ULTRATRACE ELEMENTS IN NUTRITION - CURRENT KNOWLEDGE AND SPECULATION

The term ultratrace element has been defined as an element with an est ablished, estimated, or suspected requirement generally indicated by m u g/day for humans. Between 1970 and 1984, it was suggested that 11 el ements should be added to the list of ultratrace elements that include d chromium, molybdenum, and selenium; these elements were arsenic, bor on, bromine, cadmium, fluorine, lead, lithium, nickel, silicon, tin, a nd vanadium. Since 1984, it has been suggested that three more element s, aluminum, germanium, and rubidium, should be added to the list, and circumstantial evidence has continued to accumulate which indicates t hat several of the ultratrace elements in addition to iodine and selen ium, particularly arsenic, boron, chromium, nickel, silicon, and vanad ium, are more important in nutrition than currently acknowledged. This evidence includes findings from human studies suggesting that boron h as an essential function or beneficial effect in calcium metabolism, b rain function, energy metabolism, and perhaps immune processes; and th at chromium has an essential function in potentiating insulin action i n the metabolism of glucose and lipids, and/or a beneficial effect on diabetes resulting from inadequate synthesis of insulin or insulin res istance. The major shortcoming that has prevented the unequivocal acce ptance of the nutritional importance of any of the ultratrace elements suggested as being essential since 1970 and chromium is that a specif ic biochemical function has not been identified for any of these eleme nts. The current status of the evidence suggesting essentiality, the p ossible biological function, and speculated dietary need for each of t he 15 elements without an identified biochemical function is reviewed. J. Trace Elem. Exp. Med. 11:251-274, 1998. (C) 1998 Wiley-Liss,Inc.