Within- and between-person variations in portion sizes of foods consumed by the Japanese population

Development and validation of a food frequency questionnaire for Japanese athletes (FFQJA)

Background

Food frequency questionnaires are considered an effective method for assessing habitual dietary intake, but they must be developed or validated with the target population. Portion size, supplement use and food choice are thought to be especially important methodological considerations for assessing athletes’ dietary intake. This study aimed to develop and validate a food frequency questionnaire for Japanese athletes using data from this population.

Methods

We used dietary records from 440 Japanese athletes involved in our previous projects. Food items were analyzed using cumulative percentage contributions and multiple regression analysis, to give a selection of 62 basic food items and four supplemental items. The validity of the questionnaire was evaluated among another 77 Japanese athletes by comparing nutrient intakes assessed using the questionnaire with dietary records. Reproducibility was evaluated by comparing a second questionnaire completed 2–3 weeks later by 36 of the athletes in the validation study. Validity was assessed using crude Spearman’s correlation coefficients (CCs), energy-adjusted CCs, intraclass CCs (ICCs), and Kappa index values. Reproducibility was assessed by CCs, energy-adjusted CCs, and ICCs.

Results

In the validation analysis, the median crude CC for all of the nutrients was 0.407, ranging from 0.222 for dietary fiber to 0.550 for carbohydrate. The median energy-adjusted CC was 0.478, and the median ICC was 0.369. When we divided the athletes into quartiles, 65% (vitamin B₁) to 86% (iron) of athletes were classified into the same or adjacent categories using the questionnaire and dietary records, with a median Kappa statistic of 0.32. In the reproducibility analysis, the median crude CC between the two completed questionnaires was 0.654, ranging from 0.582 (carbohydrate) to 0.743 (vitamin B₂). The median energy-adjusted CC was 0.643, and the median ICC was 0.647.

Conclusions

The new 62-item food frequency questionnaire is both reliable and valid and may be useful for assessing food intake in Japanese athletes.

Gender analysis in the development and validation of FFQ: a systematic review

FFQ comprising food items, intake frequency categories and portion sizes have been used in large-scale observational studies to assess long-term dietary exposure. Although gender is an important influence on food choice and portion size, gender differences are not often analysed during FFQ development. This study investigated whether gender differences were considered sufficiently when developing FFQ, which affects the results of validation studies. A PubMed search using combinations of 'FFQ', 'Food Frequency Questionnaire', 'Validation' and 'Validity' identified 246 validation studies available in English, published between January 1983 and May 2014, which included healthy male and female adults. The development process of the 196 FFQ used in the 246 validation studies was examined. Of these, twenty-one FFQ (10·7%) considered gender during item selection or portion size determination, and were therefore classified as gender specific (GS), but 175 (89·3%) did not consider gender, and were classified as 'not gender specific (NGS)'. When the ratios between intake levels obtained using the FFQ and a reference method for energy and seven nutrients were compared between the GS group and the NGS group, more significant differences were observed in women than in men (four v. one nutrient). Intake of three nutrients was significantly underestimated in both sexes in the GS group. In the NGS group, nutrient intakes were significantly overestimated more often in women than in men (four v. one). These results indicate that not considering gender in FFQ development causes greater inaccuracy in dietary intake assessment in women than in men. Results of nutritional epidemiological studies should be re-evaluated for their validity, especially if the studies used NGS-FFQ.

Estimation of food portion sizes frequently consumed by children 3-6 years old in Japan

No study has documented Japanese children's food portion sizes. Since this information is essential to establish valid measurement tools and effective education methods for dietary intake, we measured them using one-day, semi-weighed diet records (DRs) for 489 Japanese children aged 3-6 y. Each food's frequency of appearance on the DRs was counted. If a child consumed a certain food more than once per day, an average weight for that food was calculated and used in the portion size calculation as that child's representative value. In total, 67 food items were consumed by twenty or more children. We calculated the mean, standard deviation, median, minimum, and maximum portion size values for these food items. In addition to these 67 items, Chinese noodles and water were included in the analysis. The most frequently consumed food was well-milled rice (mean portion size for rice=79 g), which was consumed by 350 children, followed by soy sauce (4 g), eggs (26 g), and carrots (9 g). Among the five most frequently consumed foods, portion sizes of rice and pork but not milk, eggs, or carrots significantly increased with age, height, and weight. In multivariate linear regression analysis, however, the significant relationships between rice portion size and age were not observed. Regarding pork, only the relationship with height was significant. A sex difference was detected in the rice and milk portion sizes. Most of portion sizes observed here were apparently smaller than those reported among United Kingdom children. This study provides important basic information for the implementation of quantitative nutritional research and educational efforts for Japanese preschool children.

Uncertainty in intake due to portion size estimation in 24-hour recalls varies between food groups

Portion size estimation is expected to be one of the largest sources of uncertainty in dietary assessment of the individual. Therefore, we demonstrated a method to quantify uncertainty due to portion size estimation in the usual intake distributions of vegetables, fruit, bread, protein, and potassium. Dutch participants of the European Food Consumption Validation study completed 2 nonconsecutive 24-h recall interviews. In short, the uncertainty analysis consists of Monte Carlo simulations drawing values for portion size from lognormal uncertainty distributions. The uncertainty of the usual intake distribution and accompanying parameters (IQR and the shrinkage factor) were estimated. For the food groups, portion size uncertainty had the greatest effect for vegetables and the least for fruit: the relative 95% uncertainty interval (UI) of the IQR of the usual intake distribution was 0.61-1.35 for vegetables, 0.77-1.24 for bread, and 0.99-1.10 for fruit. For protein and potassium, the resulting relative width of the UI of the IQR for portion size uncertainty are similar: 0.88-1.14 for protein and 0.86-1.14 for potassium. Furthermore, a sensitivity analysis illustrated the importance of the specified uncertainty distributions. The examples show that uncertainty in portion sizes may be more important for some foods such as vegetables. This may reflect differential quantification errors by food groups that deserve further consideration. In conclusion, the presented methodology allows the important quantification of portion size uncertainty and extensions to include other sources of uncertainty is straightforward.

Meta-Analysis of Soy Intake and Breast Cancer Risk

BACKGROUND

High intake of soy foods has been proposed to contribute to the low breast cancer risk in Asian countries. However, results of epidemiologic studies of this association are highly variable, and experimental data suggest that soy constituents can be estrogenic and potentially risk enhancing. Thus, rigorous evaluation of available epidemiologic data is necessary before appropriate recommendations can be made, especially for women at high risk of breast cancer or those who have survived the disease.

METHODS

We performed a meta-analysis of 18 epidemiologic studies (12 case-control and six cohort or nested case-control) published from 1978 through 2004 that examined soy exposure and breast cancer risk. Pooled relative risk estimates were based on either the original soy exposure measure defined in each study or on an estimate of daily soy protein intake.

RESULTS

Risk estimates, levels and measures of soy exposure, and control for confounding factors varied considerably across studies. In a pooled analysis, among all women, high soy intake was modestly associated with reduced breast cancer risk (odds ratio [OR] = 0.86, 95% confidence interval [CI] = 0.75 to 0.99); the association was not statistically significant among women in Asian countries (OR = 0.89, 95% CI = 0.71 to 1.12). Among the 10 studies that stratified by menopausal status the inverse association between soy exposure and breast cancer risk was somewhat stronger in premenopausal women (OR = 0.70, 95% CI = 0.58 to 0.85) than in postmenopausal women (OR = 0.77, 95% CI = 0.60 to 0.98); however, eight studies did not provide menopause-specific results, six of which did not support an association. When exposure was analyzed by soy protein intake in grams per day, a statistically significant association with breast cancer risk was seen only among premenopausal women (OR = 0.94, 95% CI = 0.92 to 0.97).

CONCLUSIONS

Soy intake may be associated with a small reduction in breast cancer risk. However, this result should be interpreted with caution due to potential exposure misclassification, confounding, and lack of a dose response. Given these caveats and results of some experimental studies that suggest adverse effects from soy constituents, recommendations for high-dose isoflavone supplementation to prevent breast cancer or prevent its recurrence are premature.

Dietary intakes of fat and fatty acids and risk of breast cancer: a prospective study in Japan

To examine the possible association of dietary fat and fatty acids with breast cancer risk in a population with a low total fat intake and a high consumption of fish, we analyzed data from the Japan Collaborative Cohort (JACC) Study. From 1988 to 1990, 26 291 women aged 40-79 years completed a questionnaire on dietary and other factors. Intakes of fat or fatty acids were estimated by using a food frequency questionnaire. Rate ratios (RR) were computed by fitting proportional hazards models. During the mean follow-up of 7.6 years, 129 breast cancer cases were documented. We found no clear association of total fat intake with breast cancer risk; the multivariate-adjusted RR across quartiles were 1.00, 1.29, 0.95, and 0.80 (95% confidence interval [CI] 0.46-1.38). A significant decrease in the risk was detected for the highest quartile of intake compared with the lowest for fish fat and long-chain n-3 fatty acids; the RR were 0.56 (95% CI 0.33-0.94) and 0.50 (0.30-0.85), respectively. A decreasing trend in risk was also suggested with an increasing intake of saturated fatty acids (trend P = 0.066). Among postmenopausal women at baseline, the highest quartile of vegetable fat intake was associated with a 2.08-fold increase in risk (95% CI 1.05-4.13). This prospective study did not support any increase in the risk of breast cancer associated with total or saturated fat intake, but it suggested the protective effects of the long-chain n-3 fatty acids that are abundant in fish.

Influence of individually estimated portion size on the assessment of nutritional risk in colorectal cancer in Portugal

We evaluated the influence of individually estimated portion sizes on the estimate of nutrient related risk of colorectal cancer, using data from a Portuguese hospital based case-control study on diet and colorectal cancer. A total of 100 patients with colorectal adenocarcinoma (aged 15-92 years) and 211 controls (aged 36-89 years) were included. Two data sets were created for nutrient analysis, the first one allowed estimates of food intake using data on portion size as collected with visual aids during the interview. The second estimate substituted respondents' estimate with a standard portion size, as used in the semi-quantitative (SQ) food frequency approach. The two analytic approaches yielded similar energy and nutrient intakes in cases and controls. The percent range of concordance is acceptable, in the same quartile varying from 44 to 82% (mean: 56%) and very good in the same or adjacent (+/-1) quartile (mean: 91%, range: 85-97%). The two estimates lead to a similar pattern of multivariate odd's ratio, however the SQ estimates resulted in more significant findings. We conclude that little extra information is gained by including individual portion size information when assessing diet-related risk of colorectal cancer.

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.