Biomarkers of Whole Foods and Food Groups
Several biomarkers have been developed to evaluate dietary exposures at the level
of whole foods and/or food groups. The most common is the use of total plasma or
serum carotenoids as an indicator of fruit and vegetable intake. Correlations
between total carotenoids and fruit and vegetable intake generally reach 0.4–0.7 and
demonstrate a dose response (Crane et al. 2011 ). Another biomarker of whole
food/food group intake is plasma alkylresorcinols, an indicator of whole grain
wheat and rye intake (Kyro et al. 2014 ), which has been associated with disease risk
reduction including the metabolic syndrome (Magnusdottir et al. 2014 ) and BMI
(Ma et al. 2012 ). Urinary biomarkers of red meat intake have also been identified,
including 1- and 3-methylhistidine (Cross et al. 2011 ).
Biosampling of Diet/Nutritional Biomarkers
In order to evaluate the relationship between dietary biomarkers and health status,
biosamples must be properly collected, processed, and stored prior to undergoing
analytical measurement. Sources of biosamples vary across studies, with urine and
blood serving as the primary source of most samples (Fig.9.4). When considering
the appropriate biosample source for diet assessment, several factors come into
play. These include but are not limited to: (1) ease of acquisition and processing,
(2) participant burden, (3) reliability and validity in relation to bioactive deposition
of the nutrient in the specific tissue/fluid source, (4) stability of the sample during
processing and storage, and (5) cost.
Ease of Acquisition
This is generally not a concern for most nutritional biomarkers in that the majority
can be assessed in blood (whole, serum, plasma) or urine. Acquisition requires
Fig. 9.4 Biological sources
of samples used to assess
diet/nutritional exposures in
humans
9 Biomarkers of Diet and Nutritional Health 185