Micronutrients: Too Much or Not Enough?

Abstract

Micronutrients (ie, vitamins and trace elements) are considered essential for human metabolism and should be delivered to all patients receiving enteral nutrition (EN) and parenteral nutrition (PN) support. Despite incorporation into EN products or the commercial availability of parenteral multiple trace element and multivitamin preparations, episodes of deficiency and toxicity continue to occur in patients receiving specialized nutrition support. Although the micronutrient content of these preparations is based upon expert consensus recommendations to meet the demands of most patients, acute and chronic conditions may account for individual variations in requirements. Evolving research shows that micronutrient status is affected by multiple factors, such as the acute phase response, causing redistribution and changes in plasma micronutrient concentrations. Serum C-reactive protein (CRP), a positive acute phase protein, is the most important marker of the acute phase response. CRP activates the classic complement pathway and acts as an opsonin involved in the clearance of microorganisms. During the acute phase response, as reflected by an increased CRP, plasma concentrations of the trace elements iron and zinc fall as a result of decreased protein binding and transfer into other body compartments. In contrast, serum copper rises because of an increased production and release of the major copper-binding plasma protein, ceruloplasmin, from the liver during inflammatory conditions. Micronutrient requirements are frequently