In 1987, 1992, 2000, and 2005, interviewers asked, "During the past 12 months, did you take any vitamin or mineral supplements of any kind?" In 1992 only, the question continued, "such as vitamin pills, wafers, liquid vitamins or minerals?" In 2000 and 2005, interviewers were instructed to "read if necessary": "Include vitamin or mineral pills, liquids, or tinctures. Do not include vitamin-fortified foods." In all these years, the determination of what constituted a "vitamin or mineral supplement" was left up to the respondent.

In 2007, sample adults were shown a flash card containing a list of 20 vitamins and minerals and were asked, "During the past 12 months, have you taken any vitamins or minerals listed on this card for yourself?" The question to collect this information for sample children was similar, except respondents were asked whether the sample child had taken any vitamins or minerals listed on a card.

The items listed on the flash cards for both sample adults and sample children in 2007 were:

• Multivitamin and/or mineral combination

• Calcium

• Chromium

• Coral calcium

• Folic acid/folate

• Iron

• Magnesium

• Niacin

• Potassium

• Selenium

• Vitamin A

• Vitamin B complex

• Vitamin B6

• Vitamin B12

• Vitamin C

• Vitamin D

• Vitamin E

• Vitamin K

• Zinc

• Vitamin packet

In 1992, VITANY and related variables were part of the Vitamin and Mineral Intake section of the NHIS. The Field Representative's Manual for that year says,

In 2000 and 2005, VITANY was part of the Diet and Nutrition section of the Sample Adult Cancer Topical Module. According to the 2000 and 2005 Field Representative's Manuals, the section on diet and nutrition was included because "[N]utrition is believed to play some part in increasing or decreasing a person's chances of getting cancer." The Manuals further state that "[V]itamin and mineral dietary supplements currently provide a significant source of nutrients in the American diet." Thus, the purpose of questions such as VITANY was "to determine the use of certain vitamin, mineral and herbal supplements in the U.S. population." A similar rationale was provided in the 1987 Manual.

In 2007, VITANY and other variables related to vitamin supplements were part of the Alternative Health Supplement. For information on the scope of inquiry and rationale for this supplement, see ACUYR.

The following variables are available in 1987, 1992, 2000, 2002, 2005, and/or 2007.

• Took multi-vitamins, past 12 months (VITAMULTV)

• Duration and frequency took multi-vitamins, past 12 months (VITAMULTVDMO, VITAMULTVDWK, VITAMULTVMO, VITAMULTVNO, VITAMULTVTP)

• Took vitamin A, past 12 months (VITAMINA)

• Duration and frequency took vitamin A, past 12 months (VITAMINADMO, VITAMINADWK, VITAMINAMO, VITAMINANO, VITAMINATP)

• Took vitamin C, past 12 months (VITAMINC)

• Duration and frequency took vitamin C, past 12 months (VITAMINCDMO, VITAMINCDWK, VITAMINCMO, VITAMINCNO, VITAMINCTP)

• Took vitamin E, past 12 months (VITAMINE)

• Duration and frequency took vitamin E, past 12 months (VITAMINEDMO, VITAMINEDWK, VITAMINEMO, VITAMINENO, VITAMINETP)

• Took calcium, past 12 months (VITACALC)

• Duration and frequency took calcium, past 12 months (VITACALCDMO, VITACALCDWK, VITACALCMO, VITACALCNO, VITACALCTP)

• Took beta carotene, past 12 months (VITABETA)

• Frequency took beta carotene (VITABETAMO, VITABETANO, VITABETATP)

• Took selenium, past 12 months (VITASELN)

• Frequency took selenium, past 12 months (VITASELNMO, VITASELNNO, VITASELNTP)

These question addressed which vitamins/minerals were taken in the past month; whether vitamins/minerals were used to treat a particular health problem or condition; and what condition they were used to treat. A few variables related to vitamin use in the past month are also available for 1987. (See VITMO for more information on variables related to the use of vitamins in the past 30 days.)

In 2002, questions on vitamin supplements related to the use of high dose or megavitamin therapy, rather than the vitamin supplements at any dosage level addressed in other years. See VITYR for information about variables on megavitamin theraphy in 2002.

The NHIS also includes many variables related to the use of herbal supplements, rather than vitamins/minerals, in 1999, 2000, 2002, 2005, and 2007. See HERYR for more information about these variables.

These differences relate to what to include as a "vitamin or mineral supplement." For example, in 2000 and 2005, respondents were explicitly told not to include vitamin-fortified foods, but this instruction was not given in 1987 or 1992.

In 2007, respondents were shown the above list of vitamin and minerals and asked if they had taken anything on that list. In other years, respondents were asked if they had taken vitamins or minerals "of any kind." Thus, it is possible that respondents in 1987, 1992, 2000, or 2005 may have responded affirmatively to VITANY because they used a particular supplement but would have responded negatively in 2007 because that supplement was not listed on the flash card.