Essential trace minerals

The trace minerals identified as essential to humans and for which deficiency states have been described are zinc, copper, manganese, selenium, chromium, iodine, molybdenum, and iron. 

Each of these minerals participate in a variety of biologic functions and is necessary for normal metabolism. Other trace minerals essential to humans but for which deficiency states have not been recognized include nickel, vanadium, cobalt, and silicon (Table 66.2). 

Zinc deficiency is clinically characterized by the development of a moist eczematous dermatitis most apparent in the nasolabial folds and around orifices. Other presenting signs and symptoms may include hypogeusia (blunted sense of taste), alopecia, diarrhea, rash (which may vary from papular, scaly lesions to weeping, open erosions), apathy, and depression. Clinical zinc deficiency occurs most frequently in the setting of abnormal losses, such as in Crohn s disease, malabsorption states, and fistula losses, or from prolonged inadequate intake, such as with zinc-free parenteral nutrition. 

Copper deficiency may present as hematological changes (anemia, leukopenia, and neutropenia) and skeletal demineralization. In severe cases, such as in Menkes syndrome, copper deficiency is further manifested as hypothermia, depigmentation of hair and skin, progressive mental deterioration, and growth retardation. Factors predisposing to copper deficiency include malabsorption states, protein-losing enteropathy, nephrotic syndrome, copper-free parenteral nutrition, and copper-deficient enteral nutrition. 

Chromium deficiency is characterized by glucose intolerance but also may include neuropathy, increased free fatty acid concentrations, and a low respiratory quotient. Chromium deficiency has been identified in the setting of long-term, chromium-free parenteral nutrition. 

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Boron is also an essential trace mineral in plants. A trace mineral is an element needed in minute amounts for the good health of an organism. Boron is critical to production of certain essential plant proteins and to help plants extract water from the soil. Low levels of boron show up as yellowing, blackening, twisting, or crumpling of leaves. 

Selenium is an essential trace mineral that works in tandem with vitamin E to combat oxidative stress. You will find both vitamin E and selenium in barley, brown rice, broccoli, Brussels sprouts, gar-banzo beans, pumpkin, and pinto beans. 

Extra vitamin E is required to prevent the formation of toxic peroxides in the body when the dietary level of polyunsaturated fats is raised. However, diets containing ample amounts of the essential trace mineral selenium, which is a part of the enzyme that breaks down the peroxides, may also help to offset this danger. The formation of peroxides may contribute to the cocarcinogenic activity observed in some animal studies. 

Peroxide formation and the breakdown of polyunsaturated fatty acids in the body may be prevented by vitamin E (synthetic antioxidants such as BHA and BHT do not act in the cells of the body). Also, the essential trace mineral selenium is part of the enzyme which breaks down peroxides once they have been formed. Therefore, adequate dietary intakes of both vitamin E and selenium are the best forms of insurance against toxicity from peroxides, when the handling of vegetable oils leaves much to be desired. 

Because of the simplicity of swiae and poultry feeds, most feed manufacturers add vitamins (qv) and trace minerals to ensure an adequate supply of essential nutrients. Amino acids (qv) such as methionine [7005-18-7] lysiae [56-87-17, threonine [36676-50-3] and tryptophan [6912-86-3], produced by chemical synthesis or by fermentation (qv), are used to fortify swiae and poultry diets. The use of these supplements to provide the essential amino acids permits diets with lower total cmde proteia coateat. 

Molybdenum, recognized as an essential trace element for plants, animals, and most bacteria, is present in a variety of metaHo enzymes (44—46). Indeed, the absence of Mo, and in particular its co-factor, in humans leads to severe debility or early death (47,48). Molybdenum in the diet has been impHcated as having a role in lowering the incidence of dental caries and in the prevention of certain cancers (49,50). To aid the growth of plants. Mo has been used as a fertilizer and as a coating for legume seeds (51,52) (see FERTILIZERS Mineral NUTRIENTS). 

The remaining 5 % includes essential bulk minerals, Na, K, Mg, Ca and Cl, plus essential trace elements, including Mn and Fe for sure, but possibly Ni, Co, MoCW) and a small amount of Zn (see Figure 2.1). The failure to understand trace element absolute requirement is a major gap in our appreciation of life as a system. 

Tin is an essential trace element for animals. It is soft, pliable and colorless and belongs to group IV of the periodic table, and is corrosion-resistant to many media. Tin occurs in nature mostly as the oxide mineral cassiterite and is ubiquitous in the earth crust in an abundance of 2.5 x 10-4% (Clarke s number, 4 x 10 3). It is one of the earliest metals known to mankind, and evidence of its use dates back over 4000 years. The ancients... 

An enzyme cofactor can be either an inorganic ion (usually a metal cation) or a small organic molecule called a coenzyme. In fact, the requirement of many enzymes for metal-ion cofactors is the main reason behind our dietary need for trace minerals. Iron, zinc, copper, manganese, molybdenum, cobalt, nickel, and selenium are all essential trace elements that function as enzyme cofactors. A large number of different organic molecules also serve as coenzymes. Often, although not always, the coenzyme is a vitamin. Thiamine (vitamin Bj), for example, is a coenzyme required in the metabolism of carbohydrates. 

Minerals are small chemical substances that play key roles in various physiologic processes.55 Consider, for example, the ways that minerals such as sodium, potassium, chloride, and calcium influence the function and homeostasis of virtually every cell in the body. These minerals and several other major minerals (see Table 38-3) are essential for life. Other minerals, known commonly as trace minerals, are not as abundant in the body, but are still needed to promote the function of specific cells and tissues. 

Several minerals and trace elements are vital to the human organism and must be ingested with daily food in sufficient amounts. Wine can contribute not only minerals containing potassium, calcium, and magnesium but also numerous essential trace elements, such as chromium, cobalt, iron, fluorine, copper, selenium, and zinc, among others. The contents found in wine are very low ranging from mg L 1 to igL, sometimes even lower. 

Diets. Three basic diets were utilized (Table I), a 2% low fat diet (2% linoleic acid methyl esters), a 20% polyunsaturated fat diet containing 20% stripped corn oil, and a high saturated fat diet containing 18% coconut oil and 2% linoleic acid methyl esters to prevent an essential fatty acid deficiency (6 ). All diets were prepared to our specifications by ICN Life Sciences (Cleveland, OH) and analyzed both by ICN and our laboratory for fatty acids, antioxidants and some trace minerals. They are routinely stored in sealed plastic containers at 4°. Antioxidants when added (see Figure 2) were supplemented just prior to feeding and at 0.2% or 0.3% of the diet by weight as specified in each experiment. 

Manganese is an essential nutrient for humans with a daily estimated adequate safe and daily dietary intake of 2.5 to 5.0 mg (1). Yet trace mineral nutriture depends not only upon dietary intake, but also upon availability for absorption. Currently, little is known regarding the influence of dietary factors on the absorption of manganese. Thus the intent of these studies was to (a) develop a test that would readily measure Mn bioavailability in humans and (b) utilize this test to determine the influences of various dietary factors on Mn bioavailability. 

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