Validity and reliability of the Block98 food-frequency questionnaire in a sample of Canadian women

OBJECTIVE: To assess the validity and reliability of the most recent adaptation of Block's full-diet food-frequency questionnaire (FFQ) among a sample of Canadian women. DESIGN: Participants completed a self-administered FFQ (FFQ1), two unannounced 24-hour recalls (weekday and weekend) and a second FFQ (FFQ2) between October 2003 and February 2004. FFQs and recalls were analysed for 32 nutrients using Block Dietary Data Systems and the University of Minnesota's Nutrient Data System. Mean and median intakes were computed, along with crude and deattenuated Pearson correlation coefficients between FFQ1 and the average of two recalls (validity) and between FFQ1 and FFQ2 (reliability). SETTING: Ontario, Canada. SUBJECTS: A random population-based sample (n = 166) of women aged 25 to 74 years. RESULTS: One hundred and fifteen (69%) women completed FFQ1, 96 completed FFQ1 and both recalls, and 93 completed both FFQs, about 56 days apart. Mean intakes were similar for most nutrients. FFQ reliability was high, with Pearson correlation coefficients having a median of 0.75, ranging from 0.57 to 0.90 (macronutrients) and from 0.65 to 0.88 (micronutrients from supplements and food). FFQ validity was moderate to high, with deattenuated Pearson correlation coefficients having a median of 0.59, ranging from 0.11 to 0.73 (macronutrients) and from 0.50 to 0.76 (micronutrients from supplements and food). Our micronutrient correlations were similar to or higher than those of other studies that included supplements. Two correlations <0.40 were associated with fats. CONCLUSIONS: The validity and reliability of this full-diet version of the Block FFQ were moderate to high, supporting its use in future studies among Canadian women.     

The effect of personal characteristics on the validity of nutrient intake estimates using a food-frequency questionnaire

OBJECTIVE: To assess validity of the Nambour food-frequency questionnaire (FFQ) relative to weighed food records (WFRs), and the extent to which selected demographic, anthropometric and social characteristics explain differences between the two dietary methods.DESIGN: Inter-method validity study; 129-item FFQ vs. 12 days of WFR over 12 months.SETTING: Community-based Nambour Skin Cancer Prevention Trial.SUBJECTS: One hundred and fifteen of 168 randomly selected participants in the trial (68% acceptance rate) aged 25-75 years.RESULTS: Spearman correlations between intakes from the two methods ranged from 0.18 to 0.71 for energy-adjusted values. Differences between FFQ and WFR regressed on personal characteristics were significantly associated with at least one characteristic for 16 of the 21 nutrients. Sex was significantly associated with differences for nine nutrients; body mass index (BMI), presence of any medical condition and age were each significantly associated with differences for three to six nutrients; use of dietary supplements and occupation were associated with differences for one nutrient each. There was no consistency in the direction of the significant associations. Regression models explained from 7% (riboflavin) to 27% (saturated fat) of variation in differences in intakes.CONCLUSIONS: The relative validity of FFQ estimates for many nutrients is quite different for males than for females. Age, BMI, medical condition and level of intake were also associated with relative validity for some nutrients, resulting in the need to adjust intakes estimates for these in modelling diet-disease relationships. Estimates for cholesterol, beta-carotene equivalents, retinol equivalents, thiamine, riboflavin and calcium would not benefit from this.     

Issues in assessing the validity of nutrient data obtained from a food-frequency questionnaire: folate and vitamin B12 examples

OBJECTIVE: To compare methods used to assess the validity of nutrient intake data obtained from a food-frequency questionnaire (FFQ), using folate and vitamin B12 as nutrient examples. DESIGN: Cross-sectional sample from a population cohort. SETTING: Two postcode areas west of Sydney, Australia. SUBJECTS: In total, 2895 people aged 49 years and older provided dietary data using a semi-quantitative FFQ (79% of 3654 subjects examined). The validity of the FFQ was assessed against three 4-day weighed food records (WFRs) completed by 78 people (mean age 70 years). RESULTS: Folate and vitamin B12 validity data were assessed using different methods. The Spearman ranked correlations (energy-adjusted) were 0.66 for folate and 0.38 for vitamin B12. Using the Bland-Altman method, following loge transformation, no linear trend existed between the differences and means for folate and vitamin B12. Large differences existed between the FFQ and WFR in individual cases, particularly for vitamin B12. Finally, data were divided into quintile categories for the test and reference method: 79% classified folate within one quintile, 65% classified vitamin B12 within one quintile; there was no gross misclassification for folate and only 3% misclassification for vitamin B12. CONCLUSIONS: Different methods of analysis provided different information about the validity of the FFQ. Correlation coefficients should not be used alone to assess the validity of nutrient data, but should be used in conjunction with Bland-Altman analyses. Depending on the use of the data, additional assessment of classification categories is recommended. This worked example demonstrates that absolute intakes of folate and vitamin B12 should be used with caution.     

Validation of a food-frequency questionnaire for measurement of nutrient intake in a dietary intervention study

OBJECTIVE: To validate a 171-item semi-quantitative food-frequency questionnaire (FFQ) for measurement of nutrient intake in an intervention trial based on walnut supplementation. DESIGN AND SETTING: Free-living adults from Southern California were randomly assigned to either an intervention (walnut-supplemented) or a control diet. The prescribed 6-month intervention was > or = 28 g of walnuts per day for the walnut-supplemented group and > or = 2 g of walnuts per day for the control group. Participants provided at least six 24-hour dietary recalls and completed a self-administered FFQ. SUBJECTS: Eighty-seven adults aged 30-72 years (48 females, 39 males). RESULTS: Our findings from validation (by correlation with six diet recall measures) of the measurement of 32 nutrients by the FFQ are as follows. We found significant positive correlations (corrected for measurement error) between the FFQ and diet recalls for total energy (r = 0.34), total carbohydrate (r = 0.42), vegetable protein (r = 0.43), total fat (r = 0.51), polyunsaturated fat (r = 0.77), total fibre (r = 0.60), linoleic acid (r = 0.78) and alpha-linolenic acid (r = 0.79) - the last nutrient being an excellent nutrient biomarker of the intervention (walnut supplementation). Significant positive correlations were also found for vitamin C (r = 0.96) and certain minerals (r = 0.46-0.80 for calcium, phosphorus, magnesium, iron and potassium). Uncorrected correlations were also high (r>0.40) for retinol, beta-carotene, folate and alcohol. Both diet recalls and FFQ showed a similar significant difference in alpha-linolenic acid content between the walnut-supplemented and control diets. CONCLUSIONS: The FFQ demonstrated good relative validity in the estimation intake of some of the major nutrients in a dietary intervention trial and was a particularly valid estimate of an important nutrient biomarker of walnut supplementation.     

Development and simulated validation of a food-frequency questionnaire for the Colombian population

OBJECTIVE: To develop a food-frequency questionnaire (FFQ) useful for ranking of nutrient intakes. DESIGN: Subjects consuming their regular diet completed 7 days of weighed intake registry (7-WIR). Foods for the FFQ were selected by stepwise multiple regression. The FFQ was then completed for each subject using data on individual food consumption from the 7-WIR. The correlation and agreement between the extrapolated FFQ and the 7-WIR data were assessed using Spearman's rank correlation coefficients (rS) and Bland and Altman's limits of agreement (LOA). SETTING: Bucaramanga, Colombia. SUBJECTS: We studied 97 randomly selected 20-40-year-old subjects. RESULTS: Sixty foods were selected for the FFQ. The 7-WIR and the extrapolated FFQ intake estimates correlated well. rS was 0.58 for energy, 0.53 for carbohydrate, 0.50 for total fat, and 0.48 for protein. For micronutrients, rS varied from 0.46 (manganese) to 0.71 (vitamin B12). FFQ average intake estimates were 83%, 80%, 86.2% and 86.4% of 7-WIR estimates for energy, carbohydrate, total fat and protein, respectively. LOA for these nutrients ranged between 45% and 165%. FFQ micronutrient intakes were on average 96% (median) of those from the 7-WIR, and the median lower and upper LOA were 50% and 203%. However, there was no indication that the degree of agreement varied with the level of intake. CONCLUSIONS: According to our simulated validation, this FFQ may be useful to rank subjects by nutrient intake. Its validity against standard independent measurements and its applicability to other subsets of the Colombian population should be carefully considered.     

Performance of a food-frequency questionnaire in the US NIH-AARP (National Institutes of Health-American Association of Retired Persons) Diet and Health Study

OBJECTIVE: We evaluated the performance of the food-frequency questionnaire (FFQ) administered to participants in the US NIH-AARP (National Institutes of Health-American Association of Retired Persons) Diet and Health Study, a cohort of 566 404 persons living in the USA and aged 50-71 years at baseline in 1995. DESIGN: The 124-item FFQ was evaluated within a measurement error model using two non-consecutive 24-hour dietary recalls (24HRs) as the reference. SETTING: Participants were from six states (California, Florida, Pennsylvania, New Jersey, North Carolina and Louisiana) and two metropolitan areas (Atlanta, Georgia and Detroit, Michigan). SUBJECTS: A subgroup of the cohort consisting of 2053 individuals. RESULTS: For the 26 nutrient constituents examined, estimated correlations with true intake (not energy-adjusted) ranged from 0.22 to 0.67, and attenuation factors ranged from 0.15 to 0.49. When adjusted for reported energy intake, performance improved; estimated correlations with true intake ranged from 0.36 to 0.76, and attenuation factors ranged from 0.24 to 0.68. These results compare favourably with those from other large prospective studies. However, previous biomarker-based studies suggest that, due to correlation of errors in FFQs and self-report reference instruments such as the 24HR, the correlations and attenuation factors observed in most calibration studies, including ours, tend to overestimate FFQ performance. CONCLUSION: The performance of the FFQ in the NIH-AARP Diet and Health Study, in conjunction with the study's large sample size and wide range of dietary intake, is likely to allow detection of moderate (> or =1.8) relative risks between many energy-adjusted nutrients and common cancers.     

Development and validation of a food-frequency questionnaire for the determination of detailed fatty acid intakes

OBJECTIVE: To validate a fat intake questionnaire (FIQ) developed to assess habitual dietary intake while focusing on the assessment of detailed fatty acid intake including total trans unsaturated fatty acids (TUFA). DESIGN: An 88 food item/food group FIQ was developed using a meal pattern technique. Validation was achieved by comparison with dietary intake assessed by a modified diet history (DH) in a cross-over design. Eighty-four individuals supplied adipose tissue biopsies for linoleic acid and total TUFA analysis as an independent validation of the FIQ and DH. SETTING: Medical Centre, Dublin Airport, Republic of Ireland. SUBJECTS: One hundred and five healthy volunteers (43 females and 62 males aged 23-63 years). RESULTS: Significant correlations (P<0.0005) were achieved for intakes of energy (0.78), total fat (0.77), saturated fat (0.77), monounsaturated fat (0.63), polyunsaturated fat (0.73), TUFA (0.67) and linoleic acid (0.71) assessed by the FIQ compared with the DH. Linoleic acid intake assessed by the FIQ and the DH was significantly correlated with adipose tissue concentrations (r=0.58 and 0.49, respectively; P<0.005); however, total TUFA intake was poorly correlated with adipose tissue concentrations (r=0.17 and 0.10 for FIQ and DH, respectively). CONCLUSIONS: The FIQ compared favourably with the DH in assessing habitual diet, in particular fatty acid intake. In addition, the FIQ was successfully validated against the linoleic acid composition of adipose tissue, an independent biomarker of relative fatty acid status. The FIQ could therefore be used as an alternative to the DH as it is a shorter, less labour-intensive method.     

Dietary intake and development of a quantitative food-frequency questionnaire for the Barbados National Cancer Study

OBJECTIVE: To develop a quantitative food-frequency questionnaire (QFFQ) for the Barbados National Cancer Study (BNCS) that will permit examination of associations of diet with breast and prostate cancer. DESIGN: Population intake data from the year 2000 Barbados Food Consumption and Anthropometric Surveys (BFCAS 2000) were used to derive a list of foods consumed by the population. A 192-item draft QFFQ was developed from this list. SETTING: Barbados, West Indies provides an ideal environment to understand cancer risk in African-origin populations, with high relevance to African-Americans. The BNCS is a population-based case-control study examining risk factors for breast and prostate cancer in such populations. SUBJECTS: A total of 1600 persons, 18 years and older, completed a 24-hour recall in the BFCAS 2000. Fifty of 63 randomly selected residents (79% response rate) gave additional updated information on foods consumed. RESULTS: The 50 participants provided a one-time 24-hour recall and completed the draft QFFQ. The final instrument contains 148 items: breads, cakes, cereals = 17; rice, pastas, noodles = 8; dairy = 10; meat, fish, poultry = 42; fruit = 16; vegetables = 26; soft drinks = 14; alcoholic beverages = 5; others = 10. Additional questions include supplement use and food preparation methods such as grilling. CONCLUSION: The final instrument is concise, complete and the most up-to-date for assessing the food and nutrient intake of African-origin Barbadians and the associations with breast and prostate cancer.     

Food poverty and health among schoolchildren in Ireland: findings from the Health Behaviour in School-aged Children (HBSC) study

OBJECTIVES: To investigate the relationships between food poverty and food consumption, health and life satisfaction among schoolchildren. DESIGN: Analysis of the 2002 Health Behaviour in School-aged Children (HBSC) study, a cross-sectional survey that employs a self-completion questionnaire in a nationally representative random sample of school classrooms in the Republic of Ireland. SUBJECTS: A total of 8424 schoolchildren (aged 10-17 years) from 176 schools, with an 83% response rate from children. RESULTS: Food poverty was found to be similarly distributed among the three social classes (15.3% in the lower social classes, 15.9% in the middle social classes and 14.8% in the higher social classes). It was also found that schoolchildren reporting food poverty are less likely to eat fruits, vegetables and brown bread, odds ratio (OR) from 0.66 (95% confidence interval (CI) 0.45-0.87) to 0.81 (95% CI 0.63-0.99); more likely to eat crisps, fried potatoes and hamburgers, OR from 1.20 (95% CI 1.00-1.40) to 1.62 (95% CI 1.39-1.85); and more likely to miss breakfast on weekdays, OR from 1.29 (95% CI 0.33-1.59) to 1.72 (95% CI 1.50-1.95). The risk of somatic and mental symptoms is also increased, OR from 1.48 (95% CI 1.18-1.78) to 2.57 (95% CI 2.33-2.81); as are negative health perceptions, OR from 0.63 (95% CI 0.43-0.83) to 0.52 (95% CI 0.28-0.76) and measures of life dissatisfaction, OR from 1.88 (95% CI 1.64-2.12) to 2.25 (95% CI 2.05-2.45). Similar results were found for life dissatisfaction in an international comparison of 32 countries. All analyses were adjusted for age and social class. CONCLUSIONS: Food poverty in schoolchildren is not restricted to those from lower social class families, is associated with a substantial risk to physical and mental health and well-being, and requires the increased attention of policy makers and practitioners.     

Separate estimates of portion size were not essential for energy and nutrient estimation: results from the Southern Community Cohort food-frequency questionnaire pilot study

OBJECTIVE: A food-frequency questionnaire (FFQ) was developed to assess habitual dietary intake in the Southern Community Cohort Study (SCCS), a prospective epidemiological study to analyse disparities in cancer and other chronic diseases between African-Americans and Whites. DESIGN: Frequency and portion size estimates were obtained for each of 104 foods. Daily intakes of 13 food groups, energy and 18 nutrients were computed. Each participant's rank and quintile classification of nutrient intakes was determined with and without the use of the subject's reported portion size. SUBJECTS: The sample was obtained from the SCCS pilot study conducted in Tennessee, Mississippi and Florida, and consisted of 209 adults, 54% African-American, with a mean (standard deviation) age of 57.1 (12.5) years. RESULTS: Correlations between the ranks from the two methods of estimation were high, ranging from 0.66 to 0.94 for food groups and 0.81 to 0.94 for nutrients. Pearson correlations were similarly high for food groups and nutrients. Concordance in exact quintile rank across the nutrient indices ranged from 52 to 70%, rising to 90-99% for concordance within adjacent quintiles. CONCLUSIONS: To reduce the respondents' burden and to increase data completeness, the assignment of a uniform portion size when scoring the SCCS FFQ was considered acceptable.     

Comparison of children's diets as reported by the child via the Youth/Adolescent Questionnaire and the parent via the Willett food-frequency questionnaire

OBJECTIVE: A comparison of a parent-completed Willett food-frequency questionnaire (FFQ) and a self-completed Youth/Adolescent Questionnaire (YAQ) has not yet been conducted. SETTING: In the Diabetes Autoimmunity Study in the Young (DAISY), parents report their child's diet on the FFQ annually from birth until age 10 years, when the child begins to report their own diet using the YAQ. SUBJECTS: To determine the comparability of these collection methods, 89 children aged 10-17 years and their parents completed the YAQ and FFQ, respectively, for the child's previous year's diet. DESIGN: We compared reported intakes for energy, the macronutrients and a variety of micronutrients of interest to the DAISY study. RESULTS: Bland-Altman plots of energy-adjusted differences between questionnaire responses against their means suggested that the two collection methods gave similar results. The average Spearman correlation coefficient of all energy-adjusted nutrient intakes was 0.50, and did not differ significantly by gender (males, r=0.48; females, r=0.46) or age (10-11 years, r=0.49; 12-17 years, r=0.51). While correlated, the nutrient values from the FFQ were higher than the nutrient values from the YAQ. CONCLUSIONS: While reported nutrient intakes are correlated, an indicator variable defining which survey method a nutrient was collected with should be included in any longitudinal data analyses examining nutrient intakes collected with the YAQ and the FFQ as independent predictors of a disease outcome.     

Validity of protein, retinol, folic acid and n-3 fatty acid intakes estimated from the food-frequency questionnaire used in the Danish National Birth Cohort

OBJECTIVE: To validate intakes of protein, folic acid, retinol and n-3 fatty acids estimated from a food-frequency questionnaire in week 25 of pregnancy (FFQ-25). DESIGN: Validation was done against a 7-day weighed food diary (FD) and biomarkers of the nutrients in gestation week 32-38. SUBJECTS AND SETTING: The FFQ-25 to be validated was used in the Danish National Birth Cohort comprising 101 042 pregnant Danish women, of whom 88 participated in the present validation study. RESULTS: Estimated intakes of protein, retinol and folic acid did not differ significantly between the two dietary methods, but intake of n-3 fatty acids was one third larger when estimated from the FFQ-25. The intakes estimated from the two dietary methods were all significantly correlated, ranging from 0.20 for retinol intake to 0.57 for folic acid intake. Sensitivities of being correctly classified into low and high quintiles were between 0.22 and 0.77, and specificities were between 0.62 and 0.89. Urinary protein content did not correlate significantly with protein estimated from the FFQ (r = 0.17, P > 0.05), but did with intake estimated from the FD (r = 0.56, P < 0.0001). Erythrocyte folate correlated significantly with the estimated total intake from the FFQ (r = 0.55, P < 0.0001) and the FD (r = 0.52, P < 0.0001). No correlations with plasma retinol were found. Erythrocyte eicosapentaenoic acid (C20:5n-3) correlated significantly with n-3 fatty acids intake estimated from both the FFQ-25 (r = 0.37, P < 0.001) and the FD (r = 0.62, P < 0.0001). CONCLUSION: The FFQ-25 gives reasonable valid estimates of protein, retinol and folic acid intakes, but seems to overestimate intake of n-3 fatty acids.     

Dietary intake and development of a quantitative food-frequency questionnaire for a lifestyle intervention to reduce the risk of chronic diseases in Canadian First Nations in north-western Ontario

OBJECTIVES: To characterise the diet of First Nations in north-western Ontario, highlight foods for a lifestyle intervention and develop a quantitative food-frequency questionnaire (QFFQ). DESIGN: Cross-sectional survey using single 24 h dietary recalls. SETTING: Eight remote and semi-remote First Nations reserves in north-western Ontario. SUBJECTS: 129 First Nations (Oji-Cree and Ojibway) men and women aged between 18 and 80 years. RESULTS: The greatest contributors to energy were breads, pasta dishes and chips (contributing over 20 % to total energy intake). 'Added fats' such as butter and margarine added to breads and vegetables made up the single largest source of total fat intake (8.4 %). The largest contributors to sugar were sugar itself, soda and other sweetened beverages (contributing over 45 % combined). The mean number of servings consumed of fruits, vegetables and dairy products were much lower than recommended. The mean daily meat intake was more than twice that recommended. A 119-item QFFQ was developed including seven bread items, five soups or stews, 24 meat- or fish-based dishes, eight rice or pasta dishes, nine fruits and 14 vegetables. Frequency of consumption was assessed by eight categories ranging from 'Never or less than one time in one month' to 'two or more times a day'. CONCLUSION:We were able to highlight foods for intervention to improve dietary intake based on the major sources of energy, fat and sugar and the low consumption of fruit and vegetable items. The QFFQ is being used to evaluate a diet and lifestyle intervention in First Nations in north-western Ontario.