Questions for the

Dietary Supplement Subcommittee

March 25, 2003



Question 1: Is it possible to identify particular scientific criteria, principles, or conventions that enable a determination to be made about when a substance is or is not a  metabolite of another dietary ingredient?[1]


Question 2: Consider and discuss the scientific strengths and weaknesses of the following concepts with respect to their usefulness in identifying whether a substance is or is not a metabolite of another dietary ingredient:


a)      Direct or indirect participation in catabolic and/or anabolic sequences or pathways;


b)      Proximity (i.e., in terms of number of enzymatic steps away) to another dietary ingredient;


c)      Semblance to another dietary ingredient [C preceding it in a pathway or preceding reaction with respect to:


i)        Function

ii)       Structure

iii)     Combination of both


d)      Possessing qualities or similarities to another dietary ingredient relative to:


i)        Speed/time (i.e. clock-time conversion, enzymatic reaction rates, retention rates or impact on equilibrium concentrations/homeostasis)

ii)       Compartmentalization (e.g., intracellular vs. extracellular activity; intracellular compartmentalization)

iii)     Fate (i.e. final conversion, excretion or end-product retention by the body)


Question 3: Discuss the scientific validity and likely usefulness for identifying when a substance is or is not a “metabolite” of another dietary ingredient.  If so, what characteristic(s) associated with the criterion make(s) it valid or useful?


[1] For present purposes, “another dietary ingredient” means a vitamin, mineral, herb or other botanical, amino acid, or dietary substance for use by man to supplement the diet by increasing the total dietary intake.