Validity Of Dietary Assessment Methods Research Articles

Validity of dietary assessment methods compared with doubly labeled water in children: A systematic review and meta-analysis.

We aimed to validate dietary assessment methods against the gold standard, doubly labeled water (DLW), for estimating total energy intake (TEI). PubMed, Scopus, Web of Science, and Google Scholar databases were searched until May 2023. Inclusion criteria encompassed studies involving participants aged 1-18 years, employing dietary assessment methods like food records, dietary histories, food frequency questionnaire (FFQ), or 24-h recalls estimating TEI alongside DLW to measure total energy expenditure (TEE). Data were pooled using random-effects meta-analysis models. Thirty-three studies were identified, with sample sizes ranging from 9 to 118 participants. Meta-analysis of 22 studies identified underestimation of TEI (mean difference [MD] = -262.9kcal/day [95% CI: -380.0, -145.8]; I2= 93.55%) for food records compared with TEE estimated by DLW. Other dietary assessment methods, including food recalls (n= 9) (MD = 54.2kcal/day [95% CI: -19.8, 128.1]; I2= 49.62%), FFQ (n= 7) (MD = 44.5kcal/day [95% CI: -317.8, 406.8]; I2= 94.94%), and diet history (n= 3) (MD = -130.8kcal/day [95% CI: -455.8, 194.1]; I2= 77.48%), showed no significant differences in TEI compared with DLW-estimated TEE. All studies were of high quality. Food records may underestimate TEI, yet additional research is needed to identify the most accurate methods for assessing children's dietary intake.

Validity of Dietary Assessment Methods When Compared to the Method of Doubly Labeled Water: A Systematic Review in Adults

Accuracy in quantifying energy intake (EI) using common dietary assessment methods is crucial for interpreting the relationship between diet and chronic disease. The aim of this systematic review was to evaluate the validity of dietary assessment methods used to estimate the EI of adults in comparison to total energy expenditure (TEE) measured by doubly labeled water (DLW). Articles in English across nine electronic databases, published between 1973 and February 2019 were retrieved. Studies were included if participants were adults (≥18 years) and used the DLW technique to measure TEE compared to self-reported EI. A total of 59 studies were included, with a total of 6,298 free living adults and a mean of 107 participants per study. The majority of studies including 16 studies that included a technology based method reported significant (P < 0.05) under-reporting of EI when compared to TEE, with few over-reporting EI. Misreporting was more frequent among females compared to males within recall based dietary assessment methods. The degree of under-reporting was highly variable within studies using the same method, with 24 h recalls having less variation and degree of under-reporting compared to other methods.

Best Practices for Conducting and Interpreting Studies to Validate Self-Report Dietary Assessment Methods

Careful consideration of the validity and reliability of methods intended to assess dietary intake is central to the robustness of nutrition research. A dietary assessment method with high validity is capable of providing useful measurement for a given purpose and context. More specifically, a method with high validity is well grounded in theory; its performance is consistent with that theory; and it is precise, dependable, and accurate within specified performance standards. Assessing the extent to which dietary assessment methods possess these characteristics can be difficult due to the complexity of dietary intake, as well as difficulties capturing true intake. We identified challenges and best practices related to the validation of self-report dietary assessment methods. The term validation is used to encompass various dimensions that must be assessed and considered to determine whether a given method is suitable for a specific purpose. Evidence on the varied concepts of validity and reliability should be interpreted in combination to inform judgments about the suitability of a method for a specified purpose. Self-report methods are the focus because they are used in most studies seeking to measure dietary intake. Biomarkers are important reference measures to validate self-report methods and are also discussed. A checklist is proposed to contribute to strengthening the literature on the validation of dietary assessment methods and ultimately, the nutrition literature more broadly.

Validity of Dietary Assessment in Athletes: A Systematic Review.

Dietary assessment methods that are recognized as appropriate for the general population are usually applied in a similar manner to athletes, despite the knowledge that sport-specific factors can complicate assessment and impact accuracy in unique ways. As dietary assessment methods are used extensively within the field of sports nutrition, there is concern the validity of methodologies have not undergone more rigorous evaluation in this unique population sub-group. The purpose of this systematic review was to compare two or more methods of dietary assessment, including dietary intake measured against biomarkers or reference measures of energy expenditure, in athletes. Six electronic databases were searched for English-language, full-text articles published from January 1980 until June 2016. The search strategy combined the following keywords: diet, nutrition assessment, athlete, and validity; where the following outcomes are reported but not limited to: energy intake, macro and/or micronutrient intake, food intake, nutritional adequacy, diet quality, or nutritional status. Meta-analysis was performed on studies with sufficient methodological similarity, with between-group standardized mean differences (or effect size) and 95% confidence intervals (CI) being calculated. Of the 1624 studies identified, 18 were eligible for inclusion. Studies comparing self-reported energy intake (EI) to energy expenditure assessed via doubly labelled water were grouped for comparison (n = 11) and demonstrated mean EI was under-estimated by 19% (−2793 ± 1134 kJ/day). Meta-analysis revealed a large pooled effect size of −1.006 (95% CI: −1.3 to −0.7; p < 0.001). The remaining studies (n = 7) compared a new dietary tool or instrument to a reference method(s) (e.g., food record, 24-h dietary recall, biomarker) as part of a validation study. This systematic review revealed there are limited robust studies evaluating dietary assessment methods in athletes. Existing literature demonstrates the substantial variability between methods, with under- and misreporting of intake being frequently observed. There is a clear need for careful validation of dietary assessment methods, including emerging technical innovations, among athlete populations.

Advantages and Disadvantages of an Automated Weighed Intake Dietary Assessment Tool Requiring Minimal Participant Burden for Use at Congregate Meal Sites

INACCURATE DIETARY INTAKE DATA CAN RESULT IN erroneous conclusions regarding the link between diet and disease. Embracing alternative dietary assessment technology could equip clinicians, researchers, public health professionals, and policy makers directing diet-related prevention and treatment. All dietary assessment tools have some disadvantages. Self-recall methods are prone to error, 1 Johnson R.K. Yon B.A. Hankin J.H. Dietary assessment and validation. in: Monsen E.R. Van Horn L. Research: Successful Approaches. 3rd ed. American Dietetic Association, Chicago, IL2008: 187-204 Google Scholar , 2 Burrows T.L. Martin R.J. Collins C.E. A systematic review of the validity of dietary assessment methods in children when compared with the method of doubly labeled water. J Am Diet Assoc. 2010; 110: 1501-1510 Abstract Full Text Full Text PDF PubMed Scopus (476) Google Scholar , 3 McPherson R.S. Hoelscher D.M. Alexander M. Scanlon K.S. Serdula M.K. Dietary assessment methods among school-aged children: Validity and reliability. Prev Med. 2000; 31: S11-S33 Crossref PubMed Scopus (308) Google Scholar biomarkers require obtaining and handling biological samples, 4 Kuhnle G.G.C. Nutritional biomarkers for objective dietary assessment. J Sci Food Agric. 2012; 92: 1145-1149 Crossref PubMed Scopus (74) Google Scholar direct observation is costly and labor-intensive, 3 McPherson R.S. Hoelscher D.M. Alexander M. Scanlon K.S. Serdula M.K. Dietary assessment methods among school-aged children: Validity and reliability. Prev Med. 2000; 31: S11-S33 Crossref PubMed Scopus (308) Google Scholar , 5 Simons-Morton B.G. Baranowski T. Observation in assessment of children's dietary practices. J Sch Health. 1991; 61: 204-207 Crossref PubMed Scopus (71) Google Scholar , 6 Gray C. Lytle L.A. Mays R. Taylor G. Perry C. Story M. Foods on students' trays when they leave the cafeteria line as a proxy for food eaten at lunch in a school-based study. J Am Diet Assoc. 2002; 102: 407-409 Abstract Full Text Full Text PDF PubMed Scopus (10) Google Scholar , 7 Gittelsohn J. Shankar A.V. Pokhrel R.P. West K.P. Accuracy of estimating food intake by observation. J Am Diet Assoc. 1994; 94: 1273-1277 Abstract Full Text Full Text PDF PubMed Scopus (64) Google Scholar food photography is under development, 8 Weiss R. Stumbo P.J. Divakaran A. Automatic food documentation and volume computation using digital imaging and electronic transmission. J Am Diet Assoc. 2010; 110: 42-44 Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar , 9 Swanson M. Digital photography as a tool to measure school cafeteria consumption. J Sch Health. 2008; 78: 432-437 Crossref PubMed Scopus (82) Google Scholar , 10 Six B.L. Schap T.E. Zhu F.M. et al. Evidence-based development of a mobile telephone food record. J Am Diet Assoc. 2010; 110: 74-79 Abstract Full Text Full Text PDF PubMed Scopus (151) Google Scholar , 11 Higgins J.A. LaSalle A.L. Zhaoxing P. et al. Validation of photographic food records in children: Are pictures really worth a thousand words?. Eur J Clin Nutr. 2009; 63: 1025-1033 Crossref PubMed Scopus (48) Google Scholar , 12 Williamson D.A. Allen H.R. Martin P.D. Alfonso A.J. Gerald B. Hunt A. Comparison of digital photography to weighed visual estimation of portion sizes. J Am Diet Assoc. 2003; 103: 1139-1145 Abstract Full Text Full Text PDF PubMed Scopus (230) Google Scholar and weighing food before and after consumption is arduous. 5 Simons-Morton B.G. Baranowski T. Observation in assessment of children's dietary practices. J Sch Health. 1991; 61: 204-207 Crossref PubMed Scopus (71) Google Scholar , 13 Kretch M. Fong A. Validation of a new computerized technique for quantitating individual dietary intake: The National Evaluation Scale System (NESSy) vs the weighed food record. Am J Clin Nutr. 1990; 51: 477-484 Crossref PubMed Scopus (23) Google Scholar Even computer-guided technology, such as the Nutrition Evaluation Scale System, requires highly motivated subjects. 13 Kretch M. Fong A. Validation of a new computerized technique for quantitating individual dietary intake: The National Evaluation Scale System (NESSy) vs the weighed food record. Am J Clin Nutr. 1990; 51: 477-484 Crossref PubMed Scopus (23) Google Scholar , 14 Kretsch M.J. Fong A.K.H. Validity and reproducibility of a new computerized dietary assessment method: Effects of gender and education level. Nutr Res. 1993; 13: 133-146 Crossref Scopus (5) Google Scholar K. E. Spears is an assistant professor, Department of Nutrition, College of Agriculture, Biotechnology, and Natural Resources, and a nutrition state specialist, College of Cooperative Extension, University of Nevada, Reno. H. L. Himler is an adjunct faculty member, Department of Nutrition, College of Agriculture, Biotechnology, and Natural Resources, University of Nevada, Reno.

Estimating the global and regional burden of suboptimal nutrition on chronic disease: methods and inputs to the analysis

Global burdens of cardiovascular disease (CVD), diabetes and cancer are on the rise. Little quantitative data are available on the global impact of diet on these conditions. The objective of this study was to develop systematic and comparable methods to quantitatively assess the impact of suboptimal dietary habits on CVD, diabetes and cancer burdens globally and in 21 world regions. Using a comparative risk assessment framework, we developed methods to establish for selected dietary risk factors the effect sizes of probable or convincing causal diet-disease relationships, the alternative minimum-risk exposure distributions and the exposure distributions. These inputs, together with disease-specific mortality rates, allow computation of the numbers of events attributable to each dietary factor. Using World Health Organization and similar evidence criteria for convincing/probable causal effects, we identified 14 potential diet-disease relationships. Effect sizes and ranges of uncertainty will be derived from systematic reviews and meta-analyses of trials or high-quality observational studies. Alternative minimum-risk distributions were identified based on amounts corresponding to the lowest disease rates in populations. Optimal and alternative definitions for each exposure were established based on the data used to quantify harmful or protective effects. We developed methods for identifying and obtaining data from nationally representative surveys. A ranking scale was developed to assess survey quality and validity of dietary assessment methods. Multi-level hierarchical models will be developed to impute missing data. These new methods will allow, for the first time, assessment of the global impact of specific dietary factors on chronic disease mortality. Such global assessment is not only possible but is also imperative for priority setting and policy making.

A Systematic Review of the Validity of Dietary Assessment Methods in Children when Compared with the Method of Doubly Labeled Water

Measuring dietary intake in children enables the assessment of nutritional adequacy of individuals and groups and can provide information about nutrients, including energy, food, and eating habits. The aim of this review was to determine which dietary assessment method(s) provide a valid and accurate estimate of energy intake by comparison with the gold standard measure, doubly labeled water (DLW). English-language articles published between 1973 and 2009 and available from common nutrition databases were retrieved. Studies were included if the subjects were children birth to age 18 years and used the DLW technique to validate reported energy intake by any other dietary assessment method. The review identified 15 cross-sectional studies, with a variety of comparative dietary assessment methods. These included a total of 664 children, with the majority having <30 participants. The majority of dietary assessment method validation studies indicated a degree of misreporting, with only eight studies identifying this to a significant level ( P<0.05) compared to DLW estimated energy intake. Under-reporting by food records varied from 19% to 41% (n=5 studies) with over-reporting most often associated with 24-hour recalls (7% to 11%, n=4), diet history (9% to 14%, n=3), and food frequency questionnaires (2% to 59%, n=2). This review suggested that the 24-hour multiple pass recall conducted over at least a 3-day period that includes weekdays and weekend days and uses parents as proxy reporters is the most accurate method to estimate total energy intake in children aged 4 to 11 years, compared to total energy expenditure measured by DLW. Weighed food records provided the best estimate for younger children aged 0.5 to 4 years, whereas the diet history provided better estimates for adolescents aged ≥16 years. Further research is needed in this area to substantiate findings and improve estimates of total energy expenditure in children and adolescents.

Nutritional intakes in irritable bowel syndrome

Background: Irritable bowel syndrome (IBS) is a chronic and relapsing bowel disorder that affects 12% of the UK population. Two‐thirds of patients perceive their symptoms to be diet related (Simren, 2001) and restrict their food intake hoping to improve symptoms. This may put them at risk of low nutrient intakes. This study aimed to assess the dietary intake of IBS patients and compare nutrient intake to control subjects.Methods: Patients with IBS and controls were recruited from gastroenterology clinics from local hospitals. Controls were patients who were attending for colonoscopy surveillance for colon cancer or polyps and had a normal bowel habit with no history of IBS symptoms. Each consenting subject completed a validated food frequency questionnaire (FFQ; Bingham, 1997). Energy and nutrient intakes (excluding supplements) were calculated and comparisons were made between groups and with the UK DRVs. Data were compared between the IBS and control groups using unpaired t‐tests or Mann–Whitney U‐tests and a P &lt; 0.05 was considered statistically significant. For nutrients with a significant difference, one‐sample t‐tests were used to determine the significance of any differences between the IBS group and DRVs.Results: Food frequency questionnaires were completed on 34 patients with IBS (35.3 ± 10.3 years; six male) and 17 controls (46.5 ± 9.8 years; 12 male). Energy and macronutrient intakes were similar between groups (Table 1). Intakes of calcium and iron were significantly lower in the IBS group than in controls. Nine women had a calcium intake and nine women had an iron intake below the reference nutrient intake. Twenty‐five (74%) patients with IBS and eight (47%) controls (chi‐squared test, P = 0.1) were taking supplements compared with 35% of respondents in the 2003 National Diet &amp; Nutrition Survey. Nine (26%) patients with IBS and six (35%) controls (chi‐squared test, P = 0.7) were taking either multivitamins or multivitamins &amp; minerals. Energy and nutrient intakes of controls and IBS patients Energy and nutrient intakes IBS Control P‐value Mean (SD) Energy (kcal) day−1 2000 (753) 2258 (621) 0.2 Protein (g) day−1 71.0 (24.8) 71.3 (19.1) 0.9 Fat (g day−1) 83.4 (42.2) 89.7 (35.9) 0.6 Carbohydrate (g day−1) 243.4 (103.5) 270.0 (103.5) 0.3 Fibre (NSP) (g day−1) 20.6 (10.9) 20.4 (7.8) 0.9 Lactose (mg day−1) 3.4 (3.7) 2.3 (2.1) 0.5 Calcium (mg day−1) 580 (303) 673 (192) 0.03 Iron (mg day−1) 9.6 (2.9) 13.2 (4.1) 0.001 Discussion: Patients with IBS may be at risk of low micronutrient intakes. Consideration of calcium and iron intakes and multivitamin and mineral supplementation is important when giving dietary advice for the management of IBS.Conclusions: Patients with IBS should be assessed for inadequate intakes of key nutrients and supplements recommended where appropriate.References Bingham, S.A., Gill, C., Welch, A., Cassidy, A., Runswick, S.A., Oakes, S. et al. (1997) Validation of dietary assessment methods in the UK arm of EPIC using weighed records, and 24‐hour urinary nitrogen and potassium and serum vitamin C and carotenoids as biomarkers. Int. J. Epidemiol. 26, S137–S151.Simren, M., Mansson, A., Langkilde, A.M., Svedlund, J., Abrahamsson, H., Bengtsson, U. &amp; Bjornsson, E.S. (2001) Food‐related gastrointestinal symptoms in the irritable bowel syndrome. Digestion63, 108–115.

Choice of dietary protein of vegetarians and omnivores is reflected in their hair protein 13C and 15N abundance

Stable isotopic (15N, 13C) composition of tissues depends on isotopic pattern of food sources. We investigated whether the isotopic compositions of human hair protein and amino acids reflect the habitual dietary protein intake. Hair samples were analyzed from 100 omnivores (selected randomly out of the 1987-1988 German nutrition survey VERA), and from 15 ovo-lacto-vegetarians (OLV), and from 6 vegans recruited separately. Hair bulk and amino acid specific isotopic compositions were analyzed by isotope-ratio mass spectrometry (EA/IRMS and GC/C/IRMS, respectively) and the results were correlated with data of the 7 day dietary records. Hair bulk 15N and 13C abundances clearly reflect the particular eating habits. Vegans can be distinguished from OLV and both are significantly distinct from omnivores in both 15N and 13C abundances. 15N and 13C abundances rose with a higher proportion of animal to total protein intake (PAPI). Individual proportions of animal protein consumption (IPAP) were calculated using isotopic abundances and a linear regression model using animal protein consumption data of vegans (PAPI = 0) and omnivores (mean PAPI = 0.639). IPAP values positively correlated with the intake of protein, meat, meat products, and animal protein. Distinct patterns for hair amino acid specific 15N and 13C abundances were measured but with lower resolution between food preference groups compared with bulk values. In conclusion, hair 13C and 15N values both reflected the extent of animal protein consumption. Bulk isotopic abundance of hair can be tested for future use in the validation of dietary assessment methods.

Critical examination of reported energy intake in published dietary studies of Japanese subjects using the Goldberg cut-off.

Although it is now generally acknowledged in Western countries that mismeasurement (under- and overestimation) of dietary intake is a serious problem in studies on diet and health, the validity of dietary assessment methods in Japan has seldom been externally evaluated with objective measures. This study used the Goldberg cut-off to examine whether the energy intake in Japan could be regarded as a measure of habitual energy intake at the group level. Examined here were six published dietary studies in Japan providing 14 subgroups when divided by sex and dietary assessment method. Reported energy intake was expressed as a multiple of basal metabolic rate estimated using equations (EI/BMR). EI/BMR was compared with the subgroup-specific cut-off values representing the lowest and highest values of EI/BMR that could reflect the habitual energy expenditure. Mean EI/BMR was 1.49 (SD=0.09), which was lower than an expected requirement of 1.55. When all 14 subgroups were combined, seven subgroups (50%) had an EI/BMR less than the subgroup-specific lower cut-off value, and one (7%) had the ratio greater than the upper value. The percentages of subgroups having the ratio less than the lower value and greater than the upper value ranged from 43 to 57% and from 0 to 14%, respectively, when subgroups of women (n=8), men (n=6), diet record (n=7), and questionnaire method (n=7) were evaluated separately. These findings suggest that responsible investigators in Japan should critically examine dietary intake data in any study of diet and health.

Validation of energy intake estimated from a food frequency questionnaire: a doubly labelled water study.

The validation of dietary assessment methods is critical in the evaluation of the relation between dietary intake and health. The aim of this study was to assess the validity of a food frequency questionnaire by comparing energy intake with energy expenditure measured with the doubly labelled water method. Total energy expenditure was measured with the doubly labelled water (DLW) method during a 10 day period. Furthermore, the subjects filled in the food frequency questionnaire about 18-35 days after the DLW phase of the study was completed. Twenty-one healthy, non-pregnant females volunteered to participate in the study; only 17 subjects completed the study. The group energy intake was on average 10% lower than the energy expenditure, but the difference was not statistically significant. However, there was a wide range in reporting accuracy: seven subjects were identified as acceptable reporters, eight as under-reporters and two were identified as over-reporters. The width of the 95% confidence limits of agreement in a Bland and Altman plot for energy intake and energy expenditure varied from -5 to 3 MJ. The data showed that there was substantial variability in the accuracy of the food frequency questionnaire at the individual level. Furthermore, the results showed that the questionnaire was more accurate for groups than individuals.

Use of biological markers to validate self-reported dietary intake in a random sample of the European Prospective Investigation into Cancer United Kingdom Norfolk cohort

The validity of dietary assessment methods should be established before diet-disease associations are reported. Our objective was to validate a 7-d food diary and a food-frequency questionnaire (FFQ) against independent biomarkers of intake in urine (nitrogen, potassium, and sodium) and blood (plasma ascorbic acid). A total of 146 healthy middle-aged men and women were recruited from the European Prospective Investigation into Cancer UK Norfolk cohort, a free-living cohort of approximately 25000 persons. Over a 9-mo period, urinary nitrogen, potassium, and sodium were estimated from 2-6 complete 24-h urine collections in 134 subjects and plasma ascorbic acid was estimated from 2-3 fasting blood samples in 118 subjects. Subjects completed 2 FFQs and two 7-d food diaries. In men and women combined, correlations between 24-h urinary nitrogen excretion and dietary intake from the 7-d food diary were high (r = 0.57-0.67) compared with those for the FFQ (r = 0.21-0.29). Similarly, correlations between urinary potassium and dietary potassium were higher for the 7-d food diary (r = 0.51-0.55) than for the FFQ (r = 0.32-0.34). There was no overall difference in correlations between plasma ascorbic acid and dietary vitamin C between the 7-d food diary (r = 0.40-0.52) and the FFQ (r = 0.44-0.45). These data indicate that, despite increased subject burden, the 7-d food diary provided a better estimate of nitrogen and potassium intakes than did the FFQ in this study population. However, with respect to plasma ascorbic acid, both the FFQ and 7-d food diary provided a similar ranking of subjects according to vitamin C intake.

The validity of self-reported energy intake as determined using the doubly labelled water technique

In the 1980s the development of the doubly labelled water (DLW) technique made it possible to determine the validity of dietary assessment methods using external, independent markers of intake in free-living populations. Since then, the accuracy of self-reported energy intake (EI) has been questioned on a number of occasions as under-reporting has been found to be prevalent in many different populations. This paper is a review of investigations using the DLW technique in conjunction with self-reported EI measures in groups including adults, children and adolescents, obese persons, athletes, military personnel and trekking explorers. In studies where a person other than the subject is responsible for recording dietary intake, such as parents of young children, EI generally corresponds to DLW determined energy expenditure. However, in instances where the subjects themselves report their intake, EI is generally under-reported when compared with energy expenditure. It was originally believed that this phenomenon of under-reporting was linked to increased adiposity and body size, however, it is now apparent that other factors, such as dietary restraint and socio-economic status, are also involved. This paper therefore aims to present a more comprehensive picture of under-reporting by tying in the findings of many DLW studies with other studies focusing particularly on the characteristics and mechanisms for under-reporting. Awareness of these characteristics and mechanisms will enable researchers to obtain more accurate self-reports of EI using all dietary recording techniques.

Using biochemical markers to assess the validity of prospective dietary assessment methods and the effect of energy adjustment

The validity of dietary assessment methods in a group of women aged 50-65 y was evaluated with use of biochemical markers. Estimates of nitrogen, potassium, and carotene intakes from weighed-food and estimated records yielded higher correlations with urinary nitrogen, urinary potassium, and serum concentrations of carotenoids than did estimates from food-frequency questionnaires and 24-h recalls. When the residuals method of energy adjustment was used, the correlations between intakes of nitrogen and potassium estimated from food-frequency questionnaires and 24-h recalls and intakes derived from weighed-food records improved, and the high correlations between biochemical markers and estimates from weighed-food records were maintained. In addition, with use of this method, estimates for nitrogen and potassium intakes from food-frequency questionnaires showed the most improvement in comparison with the biochemical markers; however, the correlations of crude nitrogen and potassium with crude energy intake were highest. Carotene intake was not related to energy intake, so that correlations between the intake of carotene assessed by any method and the plasma beta-carotene concentration did not improve with energy adjustment and between-person variability was not reduced. Energy adjustment with either the energy density or residuals method did not alter the ranking of accuracy of various dietary assessment methods in comparison with weighed-food records or biochemical markers in either the total group of subjects or those who were identified as having provided valid weighed-food records.

Validation of dietary assessment methods in the UK arm of EPIC using weighed records, and 24-hour urinary nitrogen and potassium and serum vitamin C and carotenoids as biomarkers

In the UK EPIC validation studies, the accuracy of several methods was assessed by comparison with to-day weighed records and the biomarkers, 24-hour urine nitrogen (N) and potassium (K), plasma carotenoids and plasma vitamin C. Comparisons between methods were made on 156 women, studied over 1 year at 3-monthly intervals at home. On each of four occasions, volunteers completed 4 days of weighed records and provided two 24-hour urine collections and a fasting blood sample. In comparison with the 16 days of weighed records, a food frequency questionnaire (FFQ) yielded higher values mainly due to greater reported consumption of milk and of vegetables. A 24-hour recall was as good as the FFQ in placing individuals in the distribution of habitual diet from weighed records. Results obtained from a 7-day estimated record were closest to those obtained from the weighed record. Correlations between 24-hour urine excretion and dietary N intake from weighed records were high (0.78-0.87) as were those with estimated food diaries (0.60-0.70). Correlations between urine N and the FFQ and 24-hour recall were lower (0.10 to 0.27), but improved by energy adjustment using residuals for N and K which are correlated with total energy intake. Comparisons between dietary estimates and urinary K and serum carotenoids and vitamin C showed broadly similar results. Limited biomarker information amongst 200 UK EPIC participants supported the findings of the validation study. UK EPIC uses three methods (the 7-day diary, an improved FFQ, and the 24-hour recall) to assess diet. 93% of first food diaries are returned completed by participants. Repeated diaries are the main dietary assessment method for nested case-control analyses.

Validation of dietary assessment methods

Validation of dietary assessment methods

Development and validation of dietary assessment methods for culturally diverse populations

Culturally diverse populations with variable dietary and disease patterns provide a unique opportunity for conducting epidemiologic studies to identify the role of diet in the etiology of chronic diseases. The dietary method for epidemiologic studies, such as cohort or case-control studies, should generally be a diet history (or quantitative food frequency) of selected food items consumed during a usual month. Knowledge of the eating patterns of each ethnic group in the study is needed to develop an appropriate questionnaire. The diet history may be validated by collecting multiple 24-h recalls or food records from representative samples of each ethnic group and comparing the mean dietary intakes with the values obtained from the diet history. Examples of studies of culturally diverse populations and the development and validation of the dietary methods are discussed.

Collection of food intake data: a reappraisal of criteria for judging the methods

The relationship between diet and the development of chronic disease still remains a controversial area. One major difficulty is to obtain a valid estimate of habitual pattern and level of food consumption for each individual. There is, in fact, a voluminous and largely negative literature on the validity of dietary assessment methods. In the present paper the utility of the most frequently used dietary assessment method in epidemiological studies is discussed in terms of precision and accuracy.