The Field Representative's Manual instructed interviewers as follows:

It is possible to use both VITYCALCMG and VITYCALCPILS to determine the number of milligrams of calcium respondents were taking, on days they took calcium. The related variables VITACALCMO and VITACALCDMO report the frequency of respondents' use of calcium in number of months and number of days per month, respectively.

Analysts interested in the amount of calcium 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 vitamin C 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

• VITYVITCMG Vitamin C

• VITYVITEUN Vitamin E

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