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unit 3 assessing exposure to the environment chapter 11 dietary intake and nutritional status jiyoung ahn christian c abnet amanda j cross and rashmi sinha 1 t 3 1 i ...

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                                                                                     unit 3.
                                                                                     assessing exposure to the environment
                                                                                                                                                                  chapter 11.  
                                                                                                                         Dietary intake 
                                                                                       and nutritional status
                                                                                                     Jiyoung Ahn, Christian C. Abnet, Amanda J. Cross, and Rashmi Sinha
                                                                                                                                                                                                     1
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                                 Summary                                                                                                                                                             a
                                                                                                                                                                                                     Ch
                                                                                     damage and tissue concentrations  metabolism, as food is a complex 
                                 Though dietary factors are 
                                 implicated in chronic disease risk,  are also discussed.                                                mixture; thus, the absorption and 
                                 assessment of dietary intake has                                                                        metabolism of any single nutrient is 
                                 limitations, including problems                                                                         affected by the presence of another. 
                                                                                     Biomarkers of nutritional 
                                 with recall of complex food intake  exposure and nutritional                                            For example, iron taken with vitamin 
                                 patterns over a long period of  status: An overview                                                     C is absorbed more efficiently than 
                                 time. Diet and nutrient biomarkers                                                                      by itself, but phytate can bind iron 
                                 may provide objective measures                                                                          and make it unavailable. Cooking 
                                                                                     Food frequency questionnaires 
                                 of dietary intake and nutritional  (FFQ), multiple food records, and 24-                                is another important factor that can 
                                 status, as well as an integrated  hour recalls are the most common  change concentrations of nutrients 
                                 measure of intake, absorption and  methods to assess dietary intake  or can form compounds not normally 
                                 metabolism. Thus, the search for  in nutritional epidemiologic studies  present in foods. Obtaining this level 
                                 an unbiased biomarker of dietary  (1). The strengths and limitations of                                 of detail using dietary assessment 
                                 intake and nutritional status is an  dietary assessment methods, as well                                instruments is generally not feasible. 
                                 important aspect of nutritional as nutritional status biomarkers, are                                   Furthermore, food composition 
                                 epidemiology. This chapter reviews                  summarized in Table 11.1. Generally,                tables are not available for all 
                                 types of biomarkers related to  the accuracy of the information  nutrients, limiting the assessment 
                                 dietary intake and nutritional status,              collected depends on the ability to                 of many of them. Finally, there 
                                 such as exposure biomarkers of diet                 integrate complex eating patterns  are numerous nutrients, such as 
                                 and nutritional status, intermediate  concisely and the subject’s memory.                               selenium and vitamin D, that cannot 
                                 endpoints, and susceptibility. Novel                                                                    be measured adequately in the food 
                                                                                     Current dietary assessment 
                                 biomarkers, such as biomarkers                                                                          source.
                                                                                     methods may not completely 
                                 of physical fitness, oxidative DNA  capture nutrient interactions and 
                                                                                                                    Unit 3 • Chapter 11. Dietary intake and nutritional status    189
                          Table 11.1. Strengths and limitations of intake assessment methods and nutritional status biomarkers
                                                                Assess by                            Limitations                          Strengths
                           Estimate of dietary intake           Questionnaire                        - Prone to different types of bias   - Easier to administer in 
                                                                FFQ                                  - Dependent on memory                population-based
                                                                Food records                         - May not capture variability in     studies
                                                                24-hour recall                       eating pattern                       - Long-term intake
                                                                Diet history                         - does not account for absorption    estimate
                                                                Food composition table               or bioavailability when foods 
                                                                                                     are cooked or eaten as complex 
                                                                                                     mixtures
                                                                                                     - Not comprehensive especially 
                                                                                                     for diaries and recalls
                                                                                                     - Focused on specific nutrient
                                                                                                     - Many newer dietary compounds 
                                                                                                     of interest not covered
                           Nutritional status                   Biomarker of:                        - Collection                         - Objective measure
                                                                - absolute intake                    - Storage                            - Error structure
                                                                - correlated intake                  - Sensitivity                        different than
                                                                                                     - Specificity                        questionnaire-based
                                                                                                     - Laboratory variability             information
                                                                                                     - Single measure may not be          - Integrated measure
                                                                                                     representative of usual
                              Diet and nutrient exposure biomarker (> 0.8) (2). The two well-                                  the methods used to measure the 
                          biomarkers may be independent  studied recovery biomarkers are  recovered products are technically 
                          of the subject’s memory or urinary nitrogen and doubly-labelled                                      challenging (4).
                          the capacity to describe foods  water. Urinary nitrogen is an example                                     Urinary nitrogen and doubly-
                          consumed. Biomarkers may provide                  of a recovery biomarker of protein  labelled water are the only validated 
                          an integrated measure of intake,  intake. A 24-hour urine collection is                              recovery biomarkers, but it must 
                          absorption and metabolism, which  required, and subjects should take  still be assumed that the testing 
                          may improve the accuracy of  para-aminobenzoic acid (PABA) period is representative of the 
                          the estimation of the association  tablets with the three main meals of                              subjects’ usual habits. The relative 
                          between the nutrient and disease,  the day to validate the completeness                              complexity and high cost of these 
                          but limit the direct interpretation of            of the collection (3). The amount of               methods prevents these biomarkers 
                          the connection between intake and                 nitrogen recovered in a 24-hour  from being applied to large cohort 
                          disease. However, since biomarkers                urine collection can be converted  studies. Thus, these biomarkers 
                          may be affected by biospecimen  to protein intake using estimates of  are often used as gold standards 
                                                                            the percent of nitrogen excreted in                for validating dietary questionnaires 
                          collection methods, storage 
                          conditions and laboratory variations,             urine (~81%). Doubly-labelled water                or developing correction factors to 
                          these factors must be carefully  is another example of a recovery  estimate measurement attenuation.
                          considered in the study design.                   biomarker for energy expenditure, 
                                                                            in which the average metabolic  Biomarkers of correlated intake: 
                          Types of biomarkers                               rate of a human is measured over  Concentration biomarkers
                                                                            a period of time. A dose of doubly-
                          Exposure biomarkers                               labelled water, in which both the  Biomarkers of correlated intake are 
                                                                            hydrogen and the oxygen have  based on concentrations in the body 
                          Biomarkers of absolute intake:                    been partly or completely replaced  (i.e. in blood, urine, saliva, hair, nails 
                          Recovery biomarkers                               for tracking purposes (i.e. labelled)              or tissue), reflecting current intake 
                                                                            with an uncommon isotope of these                  status. Concentration biomarkers 
                          Biomarkers of absolute intake, elements, is administered to the  are correlated with intake, such 
                          or recovery biomarkers, reflect  individual. The loss of deuterium and                               that higher concentrations of these 
                          a balance between intake and  O-18 is then measured over time by                                     biomarkers result from higher 
                          output over a defined period, with  regular sampling of heavy isotope  intake. The measured concentration 
                          relatively high correlation between  concentrations in the body water  is a consideration of intake, uptake, 
                          the absolute dietary intake and the               (by sampling saliva, urine or blood);              and metabolism. Concentration 
                           190
                                 biomarkers can enhance dietary  For example, in the EPIC study,  useful estimate of true exposure. 
                                 assessment, or in some cases be  high serum concentrations of In addition, because menstruation 
                                 the primary method of assessment  α-tocopherol  were  associated  with                                  can lead to very different amounts 
                                 of nutrient exposure.                               significantly lower risks of gastric  of iron loss in women, the estimation 
                                                                                     cancer, but estimated dietary intake                of intake may not be biologically 
                                 Nutrients                                           of vitamin E was not (11).                          relevant. There are several 
                                                                                          Biomarkers as the primary biomarkers for iron, including 
                                 This type of biomarker may be  method of assessment. This type of                                       serum iron and serum ferritin; both 
                                 used to enhance assessment and  biomarker may be used to measure  are subject to homeostatic control 
                                 measurement of dietary components                   intake for dietary components that  and influenced by inflammation, 
                                 that are currently captured by dietary              are not currently captured by dietary               respectively.
                                 questionnaires. Vitamin C is thought                questionnaires. The selenium  Vitamin D is a third example of 
                                 to protect against oxidative stress, but            content of foods is highly dependent                a nutrient that is not well measured 
                                                                                                                                         by intake estimates. Liver, fatty 
                                 assessment of intake is complicated                 on local soil concentrations, 
                                 by the varying concentration in foods               which range over several orders  fish, ergocalciferol in mushrooms, 
                                                                                                                                         and fortified milk are major dietary 
                                 and the widespread and episodic  of magnitude. Wheat is an 
                                 use of vitamin C supplements.  important selenium source in many  sources of vitamin D; however, for 
                                 Vitamin C is water soluble and  populations, but the selenium content                                   most people, the primary source of 
                                 responsive to short-term changes  of wheat can vary considerably;  vitamin D is produced internally upon 
                                 in intake; any single measure of  therefore, wheat used to produce  exposure of the skin to ultraviolet B 
                                 vitamin C may not accurately rank  flour, bread, pasta and other noodles                                (UVB). This production depends 
                                 subjects’ typical exposure. Because                 from different geographic areas can                 on the melanin content of the skin 
                                 the serum or plasma must be stored                  result in variable levels of selenium.              and the amount of UVB exposure. 
                                 using metaphosphoric acid or other                  Several well-established biomarkers                 Estimating sun exposure is complex, 
                                 preservatives, few epidemiologic  of selenium have been developed,  because of differences in time spent                                                            1
                                                                                                                                                                                                  t 3  1
                                                                                                                                         outside, amount of exposed skin,                         i
                                 studies use vitamin C biomarkers  including serum and toenail                                                                                                    n  r
                                 (5).                                                selenium, which provide a valid  weather conditions and sunscreen                                            U  te
                                                                                                                                         use. Thus, circulating 25-hydroxy                           p
                                                                                     estimate of selenium status. More                                                                               a
                                      Vitamin E, especially 
                                 α-tocopherol, has been the focus of                 than 20 studies have examined the  vitamin D is considered a more                                               Ch
                                 a great deal of scrutiny because of                 association between serum, plasma                   reliable indicator of vitamin D status, 
                                 its potential benefits in reducing the              or nail selenium and risk of prostate               capturing both dietary intake and 
                                 risk of cancers and cardiovascular  cancer; a meta-analysis concluded  endogenous production. 25-hydroxy 
                                 diseases (6,7). The correlation that serum and plasma selenium  vitamin D has been used in several 
                                 of estimates of vitamin E intake  were consistently lower in cases  prospective epidemiologic studies 
                                 from questionnaires with serum  compared with controls (12). Serum  to assess the role of vitamin D in 
                                 concentrations is highly variable,  and toenail selenium are common  chronic disease prevention (13).
                                 since most dietary vitamin E is  validated biomarkers of selenium 
                                 obtained from vegetable oils used in                status (9).                                         Non-nutritional components
                                 cooking (8) and intake of such oils is                   Iron is another example of a 
                                 not estimated well by food frequency                concentration biomarker than may  An important aspect of the 
                                                                                     better reflect exposure and provide 
                                 questionnaires (FFQs)(9). For                                                                           connection between diet and 
                                 example, the correlation between  a more informative assessment of  chronic disease is the assessment 
                                 the FFQ-estimated vitamin E intake                  the association between iron and  of potentially hazardous dietary 
                                 and serum α-tocopherol ranged from                  disease than intake estimates. components. The human diet may 
                                 0.47 in Dutch men to −0.08 in Italian               Dietary iron is acquired from plant  contain inadvertent contaminants 
                                 men in the European Prospective  and animal sources, as well as  that are formed during food 
                                 Investigation into Cancer and fortified grain in some countries.  processing or cooking. Examples of 
                                 Nutrition (EPIC) (10). Many studies  There are large differences in  contaminants formed during cooking 
                                 have found an association between                   the bioavailability and absorption  are heterocyclic amines (HCAs) and 
                                 serum  α-tocopherol  levels  and                    pathways of heme and non-heme  polycyclic aromatic hydrocarbons 
                                 chronic disease risk, but not with  iron, suggesting that estimating  (PAHs). Some developing countries 
                                 dietary estimates of vitamin E.  total iron intake will not give a  lack an integrated food delivery 
                                                                                                                    Unit 3 • Chapter 11. Dietary intake and nutritional status    191
                     system that affords the chance to  Figure 11.1. Potential heterocyclic amines (HCAs) biomarkers (71)
                     regulate some undesirable food 
                     contaminants, such as mycotoxins 
                     or by-products of processing 
                     (e.g. silica from grinding grain or 
                     nitrosamines in salted fish).
                         Food-cooking by-products. 
                     HCAs and PAHs, both known 
                     carcinogens in animal models, are 
                     formed in the highest concentrations 
                     in meat cooked well-done using 
                     high-temperature cooking methods, 
                     such as pan-frying or grilling. The 
                     assessment of exposure to these 
                     compounds can be estimated 
                     using questionnaires, but may 
                     benefit from the use of biomarkers  With a large sample size, though,                  Mycotoxins. Fungal carcinogens 
                     of exposure. Moreover, there is  urinary HCAs could still be used to                are another example of a food 
                     no national database available for  validate intake of HCAs as estimated            contaminant whose study may 
                     food by cooking methods. A limited        by questionnaires.                        benefit from the use of an exposure 
                     database, CHARRED, has been                   HCA-DNA adducts can be biomarker. Aflatoxin (AFB1) is 
                     created that is based on the type  measured in lymphocytes and HCA                  produced by Aspergillus flavus and 
                     of meat, cooking method and the  metabolites bound to circulating  other related species, and plays an 
                     degree of doneness (http://charred.       blood proteins, such as haemoglobin       important role in the high rates of 
                     cancer.gov/).                             (Hb) or serum albumin (SA). The  hepatocellular carcinoma seen in 
                         HCAs are formed from the  measurement of these biomarkers  southern China and parts of Africa 
                     reaction at high temperatures can provide an estimate of exposure                   (20). Assessment of AFB1 exposure 
                     between creatine or creatinine and the biologically effective dose,  by questionnaire is very limited, 
                     (found in muscle meats), amino  but they do not provide a measure of                as the amount of infection in grain 
                     acids, and sugars (14–17). HCAs  genetic damage directly in the target              and the amount of toxin produced 
                     undergo extensive metabolism by  tissue. DNA and protein adducts  varies by locality, crop and storage 
                     phase I and II enzymes. Various  of HCAs have been detected in  conditions. In communities where 
                     biomarkers of HCAs have been  experimental animal models by  most food is grown and stored at 
                     investigated in urine, blood and hair,    32P-postlabelling. There is a paucity     home, the ability to develop general 
                     with each having advantages and  of data on HCA biomarkers in  exposure metrics applicable to 
                     limitations.                              humans, however, as their detection       questionnaire data is minimal. 
                         Urine is a useful biological fluid                                              Therefore, the development of 
                                                               and quantification remains a 
                     for the measurement of exposure to        challenging analytical problem: the  biomarkers of exposure to these 
                     various classes of carcinogens, since     concentration of HCAs in the diet is      dietary contaminants is critical.
                     large quantities may be obtained  at the parts-per-billion level, and the              Extensive work on the 
                     non-invasively. HCAs are rapidly  quantity of HCA biomarkers formed                 metabolism of AFB1 led to the 
                     absorbed from the gastrointestinal  in humans occurs at very low levels.            identification of AFB1 adducts 
                     tract and eliminated in urine as  Accumulation of HCAs in human  with DNA and albumin, including 
                     multiple metabolites, with several  hair, which may serve as a potential            AFB1-DNA adducts in urine (21), 
                     percent of the dose present as the        long-term biomarker to assess as correlates of the effective dose 
                     unmetabolized parent compound  chronic exposure of HCAs, has  of AFB1. Using urinary AFB1-DNA 
                     within 24 hours of consuming grilled      been suggested but not yet validated      adducts as a biomarker, a nested 
                     meats. HCAs in urine have short  (18,19). Similar, but larger, issues  case–control study demonstrated a 
                     half-lives, however, and may not be       exist for PAHs, as these compounds        5-fold increased risk of liver cancer 
                     ideal measures of “usual” intake in       are even more ubiquitous in the food      in subjects who had measurable 
                     etiologic studies, especially if there    source and environment.                   levels of these adducts (22). In the 
                     is substantial day-to-day variability.                                              same study, dietary aflatoxin intake 
                      192
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...Unit assessing exposure to the environment chapter dietary intake and nutritional status jiyoung ahn christian c abnet amanda j cross rashmi sinha t i r n u te p summary a ch damage tissue concentrations metabolism as food is complex though factors are implicated in chronic disease risk also discussed mixture thus absorption assessment of has any single nutrient limitations including problems affected by presence another biomarkers with recall for example iron taken vitamin patterns over long period an overview absorbed more efficiently than time diet itself but phytate can bind may provide objective measures make it unavailable cooking frequency questionnaires ffq multiple records important factor that well integrated hour recalls most common change nutrients measure methods assess or form compounds not normally search epidemiologic studies present foods obtaining this level unbiased biomarker strengths detail using instruments generally feasible aspect furthermore composition epidemi...

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