. "Any process that stops, prevents, or reduces the frequency, rate or extent of the chemical reactions and pathways involving a vitamin, one of a number of unrelated organic substances that occur in many foods in small amounts and that are necessary in trace amounts for the normal metabolic functioning of the body." . . . "negative regulation of vitamin metabolic process" . "down regulation of vitamin metabolic process" . "down-regulation of vitamin metabolic process" . "downregulation of vitamin metabolic process" . "inhibition of vitamin metabolic process" . "negative regulation of vitamin metabolism" . . . . . . . . . . . . . .