Differences in reported food frequency by season of questionnaire administration: the 1987 National Health Interview Survey

The utility of household Grocery Purchase Quality Index scores as an individual diet quality metric

The Grocery Purchase Quality Index (GPQI) reflects concordance between household grocery purchases and US dietary recommendations. However, it is unclear whether GPQI scores calculated from partial purchasing records reflect individual-level diet quality. This secondary analysis of a 9-month randomised controlled trial examined concordance between the GPQI (range 0-75, scaled to 100) calculated from 3 months of loyalty-card linked partial (≥50 %) household grocery purchasing data and individual-level Healthy Eating Index (HEI) scores at baseline and 3 months calculated from FFQ (n 209). Concordance was assessed with overall and demographic-stratified partially adjusted correlations; covariate-adjusted percentage score differences, cross-classification and weighted κ coefficients assessed concordance across GPQI tertiles (T). Participants were middle aged (55·4 (13·9) years), female (90·3 %), from non-smoking households (96·4 %) and without children (70·7 %). Mean GPQI (54·8 (9·1) %) scores were lower than HEI scores (baseline: 73·2 (9·1) %, 3 months: 72·4 (9·4) %) and moderately correlated (baseline r 0·41 v. 3 months r 0·31, P < 0·001). Correlations were stronger among participants with ≤ bachelor's degree, obesity and children. Scores showed moderate agreement (κ = 0·25); concordance was highest in T3. Participants with high (T3) v. low (T1) GPQI scores had 7·3-10·6 higher odds of having HEI scores >80 % at both time points. Household-level GPQI was moderately correlated with self-reported intake, indicating their promise for evaluating diet quality. Partial purchasing data appear to moderately reflect individual diet quality and may be useful in interventions monitoring changes in diet quality.

Exploring Pathways of Socioeconomic Inequity in Vegetable Expenditure Among Consumers Participating in a Grocery Loyalty Program in Quebec, Canada, 2015-2017

Vegetable consumption remains consistently low despite supportive policy and investments across the world. Vegetables are available in great variety, ranging in their processing level, availability, cost, and arguably, nutritional value. A retrospective longitudinal study was conducted in Quebec, Canada to explore pathways of socioeconomic inequity in vegetable expenditure. Data was obtained for consumers who participated in a grocery loyalty program from 2015 to 2017 and linked to the 2016 Canadian census. Vegetable expenditure share (%) was examined as a fraction of the overall food basket and segmented by processing level. Panel random effects and tobit models were used overall and to estimate the stratified analysis by median income split. Consumers allocated 8.35% of their total food expenditure to vegetables, which was mostly allocated to non-processed fresh (6.88%). Vegetable expenditure share was the highest in early winter and lowest in late summer. In the stratified analysis, the low-income group exhibited less seasonal variation, allocated less to fresh vegetables, and spent more on canned and frozen compared to the high-income group. Measures of socioeconomic status were all significant drivers of overall vegetable consumption. Consumers with high post-secondary education in the low-income group spent 2% more on vegetables than those with low education. The complexity of observed expenditure patterns points to a need for more specific vegetable consumption guidelines that include provisions by processing level. Implications for education, marketing, intersectional policies, and the role of government are discussed. Governments can scale present efforts and catalyze health-promoting investments across local, state, national, and global food systems.

Relative Validity and Reproducibility of a Short FoodFrequency Questionnaire to Assess Nutrient Intakesof New Zealand Adults

There is no recent validated short food frequency questionnaire (FFQ) for use in NewZealand (NZ) adults. This study aimed to evaluate the relative validity and reproducibility of a shortFFQ in free-living NZ adults aged 30-59 years. A 57-item, semi-quantitative FFQ was developedand pre-tested. During a 12-month study period the FFQ was administrated twice with a 9-monthinterval between administrations. Four two-day diet records were collected at months 0, 3, 6, and 9and a blood sample was taken at month 9. Spearman correlations were used to evaluate the validityof the FFQ with the eight-day diet records and selected biomarkers. Cross-classification analysisand the Bland-Altman method were used to assess the agreement between the FFQ and the dietrecord. Reproducibility over nine months was assessed using intra-class correlations. A total of 132males and females completed both FFQs, the eight-day diet record, and provided a blood sample.The highest energy-adjusted correlation coefficients were observed for alcohol (0.81), cholesterol(0.61), and carbohydrate (0.61), with the lowest for sodium (0.29), thiamin (0.33), and niacinequivalents (0.34). More than three quarters of the participants were correctly classified into thesame or adjacent quartile for most nutrients, with a low proportion of participants being grosslymisclassified (< 10%). For most nutrients, the limits of agreement from the Bland-Altman analyseswere between 50% and 250%. A positive correlation was observed between dietary intakes andplasma biomarkers for all selected nutrients. The FFQ showed moderate to good reproducibility,with almost all reliability coefficients ranging from 0.60 to 0.80. This short FFQ was shown to validlyand reliably rank individuals by their habitual intake of most major nutrients, indicating that theFFQ will offer a time-efficient way to assess the nutrient intake of NZ adults in future research.

Does Season of Reported Dietary Intake Influence Diet Quality? Analysis From the Women's Health Initiative

We evaluated the role of seasonality in self-reported diet quality among postmenopausal women participating in the Women's Health Initiative (WHI). A total of 156,911 women completed a food frequency questionnaire (FFQ) at enrollment (1993-1998). FFQ responses reflected intake over the prior 3-month period, and seasons were defined as spring (March-May), summer (June-August), fall (September-November), and winter (December-February). FFQ data were used to calculate the Alternate Healthy Eating Index (AHEI), a measure of diet quality that has a score range of 2.5-87.5, with higher scores representing better diet quality. In multivariable linear regression models using winter as the reference season, AHEI scores were higher in spring, summer, and fall (all P values < 0.05); although significant, the variance was minimal (mean AHEI score: winter, 41.7 (standard deviation, 11.3); summer, 42.2 (standard deviation, 11.3)). Applying these findings to hypothesis-driven association analysis of diet quality and its relationship with chronic disease risk (cardiovascular disease) showed that controlling for season had no effect on the estimated hazard ratios. Although significant differences in diet quality across seasons can be detected in this population of US postmenopausal women, these differences are not substantial enough to warrant consideration in association studies of diet quality.

Development and Relative Validity of a Food Frequency Questionnaire to Assess Intakes of Total and Free Sugars in Australian Toddlers

Background: Dental research into early childhood caries is hindered by a lack of suitable dietary assessment tools that have been developed and validated for the population and outcomes of interest. The aim of this study was to develop and investigate the relative validity and reproducibility of the Study of Mothers’ and Infants’ Life Events Food Frequency Questionnaire (SMILE-FFQ), to assess the total and free sugars intakes of Australian toddlers. Methods: The SMILE-FFQ was designed to capture the leading dietary contributors to dental caries risk in toddlers aged 18–30 months via a proxy report. Ninety-five parents of Australian toddlers completed the questionnaire online before and after providing three 24-h recalls (24HR), collected on non-consecutive days using the multipass method. Total and free sugars were compared between the two SMILE-FFQ administrations and between each SMILE-FFQ and the 24HR using multiple statistical tests and standardised validity criteria. Correlation (Pearson), mean difference (Wilcoxon rank test) and Bland Altman analyses were conducted to compare absolute values, with cross-classification (Chi-Square and Weighted Kappa) used to compare agreement across tertiles. Results: All reproducibility tests showed good agreement except weighted kappa, which showed acceptable agreement. Relative validity tests revealed a mix of good and acceptable agreement, with total sugars performing better at the individual level than free sugars. Compared to the 24HR, the SMILE-FFQ tended to underestimate absolute values at lower levels and overestimate them at higher levels. Conclusions: The combined findings of the various tests indicate that the SMILE-FFQ performs comparably to the 24HR for assessing both total and free sugars among individuals, is most effective for ranking participants rather than determining absolute intakes, and is therefore suitable for use in observational studies of Australian toddlers.

Measures of Diet Quality across Calendar and Winter Holiday Seasons among Midlife Women: A 1-Year Longitudinal Study Using the Automated Self-Administered 24-Hour Recall

BACKGROUND

Systematic seasonal bias may confound efforts to estimate usual dietary intake and diet quality. Little is known about dietary quality over the winter holiday season.

OBJECTIVES

The aims of this study were to test for differences in intakes of energy, percentage of energy from macronutrients, fruits and vegetables, and diet quality measured using the Healthy Eating Index 2010 (HEI-2010) by calendar and winter holiday seasons.

DESIGN

Longitudinal cohort design.

PARTICIPANTS/SETTING

Data were derived from the Life in All Seasons study. Two cohorts of women aged 40 to 60 years (N=52) from the greater Grand Forks, ND, area were followed for 1 year each between July 2012 and July 2014. Each woman completed an online diet recall using the Automated Self-Administered 24-Hour Recall every 10 days during the year, with a 92% response rate.

STATISTICAL ANALYSES

Effects of calendar and winter holiday seasons on intakes of energy, percent energy from macronutrients, HEI-2010 total and component scores, and grams per day of individual fruits and vegetables were tested using mixed linear models.

RESULTS

The mean total HEI-2010 score was 60.1±1.4. There were seasonal differences in some HEI-2010 component scores, but not in total scores. More lettuce or mixed lettuce salad was consumed during summer than during winter (P=0.034), and more fresh tomatoes were consumed during summer and fall compared with winter (P=0.001). More corn, berries, peaches and nectarines, and melons (P<0.001) were consumed during summer. There was no seasonal difference in reported intakes of energy (P=0.793). The total HEI-2010 score for dietary intake observed over the winter holiday season was lower than the rest of the year (P<0.001). Reported energy intake was not different (P=0.228).

CONCLUSIONS

In this population, diet quality is significantly lower during the winter holiday period, but mostly consistent by season. Multiple recalls in any season can give a reasonable representation of usual overall diet quality throughout the year.

Foods advertised in US weekly supermarket sales circulars over one year: a content analysis

BACKGROUND

The nutritional content of Americans' shopping carts is suboptimal despite federal dietary guidance, in this case, the MyPlate consumer icon which displays desired proportions of vegetables, fruits, dairy, grains and protein foods for consumption. Consumers mention print advertising-such as weekly sales circulars-frequently as influencing their grocery shopping decisions.

METHODS

To examine and describe the relative proportions of advertised foods aggregated into the MyPlate food grouping system, a content analysis of 9 209 foods advertised in 52 weekly supermarket newspaper sales inserts in 2009 from a local grocery chain was conducted in a Midwestern community.

RESULTS

Overall, the protein foods group was most often represented in sales circulars (25% of total items), followed by grains (18%); dairy (10%); vegetables (8%) and fruits (7%). Less than 3% of sales advertisements were for dark green and red & orange vegetables. Over twice as much whole fruit versus 100% fruit juice was advertised (70% vs. 30%, respectively; P < 0.001). Significantly fewer protein foods and more grains than expected were advertised in the fall, and slightly more dark green vegetables were advertised in winter and spring than in summer and fall (P = 0.05).

CONCLUSIONS

The average American diet, including underconsumption of fruits and vegetables but overconsumption of protein foods, was reflected in the relative frequency of food groups advertised in weekly sales circulars. Modifying sales circulars to represent healthier food groups may preserve retail profits (considering these groups' higher profit margin) while promoting adherence to federal dietary guidance.

The influence of chronological period of data collection on differences in reported dietary intake among school-aged children surveyed in 39 countries

OBJECTIVE

To examine whether dietary intake reported by school-aged children relates to the chronological period of data collection.

DESIGN

Cross-sectional surveys in 39 countries in different monthly periods of the 2009-2010 school year.

SETTINGS

Questionnaires were completed in schools anonymously.

PARTICIPANTS

Children from 39 countries, aged 11, 13, and 15 years (n = 209,320).

MAIN OUTCOME MEASURES

Daily consumption of fruits, vegetables, sweets, and soft drinks, derived from a food frequency questionnaire.

ANALYSIS

Multivariate logistic regression (applied for 3 countries); 2-level random intercept logistic regression (applied for 36 countries).

RESULTS

Monthly variations in food intake among students from Canada, England, and Norway, where data collection took place almost all months of the school year, revealed significantly lower daily consumption of food items in January to February. A 2-level random intercept logistic regression model for 36 countries, where questionnaires were administered in relatively shorter periods, indicated the lowest likelihood of fruit and soft drink consumption when the data were collected in March to April (β = -0.30; P = .006, compared with October to December) and in January to February (β = -0.65; P = .018, compared with May to June), respectively.

CONCLUSIONS AND IMPLICATIONS

The chronological period of data collection must be considered when comparing children's reported food consumption, but this effect is small relative to cross-national variations in dietary patterns.

Effect of seasonality on the estimated mean value of nutrients and ranking ability of a self-administered diet history questionnaire

BACKGROUND

We examined the effect of seasonality on the validity (ability to estimate the mean intake of a group and ranking ability) of nutrient intakes estimated with a comprehensive self-administered diet history questionnaire (DHQ) developed for the assessment of Japanese diets during the preceding one month, using semi-weighed dietary records (DRs) as a reference method.

METHODS

This study was conducted in three areas in Japan (Osaka, Nagano, and Tottori). The study population included 92 Japanese men aged 32-76 years and 92 Japanese women aged 31-69 years (30 from Osaka, 31 from Nagano, and 31 from Tottori for each sex). A DHQ and a four-day DR were completed four times at 3-month intervals, once per season. The effect of seasonality was examined by the level of agreement among seasons using mean nutrient intake and correlation coefficients.

RESULTS

Significant differences in estimated energy-adjusted intakes of 42 selected nutrients between the average of DRs administered 16 times throughout a year and that of the DHQ administered four times in each season (fall, winter, spring, and summer) were observed for 30, 29, 30, and 31 nutrients for men and 21, 28, 30, and 31 nutrients for women, respectively. Pearson correlation coefficients between the DRs and the DHQs for energy-adjusted intakes of the 42 nutrients showed significant inter-season differences in 11 nutrients for men and 13 nutrients for women. Particularly, correlation coefficients of fat, monounsaturated fat, polyunsaturated fat, n-6 polyunsaturated fat, α-linolenic acid, and cholesterol in spring and cryptoxanthin in summer for men, and fat, saturated fat, and monounsaturated fat in spring and summer and thiamin and iron in summer for women were markedly altered by seasonality.

CONCLUSIONS

Mean nutrient intake estimated by the DHQ varied by season, indicating that any consideration of nutrient intake estimated by the DHQ as a yearly average intake may be problematic. In contrast, the effect of seasonality on the ranking ability of the DHQ was relatively small, and thus the use of a DHQ to rank individuals by nutrient intake is acceptable for epidemiological studies, regardless of season.

Variação sazonal na ingestão alimentar de adultos de Niterói, Rio de Janeiro

A aferição da ingestão alimentar (IA) usual é necessária para estabelecer, com acurácia, a relação entre a dieta e o aparecimento de doenças. Na maioria dos estudos, os dados de IA usual são coletados referentes ao período de um ano, sem considerar a estação do ano em que o estudo ocorre. O objetivo do presente estudo foi verificar o efeito da sazonalidade na IA de adultos de Niterói, RJ. Um total de 102 sujeitos (69 mulheres) saudáveis, com idade entre 20 e 69 anos, responderam a seis recordatórios dietéticos de 24 horas, três no verão e três no inverno. Em ambas as estações do ano, foi determinada a ingestão energética (IE) e de 23 nutrientes, além do percentual de indivíduos que alcançavam as recomendações dos mesmos. Os dados finais foram deatenuados pela variabilidade intraindividual e ajustados pela energia. A IE e de alguns nutrientes foram significativamente diferentes entre os homens e as mulheres. A IE não se diferenciou entre as estações, para ambos os sexos, porém a ingestão de proteínas, fibras, magnésio, tiamina, piridoxina e niacina foi diferente entre as estações para ambos os sexos. Os resultados do presente estudo sugerem que a sazonalidade seja considerada na aferição da IA, servindo de base para a adequação dos métodos e instrumentos utilizados nos inquéritos dietéticos populacionais.

Using exploratory factor analysis of FFQ data to identify dietary patterns among Yup'ik people

OBJECTIVE

An FFQ developed by the Center for Alaska Native Health Research for studies in Yup'ik people includes market foods and subsistence foods such as moose, seal, waterfowl and salmon that may be related to disease risk. Because the FFQ contains >100 food items, we sought to characterize dietary patterns more simply for use in ongoing pharmacogenomics studies.

DESIGN

Exploratory factor analysis was used to derive a small number of 'factors' that explain a substantial amount of the variation in the Yup'ik diet. We estimated factor scores and measured associations with demographic characteristics and biomarkers.

SETTING

South-west Alaska, USA.

SUBJECTS

Yup'ik people (n 358) aged ≥18 years.

RESULTS

We identified three factors that each accounted for ≥10 % of the common variance: the first characterized by 'processed foods' (e.g. salty snacks, sweetened cereals); the second by 'fruits and vegetables' (e.g. fresh citrus, potato salad); and the third by 'subsistence foods' (seal or walrus soup, non-oily fish). Participants from coastal communities had higher values for the 'subsistence' factor, whereas participants from inland communities had higher values for the 'fruits and vegetables' factor. A biomarker of marine intake, δ 15N, was correlated with the 'subsistence' factor, whereas a biomarker of corn- and sugarcane-based market food intake, δ 13C, was correlated with 'processed foods'.

CONCLUSIONS

The exploratory factor analysis identified three factors that appeared to reflect dietary patterns among Yup'ik based on associations with participant characteristics and biomarkers. These factors will be useful for chronic disease studies in this population.

Comparability and repeatability of methods for estimating the dietary intake of the heterocyclic amine contaminant 2-amino-1-methyl-6-phenylimidazo[4,5b]pyridine (PhIP)

Inconsistent risk estimates for dietary heterocyclic amine (HCA) exposure and cancers may be due to differences in exposure assessment methods and the associated measurement error. We evaluated repeatability and comparability of intake estimates of the HCA 2-amino-1-methyl-6-phenylimidazo[4,5b]pyridine (PhIP) among two food frequency questionnaire (FFQ) collections, three diary collections, and three measurements of urinary PhIP and its metabolites in 36 non-smokers in Baltimore, Maryland, during 2004-2005. Collections spanned ∼9 months. Method repeatability was characterised with intraclass correlation coefficients (ICCs). Comparability among methods was assessed with Spearman correlation coefficients. Within-subject variability in PhIP intake was comparably high across all methods (ICCs of 0.20, 0.30, and 0.15 for FFQ, diary, and creatinine-adjusted urinary PhIP, respectively). Mean diary-based PhIP intake and mean urinary PhIP concentration were strongly correlated when restricting the analysis to participants with at least one non-zero diary-based estimate of PhIP intake (n = 15, r = 0.75, p = 0.001), but not in the full study population (n = 36, r = 0.18, p = 0.28). Mean PhIP intake from the FFQ was not associated with that either based on the diary or urinary PhIP separately, but was modestly correlated with a metric that combined the diary- and biomarker-based approaches (r = 0.30, p = 0.08). The high within-subject variability will result in significantly attenuated associations if a single measure is used to estimate exposure within an epidemiologic study. Improved HCA assessment tools, such as a combination of methods or validated biomarkers that capture long term exposure, are needed.

Update on the relationship of fish intake with prostate, breast, and colorectal cancers

A systematic review of prospective cohort and case-control studies investigating relationships between the intake of fish and incidence of prostate, breast, or colorectal cancers was conducted. A total of 106 studies fulfilled the requirements stated in the "Search strategy and selection criteria." Among 273 estimates of association reported by these studies, 53 indicated decreased risk while 12 indicated increased risk associated with fish intake. The hypothesis linking fish consumption and low cancer incidence appears to be supported by little epidemiological data. However, there are several factors that may mask potential protective associations with fish intake. The type and the amount of fish eaten, the cooking method, the stage of the cancer and, amongst women, menopausal status may all be important factors that relate to whether fish is protective or not. Future epidemiologic studies with a clearer assessment of these factors are needed to know more about the effects of fish consumption on cancer risk. Therefore, until there are better measures of dietary exposure or biomarkers to correlate self-report, no conclusion can be drawn regarding the recommendation for increasing fish consumption in general to reduce the risk of developing the most common cancers in Western societies.

Diet composition of pregnant Finnish women: changes over time and across seasons

Objective

To describe the diet of a population of pregnant Finnish women over a period of 7 years, with special attention paid to seasonal fluctuations in food consumption and nutrient intake.

Design

A validated 181-item FFQ was applied retrospectively, after delivery, to assess the maternal diet during the 8th month of pregnancy.

Setting

Type 1 Diabetes Prediction and Prevention Nutrition Study Cohort.

Subjects

The cohort comprised a total of 4880 women who had newly delivered during the years 1997–2004, with the offspring carrying increased genetic risk for type 1 diabetes mellitus.

Results

Over the study period, the proportion of energy derived from fat decreased while the intake from protein and carbohydrate increased. The intake of vitamin D increased from food sources. Seasonal variation was observed in the mean daily consumption of vegetables, fruits and berries and cereals. Intake of dietary fibre, total fat, MUFA, vitamins A, D, E and C, folate and iron also showed seasonal fluctuation.

Conclusions

These results show an overall positive trend in the diet of pregnant Finnish women through the study years. However, there is still room for improvement, particularly in the types of dietary fats. Although food fortification with vitamin D since 2003 was reflected in the increased intake of vitamin D from foods, the mean intake levels still fell below the recommendations. Seasonal changes in food consumption were observed and related to corresponding fluctuations in nutrient intakes. The mean folate intake fell below the recommendation throughout the year.

Use of a brief food frequency questionnaire for estimating daily number of servings of fruits and vegetables in a minority adolescent population

The validity of the 5 A Day for Better Health Program food frequency questionnaire (5 A Day FFQ) for estimating fruit and vegetable consumption was examined in a sample of 156 African-American adolescents aged 10 to 14 years. To determine validity, the correlation between 5 A Day FFQ fruit, juice, and vegetable intake and 3-day intake measured by direct observation was assessed. Correlations were calculated separately by food type (ie, fruits, juices, and vegetables) and sex and age to determine whether the accuracy of youths' recording differed based on these factors. Paired-samples t tests were used to test for differences between 5 A Day FFQ and observed intake estimates. The ability of the 5 A Day FFQ to correctly classify youths according to intake level (ie, intake of five or more daily servings) was also examined. The 5 A Day FFQ intake was significantly correlated with observed intake (r=0.39; P<0.01). Correlations were weaker by food type (r=0.15 to r=0.28) and did not differ based on youths' sex or age. Mean 5 A Day FFQ intake (6.74+/-6.00 servings) was considerably higher than mean observed intake (5.41+/-1.51 servings), and this was a result of the overestimation of vegetable intake. Sensitivity, specificity, and positive and negative predictive values of the 5 A Day FFQ were 67.1%, 68.6%, 63.5%, and 71.9%, respectively. Findings suggest that the 5 A Day FFQ may be more useful as a screening tool for identifying African-American adolescents most in need of intervention than for estimating youths' mean intake in dietary intervention programs.

Evaluating energy intake measurement in free-living subjects: when to record and for how long?

OBJECTIVE

To nutritionally analyse mean energy intake (EI) from different 3 d intervals within a 7 d recording period and to evaluate the seasonal effect on energy and nutrient intake.

DESIGN

Cross-sectional study of dietary intake collected with 7 d food diaries.

SETTING

Aberdeen, north-east Scotland, UK, between 2002 and 2004.

SUBJECTS

Participants from two long-term trials were pooled. These trials, investigating genetic and environmental influences on body weight, were the Genotyping And Phenotyping (GAP) study and a cohort observational study, Rowett Assessment of Childhood Appetite and metaboLism (RASCAL). There were 260 Caucasian adults, BMI range 16.7-49.3 kg/m2, age range 21-64 years.

RESULTS

Mean EI for Wednesday, Friday and Saturday had the closest approximation to the 7 d mean (0.1 % overestimate). A gender x season interaction (P = 0.019) with a different intake pattern for females and males was observed. For females, lower mean (se) EI was recorded in summer (8117 (610) kJ) and autumn (7941 (699) kJ) compared with spring (8929 (979) kJ) and winter (8132 (1041) kJ). For males, higher mean (se) EI was recorded in summer (10 420 (736) kJ) and autumn (10 490 (1041) kJ) compared with spring (9319 (1441) kJ) and winter (9103 (1505) kJ).

CONCLUSIONS

The study results indicate that 3 d weighed intakes recorded from Wednesday, Friday and Saturday are most representative of 7 d habitual intake in free-living subjects. They also indicate that seasonality has a limited effect on EI and no effect on macronutrient intake.

Seasonal variations in physical activity and implications for human health

This review explores the implications of seasonal changes in physical activity for fitness and human health. Photosensitivity and nutrient shortages mediate animal hibernation via the hypothalamus and changes in leptin and ghrelin concentrations. Opportunities for hunting and crop cultivation determine seasonal activity in under-developed human societies, but in developed societies temperature and rainfall are dominant influences, usually over-riding innate rhythms. Both questionnaire data and objective measurements show that many groups from children to the elderly increase their physical activity from winter to spring or summer. Measurements of maximal oxygen intake and muscle strength commonly show parallel seasonal changes. However, potential effects upon body mass and body fat may be counteracted by changes of food intake; subsistence agriculturists sometimes maintain or increase physical activity at the expense of a decrease in body mass. In developed societies, body fat commonly increases during the winter, with parallel changes in blood lipids, blood pressure and blood coagulability; moreover, these changes are not always fully reversed the following summer. Most developed societies show increased all-cause and cardiac mortalities in the winter. Health consequences of seasonal variations in physical activity including an increased vulnerability to cardiac catastrophe and a year-by-year increase in total body fat seem most likely if the average level of physical activity for the year is low. Public health recommendations should underline the importance of maintaining physical activity during adverse environmental conditions by adapting clothing, modifying behaviour and exploiting any available air-conditioned indoor facilities.

Differences in reported winter and summer dietary intakes in young adults in Spain

Representative data of usual food consumption are necessary in order to establish accurate conclusions on the relationship between diet and disease. In most studies data are collected at one particular time of the year. The aim of this study was to determine the influence of season of the year on dietary intake estimates. Three hundred and three people aged 19-40 years from northwest Spain recorded their intake twice (in winter and summer) using the seven non-consecutive-day dietary record method. A total of 247 foods (arranged into 16 major food groups) and 27 nutrients were determined. Most fruits and vegetables, as well as some milk products showed significant seasonal differences. Daily total food consumption amount (g) was higher in winter than summer in males. Higher average intakes of energy (men) and a large number of nutrients (both sexes) were observed in winter. This seasonal influence on dietary intake estimates implies significant differences in fractions of Spanish recommendations covered (lower in summer) for energy (men) and most nutrients (both sexes). As expressed in amount/MJ (densities), most nutrients showed higher values in winter in women. Data in our study suggest that the substantial variations of nutrient intakes throughout the course of the year mainly depend on food (energy) amount variations (quantitative diet changes) in males, while changes in densities of nutrients (qualitative diet changes) are mainly responsible for dietary variations in females. Results in the present study suggest that considering the season of the year it will enhance the results of dietary surveys and ensure the accuracy of studies that link diet with disease.

Omega-3 index determined by gas chromatography with electron impact mass spectrometry

Omega-3 index is a relatively new concept, defined as the sum of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) expressed as a percentage of the total fatty acids in red blood cell membranes. This index reflects medium to long-term intake of omega-3 polyunsaturated fatty acids and could be a useful tool in epidemiological studies. The standard technique used for fatty acid analysis and quantification has been gas chromatography (GC) with flame ionization detection. This method is robust and has good precision and sensitivity. However, a major disadvantage is inability to confirm spectrometrically the identity of fatty acids detected, which is important especially in complex biological samples. The current study measures omega-3 index in 12 healthy human volunteers using GC-mass spectrometry (MS). Both the intra-assay and day-to-day variations were well within 5% with linearity of response extending to a concentration of 250 microg/ml (830 micromol/L) of EPA. The limit of detection of EPA was 0.36 microg/ml (1.2 micromol/L). About 25 fatty acids were consistently detected in red blood cells from healthy volunteers including cis and trans isomers. The omega-3 index ranged from 2.4% to 6.2% among the 12 volunteers examined and there was no difference between samples taken in the fasting and postprandial states. EPA and DHA concentrations ranged from 3.53 to 105.89 microg/ml (11.7-350 micromol/L) and 12.19 to 214.42 microg/ml (37.1-652.7 micromol/L), respectively. Thus a GC-MS method has been developed for measuring the omega-3 index. Further studies are required to determine the role of this index as a predictor of disease.

Seasonal variation in fruit and vegetable consumption in a rural agricultural community

BACKGROUND

Seasonal variation in fruit and vegetable consumption has been documented in a limited number of previous investigations and is important for the design of epidemiologic investigations and in the evaluation of intervention programs.

OBJECTIVE

This study investigates fruit and vegetable consumption behaviors among Hispanic farmworkers and non-farmworkers in a rural agricultural community.

DESIGN

A larger study recruited 101 farmworker families and 100 non-farmworker families from the Yakima Valley in Washington State between December 2004 and October 2005. All families were Hispanic. An in-person administered questionnaire collected information on consumption of locally grown fruits and vegetables and sources of obtaining fruits and vegetables. Data on dietary intake asked whether or not the respondent had consumed a given fruit or vegetable in the past month. Data were collected longitudinally, coinciding with three agricultural seasons: thinning (summer), harvest (fall), and nonspray (winter).

STATISTICAL ANALYSES PERFORMED

Generalized estimating equations were used to test for statistical significance between proportions of the population who consumed a given fruit or vegetable across agricultural seasons. Multivariable logistic regression was performed and corresponding odds ratios and 95% confidence intervals are reported.

RESULTS

The proportion of respondents who ate apples, pears, plums, peaches, apricots, peppers, corn, and cucumbers was highest in the fall harvest season, whereas the proportions of those who ate cherries and asparagus were highest in the summer thinning season. Compared to non-farmworkers, a higher proportion of farmworkers reported having eaten peaches, apricots, cherries, green beans, carrots, peppers, corn, pumpkin, squash, and onions, in the past month.

CONCLUSIONS

Epidemiologic investigations and public health interventions that examine the consumption of fruits and vegetables should consider seasonal variation in consumption patterns, especially in agricultural communities.

Components of variation in serum carotenoid concentrations: the Polyp Prevention Trial

OBJECTIVES

The intra- and interindividual variations and season and center effects were estimated from a series of serum carotenoid concentrations in the Polyp Prevention Trial (PPT) participants.

SUBJECTS/METHODS

Fasting blood was collected annually for 4 years in all 1905 participants, and a subcohort of 901 participants were selected within each (of eight) center(s), by gender and dietary arm of the study, for measurement of five major carotenoid peaks. Using variance of component methods, the variation in serum carotenoid concentrations about the underlying mean was partitioned into explanatory components attributed to various sources.

RESULTS

The contributions of the inter- and intraindividual variances to the overall variation in carotenoid concentrations were in the range of 61-70 and 20-35%, respectively, whereas center and center-by-season effects provided 2.6-9.5 and 0.2-1.4%, respectively. The highest percent (35%) of intraindividual variation was exhibited by lycopene, and the highest percent (70% apiece) of interindividual variation was exhibited by lutein/zeaxanthin and beta-carotene. Serum lycopene had the highest ratio of intra- to interindividual variation of 0.57, whereas lutein had the lowest ratio of 0.29. We estimate that the ratio of intra- to interindividual variance around the mean carotenoid concentration can be reduced greatly by collecting 3-4 compared to 1 blood measurement in large-scale trials like the PPT.

CONCLUSION

In the largest study of components of variation in individuals at high risk for colorectal cancer, the largest contributors to variation in serum carotenoid concentrations were intra- and interindividual effects followed by center and center-by-season effects.

Development of a meat frequency questionnaire for use in diet and cancer studies

OBJECTIVE

To develop a meat frequency questionnaire to assess dietary heterocyclic amine intake. The meat frequency questionnaire is designed to obtain information on meat types, cooking methods, and doneness preferences that predict heterocyclic amine concentrations in different meats.

DESIGN

Total and specific meat intakes were determined by a standard food frequency questionnaire (FFQ) and compared with that determined by the meat frequency questionnaire.

SUBJECTS/SETTING

Three-hundred fourteen African-American males participating in a clinic-based study of prostate disease and heterocyclic amine intake were administered the two questionnaires in a cancer education center prior to undergoing screening evaluations for prostate disease.

MAIN OUTCOME MEASURES

Fried, broiled, and grilled vs total meat intake was assessed using the meat frequency questionnaire vs FFQ, respectively. Specific meat items included in the meat frequency questionnaire were evaluated as factors potentially explaining discrepancies in meat intake estimated using the two questionnaires. Seasonal variation in meat intake was also examined.

STATISTICAL ANALYSIS

Correlation coefficients for intake of total meat and individual meat groups determined by FFQ vs meat frequency questionnaire were calculated. Seasonal differences in meat and estimated heterocyclic amine intakes were evaluated by t test, adjusted for multiple comparisons.

RESULTS

Meat intakes determined by the two questionnaires were well-correlated (Pearson r=0.69); however, total meat assessed by the meat frequency questionnaire exceeded total meat assessed by the FFQ in 30% of participants. Total energy and intake of heterocyclic amine-associated meat were greatest when the meat frequency questionnaire was administered during winter months.

CONCLUSIONS

The heterocyclic amine meat frequency questionnaire provided a fractional measure of total meat intake and identified specific heterocyclic amine-containing meat items underreported in a standard FFQ.

Salad and Raw Vegetable Consumption and Nutritional Status in the Adult US Population: Results from the Third National Health and Nutrition Examination Survey

OBJECTIVE

To examine the relationship between reported salad consumption and serum nutrient levels as well as dietary adequacy, as defined by nutrient intakes, in relation to the National Academy of Science Food and Nutrition Board Guidelines, in pre- and postmenopausal women and in men of comparable ages.

DESIGN

Analyses of 24-hour recalls were conducted to determine dietary intake using the Third National Health and Nutrition Examination Survey data. Salad consumption was assessed based on intakes of salad, raw vegetables, and salad dressing.

SUBJECTS

Nine thousand four hundred-six women and 8,282 men aged 18 to 45 years and older than 55 years were examined between 1988 and 1994.

STATISTICAL ANALYSES

Regressions were used to model associations between salad and raw vegetable consumption and selected serum nutrient outcomes. Usual nutrient intake distributions were estimated using the Iowa State University method for adjustment of the distribution. The Estimated Average Requirement method was used to determine the proportion of subjects with inadequate intake for each nutrient.

RESULTS

The consumption of salads, raw vegetables, and salad dressing was positively associated with above-median serum micronutrient levels of folic acid, vitamins C and E, lycopene, and alpha- and beta-carotene. Each serving of salad consumed was associated with a 165% higher likelihood to meet the recommended Dietary Allowance for vitamin C in women and 119% greater likelihood in men.

CONCLUSIONS

Salad consumers tended to have more favorable intakes of vitamins C and E, folic acid, and carotenoids, after adjustment for other differences. The significant and consistently higher serum values of these vitamins among salad consumers suggest that they are being well absorbed from salad. Salad, salad dressing, and raw vegetable consumption can be an effective strategy for enhancing nutritional adequacy and increasing vegetable consumption in the population at large.

Seasonal variation in food intake, physical activity, and body weight in a predominantly overweight population

OBJECTIVE

To describe seasonal variation in food intake, physical activity, and body weight in a predominantly overweight population.

DESIGN

A longitudinal observational study.

SETTING

Most of the study participants were recruited from a health maintenance organization (HMO) in central Massachusetts, USA. Additional individuals of Hispanic descent were recruited from outside of the HMO population to increase the ethnic diversity of this sample.

SUBJECTS

Data from 593 participants, aged 20-70, were used for this investigation. Each participant was followed quarterly (five sampling points: baseline and four consecutive quarters) for 1-year period. Body weight measurements and three 24-h dietary and physical activity recalls were obtained on randomly selected days (including 2 weekdays and 1 weekend day) per quarter. Sinusoidal regression models were used to estimate peak-to-trough amplitude and phase of the peaks.

RESULTS

Daily caloric intake was higher by 86 kcal/day during the fall compared to the spring. Percentage of calories from carbohydrate, fat and saturated fat showed slight seasonal variation, with a peak in the spring for carbohydrate and in the fall for total fat and saturated fat intake. The lowest physical activity level was observed in the winter and the highest in the spring. Body weight varied by about 1/2 kg throughout the year, with a peak in the winter (P<0.001 winter versus summer). Greater seasonal variation was observed in subjects who were male, middle aged, nonwhite, and less educated.

CONCLUSIONS

Although there is seasonal variation in diet, physical activity and body weight, the magnitude of the change is generally small in this population.

SPONSORSHIP

US National Heart, Lung and Blood Institute.

Test-retest reproducibility of a food frequency questionnaire (FFQ) and estimated effects on disease risk in the Norwegian Women and Cancer Study (NOWAC)

BACKGROUND

The Norwegian Women and Cancer Study (NOWAC) is a national population-based cohort study with 102 443 women enrolled at age 30-70 y from 1991 to 1997. The present study was a methodological sub-study to assess the test-retest reproducibility of the NOWAC food frequency questionnaire (FFQ), and to study how measurement errors in the data can affect estimates of disease risk.

METHODS

A random sample of 2000 women aged 46-75 y was drawn from the cohort in 2002. A self-instructive health and lifestyle questionnaire with a FFQ section was mailed to the same subjects twice (test-retest), about three months apart, with a response rate of 75%. The FFQ was designed to assess habitual diet over the past year. We assess the reproducibility of single questions, food groups, energy, and nutrients with several statistical measures. We also demonstrate the method of regression calibration to correct disease risk estimates for measurement error. Alcohol intake (g/day) and high blood pressure (yes/no) is used in the example.

RESULTS

For single foods there were some indications of seasonal reporting bias. For food groups and nutrients the reliability coefficients ranged from 0.5-0.8, and Pearson's r, Spearman's rs, and two intraclass correlation coefficients gave similar results. Although alcohol intake had relatively high reproducibility (r = 0.72), odds ratio estimates for the association with blood pressure were attenuated towards the null value compared to estimates corrected by regression calibration.

CONCLUSION

The level of reproducibility observed for the FFQ used in the NOWAC study is within the range reported for similar instruments, but may attenuate estimates of disease risk.

Reproducibility and Validity of a Food Frequency Questionnaire among Vietnamese in Ho Chi Minh City

OBJECTIVE

Our objective was to assess the reproducibility and validity of a food frequency questionnaire (FFQ) among individuals living in Ho Chi Minh City, Vietnam.

METHODS

A total of 116 food items in our FFQ were selected by ranking food items according to their contribution to the population intake of nutrients, based on multiple 24-hour recalls (24HRs) from 144 participants in July 2001. The FFQ was validated by using three 24HRs for 118 men and women in Ho Chi Minh City, Vietnam in August 2002. The reproducibility of the FFQ was assessed by repeated administration at 7 +/- 3.4 days.

RESULTS

The reproducibility study showed that Spearman correlation coefficients, adjusted for energy intake, ranged from 0.47 to 0.72, and that weighted kappa values ranged from 0.42 for lipid to 0.65 for potassium. In the validation study, correlation coefficients, adjusted for energy intake, between the FFQ and the 24HRs ranged from 0.16 (calcium) to 0.45 (retinol). The proportion of subjects classified by the FFQ into the same third as determined by the 24HRs was between 42% and 62%.

CONCLUSIONS

This food frequency questionnaire measured the usual intake of major nutrients for Vietnamese adults living in Ho Chi Minh City and its urban area, where dietary patterns are similar to those of the Vietnamese population.

Seasonality of birth in epilepsy: a Southern Hemisphere study

A consistent pattern has emerged from research in Northern Hemisphere populations indicating differences in the seasonality of birth between patients with epilepsy and the general population. This is the first study using similar methodology to look at Southern Hemisphere data. The population studied is composed of patients discharged from Australian hospitals with a diagnosis of epilepsy, in the period 1998-1999. The results show a significantly higher incidence of epilepsy in the patients born during the Australian winter and summer and a deficit of patients born during the spring and fall. This pattern is consistent with the Northern Hemisphere findings. This study provides further evidence of the existence of a seasonal aetiological agent(s) for epilepsy acting in the perinatal period.

Ratio of n-6 to n-3 fatty acids and bone mineral density in older adults: the Rancho Bernardo Study

BACKGROUND

Several lines of evidence suggest that n-3 fatty acids reduce the risk of some chronic diseases, including heart disease, diabetes, and cancer. Other research, mainly in animals, also suggests a role in bone health.

OBJECTIVE

We aimed to investigate the association between the ratio of dietary n-6 to n-3 fatty acids and bone mineral density (BMD) in 1532 community-dwelling men and women aged 45-90 y.

DESIGN

Between 1988 and 1992, dietary data were obtained through self-administered food-frequency questionnaires, and BMD was measured at the hip and spine with the use of dual-energy X-ray absorptiometry. A medical history was obtained and current medication use was validated. Age- and multiple-adjusted linear regression analyses were performed.

RESULTS

There was a significant inverse association between the ratio of dietary linoleic acid to alpha-linolenic acid and BMD at the hip in 642 men, 564 women not using hormone therapy, and 326 women using hormone therapy; these results were independent of age, body mass index, and lifestyle factors. An increasing ratio of total dietary n-6 to n-3 fatty acids was also significantly and independently associated with lower BMD at the hip in all women and at the spine in women not using hormone therapy.

CONCLUSIONS

A higher ratio of n-6 to n-3 fatty acids is associated with lower BMD at the hip in both sexes. These findings suggest that the relative amounts of dietary polyunsaturated fatty acids may play a vital role in preserving skeletal integrity in older age.

Reproducibility and validity of coffee and tea consumption in Italy

OBJECTIVE

The reproducibility and validity of coffee, decaffeinated coffee and tea intake has not been adequately studied, particularly in Italy, where coffee drinking is peculiar in terms of type and amount of coffee consumed.

DESIGN

We compared coffee and tea consumption, measured by two interviewer-administered food frequency questionnaires (FFQ), with average intake derived from two 7-day dietary (DD) records (the reference method) on 395 volunteers. The Pearson correlation coefficients (r) were used to assess both reproducibility and validity of information on coffee intake.

RESULTS

A satisfactory level of reproducibility and validity of the pattern consumption was observed for coffee, decaffeinated coffee and tea. The reproducibility for both sex combined showed r of 0.74-0.78 for coffee, 0.57-0.65 for decaffeinated coffee and 0.61-0.67 for tea. The validity was about 0.70 for coffee, around 0.58 for decaffeinated coffee and 0.56-0.60 for tea intake.

CONCLUSIONS

The FFQ is a satisfactorily reliable and valid instrument for collecting information on coffee, decaffeinated coffee and tea intake.

Seasonal misclassification error and magnitude of true between-person variation in dietary nutrient intake: a random coefficients analysis and implications for the Japan Public Health Center (JPHC) Cohort Study

OBJECTIVE

We examine (1) the extent to which seasonal diet assessments correctly classify individuals with respect to their usual nutrient intake, and (2) whether the magnitude of true variation in intake between individuals is seasonal. These effects could lead, respectively, to bias in estimates of relative risk for associations between usual nutrient exposure and disease, and to an increase in required sample size.

SUBJECTS AND SETTING

One hundred and twenty-seven families in four regions of the Japan Public Health Center (JPHC) Cohort Study.

DESIGN

On average, 48 weighed daily food records were collected per family over six seasons of 1994 and 1995.

RESULTS

A random slopes regression model was used to predict the correlation between seasonal and annual average intakes, and to estimate true between-person variation in intakes by season. Mean vitamin C intake was greatest in summer and autumn, and seasonal variation was attributable to the consumption of fruit and vegetables. Predicted correlations between seasonal and annual average vitamin C intake ranged from 0.62 to 0.87, with greatest correlations in summer and autumn. True between-person variation in vitamin C intake was also strongly seasonal, ranging from 45 to 78% of total variance, and was again greatest in summer and autumn. These effects were less seasonal among energy and 13 other nutrients.

CONCLUSIONS

It may be possible substantially to reduce both seasonal misclassification of individuals with respect to their usual vitamin C intake, and required sample size, by asking subjects to report high-season intake of fruit and vegetables in the JPHC Study.

A methodological report from the Malmö Diet and Cancer study: development and evaluation of altered routines in dietary data processing

BACKGROUND

In the Malmö Diet and Cancer study, information on dietary habits was obtained through a modified diet history method, combining a 7-day menu book for cooked meals and a diet questionnaire for foods with low day-to-day variation. Half way through the baseline data collection, a change of interview routines was implemented in order to reduce interview time.

METHODS

Changes concentrated on portion-size estimation and recipe coding of mixed dishes reported in the menu book. All method development and tests were carefully monitored, based on experiential knowledge, and supplemented with empirical data. A post hoc evaluation study using "real world" data compared observed means of selected dietary variables before and after the alteration of routines handling dietary data, controlling for potential confounders.

RESULTS

These tests suggested that simplified coding rules and standard portion-sizes could be used on a limited number of foods, without distortions of the group mean nutrient intakes, or the participants' ranking. The post hoc evaluation suggested that mean intakes of energy-adjusted fat were higher after the change in routines. The impact appeared greater in women than in men.

CONCLUSIONS

Future descriptive studies should consider selecting subsets assessed with either method version to avoid distortion of observed mean intakes. The impact in analytical studies may be small, because method version and diet assistant explained less than 1 percent of total variation. The distribution of cases and non-cases across method versions should be monitored.

Are reliability, reproducibility and validity the correct terms to assess the correctness of dietary studies?

Nutritional studies often use the terms reliability, reproducibility and validity to indicate the correctness of the study. These terms do not appear to have a universal meaning to all researchers. The components of a dietary study are the input, the data collection instrument and the compiled data. Frequently the data collection questionnaire/tool/instrument is tested for reliability, reproducibility or validity. The data collection questionnaire/tool/instrument is simply a structure, a vehicle for gathering data. An argument is presented that demonstrates the reasons that such a structure cannot be tested for reliability, reproducibility or validity. The logical approach to the use of the terms reliability, reproducibility and validity is presented. Reliability refers to the input component of the study, reproducibility may or may not lead to strengthening the study and validity refers to the truthfulness of the database generated. Validity must be derived from reliable and reproducible data.

Sources of variability in the reproducibility of food frequency questionnaires

The reproducibility of food frequency questionnaires varies widely. Since reports of past intake are known to be biased toward the present and the forces of supply and demand affect what people eat at a given point in time, the questionnaire may capture an atypical snapshot of consumption rather than the intended view of unusual consumption. The consumption of regularly consumed foods is the same throughout the year. The consumption of these foods is likely to be highly reproducible at another point in time. The consumption of seasonally consumed foods, however, fluctuates throughout the year, and may have peaks in winter or summer or particular holidays. There may be no common denominator among these foods necessary for the purpose of assessing reproducibility. Therefore, questionnaires that contain a combination of regularly and seasonally consumed foods, will be likely to have problems with reproducibility, the variance depending upon the number of seasonally consumed foods in the questionnaire. This explanation for variability in reproducing food frequency questionnaires raises a question about the importance of assessing reproducibility as a way of evaluating the worth of questionnaires. Perhaps an improved method of collecting data for seasonal foods is what is really needed to improve the quality of data collected.

The influence of time on dietary data: differences in reported summer and winter food consumption

A pilot study was conducted to test whether or not the time of data collection affected subjects' responses to a dietary questionnaire and could therefore bias the results of a study. A 117 item food frequency questionnaire was administered to 43 subjects--16 in the summer and 27 in the winter. The summer and winter consumption per person per month was calculated and compared. Of the 117 foods, 105 (89%) showed differences between summer and winter consumption. While differences in summer fruit and hot cereal might be expected, this study showed that many other foods not usually thought of as seasonal were seasonally consumed by the population tested. Since food consumption is affected by supply and demand factors, and the reported memory of food intake is biased toward the present, the time of data collection could greatly influence reported intake for a great number of foods. Recommendations for enhancing dietary studies are given. These recommendations include the development of a gold standard of consumption for each food in a given population, incorporating the elements of person, place and time into study design, building the rate and length of data collection into the study plan and using the gold standard and improved design to produce a new generation of dietary studies.

Season of birth: aetiological implications for epilepsy

In most cases of epilepsy it is not possible to reach an aetiological diagnosis. Recent research points to a pre-perinatal disruption of the neurodevelopment as being the cause of at least some of these epilepsies of unknown aetiology. The object of this study was to corroborate this hypothesis from an epidemiological perspective and identify the most likely candidates for causes of this damage. The approach used was an analysis of the seasonal pattern of births in a large sample of epileptic patients discharged from NHS hospitals in England and Wales. The results illustrated that the seasonality of the births in the epileptic sample was significantly different from that of the general population, with an excess of patients born in December and January and a deficit of those born in September. This "seasonality' was present only in the patients born before the late 1950s. These results are suggestive of the existence of an aetiological factor for epilepsy with a seasonal presence in the environment and which is epileptogenic when acting in the pre-perinatal period. Prenatal infections, obstetric complications and nutrititional deficiencies are amongst the hypotheses developed on the nature of this agent(s).

Trends in food intake: the 1987 and 1992 National Health Interview Surveys

To examine food intake trends in the US population, cross-sectional nationally representative food intake data were obtained from the 1987 and 1992 National Health Interview Survey Cancer Control Supplements. In each of these years, approximately 10,000 respondents completed methodologically consistent food frequency questionnaires containing the same 57 food items. Between 1987 and 1992, the proportion of Americans consuming high-fat foods, including fried fish, fried chicken, bacon, eggs, whole milk, and butter, decreased. The proportion of Americans drinking alcoholic beverages also decreased: fewer drank wine and hard liquor in 1992. The proportion of fruit and vegetable consumers remained stable over time. These results are similar to those obtained from more detailed national surveys. National guidelines urge Americans to avoid intake of high-fat foods, increase consumption of fruits and vegetables, and practice moderation when drinking alcoholic beverages to prevent cancer and other chronic diseases. The direction of Americans' apparent changes in food usage between 1987 and 1992, evaluated using limited data from food frequency questionnaires, suggests greater behavioral changes in the direction of guidelines recommending avoidance of foods that may increase the risk of cancer than in the direction of guidelines recommending increased consumption of foods that may confer protection.

Reproducibility of a self-administered diet history questionnaire administered three times over three different seasons

The reproducibility of the widely used Health Habits and History Questionnaire (HHHQ) for estimating "usual past-year" nutrient intake was examined. The HHHQ was self-administered on three occasions during three different seasons; 68 women (avg age 43 yrs) provided usable data for all three questionnaires in the appropriate seasons. Intraclass correlations (ICC) among the three administrations ranged from 0.56 (carotene) to 0.82 (fat as percentage of energy), with a median of 0.72. Thus, reliability was moderate to good, and season of administration/ordinality generally had little impact on ranking of individuals. The point estimates of intake of energy and a number of nutrients were higher in the first administration (winter). Except for dietary fiber and possibly carotene, most differences disappeared when adjusted for energy using a nutrient density approach, as well as using repeated-measures regression models. The higher intake in the first administration may be due more to either learning or fatigue effect rather than an effect of seasonal food availability on perceptions of "usual" intake. These data should be used in conjunction with validity data in the future to help evaluate the gain in precision of group means (and changes in these means) and improved estimates of odds ratios and correlations between nutrients and factors such as serum values, if a questionnaire is administered more than once.

Dietary change and obesity associated with glucose intolerance in Alaska Natives

OBJECTIVE

To investigate frequency of food intake, body weight, and glucose intolerance in Alaska Natives.

DESIGN

Height, weight, and random blood glucose levels were measured and a frequency-of-food-intake questionnaire was obtained. This questionnaire classified persons as consumers of indigenous foods or nonindigenous foods within three food groups. Those with a random blood glucose measurement > or = 6.72 mmol/L received an oral glucose tolerance test.

SETTING

Community screening in 15 villages in Alaska.

SUBJECTS

Nutrition screenings were done for 1,124 Alaska Native residents aged 20 years or older. An oral glucose tolerance test was done for 202 subjects.

OUTCOMES MEASURED

Subjects were classified as consumers of indigenous or nonindigenous foods within three food groups. A diagnosis of non-insulin-dependent diabetes mellitus (NIDDM) was made on the basis of World Health Organization criteria. A determination of overweight was made on the basis of National Center for Health Statistics criteria.

STATISTICAL ANALYSIS

A chi 2 test with Yates correction, t test, and linear regression, with two-sided P values.

RESULTS

Athabascan Indians had twice the rate of NIDDM as Yup'ik Eskimos with significantly higher frequency of nonindigenous food intake, plus lower frequency of indigenous carbohydrate and fat intake. Subjects < or = 30 years old consumed significantly more nonindigenous protein and fat and low-nutrient-density carbohydrates than those > or = 60 years old. Persons who had glucose intolerance reported significantly greater consumption of nonindigenous protein and less seal oil. Incidence of overweight was significantly higher than was found 25 years ago. Participants with glucose intolerance were significantly more overweight than others.

CONCLUSION

A pattern of increased frequency of nonindigenous protein, low-nutrient-density carbohydrate, and fat intake with less indigenous carbohydrate and fat consumption was found in subjects < or = 30 years old and in association with the higher rate of NIDDM found in the Athabascan Indians. Persons with glucose intolerance were significantly more overweight than others.

APPLICATIONS

Although the nutritional value of indigenous foods for reducing disease risk should be promoted, nutrition education, especially among young adults, should also include building skills to select and prepare nonindigenous foods to attain a healthful diet. Although snacking is a concern, dietary fat was the most significant factor in obesity and NIDDM.