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limited to urinary sucrose and fructose. These biomarkers have been shown to relate


to intake (Tasevska et al. 2005 ), but imprecision has been demonstrated, suggesting


that only about 41.7% of excreted fructose plus sucrose can be explained by esti-


mations of intake (Song et al. 2013 ). Identification of reliable and valid biomarkers


to predict sucrose and fructose intake is of value given compelling evidence that


high intake of sugar and/or foods and beverages concentrated in sugars is likely


contributory to obesity (Te Morenga et al. 2013 ).


Concentration and Replacement Dietary Biomarkers


Concentration biomarkers are surrogate indicators of nutrient or bioactive“levels”


in the body. Generally measured in plasma or serum, these measures correlate with


nutrient intake but generally with lower correlation coefficients (<0.60) than


recovery or predictive biomarkers. The lower correlations are thought to be a result


of the effects of metabolism and bioavailability on concentration measures. In fact,


an advantage of concentration biomarkers over dietary self-report is the fact that


such measurements provide a more biologically relevant exposure estimate given


that concentration values reflect individual variance introduced by differences in
absorption, microbiota influences, nutrient–nutrient interactions, medication use,


tissue turnover, metabolism, and excretion (Holst and Williamson 2008 ). Common


concentration biomarkers include serum or plasma vitamins (e.g., serum ascorbic


acid, plasma B12, or plasma 25-OH vitamin D), RBC fatty acids (EPA, DHA, etc.),


and serum or plasma carotenoids (as indicators of fruit and/or vegetable intake or


supplementation). Recovery biomarkers are similar to concentration markers in


terms of correlating with intake of a select food nutrient and/or food constituent.


However, these concentration biomarkers generally refer to biomarkers used for


foods where nutrient composition data are lacking (Grace et al. 2004 ). Bioactive


compounds in foods such as phytoestrogens and alkylresorcinols as measures of


soy and grain intake, respectively, fall into this category of biomarkers.


Concentration biomarkers have been widely applied in nutritional epidemio-


logical research in an effort to quantify and qualify diet–disease associations. As an


example, a study of women previously treated for breast cancer showed a 43%


reduced risk for breast cancer recurrence in women who entered the study with the


highest plasma carotenoid concentrations (Rock et al. 2005 ). Of note, self-reported


carotenoid intake was not significantly associated with plasma levels or breast


cancer recurrence risk in this same sample of women (Natarajan et al. 2006 ).


Contrary to this, in the CAREDS trial, where serum as well as dietary intake of


lutein and zeaxanthin were assessed in relation to the formation of nuclear cataracts


in older adults, both diet and serum measures were inversely associated with risk,


although risk reduction was higher in relation to serum concentrations (32% lower


risk) as compared to dietary associations (23% lower risk) (Moeller et al. 2008 ).


Concentration biomarkers for antioxidant nutrients have also been investigated in
relation to surrogates of morbidity and mortality, including telomere length (Sen


9 Biomarkers of Diet and Nutritional Health 183

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