Consumption of black tea and cancer risk: a prospective cohort study.

BACKGROUND: Tea is one of the most frequently consumed beverages in the world. Antioxidant polyphenol compounds (such as catechins and flavonols) are abundantly present in both green and black teas and have been observed to have anticarcinogenic properties in cell and animal model studies. In black tea, however, most of the catechins have been oxidized to forms that may have reduced anticarcinogenic properties. Despite indications from experimental studies that tea may protect against cancer, epidemiologic evidence has been inconclusive. PURPOSE: The association between black tea consumption and the subsequent risk of stomach, colorectal, lung, and breast cancers was investigated in The Netherlands Cohort Study on Diet and Cancer among 58,279 men and 62,573 women aged 55-69 years. METHODS: Subjects in the cohort completed a self-administered questionnaire on dietary habits and other risk factors for cancer at base line in 1986. Follow-up for cancer was done by means of computerized record linkage with all nine regional cancer registries in The Netherlands and the national pathology database. During 4.3 years of follow-up, 200, 650, 764, and 650 cases of stomach, colorectal, lung, and breast cancers were diagnosed, respectively. The questionnaire data of case subjects and those of a random subcohort (n = 3500) were used to calculate rate ratios (RRs) of cancer in categories of consumers of black tea compared with nonconsumers. RESULTS: Tea was not used by 13% of the subjects in the cohort, whereas 37%, 34%, and 16% consumed one to two, three to four, and five or more cups of tea per day, respectively. No association was observed between tea consumption and risk of colorectal cancer: The risk among tea drinkers in each consumption category was similar to that among nondrinkers. The RR of breast cancer among consumers of five or more cups of tea per day was 1.3 (95% confidence interval = 0.9-2.0); no dose-response association was observed. In age- and sex-adjusted analyses, consumption of tea was inversely associated with stomach (two-sided P for trend = .147) and lung (two-sided P for trend < .001) cancers. However, tea drinkers appeared to smoke less and to eat more vegetables and fruits than nondrinkers. When smoking and dietary factors were taken into account, tea in itself did not appear to protect against stomach and lung cancers: The RRs in all consumption categories were close to unity. Analysis of the tea and cancer relationship in a subgroup that included subjects in the lowest two quintiles of consumption of vegetables and fruits also failed to reveal a protective effect of tea consumption on the risk of three cancer types studied (colorectal, lung, and breast cancers). CONCLUSIONS: This investigation does not support the hypothesis that consumption of black tea protects against four of the major cancers in humans; a cancer-enhancing effect was not evident, either.

Consumption of fermented milk products and breast cancer: a case-control study in The Netherlands.

In a case-control study in The Netherlands, we observed a significantly lower consumption of fermented milk products (predominantly yogurt and buttermilk) among 133 incident breast cancer cases as compared to 289 population controls (mean +/- SD among users only, 116 +/- 100 versus 157 +/- 144 g/day; P less than 0.01). The age-adjusted odds ratio of daily consumption of 1.5 glasses (greater than or equal to 225 g) of fermented milk versus none was 0.50 (95% confidence interval, 0.23-1.08). When fermented milk was entered as a continuous variable (per g) in either age-adjusted or multivariate analysis, the odds ratio expressed per 225 g was 0.63 (multivariate-adjusted 95% confidence interval, 0.41-0.96). After multivariate adjustment for intake of fat and other confounders, a statistically significant decrease in breast cancer risk was also observed for increasing intake of Gouda cheese. The multivariate-adjusted odds ratio expressed per 60 g of this fermented product was 0.56 (95% confidence interval, 0.33-0.95). For daily intake of milk, no statistically significant differences were observed between cases and controls. These results support the hypothesis that high consumption of fermented milk products may protect against breast cancer.

A prospective cohort study on the relation between meat consumption and the risk of colon cancer.

The high incidence of colon cancer in affluent societies has often been attributed to a high fat diet and, more in particular, the consumption of meat. The association of the consumption of meat and the intake of fat with risk of colon cancer was investigated in a prospective cohort study on diet and cancer, which is being conducted in the Netherlands since 1986 among 120,852 men and women, aged 55-69. The analysis was based on 215 incident cases of colon cancer (105 men and 110 women) accumulated in 3.3 years of follow-up, excluding cases diagnosed in the first year of follow-up. Dietary habits were assessed at baseline with a 150-item semiquantitative food frequency questionnaire. No trends in relative rates of colon cancer were detected for intake of energy or for the energy-adjusted intake of fats, protein, fat from meat, and protein from meat. Consumption of total fresh meat, beef, pork, minced meat, chicken, and fish was not associated with risk of colon cancer either. Processed meats, however, were associated with an increased risk in men and women (relative rate, 1.17 per increment of 15 g/day; 95% confidence interval, 1.03-1.33). The increased risk appeared to be attributable to one of the five questionnaire items on processed meat, which comprised mainly sausages. This study does not support a role of fresh meat and dietary fat in the etiology of colon cancer in this population. As an exception, some processed meats may increase the risk, but the mechanism is not yet clear.

Development of the HELIUS food frequency questionnaires: ethnic-specific questionnaires to assess the diet of a multiethnic population in The Netherlands.

OBJECTIVES: Ethnic minorities are often not included in studies of diet and health because of a lack of validated instruments to assess their habitual diets. Given the increased ethnic diversity in many high-income countries, insight into the diets of ethnic minorities is needed for the development of nutritional policies and interventions. In this paper, we describe the development of ethnic-specific food frequency questionnaires (FFQs) to study the diets of Surinamese (African and South Asian), Turkish, Moroccan and ethnic Dutch residents of The Netherlands. METHODS: An existing Dutch FFQ was adapted and formed the basis for three new FFQs. Information on food intake was obtained from single 24 h recalls. Food items were selected according to their percentage contribution to and variance in absolute nutrient intake of the respective ethnic groups. A nutrient database for each FFQ was constructed, consisting of data from the Dutch Food Composition table; data on ethnic foods were based on new chemical analyses and available international data. RESULTS: We developed four ethnic-specific FFQs using a standardised approach that included ~200 food items each and that covered more than 90% of the intake of the main nutrients of interest. CONCLUSIONS: The developed FFQs will enable standardised and comparable assessment of the diet of five different ethnic groups and provide insight into the role of diet in differences in health between ethnic groups. The methodology described in this paper and the choices made during the development phase may be useful in developing similar FFQs in other settings.

Plant sterol intakes and colorectal cancer risk in the Netherlands Cohort Study on Diet and Cancer.

BACKGROUND: Plant sterols in vegetable foods might prevent colorectal cancer. OBJECTIVE: The objective was to study plant sterol intakes in relation to colorectal cancer risk in an epidemiologic study. DESIGN: The study was performed within the framework of the Netherlands Cohort Study on Diet and Cancer in 120852 subjects who completed a baseline questionnaire in 1986. After 6.3 y of follow-up, 620 colon and 344 rectal cancer cases were detected. A case-cohort approach was used to calculate confounder-adjusted rate ratios (RRs) and their 95% CIs for quintiles of plant sterol intake. RESULTS: The total mean (+/-SD) intake of campesterol, stigmasterol, beta-sitosterol, campestanol, and beta-sitostanol was 285 +/- 97 mg/d. Major contributors to plant sterol intake were bread (38%), vegetable fats (26%), and fruit and vegetables (21%). For men, there was no clear association between intake of any of the plant sterols and colon cancer risk when age, smoking, alcohol use, family history of colorectal cancer, education level, and cholecystectomy were controlled for. Adjustment for energy did not alter the result. For rectal cancer, adjustment for energy resulted in positive associations between risk and campesterol and stigmasterol intakes. For women, there was no clear association between intake of any of the plant sterols and colorectal cancer risk. CONCLUSION: A high dietary intake of plant sterols was not associated with a lower risk of colon and rectal cancers in the Netherlands Cohort Study on Diet and Cancer.

A prospective cohort study on antioxidant and folate intake and male lung cancer risk.

Many studies have reported inverse associations between vegetable and fruit consumption and lung cancer risk. The aim of the present study was to elucidate the role of several antioxidants and folate in this relationship. In the Netherlands Cohort Study on Diet and Cancer, 58,279 men of ages 55-69 years at baseline in 1986 returned a questionnaire including a 150-item food frequency questionnaire. After 6.3 years of follow-up, 939 male lung cancer cases were registered. A new Dutch carotenoid database was used to estimate intake of alpha-carotene, beta-carotene, lutein + zeaxanthin, beta-cryptoxanthin, and lycopene, completed with the antioxidant vitamins C and E and folate. Using case-cohort analysis, rate ratios were calculated, adjusted for age, smoking, educational level, and family history of lung cancer. Protective effects on lung cancer incidence were found for lutein + zeaxanthin, beta-cryptoxanthin, folate, and vitamin C. Other carotenoids (alpha-carotene, beta-carotene, and lycopene) and vitamin E did not show significant associations. After adjustment for vitamin C, only folate remained inversely associated, and after adjustment for folate, only beta-cryptoxanthin and vitamin C remained significantly associated. Inverse associations were strongest among current smokers and weaker for former smokers at baseline. Inverse associations with carotenes, lutein + zeaxanthin, and beta-cryptoxanthin seemed to be limited to small cell and squamous cell carcinomas. Only folate and vitamin C intake appeared to be inversely related to small cell and squamous cell carcinomas and adenocarcinomas. Folate, vitamin C, and beta-cryptoxanthin might be better protective agents against lung cancer in smokers than alpha-carotene, beta-carotene, lutein + zeaxanthin, and lycopene.

Meat consumption and preparation, and genetic susceptibility in relation to colorectal adenomas.

Epidemiological evidence suggests that a high meat consumption and/or animal fat intake may increase the risk of colorectal cancer. The objective of this study is to examine the role of dietary factors, in particular meat preparation and consumption, in relation to colorectal adenomas, the pattern of DNA-mutations (e.g. K-ras and p53), and genetic susceptibility (NAT2, HNPCC). In a case control study on diet and colorectal adenomas (sporadic and HNPCC), acetylator status (NAT2) of cases and controls as well as K-ras and p53 mutations in adenomas will be assessed. Consumption and preparation of meat, the primary interest of this study, will be assessed by a food frequency questionnaire designed especially for this purpose.

Dietary fat and the risk of breast cancer.

Age-adjusted dietary fat intake of 133 incident Dutch breast cancer cases was significantly (p less than 0.01) higher than in 289 apparently healthy controls (mean and standard deviation: 102 +/- 36 g and 92 +/- 30 g, respectively). The age-adjusted relative odds of breast cancer showed a positive trend (p less than 0.05) with increasing fat intake. The multivariate adjusted relative odds was 3.5 (95% Cl = 1.6-7.6) for subjects in the highest quintile of fat intake (above 113 g) compared to those in the lowest quintile (below 65 g); this corresponds to a 30% increased risk per 10% of energy derived from fat. The association could not be attributed to energy intake, nor to the degree of saturation of the fat nor to any specific dietary source of fat.

The study population: general characteristics and potential confounding factors.

OBJECTIVE: To test the representativity of the study population and to identify potential selection bias. DESIGN: Non-response analysis and comparison with other representative samples from the Dutch population. Description of physical and clinical biochemical variables as well as health and lifestyle characteristics among low vitamin B6 groups and reference groups. RESULTS AND CONCLUSIONS: The non-response rate for the food frequency questionnaire was 54%; subsequently, non-response for the detail study was 42%. A greater proportion of respondents to the FFQ and of participants in the reference group of the study followed a special dietary regimen or a therapeutic diet or used dietary supplements compared with non-respondents, indicating that we may have selected a somewhat more health conscious reference group. There were no differences in vitamin B6 intake (absolute or per g protein) between participants and the total group of non-respondents for the detail study. Selection of a low B6 group did not result in important bias regarding physical, biochemical or general health and lifestyle characteristics. Exceptions were a difference in the proportion of dieters (younger women) and supplement users (older women) and a difference in creatinine clearance and supplement use between reference and low B6 groups. The differences found, however, were small. Nonetheless, these factors have to be taken into account when analysing and interpreting the results.

Dietary intake among adults with special reference to vitamin B6.

OBJECTIVE: To assess the adequacy of the dietary intake in general, and that of vitamin B6 intake especially. DESIGN AND SUBJECTS: Dietary intake based on 3 d diet-records was assessed among a random sample of the adult Dutch population (the reference group, n = 300) aged 20-79 y, stratified for age and gender and among a group with a low vitamin B6 intake, selected by means of a food frequency questionnaire. RESULTS: Among the reference group, absolute vitamin B6 intake on average amply met the RDA in all age-gender categories, whereas the adequate level of 20 microg vitamin B6 per gram protein, was on average met by men only. The prevalences of a vitamin B6 intake below the minimum requirement (absolute) of 1 mg/d was 1-11% and below the average minimum requirement of 15 microg/g protein was 5-12% for the various age-sex reference groups. Average intake of folate among women of childbearing age did not meet the recommendation of 400 microg/d for those who want to become pregnant. Average intake of iron and iodine was also below recommended levels among women aged 20-49 y. Both absolute vitamin B6 intake and the vitamin B6/protein ratio calculated with the diet records was lower among the low vitamin B6 groups than among the reference groups, indicating that the preselection of groups with low vitamin B6 intakes on the basis of a food frequency questionnaire was successful. Intake of energy and macro- and micronutrients, as well as a nutrient density of the diet were lower among low vitamin B6 groups than among reference groups. CONCLUSIONS: It is concluded that a low vitamin B6 intake is the result of both the quantity (energy) and quality (nutrient density) of the food consumed. The effects of this are not restricted to vitamin B6 and therefore, the low vitamin B6 groups have a combination of relatively low intakes.

Iron intake and iron status among adults in the Netherlands.

OBJECTIVE: To assess the adequacy of iron intake and status, the prevalence of marginal iron status, the physiological and lifestyle factors influencing iron status and the role of dietary factors affecting the bioavailability of iron among Dutch adults. DESIGN: Food consumption was measured with 3 d diet records. Iron status and prevalence of iron deficiency and iron accumulation were evaluated using different criteria. Physical, biochemical and lifestyle characteristics were determined and relationships with iron status were evaluated by bi- and multivariate regression analysis. SUBJECTS: A sample of 444 adults, aged 20-79 y stratified for sex and 10 y age classes, with an overrepresentation of people with a low habitual intake of vitamin B6. RESULTS: Average iron intake was higher than the recommended daily allowance for the Netherlands in all sex-age groups except women aged 20-49, in which group average iron intake was 23% below the recommendation. Early iron deficiency, as reflected in low ferritin levels, was not found among men aged 20-49, but was observed in 5% of women aged 50-79, 11% of men aged 50-79, and 16% of women aged 20-49. Iron deficiency anaemia as reflected in low haemoglobin levels was found in 0-5% of the age-sex groups. Among men and women, 16% and 13% of variance in haemoglobin level, respectively, could be explained by physiological and dietary factors. For ferritin, the proportions were 36% and 34%, respectively. Iron status was correlated negatively with the vegetable fraction of the diet, and positively with factors from the animal fraction (haem iron, animal protein, meat). Further, haemoglobin was positively correlated with body weight among men, and with both age and use of oral contraceptives among women. Both among men and women, blood donorship in the six months prior to the study was negatively associated with serum ferritin levels. CONCLUSIONS: Women aged 20-49 are the adult sex-age group with the greatest risk of developing (an early stage of) iron depletion. The most important dietary factors influencing the iron status are the type of iron (haem/non-haem) and factors affecting the bioavailability of iron.

Food consumption methods. Development, reproducibility and validation of a food frequency questionnaire for vitamin B6.

OBJECTIVE: The correct classification of adults with a habitual low vitamin B6 intake by means of a food frequency questionnaire (FFQ). Assessment of reproducibility of the food frequency questionnaire and of the relative validity as compared to 3 d diet records (DR). DESIGN: A self-administered food frequency questionnaire (FFQ) to measure habitual vitamin B6 intake was developed using the data base of the first Dutch National Food Consumption Survey 1987/88 (DNFCS). The frequency and quantity of consumption of 92 (combinations of) food products, contributing to about 95% of vitamin B6 intake, were asked for. Recent food consumption was measured with 3 d diet records. Reproducibility of the FFQ was assessed after 10 months (n = 330). SUBJECTS: Randomly selected men and women aged 20-79 y, stratified for 10 y age classes and sex. RESULTS: A total number of 2867 FFQs was adequately completed (response rate 46%). A low vitamin B6 group was selected from the lowest tertile of age-gender specific vitamin B6 intake (36 men and 36 women, aged 20-49 and 36 men and 36 women, aged 50-79) and a so-called reference group (n = 300) was selected at random. The ratio of vitamin B6 intake according to FFQ and DR (FFQ/DR) varied between 0.77 and 0.99 for the various age-gender-study groups; for vitamin B6/g protein the FFQ/DR ratio varied between 1.00 and 1.10. After correction for intraindividual variance Pearson correlation coefficients between vitamin B6 intake according to FFQ and DR varied between 0.27 and 0.95 for the various age-gender-study groups, for vitamin B6/g protein the corrected Pearson correlation coefficients varied between 0.27 and 0.65. Of the subjects selected in the low B6 groups, 61-81% fell in the lowest tertile of vitamin B6 intake according to diet records and 3-6% fell in the extreme opposite tertile. The percentage subjects selected in the same/opposite quartile of vitamin B6 intake according to FFQ and DR was 50/11 for men, and 45/18 for women. Pearson correlation coefficients for vitamin B6 intake according to the first and the second FFQ were 0.64 and 0.72 for men and women, respectively; for vitamin B6/g protein these values were 0.70 and 0.51 for men and women, respectively. The proportion of subjects classified in the same/extreme opposite tertile of vitamin B6 intake was 56/6 and 62/5 for men and women, respectively. CONCLUSIONS: It is concluded that the FFQ was adequate for the selection of subjects with a habitually low vitamin B6 intake.

Micronutrient status, with special reference to vitamin B6.

OBJECTIVE: To assess the adequacy of micronutrient status among the adult population, with special reference to vitamin B6 status. DESIGN AND SUBJECTS: Micronutrient status was assessed among a random sample of the adult Dutch population (reference group, n = 300), aged 20-79 y, stratified for age and gender, and among a group with a low vitamin B6 intake (n = 144). RESULTS: Low vitamin B6 groups had lower mean levels of erythrocyte and plasma pyridoxal (PL) and pyridoxal-5'-phosphate (PLP), urinary excretion of 4-pyridoxic acid, basal and stimulated erythrocyte aspartate aminotransferase (EAST) and erythrocyte alanine aminotransferase (EALT) activities and EAST stimulation coefficients but not of EALT stimulation coefficients, handgripstrength and 24 h homocysteine excretion before and after a methionin load test. Besides, plasma levels of vitamin C, B12 and folate were lower among low B6 than among reference groups indicating a combined low vitamin status. Direct biomarkers of vitamin B6 intake (plasma PLP and 4-pyridoxic acid excretion) were significantly related to more functional parameters (EAST, EALT and alpha-EAST). Among random reference groups the prevalence of plasma PLP values below 19 nmol/l was 3-7% for different age-gender groups, with the highest value of 16% among men aged 50-79 years. The prevalence of high values of erythrocyte glutathion reductase stimulation coefficient (alpha-EGR) and low levels of serum vitamin B12 and C was not more than 5% among different age-gender reference groups. CONCLUSIONS: Direct biomarkers of vitamin B6 intake confirmed the preselection of a group with a low vitamin B6 intake. The results suggest that the sensitivity of vitamin B6 status parameters for low vitamin B6 intake was highest for the direct vitamin B6 status parameters and lowest for handgripstrength and homocysteine excretion after a methionin load; results for enzyme stimulation coefficients were intermediate. The prevalence of below adequate status parameters for vitamin B2, B6, B12 and C was not more than 7% among the different age-gender groups, with the exception of a value of 16% for plasma PLP levels below 19 nmol/l among men aged 50-79.

Dietary and other determinants of vitamin B6 parameters.

OBJECTIVE: To assess the dietary, physical, biochemical and lifestyle determinants of vitamin B6 status parameters among healthy adults. DESIGN AND SUBJECTS: Dietary intake and status variables as well as other relevant characteristics were determined among 444 adults, aged 20-79 y and stratified for sex and 10-years age classes with a randomly selected control group (n = 300) and an over representation of persons with a low habitual vitamin B6 intake (n = 144). RESULTS AND CONCLUSIONS: The direct status parameters (plasma pyridoxal-5'-phosphate (PLP), plasma pyridoxal + PLP (PL + PLP), and 4-pyridoxic acid (4-PA) excretion) were clearly related to dietary variables and plasma concentrations of vitamin C (women only), vitamin B12 and folate. The total percentage of variance in p-PLP explained in multivariate regression analysis was 41 and 30% in men and women, respectively. The most important explaining variables besides vitamin B6 intakes were variables closely related to PLP-metabolism: albumin and alkaline phosphatase. Biochemical function related status parameters showed less statistically significant correlations with dietary variables. Four to 24% of the variance in the stimulation coefficients of erythrocyte aspartate aminotransferase (alpha-EAST) and erythrocyte alanine aminotransferase (alpha-EALT) and change in homocysteine excretion after a methionin load was explained by a combination of dietary, physiological and lifestyle related variables. The low percentages explained for some variables, notably alpha-EAST (women) and the change in homocysteine excretion after a methionin load (men), suggests that these parameters are not sensitive to the level of vitamin B6 intake as found in the present study. Alcohol contributed in many of the explaining models for vitamin B6 status parameters. Therefore, when assessing the vitamin B6 status of a population, it is important to estimate the level of alcohol intake as well. Furthermore, the results illustrate the importance of sex related differences in the metabolism of some parameters, especially homocysteine excretion. The variance in the clinical function related status parameter measured in the present study, handgripstrength, was explained for 50% by a combination of age, body weight and Quetelet Index (QI) with no important contribution of dietary variables.

Folate intake and status among adults in the Netherlands.

OBJECTIVE: To assess the adequacy of folate intake and status among adults in the Netherlands. DESIGN AND SUBJECTS: Dietary intake was measured by 3 d diet records among 444 adults, aged 20-79 y, stratified for sex and 10 y age classes, with an overrepresentation of people with a low habitual intake of vitamin B6. Serum folate and other physical, biochemical and lifestyle characteristics were determined, and interrelationships were evaluated by bi- and multivariate regression analysis. RESULTS: Mean folate intake was 325 and 308 microg/d in men aged 20-49 and 50-79 y, respectively. In both younger and older women mean folate intake was 270 microg/d. The prevalence of intakes below the lower limit of the recommended range (200-300 microg/d) was 10-20% among different age-gender groups. No intakes below the average minimum requirement of 100 microg/d were observed. The recommendation of 400 microg folate/d for women who wish to become pregnant was not met by 95% of the women aged 20-49 y. Potatoes, vegetables and fruit provided 36% of folate in the diet; other important sources were bread (18%) and dairy products (16%). Mean serum folate levels were 11.3 and 12.1 nmol/l in younger and older men, respectively. In younger and older women these levels were 12.2 and 14.2 nmol/l, respectively. Serum folate levels below 5 nmol/l (the 2.5 percentile of healthy blood donors) were present in 4% of the older men, but not in the other age-gender-groups. Serum folate levels were clearly influenced by recent folate intake. Furthermore, physiological and lifestyle variables, notably alcohol and tobacco use, were important determinants of serum folate. CONCLUSION: The folate intake among adult men and women was adequate in view of recommended daily intakes. However, the folate intake among women did not meet the recommendation for those who want to become pregnant. According to criteria derived from homocysteine metabolism as related to cardiovascular disease, folate status may not be adequate in 60-79% of adult age-sex groups.

An effective way to identify dietary risks among adults--general discussion and conclusions.

OBJECTIVE: To identify dietary risks among adults in the Netherlands, with special reference to micronutrient intake, more specifically vitamin B6, folate, iron and iodine. DESIGN AND SUBJECTS: Dietary intake, nutritional status and other physiological and lifestyle characteristics were measured among 444 adults, aged 20-79 y, stratified for 10 y age-classes and sex, with an overrepresentation of subjects with a habitual low intake of vitamin B6. DISCUSSION AND CONCLUSION: A general discussion of the study design and possible selection bias. Identification of groups at risk and the possible impact of low intake of several micronutrients. A discussion of dietary and other determinants of micronutrient status parameters. The results of the present survey suggest that even at vitamin B6 intakes in the lower tertile of the intake range there is no great effect on biochemical functioning. However, blood vitamin levels may not be optimal with regard to cardiovascular risk among a non-negligible part of the population and a recommendation for an adequate vitamin intake seems warranted, despite the many uncertainties concerning the relationship between vitamin intake and cardiovascular risk. Furthermore, the results of the present survey stress the importance of adequate dietary advice for women of childbearing age.

Iodine intake and urinary excretion among adults in the Netherlands.

OBJECTIVE: To assess the prevalence of low and marginal iodine intake and urinary iodine excretion among adults in the Netherlands and to investigate determinants of urinary iodine excretion. DESIGN AND SUBJECTS: The study population consisted of 444 people aged 20-79 y, balanced for sex and 10 y age classes with an over-representation of people with a low habitual intake of vitamin B6. Food consumption was measured by three day food records and 24 h urine was sampled twice. RESULTS AND CONCLUSIONS: On average, iodine intake (mean of three days) in men was in the recommended range of 150-300 microg/d, but average intake in women was not. Mean 24 h urinary excretion values confirmed this observation. Estimation of the prevalence of low iodine excretion depended on the parameter chosen (absolute per 24 h, per kg body weight per 24 h, as concentration or per creatinin). The prevalence of low iodine supply, based on intake <100 microg/d (mean of three days) and intake or excretion parameters per creatinin excretion or per kg body weight, varied from 4-14% among adult women and from 5-17% among adult men. The prevalence of marginal iodine intake (<50 microg/d) and excretion was less than 5% in all adult age-sex groups. Urinary iodine excretion was most strongly associated with intake of iodine as such or as bread in combination with urinary excretion of sodium or potassium, confirming the importance of iodized salt (in bread) for iodine status. Age and total energy intake had a relatively minor impact on urinary iodine excretion.

Validation of a dietary questionnaire used in a large-scale prospective cohort study on diet and cancer.

OBJECTIVE: The study was conducted to assess the validity of a self-administered 150-item food frequency questionnaire (FFQ), used in a cohort study on diet and cancer (120,852 men and women, aged 55-69). DESIGN & SUBJECTS: The study was carried out in a subgroup of the cohort (59 men and 50 women) 2 years after the baseline FFQ was completed. A dietary record, kept over three 3-day periods, 4-5 months apart, served as reference method. To evaluate the representativeness of the study population for the entire cohort, a comparison was made with the baseline questionnaire of a random sample of the cohort. RESULTS: Pearson correlation coefficients between nutrient intakes assessed by the record and the FFQ that was completed afterwards ranged from 0.40 (95% CI: 0.22-0.54) for vitamin B1 to 0.86 (95% CI: 0.80-0.90) for alcohol intake, with correlations for most nutrients between 0.6 and 0.8. Adjustment for energy intake and sex did not materially affect these correlations, except the correlation for fat intake, which changed from 0.72 to 0.52. Correlation coefficients were only slightly modified when the results were extrapolated to the cohort at large. Correction of correlation coefficients for attenuation by day-to-day variance in the record data improved them by 0.07 on average. CONCLUSIONS: It is concluded that the FFQ is able to rank subjects according to intake of food groups and nutrients. Despite a better performance of validation study participants, this conclusion also applies to the cohort at large.

Operationalization of food consumption surveys in Europe: recommendations from the European Food Consumption Survey Methods (EFCOSUM) Project.

BACKGROUND: The EFCOSUM (European Food Consumption Survey Methods) Project aims at harmonizing food consumption surveys in European countries within the perspective of an overall Public Health Monitoring Programme. Harmonization implies the need for a common framework of procedures and tools, that are applicable and feasible in all potentially interested countries. A major element in such a framework is the protocol for the operationalization of a food consumption survey, referring to all practical, logistical and material conditions that need to be fulfilled in order to guarantee a successful implementation of such a survey. OBJECTIVE: The objective of this paper was to review a number of aspects of operationalization of food consumption surveys in detail. On the basis of the currently available knowledge and experience in Europe, consensus recommendations have been elaborated for an operationalization protocol that would be feasible for all European countries. METHODS: The EFCOSUM recommendations with respect to operationalization of food consumption surveys in Europe are mainly based on three sources of information, which have been discussed at several ad hoc expert meetings: experience from previous collaborative epidemiological studies, literature searches and results of two questionnaires, distributed among representatives from 23 European countries-all experts affiliated with experienced organizations in the fields of nutrition research and related fields. RESULTS: Consensus recommendations have been set up for the following topics: sampling, recruitment, fieldwork, biomarkers, interviewer qualifications and training and quality control. These recommendations have to be considered the best achievable common denominator within Europe at this time. In a number of cases, recommendations are presented in a hierarchical way, with a gradation from first choice options towards acceptable alternatives. CONCLUSIONS: It can be concluded that a high degree of standardization of fieldwork can be achieved within Europe. A number of specific problems and constraints will have to be solved in connection with the conduction of a real survey. These problems include, amongst others, country-specific decisions on, for example, target population, detailed sampling and recruiting procedures, interview setting and support. However, on the whole, these problems can be overcome and the main recommendations presented in this paper are considered feasible for every country in Europe. Application of the EFCOSUM operationalization protocol in European countries will contribute significantly to the quality and comparability of food consumption data across Europe. It is anticipated that the policy supporting and orienting potential of this type of databases-both at the national and at the EU supranational level-will be increased accordingly.

Diet and other life-style factors in high and low socio-economic groups (Dutch Nutrition Surveillance System).

Insight into the occurrence of and the association between certain socio-economic variables and life-style characteristics is necessary for preventive nutrition and health policy. The prevalence of and the interdependencies among these variables were examined in 1930 men and 2204 women aged 19 to 85 who participated in the Dutch National Food Consumption Survey 1987-1988. Dietary data were based on a two-day record. The associations among discrete variables were analysed using log-linear models. Analysis of covariance was used to explore the effects of the aggregate socio-economic status (SES) on dietary intake and anthropometry, whereas differences in food intake and SES were assessed by the non-parametric test of Kruskal and Wallis. In comparison to subjects with a high SES in people with a low SES a higher proportion of smokers (48 vs 32 per cent) was observed, a higher prevalence of obesity (39 vs 28 per cent), a higher percentage of heavy coffee drinkers (greater than six cups per day, 23 vs 17 per cent), and more subjects who skipped breakfast (19 vs 11 per cent). In the highest SES class more subjects used nutritional supplements (18 vs 11 per cent), more subjects followed a dietary rule (five vs two per cent), such as a vegetarian diet, and a higher proportion used more than three alcoholic drinks per day (19 vs 15 per cent). A higher SES was associated with a lower fat intake, but the differences (expressed as per cent of energy intake) were rather small and even absent among women when the contribution of alcohol to energy was not taken into account. In general, dietary intake among subjects in higher SES groups tended to be closer to dietary recommendations. The results indicate that a lower SES is accompanied by a higher prevalence of several indicators of an unhealthy life-style.