Those who answered affirmatively were asked whether they had ever used any of the following:

• Multi-vitamins such as One-A-Day (VITMULTEV)

• Individual vitamin supplements (VITSUPEV)

• High dose or megavitamin therapy (VITMEGAEV)

A series of variables followed for those respondents who said "Yes" to VITMEGAEV, beginning with whether the respondent had taken such megavitamin therapy in the past 12 months (VITYR).

The flash card contained the following 20 vitamins and minerals:

• 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

Those respondents who indicated that they had ever used any of the above were then asked whether they had used vitamin or mineral supplements in the past 12 months (VITANY).

VITEV is part of a series of variables, mostly from 2002 and 2007, about the use of vitamins/minerals and herbs. For more information about the full range of variables related to vitamins and minerals, see VITYR (high doses of vitamins) and VITANY (dose unspecified).

First, respondents in 2002 were asked about their use of vitamins for health reasons, whereas the reasons for taking vitamins and minerals were left unspecified in 2007.

Second, what constituted a "vitamin or mineral supplement" was respondent-defined in 2002, while sample adults in 2007 were asked whether they had taken anything included on a specific list of vitamins and minerals.

Researchers must judge for themselves whether these differences compromise comparability for their analyses.