Frequently Asked Questions (FAQ)

Background

The DSID, an initiative of the Office of Dietary Supplements at NIH, was developed at the Methods and Application of Food Composition Laboratory, USDA. DSID-4 is the fourth release of DSID and provides analytically derived estimates of levels of vitamins and minerals in adult, children's, and non-prescription prenatal MVMs and estimates of fatty acid content in omega-3 (n-3) polyunsaturated fatty acid supplements. DSID-4 includes:

• statistical results reported as regression equations
• research summaries for each DS study
• data files containing predicted ingredient amounts and variability information available in Access, SAS and Excel formats
• data tables in SAS and Excel with linking codes for application of results to products in the National Health and Nutrition Examination Survey (NHANES) for specific cycle years of the surveys
• six ingredient calculators for four product categories

The DSID was initiated to answer questions about the actual content of commonly consumed dietary supplements. The goals are 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.

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

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.

The analytically-derived DSID estimates of mean values can replace label information to more accurately assess the intake from dietary supplements in large studies of the US population.

Both databases are initiatives of the Office of Dietary Supplements (ODS) at NIH. The DSID was developed in partnership with the Methods and Application of Food Composition 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 >70,000 dietary supplements marketed in the US.

DSID Content and Application

The DSID identified nonvitamin/mineral bioactive ingredients in DS for analysis and inclusion based on these criteria: public exposure (intake and sales), the availability of validated analytical methods and analytical reference materials, research interests and economic and safety concerns.

‘Green tea’ refers to the unfermented dried leaf of the tea plant (Camellia sinensis). The leaf may be whole, finely chopped or powdered. In a ‘green tea extract’, the leaves have been mixed with a solvent in order to extract and usually concentrate the plant bioactive compounds. The solvent is then removed from the extract, and the extract is incorporated into a tablet or capsule.

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 most commonly studied for their health effects.

A new online, interactive, Adult MVM-2017 Calculator has been released with DSID-4. This calculator allows the user to enter ingredient information from MVM labels and generate the appropriate predicted mean values, SE and CI for those labeled levels.

The adult MVM-2017 calculator is based on the chemical analysis of products purchased in 2011, and so provides more current data than the calculator with results from the original adult MVM (adult MVM-2009) study (products purchased in 2006-07). The calculator that is based on the adult MVM-2009 study is also available on the DSID website and can be used for historical data or trends analysis.

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 the 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.

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.

New labeling regulations for ingredients in DS were finalized by the FDA in 2016, and the use of the new measurement units for labeling was implemented in 2020-2021. In the next release of the DSID (DSID-5), the DSID data files and calculators will be updated to include data results using the new labeling units for vitamins A, D and E, niacin and folic acid. See the Unit Conversions page for more detail

The units of measure currently provided in the DSID-4 are the original units required by FDA and are based on the 1968 Recommended Daily Allowances (RDA). See Appendix A for a listing of ingredients, units and other reference information about DSID data

The DSID currently reports Vitamin E data in International Units (IU), which use the conversion factors that are based on the 1968 RDA. New labeling regulations for some ingredients in DS were finalized by the FDA in 2016, and the use of the new measurement units for labeling was implemented in 2020-2021. With the next release of the DSID, the DSID data files and calculators will be updated to include data results using the new labeling units for vitamins A, D and E, niacin and folic acid. See the Unit Conversions page for more details.

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. See the Unit Conversions page for more details.

Statistics

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.

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.

The mean % difference from label is the average percentage difference from a specific label level estimated by regression. Percent differences from label were calculated from the final analytical data for each study using the equation: ((analytical value – label value)/label value) × 100. The relationships between the label and percent difference from label were estimated by regression with a SAS® mixed model procedure. For each ingredient in each product category, the label value was the independent variable and the percent difference from the label level was the dependent variable.

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.

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 range identified by the 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 an observation' estimates the uncertainty associated with the predicted amount for a single new observation. The range identified by the mean ± SE of an observation has about a 2/3 probability of including the analytical ingredient content for an individual supplement at that label level. The polynomial equations to calculate the SE are described in Table 1 of the DSID-4 Data Files page and applied in Table 2 and the DSID-4 calculators.

Note: In the DSID studies, 20-30 tablets/capsules of individual products were homogenized before chemical testing. So an individual observation for this study is technically a 20-30 tablet homogenate, not an individual tablet. The SE and 95% CI are likely to be even larger for an individual tablet of a DS product.

These values are calculated from the statistical data provided in Table 1 of the DSID-4 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.

The '95% Confidence Interval (CI) for the mean' value of analytically measured ingredient content at a particular label level is a range of values that was determined using an experimental sample of products out of their entire theoretical population. If a DSID experiment was to be repeated 20 times, the 95% CI for the mean would capture the true mean 19 times out the 20 samples (or in 95% of the samples).