Epidemiological assessment of diet: a comparison of a 7-day diary with a food frequency questionnaire using urinary markers of nitrogen, potassium and sodium

Urinary potassium is as reliable as urinary nitrogen for use as a recovery biomarker in dietary studies of free living individuals

Twenty-four-hour urinary nitrogen (UN) is commonly used to validate dietary assessment methods. Potassium is more widespread in food than nitrogen, but the role of 24-h urinary potassium (UK) as a biomarker has been less studied and characterized. To investigate the performance of UK as a recovery biomarker compared with UN in subjects consuming their normal diet, 7 males and 6 females consumed known amounts of food based on their habitual varying diet (assessed beforehand from 4 consecutive 7-d food diaries) for 30 d in a metabolic suite. All daily urine samples and dietary duplicates were collected, and N and K were measured. Stool K was determined in 5-d pooled samples. Thirty-day mean analyzed K intake was 121.3 +/- 25.1 (mean +/- SD) mmol/d. Overall, 77 +/- 6.7% of K in the diet was excreted in urine and 18 +/- 5% in stool. Dietary K was correlated with UK (r = 0.89; P < 0.001). UN was 77.7 +/- 6.6% of N intake and was correlated with N in the diet (r = 0.87; P < 0.001). When 16 d of intake and 8 d of urine-collection measurements were randomly selected from the 30-d measurements, correlations were significant for both K (r = 0.86; P < 0.001) and N (r = 0.92; P < 0.001). The high correlations between UK and K in the diet show that UK is a reliable recovery biomarker for use in studies of dietary measurement error. Factors for use of urinary N as a recovery biomarker are also confirmed.

Validity and systematic error in measuring carotenoid consumption with dietary self-report instruments

Vegetables and fruits are rich in carotenoids, a group of compounds thought to protect against cancer. Studies of diet-disease associations need valid and reliable instruments for measuring dietary intake. The authors present a measurement error model to estimate the validity (defined as correlation between self-reported intake and "true" intake), systematic error, and reliability of two self-report dietary assessment methods. Carotenoid exposure is measured by repeated 24-hour recalls, a food frequency questionnaire (FFQ), and a plasma marker. The model is applied to 1,013 participants assigned between 1995 and 2000 to the nonintervention arm of the Women's Healthy Eating and Living Study, a randomized trial assessing the impact of a low-fat, high-vegetable/fruit/fiber diet on preventing new breast cancer events. Diagnostics including graphs are used to assess the goodness of fit. The validity of the instruments was 0.44 for the 24-hour recalls and 0.39 for the FFQ. Systematic error accounted for over 22% and 50% of measurement error variance for the 24-hour recalls and FFQ, respectively. The use of either self-report method alone in diet-disease studies could lead to substantial bias and error. Multiple methods of dietary assessment may provide more accurate estimates of true dietary intake.

Meat intake and risk of stomach and esophageal adenocarcinoma within the European Prospective Investigation Into Cancer and Nutrition (EPIC)

BACKGROUND

Dietary factors are thought to have an important role in gastric and esophageal carcinogenesis, but evidence from cohort studies for such a role is lacking. We examined the risks of gastric cancer and esophageal adenocarcinoma associated with meat consumption within the European Prospective Investigation Into Cancer and Nutrition (EPIC) cohort.

METHODS

A total of 521,457 men and women aged 35-70 years in 10 European countries participated in the EPIC cohort. Dietary and lifestyle information was collected at recruitment. Cox proportional hazard models were used to examine associations between meat intake and risks of cardia and gastric non-cardia cancers and esophageal adenocarcinoma. Data from a calibration substudy were used to correct hazard ratios (HRs) and 95% confidence intervals (CIs) for diet measurement errors. In a nested case-control study, we examined interactions between Helicobacter pylori infection status (i.e., plasma H. pylori antibodies) and meat intakes. All statistical tests were two-sided.

RESULTS

During a mean follow-up of 6.5 years, 330 gastric adenocarcinoma and 65 esophageal adenocarcinomas were diagnosed. Gastric non-cardia cancer risk was statistically significantly associated with intakes of total meat (calibrated HR per 100-g/day increase = 3.52; 95% CI = 1.96 to 6.34), red meat (calibrated HR per 50-g/day increase = 1.73; 95% CI = 1.03 to 2.88), and processed meat (calibrated HR per 50-g/day increase = 2.45; 95% CI = 1.43 to 4.21). The association between the risk of gastric non-cardia cancer and total meat intake was especially large in H. pylori-infected subjects (odds ratio per 100-g/day increase = 5.32; 95% CI = 2.10 to 13.4). Intakes of total, red, or processed meat were not associated with the risk of gastric cardia cancer. A positive but non-statistically significant association was observed between esophageal adenocarcinoma cancer risk and total and processed meat intake in the calibrated model. In this study population, the absolute risk of development of gastric adenocarcinoma within 10 years for a study subject aged 60 years was 0.26% for the lowest quartile of total meat intake and 0.33% for the highest quartile of total meat intake.

CONCLUSION

Total, red, and processed meat intakes were associated with an increased risk of gastric non-cardia cancer, especially in H. pylori antibody-positive subjects, but not with cardia gastric cancer.

Dietary antioxidants and asthma in adults

BACKGROUND

Several antioxidant nutrients have been reported to be inversely associated with asthma. A study was undertaken to assess the independent associations of these nutrients with asthma in adults.

METHODS

A nested case-control study was performed in 515 adults with physician diagnosed asthma and 515 matched controls using dietary data obtained from 7 day food diaries. The main outcome measures were physician diagnosed asthma and current symptomatic asthma (diagnosed asthma and self-reported wheeze within the previous 12 months).

RESULTS

Cases were similar to controls in age, sex, social class, and daily energy intake but had a lower median intake of fruit (132.1 v 149.1 g/day, p< or =0.05). 51.5% of the population reported zero consumption of citrus fruit; relative to these individuals, people who consumed >46.3 g/day had a reduced risk of diagnosed and symptomatic asthma (OR adjusted for potential confounders 0.59 (95% CI 0.43 to 0.82) and 0.51 (95% CI 0.33 to 0.79), respectively). In nutrient analysis, dietary vitamin C and manganese were inversely and independently associated with symptomatic asthma (adjusted OR per quintile increase 0.88 (95% CI 0.77 to 1.00) for vitamin C and 0.85 (95% CI 0.74 to 0.98) for manganese), but only manganese was independently associated with diagnosed asthma (OR 0.86 (95% CI 0.77 to 0.95)). Adjusted plasma levels of vitamin C were significantly lower in symptomatic cases than in controls (54.3 v 58.2 micromol/l, p = 0.003).

CONCLUSIONS

Symptomatic asthma in adults is associated with a low dietary intake of fruit, the antioxidant nutrients vitamin C and manganese, and low plasma vitamin C levels. These findings suggest that diet may be a potentially modifiable risk factor for the development of asthma.

A debriefing session with a nutritionist can improve dietary assessment using food diaries

The objective of the current study was to evaluate the effect of a debriefing call on nutrient intake estimates using two 3-d food diaries among women participating in the Women's Health and Interview Study (WISH) Diet Validation Study. Subjects were 207 women with complete data and six 24-h recalls (24-HR) by telephone over 8 mo followed by two 3-d food diaries during the next 4 mo. Nutrient intake was assessed using the food diaries before and after a debriefing session by telephone. The purpose of the debriefing call was to obtain more detailed information on the types and amounts of fat in the diet. However, due to the ubiquitous nature of fat in the diet, the debriefing involved providing more specific detail on many aspects of the diet. There was a significant difference in macronutrient and micronutrient intake estimates after the debriefing. Estimates of protein, carbohydrate, and fiber intake were significantly higher and total fat, monounsaturated fat, saturated fat, vitamin A, vitamin C, alpha-tocopherol, folic acid, and calcium intake were significantly lower after the debriefing (P < 0.05). The limits of agreement between the food diaries before and after the debriefing were especially large for total fat intake, which could be under- or overestimated by approximately 15 g/d. The debriefing call improved attenuation coefficients associated with measurement error for vitamin C, folic acid, iron, alpha tocopherol, vitamin A, and calcium estimates. A hypothetical relative risk (RR) = 2.0 could be attenuated to 1.16 for folic acid intake assessed without a debriefing but to only 1.61 with a debriefing. Depending on the nutrients of interest, the inclusion of a debriefing can reduce the potential attenuation of RR in studies evaluating diet disease associations.

Correlations between estimated and true dietary intakes: using two instrumental variables

PURPOSE

We describe a new application of the method of triads that allows an estimate of the correlation between a dietary questionnaire measure (Q) and true intake (T).

METHODS

Three surrogate variables Q, M, and P are observed where M and P are both instrumental (often biological) variables. A reference dietary method (R) is not required. The variables M and P may be concentration rather than recovery biomarkers. Estimating equations produce Corr(Q,T), Corr(M,T), Corr(P,T), conditional on assumptions about error correlations. Correlations between errors in both Q and a reference dietary measure can also be estimated if R is available. A small validation study of California Seventh-day Adventists provided food frequency, repeated 24-hour dietary recalls (R), and biological data (blood, overnight urines, and subcutaneous fat).

RESULTS

Values of Corr(Q,T) ranged between 0.40 and 0.66. Values of Corr(R,T) were higher, between 0.48 and 0.83. Estimated correlations between errors in R and Q were all positive.

CONCLUSIONS

When carefully chosen, M and P, rather than M and R, should better satisfy assumptions about error correlations. Food frequency data and repeated 24-hour recalls both provide estimates of T, but the latter has greater validity. Standard errors suggest that for good precision Corr(Q,T) requires large validation studies (2000-3000 subjects).

A practical method for collecting 3-day food records in a large cohort

BACKGROUND

Recent studies suggest that diet records are more valid measures of nutrient intake than are food-frequency questionnaires. However, food records are considered unsuitable for large studies due to the need to train participants and to review and correct completed records.

METHODS

We evaluated a self-administered 3-day food record protocol in Washington State. One hundred men and women age 50-76 years were mailed a food record and serving-size booklet. Sixty-five people returned a completed food record and were subsequently interviewed to obtain missing information. The food records were analyzed with and without added information from the interview.

RESULTS

The most common error was incomplete description, which affected 8% of recorded foods. Differences in mean nutrient intake between the uncorrected and corrected records were within 5%, and nutrient estimates from the 2 methods were highly correlated.

CONCLUSIONS

This streamlined protocol yielded data comparable to those collected by more burdensome protocols, suggesting that the use of food records may be feasible in large cohort studies.

Plasma ascorbic acid concentrations and fat distribution in 19,068 British men and women in the European Prospective Investigation into Cancer and Nutrition Norfolk cohort study

BACKGROUND

Antioxidants, such as ascorbic acid, play a role in scavenging free radicals to protect against oxidative endothelial damage. Excess fat may promote fatty acid oxidation and increase free radical concentrations, which could result in increased antioxidant use. Whether plasma ascorbic acid concentrations are associated with fat distribution remains unclear.

OBJECTIVE

Our aim was to examine the association between abdominal obesity, as measured by the waist-to-hip ratio, and plasma ascorbic acid concentrations in the general population.

DESIGN

We examined the cross-sectional relation between anthropometric measurements of fat distribution and plasma ascorbic acid concentrations in 19 068 men and women aged 45-79 y without known chronic illness. Dietary ascorbic acid intake was estimated for a subgroup of 8178 men and women who kept 7-d food diaries coded for nutrient intake.

RESULTS

The waist-to-hip ratio was inversely related to plasma ascorbic acid concentrations in both men and women. This association was independent of body mass index, age, vitamin supplement use, cigarette smoking, and socioeconomic group. Waist and hip circumferences showed separate and opposite associations with plasma ascorbic acid concentrations, independent of body mass index and other covariates. Dietary ascorbic acid intake only partly explained the observed associations.

CONCLUSIONS

Plasma ascorbic acid was associated with fat distribution independent of body mass index. Differences in dietary intake and lifestyle habits, underlying systemic oxidative stress, or both may explain the inverse relation between fat distribution and plasma ascorbic acid concentrations. Additional studies are needed to determine the underlying explanation of these observations.

Empirically derived dietary patterns and risk of postmenopausal breast cancer in a large prospective cohort study

BACKGROUND

Inconsistent associations have been reported between diet and breast cancer.

OBJECTIVE

We prospectively examined the association between dietary patterns and postmenopausal breast cancer risk in a US-wide cohort study.

DESIGN

Data were analyzed from 40 559 women who completed a self-administered 61-item Block food-frequency questionnaire in the Breast Cancer Detection Demonstration Project, 1987-1998; 1868 of those women developed breast cancer. Dietary patterns were defined by using principal components factor analysis. Cox proportional hazard regression was used to assess breast cancer risk.

RESULTS

Three major dietary patterns emerged: vegetable-fish/poultry-fruit, beef/pork-starch, and traditional southern. The vegetable-fish/poultry-fruit pattern was associated with higher education than were the other patterns, but was similar in nutrient intake to the traditional southern pattern. After adjustment for confounders, there was no significant association between the vegetable-fish/poultry-fruit and beef/pork-starch patterns and breast cancer. The traditional southern pattern, however, was associated with a nonsignificantly reduced breast cancer risk among all cases (in situ and invasive) that was significant for invasive breast cancer (relative hazard = 0.78; 95% CI = 0.65, 0.95; P for trend = 0.003). This diet was also associated with a reduced risk in women without a family history of breast cancer (P = 0.05), who were underweight or normal weight [body mass index (in kg/m(2)) < 25; P = 0.02], or who had tumors positive for estrogen receptor (P = 0.01) or progesterone receptor (P = 0.003). Foods in the traditional southern pattern associated with reduced breast cancer risk were legumes, low mayonnaise-salad dressing intake, and possibly cabbage.

CONCLUSIONS

The traditional southern diet or its components are associated with a reduced risk of invasive breast cancer in postmenopausal women.

Milk consumption, stroke, and heart attack risk: evidence from the Caerphilly cohort of older men

OBJECTIVE

To examine associations between milk consumption and incident heart disease and stroke.

DESIGN

A representative population sample of men was asked to weigh and record their food intake for seven days. The total consumption of milk was obtained from these records. Details of all deaths and vascular events were collected during the following 20 years. Incident ischaemic strokes and heart disease events were diagnosed by standard criteria.

SETTING

The Caerphilly cohort, a representative population sample of men in South Wales, aged 45-59 when first seen in 1979-83.

PARTICIPANTS

A representative 3:10 subsample of the men in the cohort.

MAIN RESULTS

665 men (87% of those approached) returned satisfactory seven day diet diaries. After adjustment, the relative odds of an event in the men whose milk consumption was the median or higher, relative to those with lower intakes of milk, were 0.52 (0.27 to 0.99) for an ischaemic stroke and 0.88 (0.56 to 1.40) for an ischaemic heart disease event. Deaths from all causes were similar in the two milk consumption groups (relative odds 1.08; 0.74 to 1.58).

CONCLUSIONS

These results give no convincing evidence of an increased risk of vascular disease from milk drinking. Rather, the subjects who drank more than the median amount of milk had a reduced risk of an ischaemic stroke, and possibly a reduced risk of an ischaemic heart disease event. These conclusions are in agreement with the results of a previously reported overview of 10 large, long term cohort studies based on food frequency intake records.

Plasma Carotenoids and Recurrence-Free Survival in Women With a History of Breast Cancer

Purpose

Previous studies suggest that diet may affect recurrence or survival rates in women who have been diagnosed with breast cancer. The purpose of this study was to examine the relationship between plasma carotenoid concentration, as a biomarker of vegetable and fruit intake, and risk for a new breast cancer event in a cohort of women with a history of early-stage breast cancer.

Methods

Participants were 1,551 women previously treated for breast cancer who were randomly assigned to the control arm of a diet intervention trial between March 1995 and November 2000. Outcome events were probed during semiannual interviews and verified by medical record review. During the period under study, 205 women had a recurrence or new primary breast cancer. Plasma carotenoid concentrations were measured in baseline blood samples. Hazard ratios (HR) and 95% CIs by quartiles of plasma carotenoids were computed, controlling for tumor stage, grade, and hormone receptor status; chemotherapy and tamoxifen therapy; clinical site; age at diagnosis; body mass index; and plasma cholesterol concentration.

Results

Women in the highest quartile of plasma total carotenoid concentration had significantly reduced risk for a new breast cancer event (HR, 0.57; 95% CI, 0.37 to 0.89), controlled for covariates influencing breast cancer prognosis.

Conclusion

Plasma carotenoids are a biologic marker of intake of vegetables and fruit, so this observation supports findings from previous studies that have linked increased vegetable and fruit intake with greater likelihood of recurrence-free survival in women who have been diagnosed with early-stage breast cancer.

Is the association with fiber from foods in colorectal cancer confounded by folate intake?

The effect of multivariate adjustment including folate on the strong protective effect of fiber in foods on colorectal cancer risk in the European Prospective Investigation into Cancer and Nutrition was investigated in 1,721 cases identified in the latest follow-up. The inclusion of an additional 656 cases confirmed our previously published results, with a strong and significant reduction in colorectal cancer risk of approximately 9% for each uncalibrated quintile increase in fiber (P(linear trend) < 0.001) compared with an 8% reduction in our previous report, which had not been adjusted for folate. Inclusion of the other covariates (physical activity, alcohol, smoking, and red and processed meat) confirmed this significant inverse association for colon cancer and strengthened the association with left-sided colon cancer (P < 0.001). After maximum adjustment, the association between fiber and rectal cancer was not significant, as in our previous analysis. The association with fiber from different food sources was analyzed, but again, there were no significance trends after maximum adjustment.

Dietary beta-cryptoxanthin and inflammatory polyarthritis: results from a population-based prospective study

BACKGROUND

Epidemiologic studies suggest that the antioxidant potential of dietary carotenoids may protect against the oxidative damage that can result in inflammation.

OBJECTIVE

We investigated the hypothesis that some dietary carotenoids are associated with a reduced risk of developing inflammatory polyarthritis (IP).

DESIGN

The European Prospective Investigation of Cancer Incidence (EPIC)-Norfolk study is a population-based, prospective study of >25,000 subjects who completed a baseline 7-d diet diary and were followed up to identify new cases of IP, which was defined as synovitis that affected > or = 2 joint groups. Dietary carotenoid intakes were computed from the diet diaries of these subjects, and a nested, case-control analysis was undertaken to compare carotenoid intake between case subjects and age- and sex-matched control subjects.

RESULTS

Eighty-eight incident cases of IP that occurred in the population surveyed were ascertained via the Norfolk Arthritis Register. The mean daily intakes of zeaxanthin and beta-cryptoxanthin were 20% and 40% lower, respectively, in the cases than in the 176 controls, but there were no significant differences in the intakes of either lutein or lycopene. Those subjects in the top one-third of intake of zeaxanthin and beta-cryptoxanthin were at a lower risk of developing IP than were subjects in the lowest one-third [odds ratios (95% CI): 0.48 (0.24, 0.94) and 0.51 (0.25, 1.02) for zeaxanthin and beta-cryptoxanthin, respectively]. The association with beta-cryptoxanthin was significant after adjustments were made for total energy and protein intakes and for cigarette smoking.

CONCLUSION

These data are consistent with previous evidence showing that a modest increase in beta-cryptoxanthin intake, equivalent to one glass of freshly squeezed orange juice per day, is associated with a reduced risk of developing inflammatory disorders such as rheumatoid arthritis.

Meat, fish, and colorectal cancer risk: the European Prospective Investigation into cancer and nutrition

BACKGROUND

Current evidence suggests that high red meat intake is associated with increased colorectal cancer risk. High fish intake may be associated with a decreased risk, but the existing evidence is less convincing.

METHODS

We prospectively followed 478 040 men and women from 10 European countries who were free of cancer at enrollment between 1992 and 1998. Information on diet and lifestyle was collected at baseline. After a mean follow-up of 4.8 years, 1329 incident colorectal cancers were documented. We examined the relationship between intakes of red and processed meat, poultry, and fish and colorectal cancer risk using a proportional hazards model adjusted for age, sex, energy (nonfat and fat sources), height, weight, work-related physical activity, smoking status, dietary fiber and folate, and alcohol consumption, stratified by center. A calibration substudy based on 36 994 subjects was used to correct hazard ratios (HRs) and 95% confidence intervals (CIs) for diet measurement errors. All statistical tests were two-sided.

RESULTS

Colorectal cancer risk was positively associated with intake of red and processed meat (highest [>160 g/day] versus lowest [<20 g/day] intake, HR = 1.35, 95% CI = 0.96 to 1.88; Ptrend = .03) and inversely associated with intake of fish (>80 g/day versus <10 g/day, HR = 0.69, 95 % CI = 0.54 to 0.88; Ptrend<.001), but was not related to poultry intake. Correcting for measurement error strengthened the associations between colorectal cancer and red and processed meat intake (per 100-g increase HR = 1.25, 95% CI =1.09 to 1.41, Ptrend = .001 and HR = 1.55, 95% CI = 1.19 to 2.02, Ptrend = .001 before and after calibration, respectively) and for fish (per 100 g increase HR = 0.70, 95% CI = 0.57 to 0.87, Ptrend<.001 and HR = 0.46, 95% CI = 0.27 to 0.77, Ptrend = .003; before and after correction, respectively). In this study population, the absolute risk of development of colorectal cancer within 10 years for a study subject aged 50 years was 1.71% for the highest category of red and processed meat intake and 1.28% for the lowest category of intake and was 1.86% for subjects in the lowest category of fish intake and 1.28% for subjects in the highest category of fish intake.

CONCLUSIONS

Our data confirm that colorectal cancer risk is positively associated with high consumption of red and processed meat and support an inverse association with fish intake.

Urinary Sucrose and Fructose as Biomarkers for Sugar Consumption

The use of 24-hour urinary sucrose and fructose as potential biomarkers for sugars consumption was investigated in two studies of 21 healthy participants living in a volunteer suite where dietary intake was known and all specimens collected. The dose-response was assessed in 12 males using a randomized crossover design of three diets containing constant levels of 63, 143, and 264 g of sugars for 10 days each. Both sugars and sucrose intake were significantly correlated with the sum of sucrose and fructose concentration in urine (0.888; P < 0.001). To assess effects with volunteers consuming their habitual varying diets, seven males and six females were fed their usual diet (assessed beforehand from four consecutive self-completed 7-day food diaries) for 30 days under controlled conditions in the volunteer suite. The mean (+/-SD) calculated total sugars intake was 202 +/- 69 g/d, 41% from sucrose. Mean (+/-SD) urinary sucrose and fructose were 36.6 +/- 16.6 and 61.8 +/- 61.3 mg/d, respectively. The sum of sucrose and fructose in urine was significantly correlated with sugars (0.841; P < 0.001) and sucrose intake (0.773; P = 0.002). In the regression, 200 g of sugars intake predicted approximately 100 mg of sucrose and fructose in urine. The correlation between individual means of randomized 16 days of sugars intake and 8 days of sugars excretion data (as used in validation studies) remained as high as that obtained with the means of 30-day measurements and the regression estimates were very similar. Twenty-four-hour urinary sucrose and fructose could be grouped into a new category of biomarkers, predictive biomarkers, that can be used in studies determining the structure of dietary measurement error in free living individuals and to relate sugars intake to disease risk.

[Adjustment for energy intake in the assessment of dietary risk factors]

Epidemiologic studies assessing the association between health status and nutritional factors raise the issue of adjusting for energy intake. Indeed, as most nutrients are highly correlated with energy intake which can itself be associated with disease risk, energy intake needs to be adjusted for upon assessing the effect of a specific nutrient. To avoid problems of estimation and interpretation incurred by the use of the standard method which rests on directly adjusting for energy intake, several other methods have been suggested. Namely, the density method uses the ratio of nutrient intake over total energy intake, the residual method relies on the residuals from the regression of nutrient intake on total energy intake, and the partition method fits energy from the nutrient and energy from other sources. These methods yield estimates of different effects but do not allow direct estimation of specific nutrient effects. Estimated effects combine specific and generic energy effects of nutrients and reflect effects of adding or substituting one nutrient for another. We review and apply these methods to the assessment of the association between protein intake and colorectal adenoma occurrence in the E3N-EPIC cohort. This example illustrates how considering findings from all of these methods rather than one single method can lead to a more in-depth understanding of such associations and provide useful guidance for nutritional recommendations.

Human exposure and internal dose assessments of acrylamide in food

This review provides a framework contributing to the risk assessment of acrylamide in food. It is based on the outcome of the ILSI Europe FOSIE process, a risk assessment framework for chemicals in foods and adds to the overall framework by focusing especially on exposure assessment and internal dose assessment of acrylamide in food. Since the finding that acrylamide is formed in food during heat processing and preparation of food, much effort has been (and still is being) put into understanding its mechanism of formation, on developing analytical methods and determination of levels in food, and on evaluation of its toxicity and potential toxicity and potential human health consequences. Although several exposure estimations have been proposed, a systematic review of key information relevant to exposure assessment is currently lacking. The European and North American branches of the International Life Sciences Institute, ILSI, discussed critical aspects of exposure assessment, parameters influencing the outcome of exposure assessment and summarised data relevant to the acrylamide exposure assessment to aid the risk characterisation process. This paper reviews the data on acrylamide levels in food including its formation and analytical methods, the determination of human consumption patterns, dietary intake of the general population, estimation of maximum intake levels and identification of groups of potentially high intakes. Possible options and consequences of mitigation efforts to reduce exposure are discussed. Furthermore the association of intake levels with biomarkers of exposure and internal dose, considering aspects of bioavailability, is reviewed, and a physiologically-based toxicokinetic (PBTK) model is described that provides a good description of the kinetics of acrylamide in the rat. Each of the sections concludes with a summary of remaining gaps and uncertainties.

Vitamin D and calcium in the prevention of prostate and colon cancer: new approaches for the identification of needs

Identification of the mechanisms involved in the pathology of nutrient deficiency provides an understanding of nutrient functions, their role in metabolism, and interactions between nutrients. However, evidence has emerged in recent years that low (suboptimal) intakes of micronutrients are associated with an elevated risk of chronic diseases. The description of micronutrient associations with chronic disease as a deficiency disease does not capture the complexity of these relations. It implies a significant oversimplification of this relation and detracts from the need for development of new approaches to this area of study. Epidemiologic study designs are essential for progress in understanding the micronutrient-chronic-disease relations, and these are described. Two areas wherein epidemiological tools could be incorporated into experimental designs have been vitamin D and prostate cancer, and vitamin D and colon cancer. In each case, biomarkers of exposure, intermediary markers, and mechanisms have been identified and could be implemented in new experimental designs. Measures of exposure would be improved by incorporation of measurements of vitamin D status such as serum 25-hydroxyvitamin D measurements. Several intermediary markers are discussed and may be useful in the characterization of responses. Such developments should aid in the interpretation of studies and identify vitamin D, as well as calcium intakes, that will aid in the prevention of prostate and colon cancer.

Dietary risk factors for the development of inflammatory polyarthritis: evidence for a role of high level of red meat consumption

OBJECTIVE

To investigate the association of red meat and other specific dietary components in predicting the development of inflammatory polyarthritis.

METHODS

This nested case-control study was conducted within a prospective population-based study of cancer incidence (European Prospective Investigation of Cancer in Norfolk [EPIC-Norfolk]). EPIC-Norfolk recruited 25,630 subjects ages 45-75 years between 1993 and 1997. Dietary intake was assessed at baseline using a 7-day food diary, and the information was analyzed using dietary analysis software. Patients with new cases of inflammatory polyarthritis were identified by linkage with the Norfolk Arthritis Register, a primary care-based inception study of inflammatory polyarthritis, and were matched for age and sex to 2 controls from EPIC-Norfolk. The risk for development of inflammatory polyarthritis was compared between subjects in the highest and lowest tertiles of dietary intake using conditional logistic regression and was expressed as odds ratios (ORs) with 95% confidence intervals (95% CIs).

RESULTS

Between 1993 and 2002, 88 new patients with inflammatory polyarthritis were identified and matched with 176 controls. Among patients, the level of red meat intake was higher (P = 0.04) and that of vitamin C was lower (P = 0.03) compared with intake among controls, but no difference in total energy intake was observed. Patients were more likely to be smokers. After adjusting for total energy intake, smoking, and other possible dietary confounders, subjects with the highest level of consumption of red meat (OR 1.9, 95% CI 0.9-4.0), meat and meat products combined (OR 2.3, 95% CI 1.1-4.9), and total protein (OR 2.9, 95% CI 1.1-7.5) were at an increased risk for inflammatory polyarthritis.

CONCLUSION

A high level of red meat consumption may represent a novel risk factor for inflammatory arthritis or may act as a marker for a group of persons with an increased risk from other lifestyle causes.

The validity and accuracy of the Work Productivity and Activity Impairment questionnaire--irritable bowel syndrome version (WPAI:IBS)

BACKGROUND

Irritable bowel syndrome is a common chronic functional gastrointestinal disorder characterized by recurrent abdominal pain and discomfort associated with alterations in bowel habit. Irritable bowel syndrome affects patients' quality of life and increases productivity loss.

AIM

To assess validity and accuracy of the Work Productivity and Activity Impairment questionnaire in irritable bowel syndrome as a tool for quantifying the effects of irritable bowel syndrome on productivity and daily activities.

METHODS

Validity and accuracy were evaluated in 135 irritable bowel syndrome patients relative to three measures of irritable bowel syndrome disease severity; a debriefing questionnaire; retrospective diary; Work Limitations Questionnaire, and an activity impairment measure (Dimensions of Daily Activities).

RESULTS

Symptom severity scores, diary scores, Work Limitations Questionnaire and Dimensions of Daily Activities were significant predictors of work productivity and activity impairment questionnaire in irritable bowel syndrome measures of work time missed, and work and activity productivity loss (P = 0.04 to < 0.0001). Impairment due to irritable bowel syndrome was estimated to be 2.9-4.3% for work time missed and 22-32% for impairment at work, the equivalent of 9.7 -14 h lost productivity per week. Activity impairment was 24-41%.

CONCLUSIONS

Discriminative validity of the Work Productivity and Activity Impairment questionnaire in irritable bowel syndrome was established, making it the only validated tool for measuring the relative differences between disease severity groups and quantifying work productivity loss and activity impairment in irritable bowel syndrome patients.

Correlations between estimated and true dietary intakes

PURPOSE

It is unclear how well questionnaire or so-called reference methods of dietary assessment correlate with true dietary intake. We develop a method to estimate such correlations.

METHODS

An error model is described that uses data from a food frequency questionnaire (Q), a reference method (R), and a biological marker (M). The model does not assume the classical error model for either R or M, or that the correlation between errors in the questionnaire and reference data is zero. Credible intervals can be placed about correlations between R, Q, M and true dietary data (T), also about the correlations between errors in reference and questionnaire data.

RESULTS

Application of this model to a validation data set mainly found correlations in the range 0.4 to 0.8, and that correlations (R,T) generally exceeded correlations (Q,T), providing evidence that R is more valid than Q. Estimated correlations between errors in R and Q were often far from zero suggesting that regression calibration to imperfect reference data is problematic unless these error correlations can be estimated.

CONCLUSION

A biological marker in addition to dietary data, allows calculation of correlations between estimated and true dietary intakes under reasonable assumptions about errors. However, sensitivity analyses are necessary on one variable.

Animal protein, animal fat, and cholesterol intakes and risk of cerebral infarction mortality in the adult health study

BACKGROUND AND PURPOSE

A traditional diet that is poor in animal products is thought to explain the high rate of stroke in Asian populations. The purpose of the present study was to examine the effect of a diet rich in animal protein, animal fat, and cholesterol on the risk of cerebral infarction mortality in a Japanese population.

METHODS

A prospective study of 3731 Japanese men and women aged 35 to 89 years was conducted from 1984 to 2001. Nutrient intake was estimated at baseline from the responses to a 24-hour diary. During the follow-up period, cases of cerebral infarction deaths (as entered on death certificates) were monitored.

RESULTS

During the follow-up period, 60 deaths were attributed to cerebral infarction. A high intake of animal fat and cholesterol was significantly associated with a reduced risk of cerebral infarction death. The risk was reduced by 62% (CI, 82% to 18%) for those in the third tertile of animal fat intake, compared with those in the first tertile, with a significant linear dose-response relationship (P=0.0073). The risk of death from infarction was reduced by 63% (CI, 82% to 22%) in the high cholesterol consumption group, compared with the low consumption group. A significant linear dose-response relationship was observed. Animal protein was not significantly associated with infarction mortality after adjustment for animal fat and cholesterol.

CONCLUSIONS

This study suggests that in Japan, where animal product intake is lower than in Western countries, a high consumption of animal fat and cholesterol was associated with a reduced risk of cerebral infarction death.

Dietary folate and vitamin b6 are independent predictors of peripheral arterial occlusive disease

BACKGROUND

It has been suggested that hyperhomocysteinemia (HHcy) is an independent risk factor for peripheral arterial occlusive disease (PAOD). However, the relationship between dietary folate and vitamin B6, cofactors in the metabolism of homocysteine (Hcy), and PAOD is unclear.

AIMS

To study the relationship between dietary folate and B6 and PAOD.

METHODS

Case-control population based study of 392 men older than 50 years living in Huntingdon, United Kingdom. PAOD, defined as an ankle-brachial pressure index (ABPI) < 0.9, was present in 86 (22%) of subjects. Folate, vitamin B6, and vitamin B12 intakes were calculated by means of the EPIC (European Prospective Investigation into Cancer) food frequency questionnaire.

RESULTS

Daily folate intake was significantly lower in case subjects (mean, 288; 95% confidence interval [CI], 266-309 microg) than in control subjects (324; 95% CI, 313-335 microg). Daily vitamin B6 intake was also lower in case subjects (2.05; 95% CI, 1.92-2.19 mg versus 2.26; 95% CI, 2.19-2.33 mg). Daily folate and vitamin B6 intakes were independent predictors of PAOD after adjusting for age, blood pressure, cholesterol levels, diabetes, and smoking status in a logistic regression model. This model suggests that increasing daily folate intake by 1 standard deviation decreased the risk of PAOD by 46%. A similar increase in daily vitamin B6 intake decreased the risk of PAOD by 29%.

CONCLUSION

In men older than 50 years, dietary folate and B6 intakes are independent predictors of PAOD. Longitudinal studies are required to determine whether dietary modification can reduce the incidence of PAOD in the population.

Fruits and vegetables and lung cancer: Findings from the European Prospective Investigation into Cancer and Nutrition

Intake of fruits and vegetables is thought to protect against the development of lung cancer. However, some recent cohort and case-control studies have shown no protective effect. We have assessed the relation between fruit and vegetable intake and lung cancer incidence in the large prospective investigation on diet and cancer, the European Prospective Investigation Into Cancer and Nutrition (EPIC). We studied data from 478,021 individuals that took part in the EPIC study, who were recruited from 10 European countries and who completed a dietary questionnaire during 1992-1998. Follow-up was to December 1998 or 1999, but for some centres with active follow-up to June 2002. During follow-up, 1,074 participants were reported to have developed lung cancer, of whom 860 were eligible for our analysis. We used the Cox proportional hazard model to determine the effect of fruit and vegetable intake on the incidence of lung cancer. We paid particular attention to adjustment for smoking. Relative risk estimates were obtained using fruit and vegetable intake categorised by sex-specific, cohort-wide quintiles. After adjustment for age, smoking, height, weight and gender, there was a significant inverse association between fruit consumption and lung cancer risk: the hazard ratio for the highest quintile of consumption relative to the lowest being 0.60 (95% Confidence Interval 0.46-0.78), p for trend 0.0099. The association was strongest in the Northern Europe centres, and among current smokers at baseline, and was strengthened when the 293 lung cancers diagnosed in the first 2 years of follow-up were excluded from the analysis. There was no association between vegetable consumption or vegetable subtypes and lung cancer risk. The findings from this analysis can be regarded as re-enforcing recommendations with regard to enhanced fruit consumption for populations. However, the effect is likely to be small compared to smoking cessation.

A comparison of a food frequency questionnaire with a 24-hour recall for use in an epidemiological cohort study: results from the biomarker-based Observing Protein and Energy Nutrition (OPEN) study

BACKGROUND

Most large cohort studies have used a food frequency questionnaire (FFQ) for assessing dietary intake. Several biomarker studies, however, have cast doubt on whether the FFQ has sufficient precision to allow detection of moderate but important diet-disease associations. We use data from the Observing Protein and Energy Nutrition (OPEN) study to compare the performance of a FFQ with that of a 24-hour recall (24HR).

METHODS

The OPEN study included 484 healthy volunteer participants (261 men, 223 women) from Montgomery County, Maryland, aged 40-69. Each participant was asked to complete a FFQ and 24HR on two occasions 3 months apart, and a doubly labelled water (DLW) assessment and two 24-hour urine collections during the 2 weeks after the first FFQ and 24HR assessment. For both the FFQ and 24HR and for both men and women, we calculated attenuation factors for absolute energy, absolute protein, and protein density.

RESULTS

For absolute energy and protein, a single FFQ's attenuation factor is 0.04-0.16. Repeat administrations lead to little improvement (0.08-0.19). Attenuation factors for a single 24HR are 0.10-0.20, but four repeats would yield attenuations of 0.20-0.37. For protein density a single FFQ has an attenuation of 0.3-0.4; for a single 24HR the attenuation factor is 0.15-0.25 but would increase to 0.35-0.50 with four repeats.

CONCLUSIONS

Because of severe attenuation, the FFQ cannot be recommended as an instrument for evaluating relations between absolute intake of energy or protein and disease. Although this attenuation is lessened in analyses of energy-adjusted protein, it remains substantial for both FFQ and multiple 24HR. The utility of either of these instruments for detecting important but moderate relative risks (between 1.5 and 2.0), even for energy-adjusted dietary factors, is questionable.

A search for truth in dietary epidemiology

Although results from epidemiologic studies of diet have taught us a great deal, much of the evidence remains mired in controversy because of the inconsistency of results among apparently good studies. I conclude that this can be largely explained by the combination of 2 problems: confounding and measurement error. This recognition allows some judgment as to which studies may be less prone to these difficulties and a search for new analytic methods that can produce less biased and more consistent results. The potential correlations between many nutrients, and to a lesser extent foods, make it difficult to know whether the nominated variable is actually the active principle or whether there is some other dietary risk factor that is closely associated. It is not generally recognized that all traditional analyses of this sort are based on a powerful but incorrect assumption: that there are no errors in dietary assessment. If the incorrect assumption is not satisfied, relative risk estimates become distorted-reduced by one-half or more in some cases. Regression calibration is a newer technique that uses a calibration substudy to provide information about errors and to correct results from the main study. There are a number of variants of this technique, all requiring assumptions about the data. Regression calibration methods that use carefully selected biological surrogates (correlates) of the dietary factor of interest in the calibration study seem to use more realistic assumptions.

Validação de Questionários de Freqüência Alimentar - QFA: considerações metodológicas

O Questionário de Freqüência Alimentar (QFA) tornou-se o método dominante nos estudos epidemiológicos para avaliação do consumo dietético, em especial para avaliar a relação da dieta com a ocorrência de doenças crônicas não transmissíveis. O QFA é um instrumento que tem como objetivo a avaliação da dieta habitual de grupos populacionais e apresenta como vantagens a rapidez na aplicação e a eficiência na prática epidemiológica para identificar o consumo habitual de alimentos, além do baixo custo. Comparado a outros instrumentos, substitui a medição da ingestão alimentar de um ou vários dias pela informação global da ingestão de um período amplo de tempo. Constitui ferramenta útil nos estudos sempre que seu desenvolvimento tenha sido precedido por procedimentos metodológicos cuidadosamente planejados que garantirão confiabilidade e precisão dos dados. Para tanto, são necessários estudos de validação que permitam estimar os erros de medição próprios do método. Sem o reconhecimento destes erros, a relação dieta-doença poderá estar prejudicada. Este artigo pretende abordar de forma sistemática considerações metodológicas para a realização de estudos de validação de QFA.

Are imprecise methods obscuring a relation between fat and breast cancer?

Pooled analyses of cohort studies show no relation between fat intake and breast-cancer risk. However, food-frequency questionnaire (FFQ) methods used in these studies are prone to measurement error. We assessed diet with an FFQ and a detailed 7-day food diary in 13070 women between 1993 and 1997. We compared 168 breast-cancer cases incident by 2000 with four matched controls. Risk of breast cancer was associated with saturated-fat intake measured with the food diary (hazard ratio 1.22 [95% CI 1.06-1.40], p=0.005, per quintile increase in energy-adjusted fat intake), but not with saturated fat measured with the FFQ (1.10 [0.94-1.29], p=0.23). Dietary measurement error might explain the absence of a significant association between dietary fat and breast-cancer risk in cohort studies.

Associations between diet and the metabolic syndrome vary with the validity of dietary intake data

BACKGROUND

Underreporting is a common problem in dietary surveys. Few studies have shown the implication of this when investigating diet-disease relations.

OBJECTIVE

We investigated how underreporting affects the associations between dietary factors and the metabolic syndrome.

DESIGN

Dietary intake measured with a 7-d food record, fasting insulin concentrations, and other variables of the metabolic syndrome were assessed in a cross-sectional study of 301 healthy men aged 63 y. Biological markers for intakes of protein, sodium, and potassium were measured in 24-h urine samples. Underreporters (URs, n = 88) were identified by Goldberg's equation, which compares energy intake with energy expenditure, both expressed as multiples of the basal metabolic rate. Physical activity level was estimated, and individual cutoffs were calculated.

RESULTS

The URs had higher nutrient and food densities in their diet than did the non-URs, which suggested that they followed a healthier diet. The URs had a higher prevalence of the metabolic syndrome than did the non-URs (18% and 9%, respectively; P = 0.029). The biological markers confirmed a low validity of the dietary data in the URs. The correlations between fasting insulin concentrations, a central component of the metabolic syndrome, and the intakes of polyunsaturated fats, n-6 fats, and fat from milk products were stronger in the URs than in the non-URs, which indicates that inaccurate data can introduce spurious associations.

CONCLUSION

The association between diet and fasting insulin differed between URs and non-URs in this study of 301 healthy men aged 63 y. If URs are not identified and excluded or treated separately in studies in nutritional epidemiology, spurious diet-disease relations may be reported.

Misclassification associated with measurement error in the assessment of dietary intake

OBJECTIVE

Dietary assessment has been used for certification to receive food supplements or other nutrition services and to provide feedback for educational purposes. The proportion of individuals correctly certified as eligible is a function of the amount of error that exists in the dietary measures and the level of dietary intake used to establish eligibility. Whether individuals are correctly counselled to increase or decrease the consumption of selected foods or nutrients is a function of the same factors. It is not clear, however, what percentage of individuals would be correctly classified under what circumstances. The objective of this study is to demonstrate the extent to which measurement error and eligibility criteria affect the accuracy of classification.

DESIGN

Hypothetical distributions of dietary intake were generated with varying degrees of measurement error. Different eligibility criteria were applied and the expected classification rates were determined using numerical methods.

SETTING AND SUBJECTS

Simulation study.

RESULTS

Cut points of dietary intake at decreasing levels below the 50th percentile of true intake were associated with lower sensitivity and predictive value positive rates, but higher specificity and predictive value negative rates. The correct classification rates were lower when two cut points of dietary intake were used. Using a single cut point that was higher than the targeted true consumption resulted in higher sensitivity but lower predictive value positive, and lower specificity but higher predictive value negative.

CONCLUSIONS

Current methods of dietary assessment may not be reliable enough to attain acceptable levels of correct classification. Policy-makers and educators must consider how much misclassification error they are willing to accept and determine whether more intensive methods are necessary.

Dietary fibre in food and protection against colorectal cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC): an observational study

BACKGROUND

Dietary fibre is thought to protect against colorectal cancer but this view has been challenged by recent prospective and intervention studies that showed no protective effect.

METHODS

We prospectively examined the association between dietary fibre intake and incidence of colorectal cancer in 519978 individuals aged 25-70 years taking part in the EPIC study, recruited from ten European countries. Participants completed a dietary questionnaire in 1992-98 and were followed up for cancer incidence. Relative risk estimates were obtained from fibre intake, categorised by sex-specific, cohort-wide quintiles, and from linear models relating the hazard ratio to fibre intake expressed as a continuous variable.

FINDINGS

Follow-up consisted of 1939011 person-years, and data for 1065 reported cases of colorectal cancer were included in the analysis. Dietary fibre in foods was inversely related to incidence of large bowel cancer (adjusted relative risk 0.75 [95% CI 0.59-0.95] for the highest versus lowest quintile of intake), the protective effect being greatest for the left side of the colon, and least for the rectum. After calibration with more detailed dietary data, the adjusted relative risk for the highest versus lowest quintile of fibre from food intake was 0.58 (0.41-0.85). No food source of fibre was significantly more protective than others, and non-food supplement sources of fibre were not investigated.

INTERPRETATION

In populations with low average intake of dietary fibre, an approximate doubling of total fibre intake from foods could reduce the risk of colorectal cancer by 40%.

Urine nitrogen as a biomarker for the validation of dietary protein intake

When validated for completeness, 24-h urine nitrogen obtained from repeated 24-h urine collections has provided useful insights into the validity of dietary assessments, underreporting behaviors and the structure of measurement errors that are associated with different methods. This is particularly so when nitrogen is combined with another marker in 24-h urine samples, potassium. Although the collection of 24-h urine is a tedious procedure, the method is readily accessible and comparatively inexpensive. Other markers of dietary intake and intermediate risk markers may also be measured in the 24-h urine that is obtained.

Estimation of usual intakes: What We Eat in America-NHANES

Usual intakes of nutrients are reliable indicators for making associations between diet and health or disease risks. Estimates of consumption of specific foods and food groups are also important for evaluating the progress in meeting key objectives in such national public health initiatives as Healthy People 2010. Reliable and valid estimates of intakes of particular foods, food ingredients, dietary supplements and other bioactive substances are also needed for dietary assessment and regulatory purposes. The ability to generate useful estimates of these constituents often requires much larger sample sizes than are needed for estimating nutrient intakes. Statistical methods recommended by the National Academy of Sciences are described that provide estimates of distributions of usual nutrient intakes and permit dietary assessment and planning at the population level. Statistical and modeling approaches for estimating intakes of foods, dietary supplements and other bioactive substances are also summarized. Based on the deliberations of discussion groups consisting of members of key stakeholder groups involved in the planning, implementation and utilization of national survey data, a high priority was placed on the need for more research to determine the best approaches for applying these methods to dietary data in the integrated What We Eat in America-National Health and Nutrition Examination Survey (NHANES).

Estimation of fruit and vegetable intake using a two-item dietary questionnaire: a potential tool for primary health care workers

BACKGROUND AND AIM

High fruit and vegetable intake is associated with health benefits for cancer and cardiovascular disease. An increase is therefore integral in recommendations for the prevention of chronic disease. However, measuring intake requires either extensive dietary assessment or the measurement of specific bio-markers which is neither cheap nor feasible for the routine assessment of an individual's diet in a community or primary care setting. Within the context of a study evaluating a dietary counselling programme to increase fruit and vegetable intake our aim was to assess the use of a simple tool to estimate fruit and vegetable intake.

METHODS AND RESULTS

We studied associations between bio-markers [plasma ascorbic acid, beta-carotene and alpha-tocopherol 24-hour urinary potassium excretion] and a two-item fruit and vegetable consumption questionnaire in 271 subjects (105 men and 166 women), aged 18 to 70 years. After controlling for age, sex, vitamin supplement use, smoking and body mass, those reporting a daily intake of > or = 5 portions of fruit and vegetables had higher potassium excretion (difference 15.6 [95% confidence interval: 6.2 to 25.0] mmol/24 h), urinary potassium/creatinine ratio (1.2 [0.5 to 2.0]) and plasma vitamin C (10.0 [-0.9 to 20.8] mumol/L) than those reporting < or = 2.5 portions per day. beta-carotene (p = 0.04), vitamin C (p = 0.01) and potassium excretion (p < 0.001) were associated with fruit rather than vegetable intake. The two-item questionnaire had high specificity; over 3/4 of participants who reported low intake also had bio-markers below the upper third of the distribution.

CONCLUSION

Self report of fruit and vegetable intake through a simple questionnaire is confirmed by bio-markers for those eating less than five portions of fruit and vegetables a day. Although the tool is amenable to improvements for the detection of vegetable portions, it may prove useful for monitoring dietary preventive approaches in primary care without the use of invasive and costly biochemical measurements.

Biomarkers in nutritional epidemiology

OBJECTIVE

To illustrate biomarkers of diet that can be used to validate estimates of dietary intake in the study of gene-environment interactions in complex diseases.

DESIGN

Prospective cohort studies, studies of biomarkers where diet is carefully controlled.

SETTING

Free-living individuals, volunteers in metabolic suites.

SUBJECTS

Male and female human volunteers.

RESULTS

Recent studies using biomarkers have demonstrated substantial differences in the extent of measurement error from those derived by comparison with other methods of dietary assessment. The interaction between nutritional and genetic factors has so far largely gone uninvestigated, but can be studied in epidemiological trials that include collections of biological material. Large sample sizes are required to study interactions, and these are made larger in the presence of measurement errors.

CONCLUSIONS

Diet is of key importance in affecting the risk of most chronic diseases in man. Nutritional epidemiology provides the only direct approach to the quantification of risks. The introduction of biomarkers to calibrate the measurement error in dietary reports, and as additional measures of exposure, is a significant development in the effort to improve estimates of the magnitude of the contribution of diet in affecting individual disease risk within populations. The extent of measurement error has important implications for correction for regression dilution and for sample size. The collection of biological samples to improve and validate estimates of exposure, enhance the pursuit of scientific hypotheses, and enable gene-nutrient interactions to be studied, should become the routine in nutritional epidemiology.

Hypertension and blood pressure among meat eaters, fish eaters, vegetarians and vegans in EPIC-Oxford

OBJECTIVE

To compare the prevalence of self-reported hypertension and mean systolic and diastolic blood pressures in four diet groups (meat eaters, fish eaters, vegetarians and vegans) and to investigate dietary and other lifestyle factors that might account for any differences observed between the groups.

DESIGN

Analysis of cross-sectional data from participants in the Oxford cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford).

SETTING

United Kingdom.

SUBJECTS

Eleven thousand and four British men and women aged 20-78 years at blood pressure measurement.

RESULTS

The age-adjusted prevalence of self-reported hypertension was significantly different between the four diet groups, ranging from 15.0% in male meat eaters to 5.8% in male vegans, and from 12.1% in female meat eaters to 7.7% in female vegans, with fish eaters and vegetarians having similar and intermediate prevalences. Mean systolic and diastolic blood pressures were significantly different between the four diet groups, with meat eaters having the highest values and vegans the lowest values. The differences in age-adjusted mean blood pressure between meat eaters and vegans among participants with no self-reported hypertension were 4.2 and 2.6 mmHg systolic and 2.8 and 1.7 mmHg diastolic for men and women, respectively. Much of the variation was attributable to differences in body mass index between the diet groups.

CONCLUSIONS

Non-meat eaters, especially vegans, have a lower prevalence of hypertension and lower systolic and diastolic blood pressures than meat eaters, largely because of differences in body mass index.

Diet and basal cell skin cancer: results from the EPIC-Norfolk cohort

BACKGROUND

The incidence of non-melanoma skin cancer (NMSC) in Britain has been increasing over the past 50 years. This has been attributed to increased sunlight exposure, but the increased exposure has not been quantified, and in any case, much of the increase in incidence has occurred in those parts of the body, mainly the head and neck, that have always been exposed to sunlight. There is evidence that increased dietary fat intake has increased the sensitivity of the skin to the carcinogenic potential of sunlight, particularly in causing squamous cell tumours.

OBJECTIVES

To test the hypothesis that increased dietary fat is a risk factor for NMSC.

METHODS

The hypothesis was tested in a nested case-control study. The cohort was that recruited for the EPIC-Norfolk study, the cases (n = 123) were subjects with NMSC diagnosed since recruitment, and the controls (n = 247) were randomly selected from the same cohort. The effect of diet on the incidence of NMSC was assessed using conditional logistic regression.

RESULTS

As there were so few cases (14) with squamous cell tumours they were excluded from the statistical analyses. Fat intake was not found to be a risk factor: the unadjusted odds ratio (OR) of basal cell cases vs. controls was estimated as 0.860/(25.5 g total fat daily) with 95% confidence interval (CI) (0.663, 1.116), P = 0.25. Exploratory analyses of diet components and food groups found a protective effect of increased vitamin E consumption: unadjusted OR of basal cell cases vs. controls was 0.731/(3.06 mg vitamin E daily), 95% CI (0.564, 0.948), P = 0.015. Adjusted analyses gave broadly similar results.

CONCLUSIONS

The potentiating factor remains unknown: if dietary fat has any effect on NMSC, it is not apparent when basal cell tumours are considered. There was no evidence of a generalized healthy eating effect. A substantial protective effect was found in exploratory analyses for the fat soluble antioxidant vitamin E.

DINER (Data Into Nutrients for Epidemiological Research) - a new data-entry program for nutritional analysis in the EPIC-Norfolk cohort and the 7-day diary method

BACKGROUND AND OBJECTIVE

A new data-entry system (DINER - Data Into Nutrients for Epidemiological Research) for food record methods has been devised for the European Prospective Investigation into Cancer (EPIC) cohort study of 25,000 men and women in Norfolk. DINER has been developed to address the problems of efficiency and consistency of data entry, comparability of data, maximising information and future flexibility in large long-term population studies of diet and disease that use record methods to assess dietary intakes. DINER captures more detail than traditional systems and enables provision of new variables for specific food types or groups. The system has been designed to be fully flexible and easy to update. Analysis of consistency of data entry was tested in a group of 3525 participants entered by 25 coders.

RESULTS

A food list of 9000 food items and values for 24,000 portion sizes have been incorporated into the database, using information from the 5979 diaries coded since 1995. Analysis of consistency of entry indicated that this has largely been achieved. The effect of coders in a multivariate regression model was significant only if the three coders involved in early use of the program were included (P < 0.013).

CONCLUSIONS

The development of DINER has facilitated the use of more accurate record methods in large-scale epidemiological studies of diet and disease. Furthermore, the retention of original information as an extensive food list allows greater flexibility in later analyses of data of multiple dietary hypotheses.