Trace elements in health and diseases.

Remarkable progress has occurred in many branches of biology and health sciences during the last few decades. Trace element (TE) research has definitely shared in this explosion of scientific knowledge. Due to the improvements in analytical technology, the discovery of TEs in organism was realized. The developments of TE research have been promoted by the demand of public health (e.g. deficiency or toxicity). The profound knowledge of nutritional importance of TEs has been achieved with application of advanced methods in biological, medical and chemical fields, etc. In this paper, a new definition of essentiality of TEs is introduced. According to this definition, only ten TEs (Fe, Zn, F, Cu, I, Se, Mn, Mo, Cr, Co) are considered to be essential to humans. The others need more evidence to prove their essentiality in humans. The recent progress on the biochemical and immunological functions of TEs and on the roles of TEs in brain development are briefly described. The TEs, mainly Se, I, Zn, Fe, are more closely related to public health. Also, emphases are laid on balancing all nutrients when new knowledge of essential TEs is applied in public health.