units (IU) in the DSID?
12. Were conversion factors for the natural and synthetic forms of vitamin E applied to the calculations of vitamin E in IUs for the DSID?
13. Why is vitamin A reported rather than separate values for beta carotene and retinol?
Statistics
14. How were the DSID predicted analytical estimates derived?
15. Why do I receive error messages when I enter certain ingredient amounts?
16. What is the 'Predicted Mean Value'?
17. What are the 'Standard Error for Predicted Mean' (SEM) and the 'Standard Error for Predicted Observation' (SEO)?
18. How are the 'Predicted Mean Value', 'Standard Error for Predicted Mean' and 'Standard Error for Predicted Observation' calculated from the regression equations?


Background
1. What is the DSID-3 and what data and data formats are provided?

The DSID, an initiative of the Office of Dietary Supplements at NIH, was developed at the Nutrient Data Laboratory, USDA. DSID-3 is the third release of DSID and provides analytically derived estimates of levels of vitamins and minerals in adult, children's, and non-prescription prenatal MVMs. 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), DHA (docosahexaenoic acid). DSID-3 includes:
  • statistical results reported as regression equations
  • research summaries for each DS study
  • data files containing predicted ingredient amounts in Access, SAS and Excel formats
  • data files containing DSID applications to products in the National Health and Nutrition Examination Survey (NHANES) for specific cycle years of the surveys in SAS and Excel
  • ingredient calculators for 3 product categories
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2. Why was the DSID developed?

The DSID was developed to:
  • provide reliable estimates of mineral, vitamin and other bioactive content in dietary supplements by analyzing dietary supplements representative of the US market
  • report on analytically derived levels of ingredients compared to labeled values, if available
  • support improved dietary intake assessments in research by providing analytical estimates of the ingredient content of dietary supplements
  • release and maintain a publicly available online composition database.
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3. How are the content and claims of dietary supplements regulated?

The responsibility for ensuring the validity of manufacturer's claims rests with the manufacturer, the Food and Drug Administration (FDA), or, in the case of advertising, with the Federal Trade Commission (FTC). In October 1994, the Dietary Supplement Health and Education Act (DSHEA) was signed into law. Under DSHEA, a firm is responsible for determining that the dietary supplements it manufactures or distributes are safe and that any representations or claims made about them are substantiated by adequate evidence to show that they are not false or misleading. The FDA does not check the contents of all dietary supplements although specific issues with ingredients or products are evaluated. FDA issued Current Good Manufacturing Practices (CGMPs) for dietary supplements, a set of requirements and expectations by which dietary supplements must be manufactured, prepared, and stored to ensure quality. If dietary supplements contain contaminants or do not contain the dietary ingredient they are represented to contain, FDA would consider those products to be adulterated or misbranded.
SOURCE: FDA, Current Good Manufacturing Practices (CGMPs) for Dietary Supplements
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4. How were dietary supplement categories and ingredients selected for the DSID?

A consortium of federal partners convened by the Office of Dietary Supplements established DSID priorities for products and ingredients of public health and research interest. MVM products and omega-3 fatty acid supplements were identified as top priorities because they are among the most commonly reported dietary supplements in the NHANES. Ingredients for analysis were determined based on prevalence of consumption, public health interest, and the availability of reliable analytical methods for specific compounds.
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5. How can the DSID predicted values be used in nutrition studies?

The analytically-derived DSID estimates of mean values can replace label information to more accurately assess the nutritional status of the US population.
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6. What is the difference between the DSID and the Dietary Supplement Label Database (DSLD)?

Both databases are initiatives of the Office of Dietary Supplements (ODS) at NIH. The DSID was developed in partnership with the Nutrient Data Laboratory, USDA and provides analytically-derived estimates of the ingredients in dietary supplements. The DSLD is a joint project of ODS and the National Library of Medicine. DSLD provides open access to full label contents of dietary supplements marketed in the US.
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DSID Content and Applications
7. Why are alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) reported for omega-3 fatty acid dietary supplement?

The three major components of omega-3 fatty acids supplements are EPA, DHA, and ALA. These are the omega-3 fatty acids most commonly labeled on supplement products and studied for their health effects.
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8. Is there an ingredient calculator for omega-3 fatty acid dietary supplements?

Approximately 85% of the products in the omega-3 fatty acid supplement study listed a label amount for at least one of the major omega-3 fatty acids (ALA, EPA or DHA). The data in the DSID-3 is based on the statistical evaluation of the analytical results for these products. NDL scientists plan to compare the analytical results for products with labeled levels of individual omega-3 fatty acids to results for products not labeled. Also being investigated is how best to evaluate total omega-3 fatty acid analytical results and label claims. The DSID will publish an omega-3 fatty acid ingredient calculator when statistical evaluations of the data are complete.
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9. Why are there 2 children's MVM calculators?

Most of the children's MVM products in this study listed more than one age group or serving size on their labels. The laboratory data and the label information for each ingredient were examined and two datasets were created and analyzed independently. One contained children's products with label information for children that were 4 years and older (n=59 products), while the other dataset was for products with label information for children 1 to <4 years of age (n=50 products). Data associated with the age group 4 years and older were determined to be the primary dataset for applying regression analysis results to products in population studies.
The results for the percent differences from label at the most common labeled levels were similar for the 2 age groups. However, there are ingredients with significant differences between the predicted values for portions of the regression range. As a result, separate regression equations and a separate online calculator were created for each age group. Please see the Children's MVM Research Summary for more details.
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10. How are non-prescription prenatal multivitamin/mineral (MVMs) defined for selection in the DSID?

Non-prescription prenatal MVMs were defined for this study as products containing >3 vitamins with or without minerals or other bioactive components, intended for prenatal use and available for purchase without a prescription from a healthcare provider. Prescription prenatal MVMs require a written order from a healthcare provider.
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11. Why are ingredients reported in the DSID in different units such as milligrams (mg), micrograms (mcg, µg), or International Units (IU) in the DSID?

The DSID uses the FDA's established units of measure for reporting ingredient amounts on labels, since the DSID reported results are compared to labeled levels. See Appendix A for a listing of ingredients, units and other reference information concerning DSID release data. See the Unit Conversions page for information on specific ingredients such as vitamins A, D, and E.
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12. Were conversion factors for the synthetic and natural forms of vitamin E applied to the calculations of vitamin E in IUs for the DSID?

For the DSID, the results from the chemical analysis of vitamin E (as alpha-tocopherol) in dietary supplements are reported by the laboratory in mg/g. This amount is converted to IU/serving using the weight of one serving of the product in grams and applying the appropriate conversion factor. The analytical result in IU is then compared to the label value in IU to calculate the percent difference from the labeled amount. The conversion factor used for each analytical result is dependent upon whether the alpha-tocopherol being measured is in a natural or synthetic form. When calculating IU equivalents, NDL uses the vitamin E labeling guidelines for manufacturers, provided by the FDA. Current manufacturing guidelines provided by the FDA are based on the 1968 RDAs (Recommended Daily Allowances), which use a factor of 0.9 for converting synthetic vitamin E as dl-alpha tocopherol from IU to mg. In contrast, the 2003 Dietary Reference Intake (DRI) guidelines are based on bioavailability standards for converting the quantity of synthetic vitamin E as dl-alpha-tocopherol from IU to mg, which is IU x0.45. For natural vitamin E as d-alpha-tocopherol, the conversion of IU units to mg units is the same for both FDA labeling guidelines and the 2003 DRI, using IUx0.67.
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13. Why is vitamin A reported rather than separate values for beta carotene and retinol?

The major components of vitamin A, retinol and beta-carotene, were measured separately for these studies. The laboratory results were converted to International Units (IU) and combined to calculate total vitamin A, for comparison to vitamin A (IU) on product labels.
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Statistics
14. How were the DSID predicted analytical estimates derived?

The data for the DSID predicted estimates were derived from national studies (conducted to identify, purchase and analyze representative MVM and omega-3 fatty acid dietary supplements). Analytical data were compared to label claims and statistically evaluated using regression analysis. Percent difference from label values were the dependent variable and the label values were the independent variable. Regression equations were used to estimate mean predicted percent difference from label for individual ingredients in each product category. Details about each study, including a summary of statistical analyses can be accessed at the Research Summaries section of this website.
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15. Why did I receive an error message when I entered an ingredient amount in the DSID calculator?

Probably one of two events has occurred. Either you have entered a decimal value that is not acceptable or a value that is outside the established regression range for that ingredient in the calculator. All ingredients allow a label value to be entered with up to 4 places after the decimal point. Each ingredient has a numeric range (shown on the screen) for which the predictions are valid. Entering a value outside this range will result in an error message.
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16. What is the 'Predicted Mean Value'?

The 'predicted mean value' is the estimated amount of that ingredient at a specific labeled level, as determined by regression analysis. Predicted means and other statistical parameters have been established within a defined label range for each ingredient in each product category. For example, the defined regression range for iodine is 15 to 200 µg for adults and 12.8 to 150 µg for children age 4 and older. For labeled levels above and below those amounts, predicted amounts are not available at this time.
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17. What are the 'Standard Error for Predicted Mean' (SEM) and the 'Standard Error for Predicted Observation' (SEO)?

The 'standard error for predicted mean' estimates the uncertainty associated with the predicted mean for a large population of supplements labeled at the same level. The predicted mean ± SEM has about a 2/3 probability of including the true mean ingredient content for supplements at that predicted label level. The 'standard error for predicted observation' estimates the uncertainty associated with the predicted amount for a single new observation, which in this case is any individual supplement. The predicted mean ± SEO has about a 2/3 probability of including the analytical ingredient content for an individual supplement at that predicted label level. The polynomial equations to calculate the SEs are described in Table 1 of the DSID-3 Data Files and applied in the DSID-3 calculators.
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18. How are the 'Predicted Mean Value', 'Standard Error for Predicted Mean' and 'Standard Error for Predicted Observation' calculated from the regression equations?

These values are calculated from the statistical data provided in Table 1 of the DSID-3 release. An 'Example Calculations' document provides definitions and instructions for applying the data in Table 1 to labeled levels of supplement product categories. A spreadsheet version of the 'Example Calculations' is available in the second tab of Table 1.
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