• Component Description
• Eligible Sample
• Interview Setting and Mode of Administration
• Data Processing and Editing
• Analytic Notes
• Codebook
  • SEQN - Respondent sequence number
  • DSDSUPID - Supplement ID Number
  • DSDSUPP - Supplement Name
  • DSD070 - Was Container Seen?
  • DSDMTCH - Matching Code
  • DSD090 - How Long Supplement Taken (Days)?
  • DSD100Q - How Often Taken, Last Month? (Quantity)
  • DSD100U - How Often Taken in Last Month? (Unit)
  • DSD120Q - Quantity of supplement taken
  • DSD120U - Dosage Form
  • DSDANTA - Antacid Reported as Dietary Supplement
• APPENDIX 1: HANDCARD DSQ1
• APPENDIX 2: MATCHING CODES
• APPENDIX 3: ASSIGNED DEFAULT SUPPLEMENTS AND ANTACIDS
• APPENDIX 4: CONVERIONS FACTORS FOR COMPOUNDS
• APPENDIX 5: RULES FOR CLASSIFYING INGREDIENTS
• APPENDIX 6: DATA FILE STRUCTURE AND RELATIONSHIPS

National Health and Nutrition Examination Survey

1999-2000 Data Documentation, Codebook, and Frequencies

Dietary Supplement Use 30-Day - File 2, Participant's Use of Supplements (DSQFILE2)

Data File: DSQFILE2.xpt

First Published: June 2002

Last Revised: July 2009

Component Description

The Dietary Supplements section (DSQ) provides personal interview data on use of vitamins, minerals, and other dietary supplements. These questions were asked for all participants during the household interview. The questions in the NHANES 1999-2000 DSQ section are basically the same as in NHANES III (1988-94), however in NHANES 1999-2000, participants were asked about use of all types of dietary supplements, not just vitamin and mineral supplements.

The first release (June 2002): contained only preliminary, unedited data on whether a participant reported taking any dietary supplement (DSQ010), and the total number of supplements reported (DSDCOUNT). This second release contains edited data for DSD010 and DSDCOUNT, as well as data on the supplements themselves and details of the participant’s use of the supplement.

Eligible Sample

All ages.

Interview Setting and Mode of Administration

The DSQ was done before the physical examination, in the home, using the Computer-Assisted Personal Interviewing-CAPI (interviewer-administered) system. Participants 16 years of age and over answered for themselves; A proxy provided information for survey participants who were under 16 years of age and for individuals who could not answer the questions themselves.

Data Processing and Editing

Participants are asked if they have taken a dietary supplement in the past month, and asked to include prescription and non-prescription supplements. They are shown a hand card that lists examples of dietary supplements (Appendix 1: Handcard DSQ1). Those who answer “yes” are asked to show the supplement containers to the interviewer. If no container is available, the interviewer asks the participant for as detailed a name as possible. For each supplement reported, the interviewer enters the supplement’s name and manufacturer into a computer. Recording the name can be a matter of judgment. A definitive name may not be obvious, as supplement labels may contain a variety of descriptive phrases, function claims, and quality claims, with wording in diverse places on the label and in various sizes and directions, including vertical. Interviewers are instructed to enter as complete a name as possible, including all qualifying words (such as “iron-free,” “high potency,” and “with lutein”).

The interviewer then views a list of supplements on her/his computer and selects one if it is judged to be an exact match for the supplement entered; otherwise, no match is made. No ingredient information is recorded by the interviewer. However, if the supplement is a single ingredient supplement, the interviewer records the strength. Participants are asked about their use of the supplement: how long they have been taking it; how often in the last month; and how much each time they took it. Up to 20 supplements can be recorded. The exact questions the interviewer asks, and a short description of the other data recorded, are included in the DSQ codebook.

Some prescription supplements are mistakenly recorded in the prescription medicine section rather than the dietary supplement section. Strength and details of the persons usage are missing for these supplements. All supplements, including prescription supplements are released in the DSQ section only, not in the medication (RXQ) section.

Information on use of non-prescription antacids was sometimes recorded in the dietary supplement section; other times in the antacid sub-section of the medication section (RXQ). Because of their nutrient content, antacids that contain calcium or magnesium are released with the DSQ data, irrespective of where they were reported. Only these antacids are reported; this is not a complete accounting of all antacids. Data users should also be aware that the section in which an antacid is recorded (e.g. DSQ or RXQ) may not accurately represent the usage of that antacid. For example, some antacids reported with the RXQ (medications) section may have been used as a dietary supplement or vice versa, and some antacids may be used as both medications and calcium supplements. Thus, users are cautioned that analyses of these data to estimate the percentage of antacids used as dietary supplements would not be appropriate.

Survey data collected by interviewers

• Taken any vitamin, mineral or other dietary supplements in past month?
• Supplement name entered and selected
• Supplement strength, if single ingredient
• Was the container was seen?
• Supplement manufacturer entered and selected
• How long supplement has been taken?
• How often supplement was taken in past month?
• How much was taken each time? 

Matching a reported supplement to known supplement

Trained nutritionists at NCHS match the product names entered or selected by the interviewer (including prescription supplements and antacids containing calcium or magnesium) to a known product when possible. These matches are made with varying degrees of precision, and a matching code (DSDMATCH) accompanies each match (Appendix 2: Matching Codes). Briefly, the codes are: 1) Exact or near exact match; 2) Probable match; 3) Generic match; 4); Reasonable match; and 5) Default match. In some cases no match can be made with any certainty. These products are coded 6) No match. Products whose names were reported as “Refused” (7777) or “Don’t know” (9999) have matching codes of 7 and 9, respectively.

NCHS communicates with many major manufacturing company representatives to determine when various product re-formulations become available. We match reported with known supplements based upon reported supplement name as entered by the interviewer and the product version on the market at that time, if known. Based upon manufacturer advice, we have used a lag time of 5 months after new product market entry in matching recorded products to these new products. Despite these precautions, there is no guarantee that the product taken was not an older or newer product than the one to which it was matched.

NCHS created generic and default dietary supplements and entered these into the supplement database. Reported supplements for which the strength of all ingredients were known were matched to a generic supplement, i.e. one which had no brand name. These were generally single ingredient supplements which included a strength (e.g. vitamin C 500 mg) or multiple vitamins and/or mineral supplements made by a private label manufacturer that was known to us and for which we had a label with identical ingredients and strengths (e.g. brand X all-purpose multivitamin was reported, and we had a label for brand Y, made by the same manufacturer). These matches are coded as 3. When all ingredient strengths were not known, the supplement was matched to a default supplement where possible. Defaults were created for single ingredient and multiple ingredient supplements where we had enough information from our own data or from sales data to be able to determine which was the best selling or most frequently reported supplement of that type. These matches were coded as 5. Created default and generic products and the actual products or strengths that were assigned to these defaults are listed in Appendix 3 (Assigned default supplements and antacids). 

Variable creation

DSDANTA: (antacid reported in DSQ section). This in an indicator variable coded 1 if an antacid was recorded in the dietary supplement (DSQ) section of the questionnaire, 2 if the antacid was recorded in the antacid (RXQ) section of the questionnaire, and 0 if the product was a dietary supplement that was not an antacid. For a few participants, the same antacid was recorded in both questionnaire sections. In these instances, the antacid was considered to be in the DSQ section and coded as 1.

DSDMTCH: (matching code). These codes (see Appendix 2 and above, Matching a reported product to a known product) describe the basis for the match of product entered or selected by the interviewer to a known product.

DSDCOUNT: (number of supplements taken). All supplements, whether reported in the DSQ or RXQ section, as well as the antacids recorded in the DSQ section of the interview (DSDANTA=1) count as 1 supplement in DSDCOUNT. Antacids that were not reported in the DSQ section of the interview (i.e. were reported as antacids in the RXQ section only; DSDANTA=2) do not count as supplements and are not included in this count. Non-supplements that were reported in the DSQ section do not count. Products whose names were entered as 7777 or 9999, that is, don’t know or refused, are counted as supplements, since there is no clear evidence that they are not and they were reported by the participant as a supplement.

DSDCNT variables give the number of ingredients of each type in the supplement, including in blends. The specific variables are DSDCNTV, DSDCNTM, DSDCNTA, DSDCNTB, DSDCNTO, which provide the number of vitamins, minerals, amino acids, botanicals, and other ingredients, respectively, in each supplement.

Data editing

As a result of data editing, the data in this second release for the variables DSD010 (indicator of any supplement use) and for DSD130 (number of supplements used), now called DSD010 and DSDCOUNT, may differ slightly from the data that were contained in the first DSQ release of the NHANES 1999-2000 data.

DSD010: Indicator of any dietary supplement use
Participants with a record of having taken a product determined to be a supplement in the last 30 days are coded 1. Some such products were mistakenly recorded in the RXQ section, either as antacids or prescription medicines. These data have been moved to the DSQ section and are counted as supplements for DSD010 and DSDCOUNT. Participants who reported taking an antacid containing calcium or magnesium in the last 30 days that was recorded only in the RXQ antacid section (DSDANTA=2), but did not take any dietary supplement are coded 2. Participants who did not take any product that was determined to be a dietary supplement in the last 30 days are also coded 2, even if they originally reported having taken a supplement. Examples of products that were determined not to be supplements included foods (garlic cloves, raisin bran cereal, PowerBar®), drinks (Ensure®, Gatorade®, tea), over the counter drugs (aspirin, laxatives, electrolyte replacement fluids), homeopathic medicines, and prescription medicines. Prescription medicines and analgesics were removed from DSQ to the appropriate RXQ section.

DSDSUPP: Name of supplement
The name that is assigned is the name of a known supplement for which ingredient information is available which was matched to the name that was keyed or selected by the interviewer, based upon the supplement label or, if no container was available, the supplement name given by the participant. As described above, these matches were made with varying degrees of certainty. When no match could be made, then the product was given a match of 6, “unknown.” For these matches, the 10 digit supplement ID begins with a 6 and the phrase “no product information” is assigned as the name. Products with brand names that are available only in a limited region of the country are released with a generic name, not a brand name, to ensure participant confidentiality. Product names that were entered as “refused” or “don’t know” are named “7777” and “9999”, respectively.

DSD090: How long has the supplement been taken? (days)
Responses were recorded in days, weeks, months, or years. To facilitate analysis, all answers are converted to days, using conversion factors of 365 days per year, 30.4 days per month, and 7 days per week, and rounded to the nearest integer. For two participants, the amount of time recorded was slightly longer (1-2 months) than a child had been alive so the data were adjusted to the length of the child’s life.

This file includes variables with the name and ID number of the supplement that was assigned by NCHS, the matching code (see Appendix 2) assigned, whether the supplement container was seen, how long the person has been taking this supplement, how often in the last month, and how much was taken each time. There is a separate record for each supplement a person took as these data are supplement specific. 

NHANES Dietary Supplement Database(Files 3, 4 and 5)

Product information is released from the in-house PLD as the NHANES Dietary Supplement Database (NHANES-DSD) which contains detailed information on the dietary supplements and antacids reported by survey participants since NHANES 1999. The NHANES-DSD release consists of three datasets (DSQ3_E, DSQ4_E, and DSQ5_E) that contain information on products.  The supplement ID numbers  (DSDSUPID) located in file 2 (DSQ2_E) of this release can be used to merge with the NHANES-DSD files.  For more information on the NHANES-DSD, please refer to the documentation and release files located on the NHANES website:
https://wwwn.cdc.gov/nchs/nhanes/search/datapage.aspx?Component=Questionnaire&CycleBeginYear=2007.

Analytic Notes

Differences between this release and the first release
DSD010 and DSDCOUNT: These variable responses may differ from the last release as a result of the following determinations: a product was determined not to have been taken in the last 30 days; a product was determined not to be a supplement; a product recorded in the antacid section was a supplement; or a product reported in the prescription medicine section was a supplement.

Matching codes
These are described in the data processing section and Appendix 2. Analysts should be aware that for default matches and matches that chose between several similarly named supplements, there is less certainty that the ingredients and ingredient amounts in the supplement assigned exactly match those in the supplement actually taken. Additionally, NCHS cannot guarantee in any case that the matched product was the exact product taken or even that any product actually was taken, as these data are self-reported.

Entries of refused and don’t know
If a respondent “refused” or answered “don’t know” to DSQ010, the codes 7777 or 9999, respectively, are used in both DSD010 and DSDCOUNT and all other variables are coded as missing. If a respondent “refused” or answered “don’t know” to a supplement name, the name of the variable is 7777 or 9999 and matching codes are 7 and 9, respectively. Other information on use of the supplement given by the participant is retained.

DSD070: Was the container seen?
A more precise name for a supplement can be recorded by the interviewer, and thus a more precise match to a known supplement can be made, when the interviewer sees the supplement container rather than recording the participant’s report of the supplement name (for example, multivitamin/multiminerals are often reported as multivitamins). In general, this is reflected in the matching code, but analysts should be aware that precision is greater when a container is seen.

Supplement ID numbers
Supplement ID numbers are 10 digits long; all Supplement IDs begin with the number ‘1’. The next 3 digits (positions 2-4) are ‘888’ if the supplement was created by NCHS as a generic or default product; otherwise the digits in positions 2-4 are coded ‘000’. The next 4 digits (positions 5-8) are assigned by the database and do not indicate anything about the product. The last 2 digits (positions 9-10) indicate formulations of the same supplement: the first formulation entered into the database = 00, the first reformulation = 01, the next = 02, etc. Note that these are reformulations of the same product: different versions (e.g. liquid vs. tablet, with iron vs. without iron, regular vs. high potency) have different 4 digit numbers (positions 5-8). When a product name was entered as “refused” or “don’t know”, the ID number is a string of 7’s or 9’s.

Unidentifiable products
For some entries made by interviewers, no corresponding product label could be found nor could a reasonable default product be assigned. These entries are counted as supplements, since there is no evidence that they are not supplements, but only the words “no product information available” are used in place of a name in this public data release.

Using self-reported data
NHANES data are self-reported and recorded by interviewers, and thus may contain inconsistencies or errors. Unless a data entry is clearly mis-recorded and the correct response can be confidently identified, possible errors or inconsistencies are not edited. Users will note that some records may indicate a person had been taking a supplement for a short time, e.g. only one day (DSD090), but report a frequency of taking it that is longer (DSD100), e.g. twice a week. Such apparent inconsistencies are not edited, as there is no obvious basis for editing. Users are advised to assess the data and edit it as deemed appropriate for the analyses being undertaken.

Special notes on DSD090, 100, and 120
Before entering values for DSD100 (how often taken) and DSD120 (how much taken), interviewers first indicated whether they were a) going to enter a number, b) the amount varied, or c) the respondent didn’t know or refused to answer the question. Responses other than “enter a number” have missing values for DSD100Q, DSD100U, DSD120Q and DSD120U. Also, supplements recorded in the prescription medicine section have missing values for DSD100Q and DSD120Q, since these questions are not asked in this section. However, most of the missing values in these fields are because the person said that the amount they took or the frequency of taking it varied. Additionally, for variables DSD090, DSD100Q, and DSD120Q, zeros were sometimes entered. There was no information about why a zero was entered - for example whether the zero was an error, was meant to be a decimal, or that a participant decided that they had not taken the supplement at all. Since there is no additional information, these zeros are included in the data release, for the analyst to use as deemed appropriate.

Release and use of supplement brand names
NCHS collects brand name information on supplements whenever feasible, to ensure as much accuracy as possible in finding the label information for the exact product taken, and providing exact ingredient information for this product to data users. Products with very similar names but manufactured by different companies may contain different ingredient strengths. Brand names are released for supplements matched with a high degree of product or brand certainty, as this information may be useful in the design of other surveys. However matching of brand names to reported products may contain errors, and many matches are made to generic or default products, especially for private label brands. Thus, analyses of consumer usage by brand name using NHANES data may not be accurate and is not recommended. Brand names that are available in a limited geographic area of the U.S. are not released; generic names are used for these products.

Serving size
When calculating the amount of a nutrient consumed from supplements, it is important to take serving size into consideration. For some supplements, the serving size may be more than one tablet, drop, teaspoon, etc. In such cases, a person taking only one tablet, for example, would only be getting a percentage of the amount listed for that ingredient. In addition, the ingredient listed may be a compound (e.g. calcium carbonate), and the amount of elemental calcium needs to be calculated. Appendix 5 contains suggestions for conversions, but analysts are advised to confirm these.

Counts of ingredients in supplements
For each supplement, this is the number (count) of ingredients in each ingredient category (vitamin, mineral, amino acid, botanical, other) listed in the facts box on the label, including ingredients listed within blends. In a few products with blends, the same vitamin or mineral was listed as both an ingredient with an amount and as part of a blend. In these cases, only the vitamin or mineral was only counted as one.

Codebook and Frequencies