Abstract
AbstractThe essential inorganic nutrients are dietary components that exert nutritional function when they are consumed as inorganic substances. Some essential inorganic nutrients such as selenium and iodine act as organic active constituents after metabolic conversion in vivo when they are consumed as organic and inorganic substances. Inadequate intake of essential inorganic nutrients results in deficiency diseases and/or interruption of life cycles. The essential inorganic nutrients consist of the major elements (sodium, potassium, calcium, magnesium, chlorine, phosphorus, and sulfur) and the trace elements (iron, copper, zinc, manganese, cobalt, chromium, molybdenum, vanadium, nickel, arsenic, selenium, iodine, fluorine, silicon, boron, tin, cadmium, lead, rubidium, and lithium). Evidence of essentiality is limited for arsenic, boron, cadmium, fluorine, lead, lithium, nickel, rubidium, silicon, tin, and vanadium. If the requirement is <1 mg day−1for humans or 1 mg kg−1diet for animals, the inorganic nutrients are calledultratrace elements. Further investigation may increase the number of essential inorganic nutrients. Deficiencies of inorganic nutrients such as iodine, iron, and zinc occur worldwide. To prevent deficiencies and toxicosis, the United States and other nations have established the dietary reference intakes or the equivalents that are composed of reference values including estimated average requirements, recommended dietary allowances, adequate intakes, and tolerable upper intake levels. Essential inorganic nutrients function in vivo through various modalities such as catalytic centers of enzymes, metabolic regulation, modulation of ion channels and receptors. The regulation and control of inorganic nutrients are a function of eight parameters: availability, solubility, permeability, ligand exchange, transport, assimilation, storage, and excretion. Excessive intakes, genetic abnormalities, and other etiologies cause pathologies of metal overload. Functions of selenium, nickel, and chromium were reviewed. Selenium manifests antioxidant activity as an active site of glutathione peroxidase. Other important selenium‐containing proteins include thioredoxin reductase, iodothyronine deiodinases, and selenoprotein P. Nickel occupies the metal centers of urease, carbon monoxide dehydrogenase, and other enzymes. Nickel deprivation results in impaired reproduction (rats and goats) and decreased spermatozoa motility and density (rats). In six clinical cases, prolonged total parenteral nutrition low in chromium caused glucose intolerance and/or neuropathy reversed by chromium supplementation. It is our challenge to determine optimal intakes of inorganic nutrients for ensuring optimal health for all.