Considerations for determining ‘optimal nutrition’ for copper, zinc, manganese and molybdenum

Abstract

Defining optimal dietary intakes of Cu and Zn throughout the life cycle continues to present a considerable challenge for nutrition scientists. Although the daily intake of these micronutrients is below that currently recommended for many groups, traditional biochemical indicators of nutritional status for these trace metals largely remain within the normal range. Thus, it is unclear whether the recommended daily intakes may be unnecessarily high, or if the commonly-used markers simply lack the necessary sensitivity and specificity that are required for accurately assessing Cu and Zn status. The increasing number of reports that daily supplements with these trace metals enhance the activities of selective metalloenzymes and specific cellular and organ processes further points out the need to differentiate between meeting the requirement and providing optimal nutriture. Results from recent studies suggesting that alternative molecular and functional markers possess sufficient sensitivity to better assess Cu and Zn status are discussed. Likewise, recent studies evaluating the impact of very low and excessive levels of dietary Mn and Mo on selective biochemical and metabolic indicators are reviewed.

An update on copper: contribution of MAFF‐funded research

“…Some of these metalloproteins are cuproenzymes, which participate in diverse cellular and extracellular activities and in which Cu serves as a catalytic cofactor. Maintenance of these activities depends on the ability of the organism to provide adequate quantities of Cu for incorporation into the apo‐cuproproteins (Failla 1999). Some of the Cu binding enzymes and proteins and their known function are listed in Table 3.…”

“…Plasma and urinary Cu, Cp enzyme activity and protein, and haematological variables were resistant to low Cu intake. Platelet CCO activity remained significantly depressed after subjects were replenished with 2 mg Cu daily for 5 weeks, whereas platelet Cu was restored to control levels during this period (Failla 1999).…”

“…Failla (1999) concluded that additional functional indicators of Cu status are required to define optimal Cu intake, as opposed to Cu deficiency, for diverse groups of free‐living individuals. The potential markers include:…”

“… Cuproenzymes: Peptidylglycine α‐amidating monooxygenase (PAM) (Prohaska 1997; Prohaska et al 1997); Diamine oxidase (DAO) (DiSilvestro et al 1997; Jones et al 1998; O'Connor et al 2000). Its usefulness may be limited because activity is higher in females than males, elevated in response to pregnancy and some types of cancer, cystic fibrosis, uraemia, intestinal ischaemia and renal dialysis, and lower in subjects with Crohn's and coeliac diseases, and severe trauma (Failla 1999). Selective activities of the skeleton and immune system: Risk factors for bone health, e.g.…”

“…synthesis of the cytokine IL‐2 (Failla & Hopkins 1998). The potential ability of physiological levels of Cu to stimulate in vitro mitogenic responsiveness and IL‐2 production in human T‐cells, as occurs in rat cells, merits consideration as a sensitive biomarker for detecting marginal Cu deficiency (Failla 1999).…”