The Field Representative's Manual instructed interviewers as follows:

It is possible to use both VITYVITCMG and VITYVITCPILS to determine the number of milligrams of vitamin C respondents were taking, on days they took vitamin C. The related variables VITAMINCMO and VITAMINCDMO report the frequency of respondents' use of vitamin C in number of months and number of days per month, respectively.

Analysts interested in the amount of vitamin C taken may wish to consult the following variables, which report similar information for other vitamins/minerals (all only available for 1987). Users should note that calcium is also measured in milligrams (a measure of quantity), but vitamins A and E are measured in international units (IUs, a measure of biological activity). Further, a direct comparison of IUs across substances is not possible. That is, 1,000 IUs of vitamin A is not equivalent to 1,000 IUs of vitamin E.

• VITYVITAUN Vitamin A

• VITYVITEUN Vitamin E

• VITYCALCMG Calcium

For more information on the full range of variables related to vitamins and minerals, see VITANY.