Assessment of the validity of a food frequency questionnaire as a measure of food use by comparison with direct observation of domestic food stores

Relative Validity and Reliability of a Food Frequency Questionnaire for a Triethnic Population of 1-Year-Old to 3-Year-Old Children from Low-Income Families

OBJECTIVE

To develop and validate a food frequency questionnaire (FFQ) for low-income, 1- to 3-year-old Hispanic, African-American, and white children.

DESIGN

A convenience sample of low-income mothers provided dietary data for their child via FFQs and 3-day diet records.

SUBJECTS/SETTING

Participants (N=77) were recruited from Special Supplemental Program for Women, Infants, and Children clinics and public health clinics. All subjects were Hispanic, African-American, or white mothers of children 1 to 3 years old, 18 years of age or older, income less than 200% of the federal poverty level, and were literate in English. Statistical analyses performed Wilcoxon signed-ranks tests were used for comparisons of food group servings on time 1 and time 2 FFQs and to examine differences in food group servings between the FFQ and diet records. Spearman correlations were calculated to assess test-retest reliability and the relative validity. Contingency tables were used to determine the degree of association between the FFQ and diet records.

RESULTS

Reliability correlations were significant for all nine food categories ( =0.69), ranging from 0.53 (soups) to 0.84 (nonstarchy vegetables). Validity correlations were significant for all food groups ( =0.41) except starchy vegetables. Thirty-six percent of children were classified into the same quartile of food group intake and 78% into the same or within one quartile.

CONCLUSIONS

The FFQ yielded excellent reliability and acceptable validity and can be used to assess food choices in a triethnic sample of low-income 1- to 3-year-old children.

Food frequency questionnaire results correlate with metabolic control in insulin-treated veterans with type 2 diabetes: the Diabetes Outcomes in Veterans Study

OBJECTIVE

To validate food frequency analysis as a predictor of metabolic status in persons with type 2 diabetes and to identify psychosocial factors affecting dietary adherence.

METHODS

Three hundred forty-seven subjects with stable, insulin-treated type 2 diabetes completed a food frequency questionnaire and six instruments measuring different psychosocial attributes. Eight metabolic parameters were used as principal endpoints. Data from the food frequency questionnaires were used to estimate daily energy intake and determine each subject's adherence to seven dietary standards derived from the 2003 Dietary Recommendations of the American Diabetes Association. We excluded 105 subjects reporting daily energy intake <1,000 kcal because these results were considered unreliable. Subjects were then categorized into three groups depending on their adherence rates to American Diabetes Association dietary standards.

RESULTS

Subjects with the lowest dietary adherence had the poorest metabolic control. Adherence to dietary standards was particularly poor among subjects with metabolic syndrome (2.1%) and/or obesity (4.1%). The most important determinants of following recommended dietary practices were positive attitudes, fewer social barriers, and a conviction that diet could control diabetes.

CONCLUSIONS

For subjects with type 2 diabetes reporting a dietary intake of >1,000 kcal/day, food frequency questionnaire data could identify those with poor metabolic control. Nutrition interventions to improve metabolic control should focus on reducing fat intake and emphasizing the importance of diet. Multidisciplinary efforts should be directed at overcoming social barriers to recommended dietary practices and to treating depression.

A short dutch questionnaire to measure fruit and vegetable intake: relative validity among adults and adolescents

A short food frequency questionnaire (FFQ) to assess fruit and vegetable (F&V) intake was validated. Forty-nine adults and fifty-one adolescents (12-18 years old) completed the FFQ at home, and subsequently kept diet records for seven successive days. Mean daily intake of F&V was overestimated by the FFQ as compared to the 7-day diet records. For adults, spearman correlations of at least 0.5 were observed between the two methods for intake of total fruit and intake of citrus fruit. For adolescents, acceptable spearman correlations (0.53-0.64) were observed between the two methods for total F&V intake, total fruit intake and consumption of fruit juice. Low correlations (0.22-0.35) between the FFQ and the diet records were found for vegetable intake. Relatively large percentages (22-37%) of respondents were incorrectly classified by the short FFQ as eating according to the Dutch recommendations for fruit and vegetable intake. Based on the results of the present study as well as an overview of the results of 34 earlier validation studies of F&V FFQ's, it is concluded that the available FFQ's have only limited capability to make valid assessment of F&V intake levels. In spite of the practical advantages of the short FFQ tested in the present study and the similar validity scores as compared with other often used F&V FFQ's, it needs further revision, especially to be used for valid measurement of vegetable intake as well as total F&V intake among adults.

Comparison of dietary assessment methods in a low-fat dietary intervention program

The food frequency questionnaire (FFQ) is commonly utilized for assessment of dietary fat intake, but its validity among individuals following a low-fat diet is unclear. We evaluated the agreement of nutrient estimates derived from FFQ, 24-h recall, and 3-day food records obtained from 104 participants in a randomized trial of a low-fat dietary intervention for women at elevated breast cancer risk. Comparisons were made for total calories, percent calories from fat, and total fat after 1 yr. Correlation was assessed using standard methods based on a null hypothesis of no agreement between instruments as well as by a methodology based on a null hypothesis that the instruments should be in agreement. With the use of standard methods, FFQ estimates for women on the low-fat diet were significantly correlated to records only for percent calories from fat (r = 0.39), whereas recall and record estimates were significantly correlated for all three dietary variables. Using the new method, we found no significant correlation between FFQ and either recalls or records for women following a low-fat diet but significant correlation between recall and record estimates for total calories (r = 0.67). Traditional correlation testing may overestimate the extent of agreement in dietary instruments among women on a low-fat diet. We found empirical support for the nontraditional method.

Reproducibility and validity of food intake measurements from a semiquantitative food frequency questionnaire

Few food frequency questionnaires have been evaluated for their ability to assess intakes of individual foods that may be related to disease independently of their nutrient content. The reproducibility and validity of food intake measurements by a 131-item semiquantitative food frequency questionnaire were evaluated in a sample of 127 men from the Health Professionals Follow-up Study, a large longitudinal study of diet and disease. Each subject completed two questionnaires 1 year apart and two 1-week diet records 6 months apart during the intervening year. Pearson correlations assessing reproducibility between food intakes from the two questionnaires ranged from .31 for pie to .92 for coffee (mean = .59). Validity was measured by comparing food intakes from the second questionnaire with those from the diet records. Pearson correlations corrected for within-person weekly variation in diet record data ranged from .17 for other nuts to .95 for bananas (mean = .63). Large within-person variation precluded the calculation of accurate validity correlations for 29 foods. As we previously observed in women, the foods most often overreported were fruits and vegetables, and meats and dairy products were most often underreported. With few exceptions, reasonable levels of reproducibility and validity were observed for intake of individual foods in this extensive food frequency questionnaire.

Validity of a short food frequency questionnaire for estimating nutrient intake in elderly people

Nutrient intakes estimated using a short self-administered semi-quantitative food frequency questionnaire (FFQ) were compared with results obtained from five 2 d diet records using household measures in a group of fifty-three elderly people (mean age 70 years) in Dunedin, New Zealand in 1989. Mean intakes for most nutrients were less than 5% different between the two methods. Correlations between the nutrient intake values (excluding supplements) from the diet records and those from the FFQ ranged from 0.34 for Zn in women to more than 0.75 for protein, Zn and Ca in men. For most nutrients, at least 70% of the subjects when classified by the food records fell into the same quintile or into the within-one-quintile category when classified by the FFQ. These data indicate that in elderly subjects a simple self-administered semi-quantitative FFQ can provide very similar information (for both group and individual intakes for many nutrients) to that obtained from 10 d of careful diet recording.