A critical assessment of some biomarker approaches linked with dietary intake

In this review many examples are given of the complexities involved in usin g some biomarkers in relation to assessing the effects of dietary exposure, when there is frequently a need to determine changes following long-term l ow level exposure to dietary components. These range from understanding why the biomarker might be valuable and how best it can be measured, to the pi tfalls which can occur in the interpretation of data. Analytical technique is considered in relation to folate and selenium, and flavonoid and carotenoid species are used to illustrate how the metabolism of a compound may alter the validity or adequacy of a marker. Vitamin A is discussed in relation to the difficulties which can arise when there are se veral biomarkers that may be available to assess exposure to one nutrient. Vitamin B-12 is discussed in relation to the dietary choices made by indivi duals. Possible interactions and the role of measuring total antioxidant ca pacity is considered in some detail. In contrast to most nutrients, there i s a marked lack of biomarkers of either exposure or effect for most non-nut rients. The role of biological effect monitoring is considered for dietary contaminants, fumonisins and polyhalogenated aromatic hydrocarbons. Aflatox ins are discussed to exemplify food contaminants for which the biomarker ap proach has been extensively studied. Finally some compounds which are delib erately added to foods and some which appear as processing contaminants are each considered briefly in relation to the requirement for a biomarker of exposure to be developed.