Molybdenum though its name may be one of the more difficult to pronounce, is not generally well known. However, this mineral’s importance has been discovered in recent years. Molybdenum is now considered one of our essential trace minerals. It has been found to be essential in most mammals, as well as in all plants. We obtain it primarily from foods, but since it is often scarce in the earth’s crust and therefore deficient in many soils, molybdenum deficiency can be a problem. In fact, it was recently discovered that molybdenum deficiency in the soil in an area of China was responsible for the highest known incidence of esophageal carcinoma over many generations.
In nature, molybdenum is found as part of other metal complexes. In the soil, it serves as a catalyst to the nitrogen-fixing process; thus, decreased soil molybdenum can lead to deficient plant growth.
The body contains minute amounts, about 9 mg., of molybdenum. It is found mainly in the liver, kidneys, adrenal glands, bones, and skin, but it is present in all tissues. It is important to several enzyme systems, most significantly that of xanthine oxidase, which supports many functions, including uric acid metabolism and mobilization of iron from the liver for body use. Molybdenum is fairly easily absorbed from the gastrointestinal tract, though it competes with copper at absorption sites. It is eliminated through the urine and the bile.
As with chromium, depletions or deficiencies of molybdenum are common, and its availability in foods is decreased through soil depletion and food technology. This mineral has come to the nutritional forefront in the last decade with the recognition of its essential nature and the concern about deficiency.
Sources: The food levels of molybdenum depend largely on soil content. The amount in food may be increased a hundredfold with molybdenum-rich soil; in certain areas, hard water may contain some molybdenum. Soft water and refined foods contain hardly any. Whole grains, particularly the germ, usually have substantial amounts; oats, buckwheat, and wheat germ are some examples of grains containing molybdenum. Many vegetables and legumes are also good sources; these include lima beans, green beans, lentils, potatoes, spinach and other dark leafy greens, cauliflower, peas, and soybeans. Brewer’s yeast also has some, and liver and organ meats are often fairly high in molybdenum.
Functions: Molybdenum is a vital part of three important enzyme systems—xanthine oxidase, aldehyde oxidase, and sulfite oxidase—and so has a vital role in uric acid formation and iron utilization, in carbohydrate metabolism, and sulfite detoxification as well. In the soil and possibly in the body, as the enzyme nitrate reductase, molybdenum can reduce the production or counteract the actions of nitrosamines, known cancer-causing chemicals, especially in the colon. Found more in molybdenum-deficient soils, nitrosamines have been associated with high rates of esophageal cancer.
Xanthine oxidase (XO) helps in the production of uric acid, an end product of protein (purine) metabolism. Though an excess of uric acid is known to cause gout, recent studies show that, in proper concentrations in the blood, it has antioxidant properties and helps protect the cells and tissues from irritation and damage caused by singlet oxygens and hydroxyl free radicals. This protection may prevent tissue wear and aging, in addition to other free-radical diseases discussed throughout this book. Thus, uric acid has a new image as being an important part of balanced human function and not just a waste product.
With its different effects, uric acid is somewhat like cholesterol in its biochemistry. As with cholesterol, it is both made in the body and obtained through the diet; some people are genetically inclined to elevated levels; and, whereas the right amount is essential to important functions, excesses can lead to problems (cholesterol appears to be much more of a concern on this count than uric acid). Xanthine oxidase may also help in the mobilization of iron from liver reserves.
Aldehyde oxidase helps in the oxidation of carbohydrates and other aldehydes, including acetaldehyde produced from ethyl alcohol. Sulfite oxidase helps to detoxify sulfurs in the body, particularly sulfites, which are used to preserve food. These potentially toxic and harmful substances can cause nausea or diarrhea and precipitate asthma attacks in sensitive individuals. The “salad bar” syndrome is caused by sulfite sprays used on vegetables to keep them “fresh” longer. It is possible that adequate tissue levels of molybdenum keep the sulfite oxidase activity levels high enough to counteract this chemical and reduce potential symptoms; molybdenum deficiency may be a factor in those people who are more sensitive to sulfites. Luckily, though, the use of sulfites in food preservation is being made illegal.
Uses: Since molybdenum’s activities in humans are so newly known, it does not have wide usage. Even the uses suggested in some nutritional texts are under question and require more research. Molybdenum may help prevent anemia by helping mobilize iron, provided there are sufficient iron stores. The suggestions that it protects the teeth from dental caries and that it prevents sexual impotence are not yet supported by definitive research. Molybdenum deficiency may reduce uric acid formation; this was not previously thought to be a problem, but it may be important to supplement molybdenum to maintain uric acid levels in midnormal range for the antioxidant function as well as possible others.
There are few research findings to suggest that molybdenum may play a role in preventing cancer and definitely none to suppport its use in cancer treatment. Adding molybdenum to the soil and diet has helped reduce the incidence of esophageal cancer in the Lin Xian area of China’s Hunan Province, which had the highest incidence in the world of this deadly disease. It is unlikely, however, that lack of molybdenum in the soil and, thus, in the diet was a direct cause of the cancer; it was probably due to the production of nitrosamines in the soil that could not be metabolized because of a deficiency in the plants’ roots activity of the molybdenum enzyme, nitrate reductase. Nitrates and nitrites, such as those in hot dogs, lunch meats, and other cured meats, also increase food levels of nitrates, which can lead to the formation of carcinogenic nitrosamines in the stomach. Both vitamin C, which helps detoxify nitrosamine, and nitrate reductase, which needs molybdenum to function, can help reduce the levels of this carcinogenic chemical as it has done for the Chinese esophageal cancer rates secondary to low soil molybdenum. It is also possible that molybdenum can help protect the body from nitrosamine formation after consumption of foods high in nitrates or nitrites, such as lunch meats.
Deficiency and toxicity: Molybdenum, like most trace minerals, is required in a specific narrow range of daily intake; amounts much greater than this may be toxic. Animals given large amounts experience weight loss, slow growth, anemia, or diarrhea, though these effects may be more the result of low levels of copper, a mineral with which molybdenum competes. In people who are sensitive to it, high doses of molybdenum may lead to high uric acid levels and gouty arthritis symptoms related to increased action of the enzyme xanthine oxidase.
Information about molybdenum deficiency is limited as well. Low soil levels of molybdenum lead to increased soil and plant levels of nitrates and nitrosamines, which increase risk of cancer, especially in the esophagus and stomach. Increased sensitivity to sulfites used in foods may be related to low molybdenum and deficient sulfite oxidase enzymes. In animals, molybdenum-deficient diets seem to produce anorexia, weight loss, and decreased life span. In humans, deficiency may lead to visual problems, rapid heart rate and breathing, and depression of consciousness.
Requirements: As with other newly recognized trace minerals, there is no specific RDA for molybdenum. The amount provided by the average diet ranges widely, from 50-500 mcg. a day. A safe and sensible amount of added molybdenum is from 150-500 mcg. for adults and 50-300 mcg. for children. A molybdenum-rich yeast may be available as an added nutrient, which usually contains a lot of other minerals and B vitamins. Sodium molybdate, which recently has come on the market, can be taken by people who want more molybdenum, though intake should be limited to 500 mcg. daily. It is probably best to take molybdenum in a general multivitamin and to take 2-3 mg. of copper daily as well, because of the potential copper loss with molybdenum supplementation. Further research is required, but it appears that molybdenum is very important for optimum health and longevity.