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Cobalt is an essential ultra trace mineral that is the base for the vitamin B-12 molecule, which is the most important function of cobalt. It has been known that this mineral is vital for human nutrition .
The body uses this vitamin for numerous purposes. Vitamin B-12 is necessary for the normal formation of all cells, especially red blood cells. Vitamin B-12 also helps vitamin C to perform its functions, and is necessary for the proper digestion of the food that we eat. Additionally, vitamin B-12 prevents nerve damage by contributing to the formation of the protective sheath that insulates nerve cells .
A deficiency of vitamin B-12 can causes red blood cells to form improperly. This can prevent red blood cells from carrying enough oxygen from our lungs to the different parts of our bodies, thus causing a condition called anemia. Symptoms of anemia include loss of energy, loss of appetite, and moodiness. B-12 deficiency can also cause nerve cells to form improperly, resulting in irreversible nerve damage. This situation is characterized by symptoms such as delusions, eye disorders, dizziness, confusion and memory loss.
Unlike other B complex vitamins, vitamin B-12 can be stored in the body. Deficiencies of B-12 are rare in young people, but do occasionally occur in adults due to digestive disorders or poor absorption by the digestive system. Strict vegetarians are also at risk of B-12 deficiency, because vegetables do not contain this important vitamin. B-12 is only found in animal sources such as red meat, fish, eggs, cheese and milk. Fortunately for vegetarians, one can also get plenty of vitamin B-12 from most multi-vitamin pills.
Cobalt also can substitute for zinc in metalloenzymes, but the significance of this is not clear.
The average diet contains about 300mg of cobalt. Cobalt is readily absorbed in the gastrointestinal tract [68, 69]. Inadequate cobalt causes vitamin B-12 deficiency.
Cobalt is found in steel alloys of diamond grinding discs, other industrial tools, and jet engines and in pigments in paints. Most commonly, occupational hazard is associated with the dust or fumes that are produced during use of cobalt containing tools. Direct contact with this dust and fumes causes dermatitis, conjunctivitis, and rhinitis, and prolonged inhalation results in pulmonary disorders, such as allergic asthma, intestitial pneumonitis, and pulmonary fibrosis. Cobalt ingestion is associated with cardio toxicity. Formerly, cobalt was used as foam stabilizer commonly added to beer. Prolonged excessive ingestion of cobalt-containing beer leads to polycythemia, goiter and heart disease characterized by cardiomyopathy, pericardial effusion, and congestive heart failure ("beer drinker's cardiomyopathy"). The toxicity in these cases may have been exacerbated by concomitant nutritional deficiencies and ethanol. Accumulation of cobalt also occurs in uremic patients and may contribute to uremic cardiomyopathy [70, 71].
The ultra trace element nickel (Ni) is both essential and toxic for animals and humans . Nickel has been shown to be essential for a wide variety of animal species including chickens, rats, pigs, cows, sheep, and goats .
Nickel has been found to participate in hydrolysis and redox reactions and to regulate gene expression. In these roles, nickel forms complexes with sulfur, nitrogen and oxygen and exists in oxidation states of 3+, 2+, 1+ and possibly 0 and 4+. Without nickel, plants and some bacteria cannot complete their life cycle. Because nickel is so important and dynamic for lower forms of life, it most likely has an essential role in higher forms of life, including humans.
In higher animals, vitamin B-12 is necessary for the optimal expression of the biological role of nickel, or that nickel has an essential function closely related to vitamin B-12 metabolism. Nickel acted in synergy with vitamin B-12 in stimulating hematopoiesis .
In higher animals nickle function is considered as an enzyme cofactor or activator. A possible enzyme utilizing nickel in higher animals is calcineurin, a multifunctional calmodulin-stimulated protein phosphatase that apparently is an important regulatory enzyme in brain, skeletal muscle and possible several other tissues .
In skeletal muscle, calcineurin apparently is involved in glycogen metabolism; that is, it regulates the state of phosphorylation of many glycolytic enzymes. Calcineurin also possesses phosphotyrosyl-protein phosphatase activity which affects the action of receptors of epidermal growth factor and insulin, and thus probably influences growth and glucose metabolism. Growth and plasma glucose are two of the variables most consistently affected by nickel deprivation .
Another enzyme present in higher animals is urease . It has been hypothesized that the urease, possibly nickel-dependent, produced ammonia to influence lung fluid balance, or to neutralize acidic aerosols present in the air entering the lungs.
No sign of nickel deficiency has been reported for humans. The potential importance of nickel in human nutrition is not limited to deficiency. Like other mineral elements, nickel ingested in high amounts can have adverse effects . However, in body an excellent homeostatic regulation is present, and life threatening toxicity of nickle through oral intake is not common. If the intake of nickle exceeds over 250 mg daily, it could produce toxic symptoms in humans. A relatively common form of dermatitis is caused by a sensitivity to nickel .
The essentiality of nickle is also supported by findings showing that it is homeostatically regulated. It does not accumulate in the body like some toxic elements e.g. cadmium. Food of animal origin contain low amount of nickle as compared to food of plant origin, that's why total dietary nickel intakes of humans vary greatly with the amounts and proportions of food taken. Rich sources of nickle include chocolate, nuts, dried beans peas and whole grains .
1.6.1 Interaction of nickel with other metals
Among animals, plants, and microorganisms, nickel interacts with at least 13 essential elements (Ca, Cr, Co, Cu, I, Fe, K, Mg, Mn, Mo, Na, P, and Zn). Competitive interactions have been reported with Ca, Co, Cu, Fe, Mg, Mn and Zn [80,81]. In most cases it is not known whether competition occurs at the cell-surface uptake sites or at intracellular metabolic sites . However, competition at both sites is likely to occur because metal-chelating functional groups found in both membrane transport proteins and intracellular enzymes are never completely specific for one metal . The effect of nickel-zinc interactions is dependent on the zinc concentration. In low zinc concentration (0.5 mg Zn2+/L) there is no effect on nickel concentration. At intermediate zinc concentration (2 to 20 mg Zn2+/L) a synergistic effect, and a beneficial effect at the highest concentrations (30 mg Zn2+/L) was reported . A synergistic effect of copper and nickel was reported for several algal species . Mixtures of metals (arsenic, cadmium, copper, chromium, mercury, lead, zinc) containing nickel salts are more toxic to daphnids and fish than are predicted on the basis of individual components . The interaction of chromium with nickel is also reported. [87, 88]. Cobalt can also interact and replace nickel. [89, 90]. The interaction of manganese and molybdenum with nickel is also reported [91, 92].
Zinc demonstrated as an essential component of the human diet and found throughout the plant and animal kingdoms .
Zinc has a wide range of functions. It helps in the healing of wounds and is a vital component of many enzyme reactions. Zinc is vital for the healthy working of many of the body's systems. It is particularly important for healthy skin and is essential for a healthy immune system and resistance to infection . It plays a crucial role in growth and cell division where it is required for protein and DNA synthesis, in insulin activity, in the metabolism of the ovaries and testes, and in liver function. As a component of many enzymes, zinc is involved in the metabolism of proteins, carbohydrates, lipids and energy .
Our body contains about 2-3 g of zinc. There are no specific storage sites known for zinc and so a regular supply in the diet is required. The mineral zinc is present in every part of the body. 60% of it is found in muscle, 30% in bone and about 5% in our skin. Particularly high concentrations are in the prostate gland and semen. Men need more zinc than women because male semen contains 100 times more zinc than is found in the blood. The more sexually active a man the more zinc he will require. The recommended amounts of zinc for adult men are 1/3 higher than those for women.
The body best absorbs smaller amounts of zinc at one time. Overall, the body absorbs 15-40% of dietary zinc, depending on the body's requirement for this mineral. Zinc is lost via the faeces, urine, hair, skin, sweat, semen and also menstruation. The first signs of zinc deficiency are impairment of taste, a poor immune response and skin problems. Other symptoms of zinc deficiency can include hair loss, diarrhoea, fatigue, delayed wound healing, and decreased growth rate and mental development in infants. It is thought that zinc supplementation can help skin conditions such as acne and eczema, prostate problems, anorexia nervosa, alcoholics and those suffering from trauma or post-surgery [96-99].
Zinc is present in a wide variety of foods, particularly in association with protein foods. A vegetarian diet often contains less zinc than a meat based diet and so it is important for vegetarians to eat plenty of foods that are rich in this vital mineral. Good sources for vegetarians include dairy products, beans and lentils, yeast, nuts, seeds and wholegrain cereals. Pumpkin seeds provide one of the most concentrated vegetarian food sources of zinc.
Since minerals may compete for absorption sites in the intestine, excess intakes of iron or copper can adversely interfere with zinc absorption. Likewise, excess intake of zinc (from supplements or fortified foods) can impair iron and copper absorption. Although phytates and fiber found in unprocessed grains inhibit the bioavailability of zinc, whole grains are still a better source of zinc than that found in refined grains (e.g. white bread). Whole grain yeast breads enhance the absorption of zinc by producing enzymes that destroy phytates. Zinc from meat products, on the other hand, is four times more bioavailable than that found in fiberous grain foods. High levels of the toxic mineral cadmium can also prevent zinc absorption because these two minerals compete for absorption. Conversely high levels of zinc in the diet can prevent the absorption of cadmium. Various chemicals added to many processed foods can also reduce zinc absorption eg phosphates, EDTA.
Excess zinc is toxic. Too much zinc will interfere with the metabolism of other minerals in the body, particularly iron and copper. Symptoms of zinc toxicity occur after ingestion of 2g of or more and include nausea, vomiting and fever.
Clinical manifestations of zinc toxicity (doses > 80 mg/day) include decreased levels of HDL-cholesterol, white blood cells and copper. Impaired cholesterol metabolism and gastrointestinal disturbances can also result from excess intake of zinc supplements [100, 101].