related to dietary intake, urinary molybdenum alone does not reflect status.

Several biochemical changes have been observed in special situations. In molybdenum cofactor deficiency and in the one case of molybdenum deficiency reported, urinary sulfate was low and urinary sulfite was present. Serum uric acid concentrations were low, urinary xanthine and hypoxanthine increased, and plasma methionine was increased (Abumrad et al., 1981; Johnson et al., 1993). However, these observations have not been associated with molybdenum intakes in normal, healthy people and cannot be used as indicators for estimating the molybdenum requirement.

Balance studies are used to establish whether homeostasis is maintained and whether body stores are being depleted or increased. Ideally, sufficient time (at least 12 days or longer) is allowed for the body to adapt to each dietary intake before collecting balance data, diets are constant, and conditions are controlled to assure food consumption and sample collections are complete. Two balance studies have been conducted in adult men (Turnlund et al., 1995a, 1995b). These studies provided adaptation periods and were conducted in metabolic research facilities. Diets were controlled and molybdenum intake was constant at each amount. Balance in these studies could be achieved over a broad range of intakes. In one study, five levels of molybdenum ranging from 22 to 1,490 μg/day were provided for 24 days each (Turnlund et al., 1995a). In another study, a low molybdenum diet (22 μg/day) was provided for 102 days, followed by a higher molybdenum diet (467 μg/day) (Turnlund et al., 1995b). Miscellaneous losses, such as sweat and integument, were too low to measure and were not accounted for. The minimum requirement was estimated to be approximately 25 μg/day. Balance studies were conducted among preadolescent girls between 1956 and 1962 for 6 to 56 days (Engel et al., 1967). They demonstrated that balance was positive (3 to 33 μg/day) in all of 36 girls between the ages of 6 and 10 years when intake ranged from 43 to 80 μg/day.