Molybdenum (Mo) is an essential nutrient for animals and humans. Tissue content of molybdenum is low, with the highest concentrations in the liver, kidney, adrenal gland and bone. It is a component of a number of enzymes, including sulfite oxidase (involved in the metabolism of sulfur amino acids), xanthine oxidase (involved in the oxidation of purines and pyrimidines and the production of uric acid), and aldehyde oxidase (involved in the oxidation of aldehydes). These enzymes share a common "molybdenum cofactor."

Deficiencies: Molybdenum deficiency is extremely rare and has only been identified in the presence of other serious disorders. Metabolic defects in the molybdenum cofactor are characterized by the absence of the three molybdoenzymes. Both the deficiency and the metabolic disorders are accompanied by abnormal excretion of sulfur metabolites, low uric acid concentrations, and elevated hypoxanthine and xanthine excretion. The absence of sulfite oxidase in the metabolic disorder leads to death at an early age.

Diet recommendations: The Estimated Safe and Adequate Dietary Intakes of molybdenum (�g/day) are: 15-30 at age 0-6 months, 20-40 for 6-12 months, 25-50 for 1-3 years, 30-75 for 4-6 years, 50-150 for 7-10 years, and 75-250 for adolescents and adults. This range is based on the usual dietary intake, about 75 to 240 �g/day by adults. The range was extrapolated for other age groups on the basis of body weight.

Food sources: Rich sources of molybdenum include legumes, cereal products, and leafy vegetables. The amount in foods depends on the soil molybdenum content. Molybdenum is very well absorbed, but its bioavailability may be affected by some food components.

Toxicity: Molybdenum toxicity is much more likely than deficiency. Toxicity is common in cattle grazing in pastures with high molybdenum soil. A high incidence of gout has been reported in humans with intakes of 10-15 mg/day.

Recent research: Controlled studies in humans suggest that the molybdenum requirement is well below the usual dietary intake, which is consistent with lack of molybdenum deficiency in the US population. Bioavailability studies suggest that molybdenum is less well absorbed from soy products than from leafy vegetables.