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.     

Validation of a food-frequency questionnaire for use in pregnancy

OBJECTIVES: As a part of an ongoing project to develop a nutritional screening tool, we evaluated the performance of a semi-quantitative food-frequency questionnaire (FFQ) in terms of validity in a Sheffield Caucasian pregnant population using two different statistical approaches--the correlation coefficient and the limits of agreement (LOA). The FFQ was designed specifically for pregnant women and previously used in a large-scale study. DESIGN: A validation study. SETTING: A community-based field study of a general population of pregnant women booked for their first antenatal appointment at the Jessop Wing, Royal Hallamshire Hospital, Sheffield, UK. SUBJECTS: One hundred and twenty-three women of different socio-economic status, aged between 17 and 43 years, provided complete dietary data. RESULTS: The validity of the FFQ was tested against a series of two 24-hour recalls. As expected, the intakes of all examined nutrients, except for iodine, carotene, vitamin E, biotin, vitamin C and alcohol, were higher when determined by the FFQ than when determined by 24-hour recall. Pearson's correlation coefficient between the two methods ranged from 0.19 (added sugar, zinc) to 0.47 (Englyst fibre). The LOA were broader for some of the nutrients, e.g. protein, Southgate fibre and alcohol, and an increasing lack of agreement between the two methods was identified with higher dietary intakes. CONCLUSIONS: The FFQ gave useful estimates of the nutrient intakes of Caucasian pregnant women and appears to be a valid tool for categorising pregnant women according to dietary intake. The FFQ performed well for most nutrients and had acceptable agreement with the 24-hour recall.     

Validity of carbohydrate, glycaemic index and glycaemic load data obtained using a semi-quantitative food-frequency questionnaire

OBJECTIVE: To assess the ability of a food-frequency questionnaire (FFQ) to rank Australians according to their intake of total carbohydrate, sugar, starch, fibre, glycaemic index (GI) and glycaemic load (GL). DESIGN: Cross-sectional sample from a population cohort. SETTING: Two postcode areas west of Sydney, Australia. SUBJECTS: From 1992 to 1994, a total of 2868 older Australians provided dietary data using a 145-item Willett-derived FFQ. A representative sub-sample of 78 subjects completed three 4-day weighed food records (WFRs). Pearson and Spearman correlations, Bland-Altman plots and weighted kappa values were calculated. RESULTS: Compared with the WFR, the FFQ provided higher mean estimates of all nutrients except starch and GI. All Pearson and/or Spearman correlations were greater than 0.5, except for GL. For GI, sugar, starch and fibre, the regression lines from the Bland-Altman analysis indicated a non-significant linear trend (P = 0.07, P = 0.36, P = 0.28 and P = 0.10, respectively). For GL and total carbohydrate, however, there was a significant linear trend (P = 0.006 and P < 0.0001, respectively), indicating that as the GL and carbohydrate intake of individuals increased, so did the magnitude of the error between the FFQ and WFR. Weighted kappa values all indicated moderate to good agreement, with the exception of GL which was only fair. The proportions of subjects correctly classified within one quintile for all of the nutrients were over 50% and gross misclassification was low (<10%). CONCLUSION: This FFQ was able to rank individuals according to their intakes of total carbohydrate, sugar, starch, fibre and GI, but not as well for GL.     

Selection of food items for inclusion in a newly developed food-frequency questionnaire

OBJECTIVES: To highlight the differences between the food list required in a food-frequency questionnaire (FFQ) to rank people by their intake and the food items that contribute to absolute intake, and to discuss possible applications. METHODS: We conducted a nutritional survey among 1173 adults using an adapted 24-hour recall questionnaire. STATISTICAL ANALYSIS: To develop an FFQ, we analysed the 24-hour recall survey data by performing a stepwise multiple regression after grouping conceptually similar food items into 175 food groups. RESULTS: In total, 126 food groups were included in the developed FFQ in order to explain at least 80% of the variance in the consumption of each of 27 nutrients. The nutrients that were explained by a few food groups were vitamin A (one food group), alcohol (two), beta-carotene (two), vitamin E (three) and cholesterol (five). Nutrients that were explained by a large number of food groups were energy (37 food groups), potassium (31), magnesium (31), dietary fibre (30), phosphorus (31) and sodium (29). Using energy intake as an example, soft drinks were the best between-person energy classifiers, while providing only 2.4% of the total energy intake. Wine, seeds and nuts, which contributed highly to the variance, were minor energy contributors. In contrast, milk, sugar, fried chicken/turkey breast or whole chicken/turkey, which explained little of the variation in the population, were major energy contributors. CONCLUSIONS: Developing an FFQ on the basis of common foods may not explain the between-person variation required for ranking individual intake in diet-disease studies. Producing lists of "discriminating items" can be a useful application in developing mini-FFQs for selected nutrients.     

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.     

A regional food-frequency questionnaire for the US Mississippi Delta

OBJECTIVE: To describe food sources of nutrient intake for white and African American adults in the Lower Mississippi Delta (LMD), and their use in the development of a regional food-frequency questionnaire (FFQ) based on an earlier version of the National Cancer Institute's Health Habits and History Questionnaire. DESIGN: We ranked food sources of energy, macronutrients, vitamins and minerals, and examined portion size distributions for 842 white and 857 African American residents aged 19 years and older, using 24-hour dietary intake recall data from a telephone survey of 36 LMD counties. These values were used to develop a regional FFQ, which was then field-tested with 100 subjects and revised to improve interpretability. SETTING: The LMD region of the USA. SUBJECTS: White and African American adult residents of the LMD. RESULTS: LMD African Americans obtained more of their energy and nutrient intakes from poultry, processed meat, salty snacks, fruit drinks, pork and cornbread; and less from milk, alcohol, legumes, salad dressing, butter/margarine and sweetened tea than did white residents. Regional foods not on nationally used FFQs included grits, turnip greens, okra, ham hocks, chitterlings, crawfish, catfish, cracklings, jambalaya, potato logs, chicken and dumplings, and sweet potato pie. Based on responses during field-testing, the questionnaire was also designed to add four portion sizes for each food item, presented as questions, rather than in grid format. CONCLUSIONS: Regional food use patterns differ from national patterns and furthermore differ between African American and white adults in the LMD. The resulting Delta NIRI FFQ for Adults should contribute to improved assessment of usual intake for use in studies of diet and health in this region.     

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.     

Validation of a semi-quantitative food-frequency questionnaire used among 2-year-old Norwegian children

OBJECTIVES: An adequate diet is of profound importance in infancy and early childhood. To ensure an optimal diet, knowledge about actual intake must be obtained. The aims of this study were to assess the validity of a semi-quantitative food-frequency questionnaire (SFFQ) applied in a large nation-wide survey among 2-year-old children and to examine the validity of the SFFQ in relation to different background parameters. DESIGN: The SFFQ was administered to the parents close to the child's second birthday, and one to two weeks later they started to weigh and record the child's diet for 7 days. SUBJECTS: One-hundred and eighty-seven families with a 2-year-old child completed both methods. RESULTS: There were no differences between the intakes of protein, saturated fatty acids, total carbohydrates and calcium estimated from the two methods. The average intake of all micronutrients, except for calcium, was overestimated by the SFFQ. Bland-Altman plots showed a systematic increase in difference between the two methods with increasing intake for most nutrients. Spearman correlation coefficients between methods for nutrient intakes ranged from 0.26 to 0.50, the median correlation was 0.38. The correlations increased when estimates were adjusted for energy intake, the median correlation being 0.52. Differences in observed validity were found according to the number of siblings.CONCLUSIONS: This study indicates that the SFFQ may be a valuable tool for measuring average intakes of energy, macronutrients and several food items among a 2-year-old population in Norway. The ability of the questionnaire to rank children according to intakes of nutrients and food items was rather low.     

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.     

Underreporting of energy intake from a self-administered food-frequency questionnaire completed by adults in Montreal

BACKGROUND: Energy intake determined from self-reported dietary assessment methods may be underreported. Therefore, it is important that such methods be validated against another with known validity for energy intake or energy expenditure. METHODS: We investigated potential underestimation of energy intake obtained from our semi-quantitative food-frequency questionnaire (FFQ) administered between 2000 and 2001 in the metropolitan area of Montreal, Canada. The study population included 246 adults aged 18 to 82 years. The ratio of energy intake to estimated basal metabolic rate (EI/BMR) was used to assess underreporting and physical activity was determined from self-administered questions. Comparison of the EI/BMR ratio with the Goldberg statistical cut-off allowed us to detect individuals who were low energy reporters (LERs). LERs and non-LERs were compared to determine if they differed on sociodemographic, anthropometric and lifestyle variables. RESULTS: The EI/BMR ratio was 1.26 for men and 1.32 for women. LERs represented 43% of the sample of individuals. Male LERs accounted for 54% compared with 35% among females. Underreporting of energy intake was highest in men and individuals who were older, heavier, with higher body mass index and lower education level. A higher proportion of male LERs perceived their financial situation as adequate while a greater proportion of female LERs considered themselves poor. CONCLUSION: Our data suggest that underreporting of energy intake from the FFQ was considerable and may bias dietary interpretation. As this was uneven across the sample, it is crucial to recognise the characteristics of LERs in order to increase the validity of reported energy intake.     

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.     

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.