Perhaps the most remarkable fact about trace elements is not their scarcity, but their abundance in the tissues of the human body. Table 1 gives the relative amounts in a baby at term of some of the substances that are thought to be essential for normal growth and development. From such data one can calculate that a full-term infant, comprising some 3.4 × 1026 atoms, contains 1.4 × 1022 trace element atoms. Chromium is perhaps one of the least abundant essential trace elements in the body, and yet the newborn baby contains about 3.6 × 1018 chromium atoms, and even a single hepatocyte contains some 4.5 million atoms of this element. The name "trace element" is, of course, quite arbitrary and survives from the time when early investigators, with the methods then available, were experiencing great difficulties in measuring these substances in plant and animal tissues. The
Shaw JCL. Trace Elements in the Fetus and Young Infant: I. Zinc. Am J Dis Child. 1979;133(12):1260–1268. doi:10.1001/archpedi.1979.02130120052011
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