Responses to VITMOIRON by sample adults were obtained as follows: While administering the NHIS, interviewers showed respondents a flash card containing a list of vitamins and minerals and asked, "During the past 12 months, have you taken any vitamins or minerals listed on this card for yourself?" Respondents who answered affirmatively (i.e., a "Yes" response in VITYR) were asked, "During the past 30 days, did you take any of these vitamins or minerals?" Sample adults who answered that question affirmatively (i.e., a "Yes" response in VITMO) were instructed, "Please tell me which of these vitamins or minerals you took in the past 30 days. If you take a multi-vitamin or mineral, include it as one supplement." Interviewers were told to "enter all that apply." The questions to collect this information for sample children were similar, except respondents were asked whether the sample child had taken any vitamins or minerals listed on a card.

Thus, in the case of both sample adults and sample children, persons with an affirmative response to VITMOIRON took iron as a stand-alone supplement, rather than as part of a combination vitamin and/or mineral supplement. Persons taking such a combination supplement (VITMOCOMBO) were not asked which particular vitamins or minerals were included in those supplements, so it is not possible to ascertain whether iron was included in a given sample person's multi-vitamin/multi-mineral supplement.

Iron was one of 20 possible specific vitamins and minerals that sample adults and respondents for sample children could indicate using in the past month. The other such vitamins/minerals recognized by the NHIS are:

• Calcium (VITMOCALC)

• Coral calcium (VITMOCCALC)

• Chromium (VITMOCHRO)

• Folic acid/folate (VITMOFOLIC)

• Magnesium (VITMOMAG)

• Niacin (VITMONIA)

• Vitamin Packet (VITMOPACK)

• Potassium (VITMOPOTA)

• Selenium (VITMOSELN)

• Vitamin A (VITMOVITA)

• Vitamin B6 (VITMOVITB6)

• Vitamin B12 (VITMOVITB12)

• Vitamin B complex (VITMOVITB)

• Vitamin C (VITMOVITC)

• Vitamin D (VITMOVITD)

• Vitamin E (VITMOVITE)

• Vitamin K (VITMOVITK)

• Zinc (VITMOZINC)

• Multivitamin and/or mineral combination (VITMOCOMBO)

The summary variables VIT1MOST and VIT2MOST report the vitamins and minerals taken most often by sample adults and sample children during the past month. For more information about the full range of variables related to the use of vitamins and minerals, see VITMO.