Fundamentals of Human Nutrition/Molybdenum
Although molybdenum can be found in a large number of plant foods its levels depend greatly on the molybdenum soil content in the regions where plants are grown. Legumes, grain products, nuts, and leafy green vegetables are all sources of molybdenum. Animals don’t have concentrations of the mineral that are as high but sufficient quantities for nutritional sources may be found in liver and milk. Reaching the recommended daily intake of dairy will often be an adequate nutritional source of molybdenum in the diet. Average dietary intake of molybdenum is difficult for researchers to determine because there isn’t yet a uniform analytical utilized in studies to determine molybdenum levels. In addition to this reports vary widely across the globe due to the changing levels of the mineral in the soils where crops are grown. Even with variations molybdenum intake is consistently above the daily requirement.
The three primary metalloenzymes which utilize molybdenum are xanthine dehydrogenase/oxidase, aldehyde oxidase, and sulfite oxidase. Xanthine dehydrogenase/oxidase works actively in different types of tissue to convert purines into uric acid. A genetic condition called xanthinuria causes low output of uric acid. This condition may eventually lead to slight myopathy in muscle tissue. Sulfite oxidase is an enzyme responsible for the conversion of some forms of sulfite into inorganic sulfite. Genetic conditions can cause a deficiency in sulfite oxidase that results in the death of the infant around 2–3 years of age. Varying levels of molybdenum in the diet have not been observed causing toxic effects on this level but researchers believe that these genetic conditions are cause by a failure to synthesize the molybdopterin cofactor of these enzymes
There are different ways to figure out the requirements of Molybdenum; these methods are to check the plasma and serum Molybdenum concentration, urinary Molybdenum levels, biochemical indicators, and molybdenum balance (“Dietary Reference Intakes…”, 2001). There are also factors that affect the Molybdenum requirements due to interactions with other minerals and substances; tungsten, cooper and sulfate, and bioavailability factors all determine how it is absorbed.
Depending on one's age and gender, there are different requirements for the amount of Molybdenum that should be ingested everyday through one's diet. Between the ages of zero to twelve months, because there have been no sources of information as to how much Molybdenum should be ingested, the intake values that are instated are due to the Adequate Intake (AI) levels that have been instated due to the mean intake of infants that have been fed milk from humans. The study demonstrated that as the infant gets older, the levels of molybdenum decreased over time; what started at 5 µg/L went down to 1.7 µg/L over the course of almost a year. The AI for Molybdenum for infants ages zero to six months is 2 µg/day or 0.3 µg/kg/day. For ages seven to twelve months, it is 3 µg/day or 0.3 µg/kg/day. The Estimated Average Requirement (EAR) for children one to three years is 13 µg/day and for children ages four to eight years it is 17 µg/day. After the age of eight, boys and girls require different amounts of Molybdenum. The EAR for boys ages nine to thirteen years is 26 µg/day of molybdenum and for those who are fourteen to eighteen years, the value is 33 µg/day. Additionally, the EAR for girls nine to thirteen years if 26 µg/day of molybdenum and for girls who are fourteen to eighteen years old, they need 33 µg/day. The Molybdenum Recommended Daily Allowance (RDA) for children ages one to three is 17 µg/day and for ages four to eight years is 22 µg/day. The RDA for boys nine to thirteen years it is 34 µg/day and for those who are fourteen to eighteen years it is 43 µg/day. Finally, the Molybdenum RDA for girls who are nine to thirteen years is 34 µg/day and for girls fourteen to eighteen years, they need 43 µg/day.
Men and women over the age of nineteen both have the same EAR and RDA values for Molybdenum (“Molybdenum”, 2006). For men and women who are nineteen years old and greater, the EAR is 34 µg/day and the RDA is 45 µg/day. Molybdenum values for women who are pregnant between the ages of fourteen to fifty years old, are 40 µg/day for the EAR and 50 µg/day for the RDA. Additionally, for lactation, between the years of fourteen to eighteen the EAR is 35 µg/day and the RDA is 50 µg/day; then from ages nineteen to fifty, the EAR value increases slightly to 36 µg/day and the RDA remains the same 50 µg/day.
There are also upper level intake values that can pose to be toxic if one goes above it. Children one to three years cannot go above 300 µg/day, four to eight years cannot go above 600 µg/day, nine to thirteen year old cannot go above 1,100 µg/day, and children fourteen to eighteen cannot pass 1,700 µg/day. Adult men and women above the age of nineteen should not surpass 2,000 µg/day. Pregnant women should not go above 1,700 µg/day if they are fourteen to eighteen years old, and they need to stay below 2,000 µg/day if they are nineteen to fifty years old. If one is lactating, the same values as pregnant women are instated. High levels are not recommended because even though a human model has not been completed and there are mostly animal studies, in a mouse study, high levels of Molybdenum lead to carcinogenic results (“Molybdenum”, 2013). Toxicity can also lead to problems regarding growth, less hemoglobin, renal failure, and problems with the reproductive system (Novotny, 2006). Additionally, a deficiency, even though they are not common, can lead to reproductive problems and problems again with growth.
Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. (2001). Retrieved November 28, 2015, from http://www.nal.usda.gov/fnic/DRI/DRI_Vitamin_A/420-441_150.pdf (Links to an external site.) Molybdenum. (2006). Retrieved November 28, 2015, from https://www.nrv.gov.au/sites/default/files/page_pdf/n35-molybdenum_0.pdf (Links to an external site.)
Molybdenum. (2013, December 4). Retrieved November 28, 2015, fromhttp://www.cdc.gov/biomonitoring/Molybdenum_BiomonitoringSummary.html (Links to an external site.)
Novotny, J., & Turnlund, J. (2006, September 29). Molybdenum Intake Influences Molybdenum Kinetics in Men. Retrieved November 28, 2015, from http://jn.nutrition.org/content/137/1/37.full.pdf (Links to an external site.)
Deficiencies in molybdenum have only been recorded in humans in a few cases that have not been replicated. In one study two young men with Crohn’s disease had very extensive losses of trace minerals. These participants had symptoms of elevated uric acid levels in their plasma and urine after infusion with molybdenum, consistent with the purpose of xanthine dehydrogenase/oxidase. While this shows that molybdenum is utilized and essential in trace quantities it does not provide researchers any information with which to calculate a minimum dietary recommendation. Molybdenum toxicity is known as molybdenosis. Some of the most prevalent symptoms in molybdenum toxicity are actually those of copper deficiency because the excess molybdenum interferes with the utilization of copper by the body. Other effects of toxicity are thought to be kidney damage and reproductive abnormalities. Molybdenosis is very rare in humans and most of the research done on intake of the mineral has been conducted in animal studies. Ruminants, specifically, are more sensitive to molybdenum and therefore can be more easily utilized in studies for toxicity but this often is not relevant information when applied to human health. There are many surfacing claims about other health effects of molybdenum but almost all require further investigation. Molybdenum deficiency has been linked to cancer in both the Bantu tribes of Africa and in the Hunan province of China, where naturally low soil levels of the mineral can be found. Studies that which reported that molybdenum may be anticariogenic, or prevent dental caries, were deemed inconclusive but warranted further investigation. There has also been evidence that areas where Keshan’s disease is prevalent also have low levels of molybdenum in the soil and that upon fertilization with the mineral the prevalence decreased.
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Panel on Micronutrients. (2001) Dietary Reference INtakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academy of Science. Jan 9. pp 420–441.
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WHO (World Health Organization). 1996. Trace Elements in Human Nutrition and Health. Geneva: WHO. pp. 144–154.