Estimation of apparent conversion factors
To estimate apparent conversion factors, we used changes in
serum retinol concentrations, as calculated above, because in the
low-retinol, low-carotene group the concentration had not
changed; we used the amount of retinol and carotene provided
because the intake of food other than that provided by us was relatively small, almost the same in all groups, and its composition
was less precisely known. With use of equation 1 given above,
the mean apparent factor for converting b-carotene into retinol
equivalents was estimated to be 26 (95% CI: 13, 76) for vegetables and 12 (95% CI: 6, 29) for fruit.