Molybdenum (Mo) is an essential trace mineral required in minute quantities for human health and nearly all life forms. This metal is a naturally occurring component of the environment, found in rocks, soil, and water. Its biological necessity stems from its role as a cofactor for several enzymes that drive important metabolic processes within the body.
Molybdenum in the Earth and Environment
Molybdenum is a component of the Earth’s crust, with an average concentration estimated at 0.6 milligrams per kilogram. This element is often found associated with other minerals and is slightly more concentrated in felsic rocks, such as granite, and certain sedimentary rocks, like shale. Soil concentration is highly variable globally, which primarily influences the element’s entry into the food chain.
Molybdenum exists in soil as the molybdate anion (MoO4 2-). Unlike many other micronutrients, its availability to plants increases as the soil pH rises. In highly acidic soils, molybdenum tends to bind tightly to mineral surfaces and iron oxides, making it less accessible for biological uptake by plant roots. Conversely, it is more soluble and readily taken up by crops in neutral or alkaline soils.
The environmental cycle involves uptake by deep-rooted plants, which incorporate it into their leaves. When these leaves decompose, the enriched organic matter is deposited into the upper soil layers. This process makes the element available to nitrogen-fixing bacteria, which are essential for soil fertility. Molybdenum is also present in natural water sources, but drinking water typically contributes only a small amount to overall daily intake.
Storage and Function in the Human Body
Once consumed, molybdenum is rapidly absorbed and distributed throughout the body. It is stored predominantly in the liver and kidneys, which are the main organs for processing nutrients and waste products. Smaller amounts are also stored in the adrenal glands and bone.
The primary function of molybdenum is to form the molybdenum cofactor (Moco), incorporated into the active site of four known human enzymes. These molybdoenzymes catalyze oxidation and reduction reactions fundamental to metabolism. For example, sulfite oxidase requires molybdenum to convert sulfite, a potentially harmful compound, into harmless sulfate for excretion.
Other molybdenum-dependent enzymes include xanthine oxidase, which breaks down purines into uric acid, and aldehyde oxidase, which helps metabolize various drugs and toxins. The presence of molybdenum in these enzyme structures is integral, facilitating the chemical transformations of sulfur, nitrogen, and carbon compounds necessary for health.
Food Sources of Molybdenum
The molybdenum content in foods directly reflects the soil quality where the plant or animal feed was grown. While widely distributed in the diet, concentrations can vary significantly. Plant sources are generally richer in this mineral than most animal products, with the exception of organ meats.
Legumes are consistently the richest dietary source of molybdenum. They contain substantial concentrations due to their symbiotic relationship with nitrogen-fixing bacteria, which have a high requirement for the element. Other good sources include various whole grains and nuts.
Specific examples of rich sources include:
- Lentils, which may provide approximately 49 micrograms per cup cooked.
- Black-eyed peas, which can contain even higher amounts.
- A half-cup serving of cooked long-grain white rice (around 13 micrograms).
- A quarter-cup of almonds (about 25 micrograms).
Although animal products are generally lower in concentration, beef liver is a notable source. Dairy products, such as milk and yogurt, also contribute to the daily intake of the mineral, especially for children and teens.