Calibration of the dietary questionnaire for a multiethnic cohort in Hawaii and Los Angeles

Green tea and risk of breast cancer in Asian Americans

There is substantial in vitro and in vivo evidence implicating tea polyphenols as chemopreventive agents against various cancers. However, epidemiologic data obtained from mainly Western populations are not supportive of a protective role of tea, mainly black tea, in the etiology of breast cancer. Much less is known about the relationship between green tea and breast cancer risk. During 1995-1998, we conducted a population-based, case-control study of breast cancer among Chinese, Japanese and Filipino women in Los Angeles County and successfully interviewed 501 breast cancer patients and 594 control subjects. Detailed information on menstrual and reproductive factors; dietary habits, including intake of black and green tea; and other lifestyle factors was collected. Risk of breast cancer was not related to black tea consumption. In contrast, green tea drinkers showed a significantly reduced risk of breast cancer, and this was maintained after adjusting for age, specific Asian ethnicity, birthplace, age at menarche, parity, menopausal status, use of menopausal hormones, body size and intake of total calories and black tea. Compared to women who did not drink green tea regularly (i.e., less than once a month), there was a significant trend of decreasing risk with increasing amount of green tea intake, adjusted odds ratios being 1.00, 0.71 (95% confidence interval [CI] 0.51-0.99) and 0.53 (95% CI 0.35-0.78), respectively, in association with no, 0-85.7 and >85.7 ml of green tea per day. The significant inverse association between risk of breast cancer and green tea intake remained after further adjustment for other potential confounders, including smoking; alcohol, coffee and black tea intake; family history of breast cancer; physical activity; and intake of soy and dark green vegetables. While both green tea and soy intake had significant, independent protective effects on breast cancer risk, the benefit of green tea was primarily observed among subjects who were low soy consumers. Similarly, the protective effect of soy was primarily observed among subjects who were nondrinkers of green tea. In summary, our results point to an important role of both green tea and soy intake in relation to breast cancer risk in Asian-American women.

Adherence to the Food Guide Pyramid recommendations among Japanese Americans, Native Hawaiians, and whites: results from the Multiethnic Cohort Study

The Food Guide Pyramid is designed to help Americans make healthful food choices. Whereas national data have been collected to examine adherence to the pyramid recommendations in whites, African-Americans, and Latinos, there are virtually no data available for Japanese Americans or Native Hawaiians. Here we present data on intakes of the Food Guide Pyramid food groups (as servings per day) as well as of the components of the pyramid tip (discretionary fat, added sugar, and alcohol) in these ethnic groups and examine adherence to each of the food group recommendations. Degree of adherence to the fruit group recommendation was similar among the ethnic groups and energy-intake categories, but adherence to the other recommendations was greatest for those consuming more than 2,800 kilocalories per day. However, subjects in this energy-intake group also consumed more than three times as much discretionary fat, added sugar, and alcohol.

Ingestão alimentar em estudos epidemiológicos

A epidemiologia da nutrição dispõe de uma gama de metodologias para avaliar o estado nutricional. Entretanto, os métodos dietéticos são os únicos capazes de detectar a deficiência nutricional em seu estágio inicial, sendo por isso bastante utilizados em estudos epidemiológicos de associação entre exposições e eventos. Atualmente, o método dietético mais indicado para estudos epidemiológicos, principalmente aqueles envolvendo doenças crônico-degenerativas, tem sido o questionário semiquantitativo de freqüência alimentar (QSFA). Este instrumento, não diferente de outros, está sujeito à variabilidade e a erros de medida. Entretanto, estes podem ser identificados e tratados utilizando-se métodos como comparação de médias dietéticas, estudos de confiabilidade, de validação relativa e de calibração. Em estudo realizado em Bambuí-MG, o consumo de nutrientes foi avaliado por três diferentes métodos: QSFA e recordatórios 24 horas (R24) com e sem réplicas de alimentos, tendo suas médias comparadas e calibradas. As médias encontradas pelo QSFA foram consistentemente maiores do que as dos R24. No entanto, quando essas foram ajustadas pelo consumo calórico total não apresentaram diferenças importantes, exceto para fibras; zinco; vitaminas C; B6, e E; e colesterol. E as médias calibradas foram, em geral, menores do que as não calibradas, sendo estatisticamente significantes para ingestão de lipídeos; fibras; zinco; vitaminas C, E e A; ácidos graxos saturados, monoinsaturados e poliinsaturados; e colesterol.

Factors associated with dietary supplement use among healthy adults of five ethnicities: the Multiethnic Cohort Study

Participants of the Multiethnic Cohort Study in Hawaii and Los Angeles, California, a representative sample of African-American, Native Hawaiian, Latino, Japanese-American, and White adults, completed a baseline questionnaire in 1993-1996 assessing dietary supplement use during the past year as well as demographic, dietary, and other lifestyle factors. Factors associated with supplement use were examined among those who reported an absence of chronic disease (n = 100,196). Use of any of eight supplements at least once per week during the past year ranged from 44% among Hawaiian men to 75% among Japanese-American and White women. Multivitamins were the most frequently reported supplement; 48% of the men and 56% of the women reported regular use. Dietary supplement use was high across all ethnic groups, although levels and length of regular use varied. In all gender-specific ethnic groups, supplement use tended to increase with age, education, physical activity, fruit intake, and dietary fiber intake and to decrease with obesity, smoking, and dietary fat intake. Participants whose lifestyles were healthier were more likely to use dietary supplements. Therefore, it may be difficult to separate the effects of supplement use from other lifestyle factors when studying disease etiology.

Calibration of the dietary questionnaire for the Canadian Study of Diet, Lifestyle and Health cohort

OBJECTIVE

For proper interpretation of results from epidemiological studies that use food-frequency questionnaires (FFQs), it is necessary to know the relationship between reported intakes from the FFQ and true usual intake. In this paper, we report a calibration study conducted to investigate the performance of the FFQ used in a cohort study, the Canadian Study of Diet, Lifestyle and Health.

METHODS

Over a 1-year period, 151 men and 159 women completed a full set of questionnaires including a self-administered baseline FFQ, three 24-hour diet recalls administered by telephone, and a second FFQ self-administered subsequently. The association between the nutrient estimates derived from the FFQs and the diet recalls was evaluated by calculating deattenuated Pearson's correlation coefficients.

RESULTS

FFQs estimated mean daily nutrient intakes higher than the diet recalls. When the log-transformed and energy-adjusted nutrient intakes from the average of three 24-hour recalls were compared against the baseline FFQ, the following deattenuated correlations were obtained in men and women, respectively: total energy 0.44 and 0.32, total fat 0.64 and 0.68, saturated fat 0.68 and 0.70, dietary fibre 0.65 and 0.44, vitamin E 0.32 and 0.37, vitamin C 0.40 and 0.37, beta-carotene 0.34 and 0.29, alcohol 0.74 and 0.67, caffeine 0.81 and 0.76, with a median correlation of 0.49 and 0.53. Correlations between the second FFQ and diet recalls were similar. The correlations between the two FFQs as a test of reliability had a median value 0.64 for men and 0.63 for women for selected nutrients.

CONCLUSIONS

The study suggests that the FFQ method gives acceptable levels of nutrients or food component estimates, as assessed by this calibration study against diet recalls, when limited to energy-adjusted and deattenuated values.

Validation of a soy questionnaire with repeated dietary recalls and urinary isoflavone assessments over one year

This study assessed the validity and reliability of a 12-item soy questionnaire designed for use in cancer prevention research. The questionnaire measures soy intake over the past year. Subjects were 199 healthy 35- to 46-yr-old premenopausal women participating in an ongoing soy intervention study. Soy questionnaire estimates of isoflavone intake over 1 yr were compared with individual and combined estimates from two reference measures covering the same period: three or four repeated 24-h recalls and one or two repeated urine analyses. The sensitivity and specificity of the soy questionnaire in classifying high vs. low exposure (high exposure = soy intervention group membership) were comparable with 24-h recalls and were superior to urine analyses (sensitivity = 94.8%, 97.9%, and 71.1%; specificity = 95.1%, 97.1%, and 90.3% for the soy questionnaire, 24-h recalls, and urine analyses, respectively). Soy questionnaire isoflavone estimates were highly correlated with the combination of the two reference measures for the entire study population. Its brevity, ease of administration, and good measurement properties over a 1-yr period make the soy questionnaire well suited to the needs of researchers who wish to identify high and low consumers of soy foods, especially in populations who consume traditional Asian soy foods.

European Prospective Investigation into Cancer and Nutrition (EPIC) calibration study: rationale, design and population characteristics

The European Prospective Investigation into Cancer and Nutrition (EPIC), which covers a large cohort of half a million men and women from 23 European centres in 10 Western European countries, was designed to study the relationship between diet and the risk of chronic diseases, particularly cancer. Information on usual individual dietary intake was assessed using different validated dietary assessment methods across participating countries. In order to adjust for possible systematic over- or underestimation in dietary intake measurements and correct for attenuation bias in relative risk estimates, a calibration approach was developed. This approach involved an additional dietary assessment common across study populations to re-express individual dietary intakes according to the same reference scale. A single 24-hour diet recall was therefore collected, as the EPIC reference calibration method, from a stratified random sample of 36 900 subjects from the entire EPIC cohort, using a software program (EPIC-SOFT) specifically designed to standardise the dietary measurements across study populations. This paper describes the design and populations of the calibration sub-studies set up in the EPIC centres. In addition, to assess whether the calibration sub-samples were representative of the entire group of EPIC cohorts, a series of subjects' characteristics known possibly to influence dietary intakes was compared in both population groups. This was the first time that calibration sub-studies had been set up in a large multi-centre European study. These studies showed that, despite certain inherent methodological and logistic constraints, a study design such as this one works relatively well in practice. The average response in the calibration study was 78.3% and ranged from 46.5% to 92.5%. The calibration population differed slightly from the overall cohort but the differences were small for most characteristics and centres. The overall results suggest that, after adjustment for age, dietary intakes estimated from calibration samples can reasonably be interpreted as representative of the main cohorts in most of the EPIC centres.

Development of a life events/icon calendar questionnaire to ascertain occupational histories and other characteristics of migrant farmworkers

BACKGROUND

Specialized methods are necessary to collect data from migrant farmworkers for epidemiologic research.

METHODS

We developed a questionnaire that collected lifetime occupational histories and other lifestyle risk factors via a life events/icon calendar, and administered the questionnaire to a convenience sample of 162 migrant farmworkers in nine areas of the U.S.

RESULTS

The average duration of the interviews was about 1 h 30 min, with an average of 45 min for the work history section. The occupational histories covered a median of 27.6 years per person for men and 20.8 years per person for women. The median number of years spent in farm jobs was 11.3 for men and 5.8 for women. The median number of farm jobs (crop/task combination) per person was 59 among men and 27 among women. Many farmworkers performed the same crop/task combinations at multiple times throughout their lives, yielding a median of 13 unique farm jobs and 8 unique crops among men and 7 jobs and 5 crops among women.

CONCLUSIONS

The project demonstrated that it is feasible to collect detailed work histories and other risk factor data from farmworkers, documented the complexity of work histories encountered among farmworkers, and yielded recommendations for refining a questionnaire that will facilitate future epidemiologic research on farmworkers.

Physical activity and cancer: lessons learned from nutritional epidemiology

Convincing epidemiologic evidence currently exists for an association between physical activity and the prevention of colon and breast cancer Physical activity may also reduce the risk of cancer at several other sites. With increasing research on this topic, it is apparent that studies of physical activity and cancer have numerous methodological similarities with studies of nutrition and cancer Lessons learned from nutritional epidemiology that can be applied to studies of physical activity and cancer prevention and recommendations for future research are discussed in this review.

An investigation of soy intake and mammographic characteristics in Hawaii

This cross-sectional investigation in Hawaii explored the relation between soy foods and mammographic characteristics using two food frequency questionnaires and a computer-assisted density assessment method. Japanese and Chinese women reported significantly greater soy food intake than Caucasian women. Whereas soy intake and the size of the dense areas were not related, soy intake and percent mammographic densities were positively associated. The size of the entire breast and the nondense area (ie the fatty part of the breast) were inversely related to soy intake. These results suggest the hypothesis that soy foods by themselves or as part of an Asian dietary pattern may affect the growth of the female breast before adulthood, but the possible mechanisms of action have to be explored in future studies.

Singapore Chinese Health Study: development, validation, and calibration of the quantitative food frequency questionnaire

This report describes the development and validation/calibration of a structured food frequency questionnaire for use in a large-scale cohort study of diet and health in Chinese men and women aged 45-74 years in Singapore, the development of a food composition database for analysis of the dietary data, and the results of the dietary validation/calibration study. The present calibration study comparing estimated intakes from 24-hour recalls with those from the food frequency questionnaires revealed correlations of 0.24-0.79 for energy and nutrients among the Singapore Chinese, which are comparable to the correlation coefficients reported in calibration studies of other populations. We also report on the nutritional profiles of Singapore Chinese on the basis of results of 1,880 24-hour dietary recalls conducted on 1,022 (425 men and 597 women) cohort subjects. Comparisons with age-adjusted corresponding values for US whites and blacks show distinct differences in dietary intakes between the Singapore and US populations. The Singapore cohort will be followed prospectively to identify dietary associations with cancer risk and other health outcomes.

Dietary patterns are associated with body mass index in multiethnic women

This cross-sectional study investigated the relationship between dietary patterns and body mass index among 514 women with different ethnic backgrounds who completed a validated food-frequency questionnaire. An exploratory factor analysis with orthogonal rotation started with 23 food items and resulted in four factors that accounted for 93% of the total variance. Confirmatory factor analysis with the 16 items that had factor loadings of at least 0.60 validated the four dietary patterns. The most significant dietary pattern, "meat," was characterized by high intake of processed and red meats, fish, poultry, eggs, fats and oils, and condiments. The "vegetable" pattern loaded high on different vegetables, whereas the third pattern named "bean" was high in legumes, tofu and soy protein. The major components of the "cold foods" pattern were fruit, fruit juice and cold breakfast cereals. Although the "meat" pattern was predominant among Hawaiians and the "bean" pattern very common among Chinese and Japanese women, factors two and four were not related to ethnicity. After adjustment for daily energy intake, the "meat" pattern was positively associated with body mass index (r = 0.17, P: = 0.0001), whereas the other three patterns showed negative relationships to body mass index (r = -0.076, P: = 0.084, r = -0.13, P: = 0.003, and r = -0.13, P: = 0.003) for vegetables, beans and cold foods, respectively. The associations were similar in direction and magnitude for all ethnic groups. The study results support the ideas that choosing the right foods may be important in weight control and that food-based dietary patterns may be useful in dietary counseling.

A multiethnic cohort in Hawaii and Los Angeles: baseline characteristics

The authors describe the design and implementation of a large multiethnic cohort established to study diet and cancer in the United States. They detail the source of the subjects, sample size, questionnaire development, pilot work, and approaches to future analyses. The cohort consists of 215,251 adult men and women (age 45-75 years at baseline) living in Hawaii and in California (primarily Los Angeles County) with the following ethnic distribution: African-American (16.3%), Latino (22.0%), Japanese-American (26.4%), Native Hawaiian (6.5%), White (22.9%), and other ancestry (5.8%). From 1993 to 1996, participants entered the cohort by completing a 26-page, self-administered mail questionnaire that elicited a quantitative food frequency history, along with demographic and other information. Response rates ranged from 20% in Latinos to 49% in Japanese-Americans. As expected, both within and among ethnic groups, the questionnaire data show substantial variations in dietary intakes (nutrients as well as foods) and in the distributions of non-dietary risk factors (including smoking, alcohol consumption, obesity, and physical activity). When compared with corresponding ethnic-specific cancer incidence rates, the findings provide tentative support for several current dietary hypotheses. As sufficient numbers of cancer cases are identified through surveillance of the cohort, dietary and other hypotheses will be tested in prospective analyses.