Molybdenum
Description
Molybdenum is an essential constituent of two enzymes found in humans: xanthine oxidase, which is involved in uric acid formation, and aldehyde oxidase, which catalyzes the chemical oxidation of aldehydes.
Molybdenum is concentrated primarily in the liver, kidney, bone, and skin. There is estimated to be approximately nine milligrams of molybdenum in the adult human body.
Molybdenum is an antagonist to copper absorption, as is copper to molybdenum absorption.
Excess molybdenum intake can induce copper deficiencies with the subsequent symptoms.
Method of Action
Molybdenum is an important constituent of aldehyde oxidase and xanthine oxidase. Aldehyde oxidase catalyzes the oxidation of an aldehyde functional group to the corresponding carboxylic acid. Xanthine oxidase catalyzes the oxidation of xanthine to uric acid for excretion. Xanthine is a product formed in the chemical degradation of purine nucleotides found in DNA and RNA.
Molybdenum, in the presence of inorganic sulfate, tends to reduce copper absorption and retention. Several theories for why this antagonistic relationship occurs have been postulated. There is evidence that copper and molybdenum form an insoluble complex called lindgrenite, which cannot be absorbed easily. Other theories include the postulated interference of ceruloplasm synthesis; ceruloplasm is a protein necessary for copper transport into blood.
Molybdenum absorption occurs readily in the gastrointestinal tract, and excretion occurs primarily via the urine.
Properties & Uses
Molybdenum has been implicated as a possible contributor to decreased incidence of dental caries.
Adequate molybdenum intake has been linked to a reduced incidence of esophageal cancer.
Consequence of Deficiency
Molybdenum deficiencies in humans have not been conclusively linked to any specific set of symptoms; however, one source indicates a high incidence of esophageal cancer may be the result of low molybdenum intake.
Toxicity Factors
Symptoms of molybdenum toxicity include diarrhea, depressed growth rate, and anemia. Gout-like symptoms may result from excess intake.
High levels of molybdenum intake can induce a high rate of copper excretion (due to the antagonistic effect the two minerals have on each other), which can possibly result in a copper deficiency.
High intake of molybdenum can alter the activity of alkaline phosphatase, resulting in certain bone abnormalities. Alkaline phosphatase enzymatically releases phosphate groups from the molecule glucose 1-phosphate, thereby producing high levels of inorganic phosphate; phosphate is necessary to produce hydroxyapatite crystals in bone.
Recommended Dietary Allowance
The RDA is estimated to be relatively small amounts for children.
RDA for adults: 0.15 - 0.5 mg
The above is 1980 values for RDA.
For over thirty years, Recommended Daily Amounts has existed in the United Kingdom. It has been used to measure the adequacy of an individual's diet. However, in 1991 the Committee on Medical Aspects of Food Policy (COMA) gave forth a whole new set of figures upon the request of the Department of Health's Chief Medical Officer. Reference Nutrient Intake (RNI) is one of these sets collectively known as "Dietary Reference Values." RNI is an amount of a nutrient that is enough for almost every individuals, even someone who has high needs for the nutrient. This level of intake is, therefore, considerably higher than what most people would need. If individuals are consuming the RNI of a nutrient they are most unlikely to be deficient in that nutrient.
Food Sources
| Barley | Beef kidney |
| Beef liver | Buckwheat |
| Egg | Green leafy vegetables |
| Hot cocoa | Legumes |
| Milk | Oat flakes |
| Potato | Rye bread |
| Spinach | Sunflower seed |
| Wheat germ | Yam |
References
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