Comparing biological measurements of vitamin C, folate, alpha-tocopherol and carotene with 24-hour dietary recall information in nonhispanic blacks and whites.

PURPOSE: To assess intake of several vitamins in preparation for a large cohort study investigating the effect of diet on risk of colon and prostate cancer. METHODS: The dietary intake of several vitamins were assessed using eight different 24-hour recalls and a 200-item food frequency questionnaire (FFQ) from each subject. Participants also attended a clinic where blood was drawn and body composition, weight, height, and blood pressure were measured. A total of 97 black and 96 nonhispanic white subjects participated. The levels of alpha-tocopherol, carotene, folate, and vitamin C in the blood were correlated with the dietary intakes as measured by both 24-hour recalls and FFQ. RESULTS: Correlations between blood levels and energy-adjusted dietary intake assessed by 24-hour recalls (with supplements) were as follows: carotene (adjusted for serum cholesterol): 0.47 and 0.55 in black and white subjects, respectively; alpha-tocopherol (adjusted for serum cholesterol): 0.61 (blacks) and 0.50 (whites); vitamin C: 0.22 (blacks) and 0.17 (whites); folate: 0.54 (blacks) and 0.55 (whites). Correlations between blood levels and FFQ indices were smaller in magnitude: 0.34 and 0.28 for carotene in black and white subjects, respectively, 0.37 and 0.56 for alpha-tocopherol (adjusted for serum cholesterol), 0.20 and 0.03 for vitamin C and 0.24 and 0.32 for folate. CONCLUSIONS: The correlations observed were generally of modest to moderate size and were similar to or larger than those reported by others. This is despite variations in absorption, metabolism, and excretion of the vitamins and suggests that both the 24-hour recalls and the FFQ contain valid information.     

Validity and reliability of a new food frequency questionnaire compared to 24 h recalls and biochemical measurements: pilot phase of Golestan cohort study of esophageal cancer

BACKGROUND: A pilot study was carried out to evaluate validity and reproducibility of a food frequency questionnaire (FFQ), which was designed to be used in a prospective cohort study in a population at high risk for esophageal cancer in northern Iran. METHODS: The FFQ was administered four times to 131 subjects, aged 35-65 years, of both sexes. Twelve 24-h dietary recalls for two consecutive days were administered monthly during 1 year and used as a reference method. The excretion of nitrogen was measured on four 24-h urine samples, and plasma levels of beta-carotene, retinol, vitamin C and alpha-tocopherol was measured from two time points. Relative validity of FFQ and 24-h diet recall was assessed by comparing nutrient intake derived from both methods with the urinary nitrogen and plasma levels of beta-carotene, retinol, vitamin C and alpha-tocopherol. RESULTS: Correlation coefficients comparing energy and nutrients intake based on the mean of the four FFQ and the mean of twelve 24-h diet recalls were 0.75 for total energy, 0.75 for carbohydrates, 0.76 for proteins and 0.65 for fat. Correlation coefficients between the FFQ-based intake and serum levels of beta-carotene, retinol, vitamin C and vitamin E/alpha-tocopherol were 0.37, 0.32, 0.35 and 0.06, respectively. Correlation coefficients between urinary nitrogen and FFQ-based protein intake ranged from 0.23 to 0.35. Intraclass correlation coefficients used to measure reproducibility of FFQ ranged from 0.66 to 0.89. CONCLUSION: We found that the FFQ provides valid and reliable measurements of habitual intake for energy and most of the nutrients studied.     

Reliability and validity of a brief questionnaire to assess calcium intake of middle-school-aged children

OBJECTIVE: Evaluate the validity and reliability of a short (10-item) calcium food frequency questionnaire (FFQ) for use with middle-school-aged (11 to 14 years of age) children. DESIGN: The calcium FFQ was completed twice, with 1 week between administrations. Three 24-hour dietary recalls were collected from each participant after the second administration of the calcium FFQ. SUBJECTS/SETTING: Students in an ethnically diverse middle school in Minneapolis, MN (n=248). MAIN OUTCOME MEASURES: Calcium intake estimates from the calcium FFQ and dietary recalls. STATISTICAL ANALYSES: Correlations between calcium intake estimates from the first and second questionnaire administrations of the calcium FFQ were calculated and paired t tests were conducted to compare mean calcium intake estimates from each questionnaire administration. Mean intake estimates from the calcium FFQ and the dietary recalls were compared. Also, correlations between intake estimates from the calcium FFQ and the recalls were calculated. RESULTS: Correlation between calcium intake estimates derived from the first and second administration of the calcium FFQ was 0.74. Mean calcium intake estimates from the calcium FFQ and the average of the three dietary recalls were 856 mg/day and 993 mg/day, respectively (P<0.001). The correlation between calcium intake estimates derived from the calcium FFQ and the average of the recalls was 0.43. CONCLUSIONS: Reliability of the FFQ was found to be good while validity was weaker, with calcium intake from the calcium FFQ moderately associated with estimates from dietary recalls. Where a brief instrument for assessing calcium intake of middle-school-aged children is needed, the calcium FFQ evaluated in this study may be useful.     

北京市儿童青少年食物频率问卷的信度和效度研究

目的 对研制的北京市儿童青少年食物频率问卷的信度和效度进行评价,为儿童青少年营养状况评估和健康干预以及饮食习惯与慢性疾病关联性的研究提供一个简便、可信的研究工具。方法 对北京市130名10~17岁儿童青少年进行4次24 h饮食回顾调查和2次食物频率问卷调查,24- h饮食回顾作为“标准”方法与食物频率问卷比较来评价其效度, 2次间隔6个月的食物频率问卷调查结果相比较来评价其信度。结果 两次食物频率问卷调查结果间能量及营养素摄入量估计差异较小,除蛋白质、磷和锌的摄入量第二次低于第一次外(P<0.05),其他营养素摄入量间差异无统计学意义(P>0.05)。两次食物频率问卷调查结果间所有能量及营养素摄入量均呈正相关(P<0.01),Pearson相关系数从0.315(钙)至0.521(锌),平均为0.431,女性高于男性(0.49 vs 0.32)。食物频率问卷调查的能量及营养素摄入量均高于24 h饮食回顾(P<0.01),食物频率问卷高估明显。调整总能量摄入和个体内变异等影响后,食物频率问卷与24 h饮食回顾调查结果的能量和所有营养素摄入量均呈正相关(P<0.05),Pearson相关系数从0.27(维生素A)至0.53(锌),平均0.38。四分位分组显示:研究对象被良好区分(相同组或相邻组),比例从66.2%(维生素E、钙)至79.2%(铁),平均73.0%,研究对象被严重错分(相隔2组),比例平均为6.2%。结论 此食物频率问卷有较好的信度和效度,可作为今后儿童青少年膳食营养摄入状况调查和评价的适用工具。     

Validation of three food frequency questionnaires and 24-hour recalls with serum carotenoid levels in a sample of African-American adults

The validity of self-reported fruit and vegetable intake in minority populations has not been adequately established. In this study, the authors examined the association of three food frequency questionnaires (FFQs) and 24-hour dietary recalls with serum carotenoid levels. Approximately 1,000 African-American adults recruited from 15 churches in Atlanta, Georgia (1997-1998) completed three fruit and vegetable FFQs: a seven-item instrument assessing intake during the past month; a two-item measure assessing usual intake; and a 36-item measure adapted from the Health Habits and History Questionnaire. A total of 414 participants received a 24-hour recall by telephone, and 105 of them received two additional recalls. Serum levels of lycopene, lutein, cryptoxanthin, alpha-carotene, and beta-carotene were assessed in 813 participants and used as the validity criterion. The correlations of fruit and vegetable servings with specific and total serum carotenoid levels were generally higher for the 36-item FFQ than for the two-item and seven-item instruments. The strongest correlation of fruit and vegetable servings with total carotenoid levels was observed for the three recalls (r = 0.42), with the 36-item FFQ and the single 24-hour recall yielding comparable correlations (r = 0.35 and r = 0.37, respectively). The validity of the 36-item fruit and vegetable FFQ was generally as strong as the validity of both 1 and 3 days of recalls. Given the lower cost and time needed for administration relative to recalls, it appears that the 36-item FFQ has merit for evaluating fruit and vegetable health interventions.     

Relative validity of food frequency questionnaire nutrient estimates in the Black Women's Health Study

PURPOSE: The Black Women's Health Study (BWHS) was designed to investigate determinants of health and disease in US black women. More than 64,000 women are enrolled in the BWHS cohort. This study assessed the relative validity of the 68-item food frequency questionnaire (FFQ) used in the BWHS baseline questionnaire. METHODS: Four hundred and eight BWHS enrollees were asked to provide three telephone, 24-hour recalls and one written 3-day food diary over a one-year period. Means and Pearson correlations were computed to compare estimates for energy, total fat, saturated fat, protein, carbohydrate, dietary fiber, calcium, iron, vitamin C, folate, beta-carotene, and vitamin E from the FFQ, recalls, and diaries. RESULTS: Mean energy intake (kcal) was higher for the diary (1716) than the FFQ (1601) or recalls (1510). Other nutrient estimates (% kcal or per 1000 kcal) were similar across methods, except beta-carotene (FFQ higher). Correlations (energy-adjusted, except for energy, and corrected for intraperson variation) between the FFQ and the recalls were higher than for the diary data and were between 0.5 and 0.8, except for energy and vitamin E (both <0.3). CONCLUSION: The BWHS FFQ will support meaningful analyses of diet-health associations for 10 of the 11 energy-adjusted nutrient intake variables analyzed.     

Assessing the validity of a food frequency questionnaire among low-income women in São Paulo, southeastern Brazil

This study describes the validity of a food frequency questionnaire (FFQ) in 93 low-income women (20-65 years), participating in a case-control study in S?o Paulo, Brazil. Two FFQ (FFQ1 and FFQ2, 12 months apart) and three 24-hour dietary recalls (24hR) were conducted between 2003 and 2004 to estimate dietary intake during the past year. The Pearson correlation coefficients (crude, energy-adjusted and de-attenuated) were used for comparisons between FFQ and 24hR. The agreement between the methods was further examined by the Bland-Altman analysis. For the assessment of long-term reliability, the energy-adjusted intra-class correlation coefficients were mostly around 0.40, but higher for vitamin A and folate (0.50-0.56). Energy-adjusted, attenuation-corrected Pearson validity correlations between FFQ and DR ranged from 0.30-0.54 for macronutrients to 0.20-0.48 for micronutrients, with higher value for calcium (0.75). There were small proportions of grossly misclassified nutrient intakes, while Bland-Altman plots indicated that the FFQ is accurate in assessing nutrient intake at a group level.     

Evaluation of the Validity of a Food Frequency Questionnaire and 24-Hour Dietary Recall to Assess Dietary Iron Intake in Children and Adolescents from the South American Youth/Child Cardiovascular and Environmental Study

BackgroundA food frequency questionnaire (FFQ) for South American children and adolescents was developed, but its validity for assessing dietary iron intake has not been evaluated.ObjectiveTo evaluate the validity of the FFQ and 24-hour dietary recalls (24h-DR) for assessing dietary iron intake in children and adolescents.DesignThe South American Youth/Child Cardiovascular and Environmental study is a multicenter observational study, conducted in five South American cities: Buenos Aires (Argentina), Lima (Peru), Medellin (Colombia), Sao Paulo, and Teresina (Brazil). The FFQ assessed dietary intake over the previous 3 months, and the 24h-DR was completed three times (2 weekdays and 1 weekend day) with a minimum 5-day interval between recalls. Blood samples were collected to assess serum iron, ferritin, and hemoglobin levels.Participants and settingData of 99 children (aged 3 to 10 years) and 50 adolescents (aged 11 to 17 years) from public and private schools were collected during 2015 to 2017.Main outcome measuresDietary iron intake calculated from the FFQ (using the sum of daily iron intake in all food/food groups) and 24h-DR (mean of 3 days using the multiple source method).Statistical analyses performedDietary iron intake in relation to blood biomarkers were assessed using Spearman rank correlations adjusted for sex, age, and total energy intake, and the quadratic weighted κ coefficients for agreement.ResultsSpearman correlations showed very good coefficients (range = 0.78 to 0.85) for the FFQ in both age groups; for the 24h-DR, the coefficients were weak in children and adolescents (range = 0.23 to 0.28). The agreement ranged from 59.9% to 72.9% for the FFQ and from 63.9% to 81.9% for the 24h-DR.ConclusionThe South American Youth/Child Cardiovascular and Environmental study FFQ exhibited good validity to rank total dietary iron intake in children and adolescents, and as well as the 24h-DR, presented good strength of agreements when compared with serum iron and ferritin levels.     

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

BACKGROUND: The validity of dietary assessment methods should be established before diet-disease associations are reported. OBJECTIVE: 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). DESIGN: 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. RESULTS: 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). CONCLUSIONS: 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.     

Comparison of intakes of US Chinese women based on food frequency and 24-hour recall data

The objective of this cross-sectional study was to compare dietary reports from a food frequency questionnaire (FFQ) for US Chinese women with 24-hour recall estimates. The subjects were 56 women recruited through organizations in Philadelphia's Chinese community. Spearman correlations were used to describe FFQ estimates of food servings per month and nutrient intake per day vs estimates from three 24-hour recalls over 1 month. On average, women reported at least weekly consumption of 28 of 96 FFQ food items. The three most frequently consumed were rice (38 times/month), tea (29 times/month), and dark green, leafy vegetables (18 times/month). Comparing reported frequencies of the 28 foods to 24-hour recall estimates, the median Spearman correlation was 0.36. For nutrient estimates, correlations were high (r >0.5) for dietary fiber and calcium; moderate ( r =0.25 to 0.5) for energy, saturated fat, cholesterol, carbohydrates, protein, folic acid, and iron; but poor (r <0.25) for total fat, vitamin C, vitamin A, and carotene. These findings provide some assurance of the FFQ's adequacy for describing US Chinese women's intake of commonly consumed foods and selected nutrients. They also provide a basis for further improvements to, and evaluations of, the FFQ.     

Validation of the assessment of folate and vitamin B12 intake in women of reproductive age: the method of triads

OBJECTIVE: To validate the folate and vitamin B12 intakes estimated by a food-frequency questionnaire (FFQ) designed to be used in a case-control study on the association between maternal dietary intake and the risk of having a child with a congenital heart defect. DESIGN AND SUBJECTS: The FFQ was filled out by 53 women of reproductive age. Immediately thereafter, blood samples were taken to determine serum folate, red blood cell (RBC) folate and serum vitamin B12 concentrations. Subsequently, three dietary 24-h recalls (24HR) were completed during a period of three successive weeks and used as a reference method. The recalls comprised two weekdays and one weekend day. Using the method of triads, validity coefficients were calculated by comparing nutrient intakes derived from the FFQ and 24HR with the corresponding nutritional biomarkers in blood. The validity coefficient is the correlation between the dietary intake reported by the FFQ and the unknown 'true' dietary intake. RESULTS: The comparison of B-vitamin intakes reported by the FFQ and the mean of the 24HR revealed deattenuated correlation coefficients of 0.98 for folate and 0.66 for vitamin B12. The correlation coefficients between the B-vitamin intakes estimated by the FFQ and concentrations of serum folate, RBC folate and serum vitamin B12 were 0.20, 0.28 and 0.21, respectively. The validity coefficients for serum folate, RBC folate and serum vitamin B12 were 0.94, 0.75 and 1.00, respectively. The estimated folate and vitamin B12 intakes were comparable with the results of the most recent Dutch food consumption survey. CONCLUSIONS: The adapted FFQ is a reliable tool to estimate the dietary intake of energy, macronutrients, folate and vitamin B12 in women of reproductive age. Therefore, this FFQ is suitable for the investigation of nutrient-disease associations in future. SPONSORSHIP: Funding was provided by the Netherlands Heart Foundation (Grant 2002.B027).     

Measurement characteristics of the Women's Health Initiative food frequency questionnaire

PURPOSE: The Women's Health Initiative (WHI) is the largest research program ever initiated in the United States with a focus on diet and health. Therefore, it is important to understand and document the measurement characteristics of the key dietary assessment instrument: the WHI food frequency questionnaire (FFQ). METHODS: Data are from 113 women screened for participation in the WHI in 1995. We assessed bias and precision of the FFQ by comparing the intake of 30 nutrients estimated from the FFQ with means from four 24-hour dietary recalls and a 4-day food record. RESULTS: For most nutrients, means estimated by the FFQ were within 10% of the records or recalls. Precision, defined as the correlation between the FFQ and the records and recalls, was similar to other FFQs. Energy adjusted correlation coefficients ranged from 0.2 (vitamin B12) to 0.7 (magnesium) with a mean of 0.5. The correlation for percentage energy from fat (a key measure in WHI) was 0.6. Vitamin supplement use was common. For example, almost half of total vitamin E intake was obtained from supplements. Including supplemental vitamins and minerals increased micronutrient correlation coefficients, which ranged from 0.2 (thiamin) to 0.8 (vitamin E) with a mean of 0.6. CONCLUSIONS: The WHI FFQ produced nutrient estimate, that were similar to those obtained from short-term dietary recall and recording methods. Comparison of WHI FFQ nutrient intake measures to independent and unbiased measures, such as doubly labeled water estimates of energy expenditure, are needed to help address the validity of the FFQ in this population.     

Population-based study of alpha- and gamma-tocopherol in plasma and adipose tissue as biomarkers of intake in Costa Rican adults

BACKGROUND: gamma-Tocopherol is the most abundant form of vitamin E in the US diet, but alpha-tocopherol concentrations are the highest in plasma and tissues. Although plasma and adipose tissue concentrations of alpha-tocopherol have been used as biomarkers of intake, the relation between gamma-tocopherol intake and concentrations in plasma and adipose tissue is unknown. OBJECTIVE: Our goal was to investigate in a randomly selected population from Costa Rica whether plasma or adipose tissue concentrations of alpha- and gamma-tocopherol are suitable biomarkers of intake. DESIGN: A total of 361 men (x +/- SD age: 55 +/- 11 y) and 121 women (aged 59 +/- 10 y) completed a 135-item food-frequency questionnaire and provided a fasting blood sample and adipose tissue biopsy sample. RESULTS: Dietary gamma-tocopherol correlated with adipose tissue (r = 0.37, P < 0.001) and plasma (r = 0.42, P < 0.001) concentrations, regardless of supplement use. Dietary alpha-tocopherol correlated poorly with adipose tissue (r = 0.15, P < 0.01) and plasma (r = 0.16, P < 0.001) concentrations, and these correlations were even lower when users of vitamin supplements (n = 24) were excluded (adipose tissue: r = 0.10, P < 0.05; plasma: r = 0.09, P < 0.05). Compared with subjects who reported palm shortening (36%) as the major type of fat used for cooking, subjects using soybean oil (52%) had higher amounts of both alpha- and gamma-tocopherol in their diets. However, only gamma-tocopherol concentrations were higher in the plasma and adipose tissue of soybean oil users. CONCLUSIONS: Plasma and adipose tissue concentrations of gamma-tocopherol are equally good biomarkers of intake. The weak associations between alpha-tocopherol intake and plasma or adipose tissue concentrations suggest that these biomarkers are influenced more by factors other than alpha-tocopherol intake.     

Meal distribution, relative validity and reproducibility of a meal-based food frequency questionnaire in Taiwan

Food frequency questionnaire is an important assessment tool for public health nutrition research. We describe the development history and conducted the validity and reproducibility studies for a meal-based Chinese food frequency questionnaire (Chinese FFQ) by five meal sequences. A total of 51 subjects were recruited to collect dietary information twice (6 months apart) with one 24-hr recall, 7-day food records and the Chinese FFQ. Combining data from both time sets, Chinese FFQ showed strong correlations of macro and micronutrients with 7-day records (n = 60, r = 0.29-0.50, p < 0.05), but not with 24-hr recalls (n = 60, r = 0.01-0.23, p > 0.05). The reproducibility of this Chinese FFQ (n = 22) was consistently high for most nutrients, with Spearman correction coefficients between 0.42 for vitamin A to 0.79 for vitamin B12. From a larger sample of 231 subjects who completed the Chinese FFQ and one 24-hr recall, we found the energy distributions of breakfast, lunch, dinner, afternoon and evening snacks combined from Chinese FFQ were 20%, 37%, 37% and 6%, and from 24-hour recalls were 19%, 36%, 44% and 1%, respectively. These results showed acceptable reproducibility and relative validity of this meal-based Chinese FFQ.     

Validation of a simplified food frequency questionnaire as used in the Nutrition and Health Survey in Taiwan (NAHSIT) for the elderly

A 28-item simplified food frequency questionnaire (SFFQ) combined with 9 open questions about basic commodities was designed for the Elderly Nutrient and Health Survey in Taiwan (NAHSIT) to collect participants' usual intake of the previous month. We have examined the validity this SFFQ as assessed by multiple 24-hour dietary recall (n=81) and biomarkers (n=1473). All questionnaires were completed by face-to-face interview and fasting blood taken. Thirty seven males and 44 females were randomly selected from NAHSIT participants. Of these, 31 and 50 subjects completed 2 or 3 24-hour dietary recalls within one month, respectively. Mean daily intake frequencies for each food group were calculated from the SFFQ and 24-hr recalls, respectively. Spearman rank correlation coefficients between frequencies of food intake from the FFQ and dietary recalls ranged from 0.132 to 0.678 for men; 0.052 to 0.759 for women. For food weight, the trends were similar to frequency findings. For biomarkers, the most correlated were dairy intake frequency judged by vitamin B-2 and calcium intakes and by erythrocyte glutathione reductase (EGRAC) for B-2 functionality, where the correlation coefficients were, respectively, 0.533, 0.518 and -0.205 for men; 0.494, 0.475 and -0.174 for women; fish and fruit followed in overall validity. The SFFQ measured the food patterns of elderly NAHSIT elders with validity high for dairy and good for fish, and fruit intakes in both genders.     

Relative Validity and Reproducibility of a Food Frequency Questionnaire to Assess Food Group Intake in Pregnant Jordanian Women

BackgroundResearch on the relationship between maternal diet and pregnancy outcomes requires valid dietary assessment tools in pregnancy.ObjectiveThis study aimed to develop and examine the relative validity and reproducibility of a quantitative food frequency questionnaire (FFQ) to estimate food group intake in a sample of pregnant Jordanian women.DesignIn this validation study, food group intake from a culturally sensitive quantitative FFQ was compared with food group intake from three 24-hour dietary recalls.Participants and settingThe validation study was conducted from 2015 to 2017 at the maternity clinics in Jordan University Hospital among 131 healthy singleton pregnant Jordanian women. Of these women, 30 also took part in the reproducibility phase, which involved repeated completion of the FFQ in a time frame of 1 month. Pregnant women who had gestational diabetes, preeclampsia, and chronic diseases were excluded.Main outcome measuresRelative validity and reproducibility of a 117-item quantitative FFQ used to estimate usual food intake over a period of 1 month.Statistical analyses performedIntraclass correlation coefficients and weighted κ statistics were calculated to test the reproducibility between the two administrations of the FFQ. Pearson correlations were estimated to validate the FFQ against 24-hour dietary recalls. Cross-classification and Bland-Altman plots were used to examine the agreement between the two dietary assessment methods.ResultsThe intraclass correlation coefficients between the two FFQs ranged from 0.24 for legumes to 0.93 for processed meats. A moderate level of agreement was observed between two FFQs. De-attenuated and energy-adjusted correlations ranged from 0.08 for sweets and sugar to 0.93 for sugary drinks. On average, 50.9% and 45.2% of participants were classified by the FFQ and the 24-hour dietary recalls into the same quartile based on their crude and energy-adjusted food group intake, respectively. Bland-Altman plots showed satisfactory agreement between two methods for most food groups.ConclusionsThe FFQ showed moderate reproducibility and good relative validity for most food groups.     

Validation of a food-frequency questionnaire assessment of carotenoid and vitamin E intake using weighed food records and plasma biomarkers: the method of triads model

BACKGROUND: Reliability or validity studies are important for the evaluation of measurement error in dietary assessment methods. An approach to validation known as the method of triads uses triangulation techniques to calculate the validity coefficient of a food-frequency questionnaire (FFQ). OBJECTIVE: To assess the validity of an FFQ estimates of carotenoid and vitamin E intake against serum biomarker measurements and weighed food records (WFRs), by applying the method of triads. DESIGN: The study population was a sub-sample of adult participants in a randomised controlled trial of beta-carotene and sunscreen in the prevention of skin cancer. Dietary intake was assessed by a self-administered FFQ and a WFR. Nonfasting blood samples were collected and plasma analysed for five carotenoids (alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein, lycopene) and vitamin E. Correlation coefficients were calculated between each of the dietary methods and the validity coefficient was calculated using the method of triads. The 95% confidence intervals for the validity coefficients were estimated using bootstrap sampling. RESULTS: The validity coefficients of the FFQ were highest for alpha-carotene (0.85) and lycopene (0.62), followed by beta-carotene (0.55) and total carotenoids (0.55), while the lowest validity coefficient was for lutein (0.19). The method of triads could not be used for beta-cryptoxanthin and vitamin E, as one of the three underlying correlations was negative. CONCLUSIONS: Results were similar to other studies of validity using biomarkers and the method of triads. For many dietary factors, the upper limit of the validity coefficients was less than 0.5 and therefore only strong relationships between dietary exposure and disease will be detected.     

Application of the method of triads to evaluate the performance of food frequency questionnaires and biomarkers as indicators of long-term dietary intake.

Little is documented about the performance of the food frequency questionnaire (FFQ) in US minority groups and in populations in developing countries. The authors applied a novel technique, the method of triads, to assess the validity and reproducibility of the FFQ among Hispanics. The subjects were men (n = 78) and women (n = 42) living in Costa Rica. Seven 24-hour dietary recalls and two FFQ interviews (12 months apart) were conducted between 1995 and 1998 to estimate dietary intake during the past year. Plasma and adipose tissue samples were collected from all subjects. Validity coefficients, which measure the correlation between observed and "true" dietary intake, were also estimated. The median validity coefficients for tocopherols and carotenoids estimated by dietary recall, the average of the two FFQs, and plasma were 0.71, 0.60, and 0.52, respectively. Compared with adipose tissue, plasma was a superior biomarker for carotenoids and tocopherols. Adipose tissue was a poor biomarker for saturated and monounsaturated fatty acids but performed well for polyunsaturated fatty acids (validity coefficients, 0.45-1.01) and lycopene (validity coefficient, 0.51). This study also showed that biomarkers did not perform better than the FFQ and that they should be used to complement the FFQ rather than substitute for it.     

The food propensity questionnaire: concept, development, and validation for use as a covariate in a model to estimate usual food intake

OBJECTIVE: Twenty-four-hour recalls capture rich information on food consumption, but suffer from inadequately measuring usual intakes of episodically consumed foods. We explore using food frequency questionnaire (FFQ) data as covariates in a statistical model to estimate individual usual intakes of episodically consumed foods and their distributions and describe the development of the Food Propensity Questionnaire, an FFQ introduced in the 2003-2004 National Health and Nutrition Examination Survey. DESIGN: We analyzed data from 965 adult participants in the Eating at America's Table Study who completed four 24-hour recalls and an FFQ. We assessed whether or not increasing FFQ-reported frequency was associated with both number of 24-hour recall consumption days and amounts reported. RESULTS: For 52 of 56 food groups (93%), and 218 of 230 individual foods (95%), there were significant monotonically increasing relationships between FFQ frequency and 24-hour recall probability of consumption. For 47 of 56 food groups (84%) and 55 of 230 (24%) individual foods, there were significant positive correlations between FFQ frequencies and consumption-day mean intake. CONCLUSIONS: We found strong and consistent relationships between reported FFQ frequency of food and food-group consumption and probability of consumption on 24-hour recalls. This supports the premise that frequency data may offer important covariate information in supplementing multiple recalls for estimating usual intake of food groups.     

Reasonable estimates of serum vitamin E, vitamin C, and beta-cryptoxanthin are obtained with a food frequency questionnaire in older black and white adults

Few studies provide correlations between different indicators of the dietary intakes of older (>or= 65 y) black and white adults. This study compared the usual intakes of vitamin E, vitamin C, and selected carotenoids estimated by a modified Harvard food frequency questionnaire (FFQ) to those estimated by multiple 24-h recalls, and to blood concentrations of components in a randomly selected sample of participants in the Chicago Health and Aging Project (CHAP). Subjects (n = 59) were interviewed to complete multiple 24-h recalls over a year's time, then completed an FFQ and subsequently provided a fasting blood specimen within 2 mo. Dietary estimates were energy-adjusted separately for men and women. Significant (P < 0.05) correlations between total (diet and supplement) FFQ estimates and serum measures of vitamin E and vitamin C were as follows: 0.49 and 0.39 for blacks, and 0.42 and 0.29 for whites, respectively. The highest correlations between serum and FFQ indicators were for dietary beta-cryptoxanthin (0.46), total alpha-tocopherol (0.46) and total beta-carotene (0.44) among whites; among blacks, the highest correlations were for dietary alpha-carotene (0.81), total alpha-tocopherol (0.53) and total beta-cryptoxanthin (0.50); all were significant (P < 0.05). Further adjustment for age, gender, BMI, and educational level minimally altered these coefficients. These findings indicate that the modified Harvard FFQ provides reasonable estimates of serum levels of vitamin E, vitamin C and beta-cryptoxanthin among CHAP participants.