Nutritional epidemiology 
                Dietary assessments: use, design concepts, biological markers, 
                pitfalls and validationn 
                Gunnar Johansson 
                                          Halmstad University Press 
                                                         
               
                
         Nutritional epidemiology. 
         Dietary assessments: use, design concepts, biological markers, pitfalls and validation 
         © Gunnar Johansson 
         ISBN 978-91-87045-07-3 
         E-published 2014 
         Halmstad University Press, 2014 | www.hh.se/hup 
                                                        
                   
                  Contents 
                  1  Who needs information on individuals and groups food and nutrient intake? .................. 5 
                     1.1   Education, research and health care .......................................................................................................... 5 
                     1.2   The food industry ........................................................................................................................................... 5 
                     1.3   Authorities and politicians ............................................................................................................................ 5 
                  2  Dietary data on a national level. Per capita consumption ..................................................... 7 
                  3  Dietary data on the household level. Household based surveys ......................................... 8 
                  4  Food consumption of individuals. Dietary assessment methods.......................................... 9 
                     4.1   Prospective methods ..................................................................................................................................... 9 
                        4.1.1  Menu records .......................................................................................................................................... 9 
                        4.1.2  Estimated food records ......................................................................................................................... 9 
                        4.1.3  Weighed food records ............................................................................................................................ 9 
                        4.1.4  The duplicate portion technique ........................................................................................................ 10 
                        4.1.5  Advantages with prospective methods ............................................................................................. 10 
                        4.1.6  Disadvantages with prospective methods ....................................................................................... 10 
                     4.2   Retrospective methods ............................................................................................................................... 10 
                        4.2.1  24 hour and 48 hour recalls ............................................................................................................... 10 
                        4.2.2  Diet histories ......................................................................................................................................... 11 
                        4.2.3  Food frequency questionnaires .......................................................................................................... 12 
                        4.2.4  Assessment of intake in the distant past ......................................................................................... 12 
                  5  Calculation of nutrient intake from data on food intake ......................................................13 
                  6  Level of output data .....................................................................................................................14 
                     6.1   Level 1. Mean consumption of a group .................................................................................................... 14 
                     6.2   Level 2. Mean and distribution of consumption in a group .................................................................. 14 
                     6.3   Level 3. The relative magnitude of the consumption of an individual (rank order) ........................ 14 
                     6.4   Level 4. The absolute magnitude of the consumption of an individual .............................................. 15 
                  7  Number of days required to classify individuals’ dietary intake .........................................16 
                  8  The validation of dietary assessment .......................................................................................17 
                     8.1   Relative validation ....................................................................................................................................... 17 
                        8.1.1  Comparison of the mean and median values .................................................................................. 17 
                        8.1.2  Regression and correlation ................................................................................................................. 17 
                        8.1.3  Classification into fractiles .................................................................................................................. 18 
                        8.1.4  Bland-Altman analysis ......................................................................................................................... 19 
                     8.2   Observation ................................................................................................................................................... 20 
                     8.3   Biological markers for food intake ............................................................................................................ 20 
                        8.3.1  Energy .................................................................................................................................................... 22 
                        8.3.2  Protein .................................................................................................................................................... 24 
                        8.3.3  Sodium ................................................................................................................................................... 26 
                        8.3.4  Iodine, fluoride and chloride .............................................................................................................. 26 
                        8.3.5  Selenium ................................................................................................................................................ 26 
                   
                        8.3.6  Potassium .............................................................................................................................................. 27 
                        8.3.7  Verification of the completeness of 24 hour urine collections ..................................................... 27 
                        8.3.8  Fibre ........................................................................................................................................................ 29 
                        8.3.9  Cadmium and lead ............................................................................................................................... 30 
                        8.3.10 Vitamin C ............................................................................................................................................... 30 
                        8.3.11 Fat and carbohydrates ........................................................................................................................ 31 
                        8.3.12 Fatty acids ............................................................................................................................................. 31 
                     8.4   New biological markers for food intake ................................................................................................... 32 
                        8.4.1  Sucrose and fructose ........................................................................................................................... 32 
                        8.4.2  Thiamine ................................................................................................................................................ 32 
                        8.4.3  Whole grain intake of wheat and rye................................................................................................ 32 
                        8.4.4  Fruits and vegetables .......................................................................................................................... 32 
                  9  Misreporting ...................................................................................................................................33 
                  10 Energy adjustments .....................................................................................................................37 
                  11 Statistical corrections for the effect of measurement error ................................................38 
                  12 Estimating a sample size ............................................................................................................39 
                  13 Future research directions ..........................................................................................................40 
                  14 Conclusions and practical recommendations ..........................................................................41