Validity of a food frequency questionnaire for estimating calcium intake among Japanese and white women

Dietary Vitamin D Intake in Italian Subjects: Validation of a Frequency Food Questionnaire (FFQ)

Vitamin D plays a crucial role in calcium and phosphate metabolism, relating to bone health and preventing metabolic bone disorders such as rickets and osteomalacia. Vitamin D deficiency (serum 25-OH-D values <20 ng/mL or 50 nmol/L) is common also in Italian people; it is recommended to maintain levels above 30 ng/mL (75 nmol/L) in categories at risk. Supplementation and/or fortification with either ergocalciferol (vitamin D2) or cholecalciferol (vitamin D3) aimed to modify this condition have commonly been proposed. Studies about vitamin D intake are numerous in the literature but not adequately designed and are very often incomplete in Mediterranean Countries such as in the Italian population. On these bases, we performed a survey to validate a frequency food questionnaire (FFQ) specifically created to rapidly assess dietary vitamin D intake in Italian people. For this aim, the data of questionnaires were compared with results derived in the same population from a designed 14-day frequency food diary (FFD). Overall, a good correlation between FFQ and FFD was observed (r = 0.89, p < 0.001), both demonstrating a remarkably low vitamin D intake, irrespective of age and gender. Our data confirm that the vitamin D intake is very low in Italy, which likely contributes to hypovitaminosis D.

Relative validation of a short food frequency questionnaire to assess calcium intake in older adults

OBJECTIVE

To develop and validate a food frequency questionnaire (FFQ) for estimating calcium intake in community-dwelling older adults using a food record as the reference method.

METHOD

A validation study involving 102 subjects (67 females) aged > or =65 years and residing independently in Adelaide, Australia, between 2002-06 was performed. Estimates of calcium intake over the last year were calculated from two versions (35 and 15 items) of the FFQ and compared with average intake from four days of non-consecutive food records (4DFR).

RESULTS

Mean calcium intake from the 4DFR was 987 mg/day (95% CI 922-1051). The 35 and 15-item questionnaires gave mean intakes of 992 mg/day (95% CI 913-1,071) and 1017 mg/day (95% CI 927-1,106) respectively. Mean difference (95% limits of agreement) between the food record and the 35 and 15-item questionnaires was 5 mg (-739-729) and 28 mg (-936-879) respectively. The 15-item questionnaire demonstrated 82% sensitivity for classifying subjects with calcium intake below the estimated average requirement (EAR, 840 mg for males 51-70 years; 1,100 mg for females >51 years and males >70 years of age) and 46% specificity for classifying subjects with intake above the EAR.

CONCLUSION

The FFQ evaluated as part of this study is one of very few that has been tested across both genders and in older adults specifically. The 15-item version has demonstrated a level of sensitivity and specificity comparable with other FFQs for evaluating calcium intake.

IMPLICATIONS

The 15-item FFQ can be confidently used for measuring group mean calcium intake in older Australians or as a screening tool to allow health professionals to identify those who are most at risk of inadequate dietary calcium intake.

Validation of three food frequency questionnaires to assess dietary calcium intake in adults

OBJECTIVE

To assess the accuracy of three self-administered food frequency questionnaires (FFQs) to measure dietary calcium intake in healthy adults.

DESIGN

Estimates of dietary calcium intake from one previously validated and two recently developed FFQs were compared with those from 7-day food records.

SUBJECTS/SETTING

Healthy adults enrolled in an outpatient study of calcium supplementation completed the 36-page Dietary History Questionnaire (DHQ), a 3-page Calcium Questionnaire, and a 1-page Short Calcium Questionnaire. Subjects then completed a 7-day food record.

MAIN OUTCOME MEASURES

Differences between calcium intake reported on FFQs and calcium intake from food records were compared.

STATISTICAL ANALYSES

Spearman correlations were used to measure associations among variables; Bland-Altman pairwise comparisons were conducted to assess systematic and magnitude biases.

RESULTS

We studied 341 subjects, 74.5% female, mean (+/-standard deviation) age of 38+/-11 years and body mass index (calculated as kg/m(2)) of 31.8+/-7.1. Mean (+/-standard deviation) food record calcium intake was 896+/-380 mg/day; data from all three FFQs were positively related to food record calcium intake, but accounted for <40% of the variance in food record dietary calcium intake (DHQ: r(2)=0.21; Calcium Questionnaire: r(2)=0.33; Short Calcium Questionnaire: r(2)=0.37; all P<0.001). The DHQ underestimated daily calcium intake (systematic bias: -94 mg/day, P<0.001; magnitude bias r=-0.40; P<0.001), whereas the Calcium Questionnaire overestimated calcium intake (systematic bias +177 mg/day, P<0.001), but had no significant magnitude bias (r=-0.09; P=0.11). The Short Calcium Questionnaire showed minimal systematic bias (+34 mg/day, P=0.09), but had magnitude bias (r=-0.33; P<0.001).

CONCLUSIONS

All three FFQs performed reasonably well at estimating dietary calcium intake compared to food records; each may be appropriate for use in select clinical and research settings.

Differences in the quantitative and qualitative performance of a calcium-specific food frequency questionnaire across age and sex

OBJECTIVE

To examine putative differences in the quantitative and qualitative performance of a food frequency questionnaire (FFQ) for assessing dietary calcium intake across age and sex in the Greek population.

MATERIALS AND METHODS

A total of 351 children (189 girls and 162 boys, aged 11.9 +/- 1.2 years), 260 adults (192 women and 68 men, aged 29.6 +/- 2.7 years) and 390 elderly individuals (317 women and 73 men, aged 68.6 +/- 4.6 years) were recruited. Estimates of calcium intake from the 30-item FFQ were compared with those from a multi-pass 24-h recall.

RESULTS

The FFQ significantly underestimated mean calcium intake in all age groups and both sexes (P < 0.05). The magnitude of underestimation, however, was greater in adults (-207 +/- 344 mg day(-1)), less in the elderly (-137 +/- 310 mg day(-1)) and even less in children (-74 +/- 340 mg day(-1); P < 0.025), with no differences between sexes. Calcium intakes by the two methods were positively and significantly correlated in all study groups (r = 0.536-0.739, P < 0.001). Cohen's weighted kappa statistic ranged from 0.39 to 0.57, indicating moderate agreement between the two methods. The 95% limits of agreement were comparably wide across age and sex (boys: -762, 585 mg day(-1); girls: -747, 624 mg day(-1); adult men: -972, 505 mg day(-1); adult women: -867, 412 mg day(-1); elderly men: -858, 486 mg day(-1); elderly women: -732, 480 mg day(-1)). A significant association between age, sex and the classification of individuals as true/false positive/negative was detected (P < 0.001), implying that sensitivity, specificity, positive and negative predictive values of the FFQ were not independent of the age and sex of the participants. Gross misclassification by the FFQ ranged from 0% to 4.2%, whereas 75.3-87.3% of the subjects were correctly classified. In this respect, the FFQ performed similarly across the study groups (P = 0.065). Without controlling for age, however, gross misclassification appeared to be higher in females than in males (3.2% versus 0.7%, respectively, P = 0.048).

CONCLUSIONS

There may be several significant differences in the quantitative and qualitative performance of a calcium-specific FFQ across age and sex. This should be taken into account when attempting to evaluate dietary calcium intake in men and women or in different age groups, as some of the differences between study groups may actually be due to the different response of these groups to the FFQ.

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.

Development and validation of a food frequency questionnaire for assessing dietary calcium intake in the general population

The aim of this study was to develop and evaluate a food frequency questionnaire (FFQ) for assessing dietary calcium intake in the general population, since all available questionnaires at present are age- and/or gender-specific. A total of 1001 individuals (including children, adults, and elderly people of both genders) were randomly recruited throughout Greece. Estimates of calcium intake from the 30-item FFQ were compared with those from a multi-pass 24-h recall. The FFQ underestimated mean calcium intake compared to the 24-h recall by (mean+/-SD) -133+/-333 mg/day or -5.4+/-47.6% (P<0.001). The two methods were strongly correlated (r=0.639, P<0.001), but the 95% limits of agreement for individual assessment were rather wide, as the FFQ could provide estimates of calcium intake from 533 mg/day above to 799 mg/day below the 24-h recall. Actual values for surrogate FFQ quartiles manifested a progressive increase, with significant differences between mean calcium intakes (P<0.001). The FFQ could identify individuals who consumed less calcium than 800 mg/day or less than the age-specific adequate intake with a relatively high sensitivity (82.8 and 95.5%, respectively), but low specificity (54.9 and 34.1%, respectively). Cross-classification analysis indicated that only 17 subjects (1.7%) were grossly misclassified (lowest quartile for one method and highest quartile for the other), while 827 subjects (82.6%) were correctly classified (into the same or adjacent quartiles). The FFQ could be used in population-based epidemiological studies or screening programs involving individuals of all ages and both genders, where the discrimination of subjects with relatively low (<500 mg/day) and relatively high (>1000 mg/day) calcium intakes is of primary interest. Results, however, do not support its use for the quantitative assessment of individual calcium intakes.

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.

Development, validation and utilisation of food-frequency questionnaires - a review

OBJECTIVE

The purpose of this review is to provide guidance on the development, validation and use of food-frequency questionnaires (FFQs) for different study designs. It does not include any recommendations about the most appropriate method for dietary assessment (e.g. food-frequency questionnaire versus weighed record).

METHODS

A comprehensive search of electronic databases was carried out for publications from 1980 to 1999. Findings from the review were then commented upon and added to by a group of international experts.

RESULTS

Recommendations have been developed to aid in the design, validation and use of FFQs. Specific details of each of these areas are discussed in the text.

CONCLUSIONS

FFQs are being used in a variety of ways and different study designs. There is no gold standard for directly assessing the validity of FFQs. Nevertheless, the outcome of this review should help those wishing to develop or adapt an FFQ to validate it for its intended use.

Validation of a food frequency questionnaire for nutritional calcium intake assessment in Italian women

OBJECTIVE

To evaluate a food frequency questionnaire assessing calcium intake in women.

DESIGN

: Estimates of calcium intake from the food frequency questionnaire were compared with those from 14 day records from 206 Caucasian women aged 25-75 y in Siena, Italy.

SUBJECTS

Subjects were randomly recruited from the residents list of the city of Siena, Italy. Of the 250 initially recruited, 39 did not meet the inclusion criteria or failed to complete the diet record and five outliers were excluded before the statistical analysis on the basis that their diet record was unlikely to represent habitual intake.

RESULTS

Mean dietary calcium intakes were 829+/-255 (s.d.) mg/day from the questionnaire and 818+/-260 (s.d.) mg/day from the diet record. The mean difference in intake by the two methods (-11.3+/-116.4 mg/day) did not differ significantly from zero. Specificity in classifying women consuming less than 800 mg/day calcium was 86.6%, and sensibility in classifying women consuming more than 800 mg/day calcium was 89.4%.

CONCLUSIONS

The food frequency questionnaire could be used in epidemiological studies to assess calcium intake in young to elderly women. The specificity in identifying low calcium intake subjects makes it useful also as an educational tool in diet counselling and for prescribing calcium supplementation.

Calcium intake and bone mass development among Israeli adolescent girls

OBJECTIVE

To determine the possible relationship between food and life style habits and bone health in adolescent Israeli females.

METHODS

2,000 adolescent Israeli Jewish and Arab high-school girls (mean age 14.5) completed a semi-quantitative food frequency questionnaire and a personal history questionnaire. 27 food components were calculated for each subject. Bone mineral content and density were determined for 112 subjects with calcium intake below 800 mg/day.

RESULTS

Average calcium intake was found to be 1,260 mg/day, but 20% of all girls had a calcium intake below 800 mg/day. All low-energy diets were very low in calcium, as mean calcium intake per 1,000 calories was 411 128 grams. A large percentage of diets with less than 800 mg calcium were also deficient in phosphorus (95.2%), magnesium (84.8%). iron (90.5%) and zinc (100%). Due to differences in food sources. Jewish girls had more phosphorus in their diet, but less magnesium and iron compared to Arab girls. Calcium and zinc deficiencies in Jewish and Arab diets were similar. A negative correlation was found between body mass index (BMI) and age at menarche for all girls in the study. Bone mineral density (BMD) measured for girls with calcium intake below 800 mg/day distributed normally around the average when compared to age matched controls despite their low calcium intake. There was a strong positive correlation between BMD and bone mineral content (BMC) at all sites and body weights.

CONCLUSIONS

Low calcium intake, other nutritional deficiencies and delayed menarche due to low-energy diet in the growing period and in adolescence may prevent the formation of healthy bones. There is no evidence of lower bone mass among the low calcium intake group in the study population at this stage. It remains to be documented if the window of opportunity for optimal bone accretion for this group will be missed in the future. possibly leading to increased risk of osteoporosis.

Dieting behavior of Asian college women attending a US university

Dieting behavior, body dissatisfaction, self-esteem, and food intake of 73 Asian women attending a US university were investigated and compared retrospectively with attitudes of 247 US-born female students at the same university. The Asian women reported restrained eating and body dissatisfaction only about half as often as the US women did. In both the Asian and US college women, body dissatisfaction scores were significantly correlated to body mass index and self-esteem scores. Fourteen percent of the Asian women in the restrained eating/body dissatisfied group, and 40% of the US students in that group reported intentional vomiting for weight control. Some of the Asian international students practiced undesirable dieting behaviors and reported body dissatisfaction levels similar to those of many US college women. College health professionals should recognize that disordered eating among Asian women must not be overlooked because of stereotypical perceptions about Asian women's body size and type.