. "Any process that decreases the rate, frequency or extent of calcidiol 1-monooxygenase activity. Calcidiol 1-monooxygenase activity is the catalysis of the reaction: calcidiol + NADPH + H+ + O2 = calcitriol + NADP+ + H2O." . . . "negative regulation of calcidiol 1-monooxygenase activity" . . .