Recall bias in the association of micronutrient intake and breast cancer

Dietary intake of vitamin C and gastric cancer: a pooled analysis within the Stomach cancer Pooling (StoP) Project

BACKGROUND

Previous studies suggest that dietary vitamin C is inversely associated with gastric cancer (GC), but most of them did not consider intake of fruit and vegetables. Thus, we aimed to evaluate this association within the Stomach cancer Pooling (StoP) Project, a consortium of epidemiological studies on GC.

METHODS

Fourteen case-control studies were included in the analysis (5362 cases, 11,497 controls). We estimated odds ratios (ORs) and corresponding 95% confidence intervals (CIs) for the association between dietary intake of vitamin C and GC, adjusted for relevant confounders and for intake of fruit and vegetables. The dose-response relationship was evaluated using mixed-effects logistic models with second-order fractional polynomials.

RESULTS

Individuals in the highest quartile of dietary vitamin C intake had reduced odds of GC compared with those in the lowest quartile (OR: 0.64; 95% CI: 0.58, 0.72). Additional adjustment for fruit and vegetables intake led to an OR of 0.85 (95% CI: 0.73, 0.98). A significant inverse association was observed for noncardia GC, as well as for both intestinal and diffuse types of the disease. The results of the dose-response analysis showed decreasing ORs of GC up to 150-200 mg/day of vitamin C (OR: 0.54; 95% CI: 0.41, 0.71), whereas ORs for higher intakes were close to 1.0.

CONCLUSIONS

The findings of our pooled study suggest that vitamin C is inversely associated with GC, with a potentially beneficial effect also for intakes above the currently recommended daily intake (90 mg for men and 75 mg for women).

Dietary intake of copper and gastric cancer: a pooled analysis within the Stomach cancer Pooling (StoP) Project

BACKGROUND

Evidence on the potential association between dietary copper intake and gastric cancer (GC) is lacking. Thus, we aimed to evaluate this association within the Stomach cancer Pooling (StoP) Project-an international consortium of epidemiological studies on GC.

METHODS

Data from five case-control studies within the StoP Project were included (2448 cases, 4350 controls). We estimated adjusted odds ratios (ORs) and 95% CIs for the association between dietary copper intake and GC using multivariable mixed-effects logistic regression models. We also modelled the dose-response relationship between copper intake and GC using a logistic mixed-effects model with fractional polynomial.

RESULTS

The OR for the highest quartile of copper intake compared with the lowest one was 0.78 (95% CI: 0.63-0.95; P for trend = 0.013). Results were similar for non-cardia-type (OR: 0.72; 95% CI: 0.57-0.91), intestinal-type (OR: 0.75; 95% CI: 0.56-0.99) and other histological-type GC (OR: 0.65; 95% CI: 0.44-0.96). The dose-response analysis showed a steep decrease in ORs for modest intakes (<1 mg/day), which were subsequently steady for ≤3 mg/day (OR: 0.09; 95% CI: 0.02-0.41) and slowly increased for higher intakes.

CONCLUSIONS

The findings of our large study suggest that copper intake might be inversely associated with GC, although their confirmation by prospective studies is required.

Short interpregnancy intervals and risks for birth defects: support for the nutritional depletion hypothesis

BACKGROUND

Research suggests short interpregnancy intervals increase risks for adverse perinatal outcomes, including some birth defects. A hypothesized cause is nutritional depletion, including folic acid (FA).

OBJECTIVES

We evaluated associations between short interpregnancy intervals, alone and in combination with FA intake, and the occurrence of select malformations.

METHODS

Data were from the National Birth Defects Prevention Study (US case-control, 1997-2011). Participants included multiparous women whose prior pregnancy resulted in live birth. Cases included 8 noncardiac and 6 cardiac defect groups (n = 3219); controls were nonmalformed live-borns (n = 2508). We categorized interpregnancy interval (<6, 6-11, 12-17, and 18-23 mo) and periconceptional FA intake [no FA supplement use and dietary folate equivalents (DFE) <400 µg/d, no FA supplement use and DFE ≥400 µg/d, or any FA supplement use]. We controlled for age, race/ethnicity, income, pregnancy intention, and study center. ORs <0.8 or >1.2 were considered to represent potentially meaningful associations.

RESULTS

ORs for <6 compared with 18-23 mo were >1.2 for 4/8 noncardiac and 3/6 cardiac malformations. Among participants with any FA supplement use, ORs comparing <6 with 6-23 mo were <1.2 for most defects. Conversely, most ORs were >1.2 for <6 mo + no FA supplement use and DFE <400 µg/d compared with 6-23 mo + any FA supplement use. Magnitude and precision varied by defect.

CONCLUSIONS

Short interpregnancy intervals were associated with a trend of higher risks for several defects, notably in the absence of FA supplement use. To our knowledge, our study is the first to provide preliminary empirical support that these etiologies may be related to shorter interpregnancy intervals and possible nutritional deficiencies. Because FA intake is highly correlated with other nutrients, and because our estimates were generally imprecise, more research with larger sample sizes is needed to better understand the role of FA compared with other nutrients in each defect-specific etiology.

Sugar-sweetened beverage intake, chromosome 9p21 variants, and risk of myocardial infarction in Hispanics

BACKGROUND

Chromosome 9p21 variants are among the most robust genetic markers for coronary artery disease (CAD), and previous studies have suggested that genetic effects of this locus might be modified by dietary factors. Intake of sugar-sweetened beverages (SSBs), which are the main dietary source of added sugar, has been shown to interact with genetic factors in affecting CAD risk factors such as obesity.

OBJECTIVE

We aimed to test whether SSB intake modified the association between chromosome 9p21 variants and CAD risk in Hispanics living in Costa Rica.

DESIGN

The current study included 1560 incident cases of nonfatal myocardial infarction (MI) and 1751 population-based controls. Three independent single nucleotide polymorphisms (SNPs) at the chromosome 9p21 locus were genotyped. SSB intake was assessed with the use of a food-frequency questionnaire and was defined as the frequency of intake of daily servings of sweetened beverages and fruit juice.

RESULTS

We showed a significant interaction between SSB intake and one of the 3 variants (i.e., rs4977574) on MI risk. The per–risk allele OR (95% CI) of rs4977574 for MI was 1.44 (1.19, 1.74) in participants with higher SSB consumption (>2 servings/d), 1.21 (1.00, 1.47) in those with average consumption (1–2 servings/d), and 0.97 (0.81, 1.16) in subjects with lower consumption (<1 serving/d; P-interaction = 0.005). A genetic risk score derived from the sum of risk alleles of the 3 SNPs also showed a significant interaction with SSB intake on MI risk (P-interaction = 0.03).

CONCLUSION

Our data suggest that unhealthy dietary habits such as higher intake of SSBs could exacerbate the effects of chromosome 9p21 variants on CAD.

Chemopreventive activity of vitamin E in breast cancer: a focus on γ- and δ-tocopherol

Vitamin E consists of eight different variants: α-, β-, γ-, and δ-tocopherols (saturated phytyl tail) and α-, β-, γ-, and δ-tocotrienols (unsaturated phytyl tail). Cancer prevention studies with vitamin E have primarily utilized the variant α-tocopherol. To no avail, a majority of these studies focused on variant α-tocopherol with inconsistent results. However, γ-tocopherol, and more recently δ-tocopherol, have shown greater ability to reduce inflammation, cell proliferation, and tumor burden. Recent results have shown that γ-enriched mixed tocopherols inhibit the development of mammary hyperplasia and tumorigenesis in animal models. In this review, we discuss the possible differences between the variant forms, molecular targets, and cancer-preventive effects of tocopherols. We recommend that a γ-enriched mixture, γ- and δ-tocopherol, but not α-tocopherol, are promising agents for breast cancer prevention and warrant further investigation.

Cancer-preventive activities of tocopherols and tocotrienols

The cancer-preventive activity of vitamin E has been studied. Whereas some epidemiological studies have suggested a protective effect of vitamin E against cancer formation, many large-scale intervention studies with alpha-tocopherol (usually large doses) have not demonstrated a cancer-preventive effect. Studies on alpha-tocopherol in animal models also have not demonstrated robust cancer prevention effects. One possible explanation for the lack of demonstrable cancer-preventive effects is that high doses of alpha-tocopherol decrease the blood and tissue levels of delta-tocopherols. It has been suggested that gamma-tocopherol, due to its strong anti-inflammatory and other activities, may be the more effective form of vitamin E in cancer prevention. Our recent results have demonstrated that a gamma-tocopherol-rich mixture of tocopherols inhibits colon, prostate, mammary and lung tumorigenesis in animal models, suggesting that this mixture may have a high potential for applications in the prevention of human cancer. In this review, we discuss biochemical properties of tocopherols, results of possible cancer-preventive effects in humans and animal models and possible mechanisms involved in the inhibition of carcinogenesis. Based on this information, we propose that a gamma-tocopherol-rich mixture of tocopherols is a very promising cancer-preventive agent and warrants extensive future research.

Influence of observational study design on the interpretation of cancer risk reduction by carotenoids

Recently published literature has been reviewed to determine whether lycopene, beta-carotene, alpha-carotene, and beta-cryptoxanthin are associated with reductions in cancer risk and whether study findings differ by study design. A total of 57 publications meeting pre-defined inclusion and exclusion criteria were identified, with the majority (55) being observational studies. None of the intervention studies supported a significant reduction in cancer risk with carotenoid (beta-carotene) supplementation. The majority of observational studies did not support significant reductions in cancer risk with increased carotenoid dietary intakes/circulating levels. A larger percentage of case-control studies supported significant associations between increased dietary intakes/circulating levels of carotenoids relative to prospective (cohort and nested case-control) studies. Compared to prospective studies, case-control studies cannot be used to establish temporality and may be more susceptible to selection and recall biases. Thus, diet-disease relationships suggested by case-control studies should ideally be confirmed by additional evidence from prospective studies.

Physical activity and premenopausal breast cancer: an examination of recall and selection bias

BACKGROUND

Compared with cohort studies, case-control investigations have tended to report clearer protective associations for the relationship between physical activity and premenopausal breast cancer risk.

METHODS

We conducted a case-control study within the Nurses' Health Study II cohort to examine whether recall or selection bias could explain the stronger protective associations. Self-reported total recreational physical activity during adulthood and over a woman's lifetime (ages 12 years to current) were assessed in 1997 before diagnosis and, again, from one to seven years after breast cancer diagnosis among the same women.

RESULTS

Eighty-seven percent of cases (417 of 479) and 82% of controls (390 of 474) responded. Selection bias was observed for activity during adulthood but not for activity over a woman's lifetime. Recall bias was not observed in the direction we expected: the odds ratios (ORs) for breast cancer comparing the highest versus lowest quintile of prospectively reported total activity were not significantly different than the corresponding estimates from retrospective reports (e.g., lifetime activity: prospective OR = 0.58, 95% CI: 0.37, 0.93 versus retrospective OR = 0.80; 95% CI: 0.50, 1.29).

CONCLUSION

Recall or selection bias may not have been accounted for protective associations among case-control investigations examining lifetime recreational physical activity and breast cancer. Selection bias related to recreational physical activity during adulthood and random error in the measurement of physical activity remain concerns.

Dietary zinc intake and brain cancer in adults: a case–control study

Little is known about the aetiology of brain tumours. One putative factor suggested from animal models is a protective effect of dietary Zn. We tested the hypothesis that increased compared with low dietary Zn intake is protective against brain tumour development. We conducted a population-based case–control study in the UK, of adults aged 18–69 years, between 2001 and 2004 aiming to identify possible risk factors. Dietary information was collected from 637 cases diagnosed with a glioma or meningioma, and 876 controls. Data were obtained from a self-completed FFQ. Multivariate logistic regression analysis was conducted, adjusting for socio-demographic factors, season of questionnaire return, multivitamin supplementation and energy intake. Although a weak protective effect was observed for the third quartile of intake (normal compared with low intake) in the meningioma group, this was limited to the specific brain tumour subtype and quartile, and was not significant after also adjusting for intake of other elements. Overall there was no significant effect of Zn intake. No association or dose–response relationship was observed between increased compared with low Zn intake and risk of glioma or meningioma.

The investigation and correction of recall bias for an ordinal response in a case-control study

Consider a case-control study designed to investigate the possible association between development of a particular disease and the value of a putative risk factor measured on an ordinal scale. Let E denote a subject's true risk factor value and let E* denote a subject's recorded risk factor value. Misclassification bias occurs if conclusions reached regarding the relationship between disease status and E* do not also apply to the relationship between disease status and E. We propose a model for the conditional probability distribution of E* given E. We show how the model may be used to investigate misclassification bias in a validation study where measurements of E* and E are available for both cases and controls and apply the methods developed to data from a test-retest study of recall bias in the context of screening for hypertension. We also consider a situation where the validation study is carried out on a subset of the subjects within a larger case-control study. In that case, values for E* are available for all subjects but values for E are available only for those subjects included in the validation study. We show how correct likelihood-based inference concerning association between disease status and risk factor value may be carried out using all of the available data. A Monte Carlo study shows how the inclusion of a validation study leads to a correction of recall bias problems at the cost of an increased standard error for the estimated association parameter.

Parental occupational exposures and Ewing's sarcoma

A case-control study of Ewing's sarcoma (ES) was conducted to search for occupational exposures associated with ES. The study consisted of 196 cases and 196 random-digit controls matched on geographical region, gender, ethnic origin and birth date. A questionnaire was administered to mothers of participants to obtain information on medical conditions, medications, and parental occupations during and after the index pregnancy. An occupational exposure expert coded jobs and industries for possible and probable exposure to selected occupational hazards. Risk of ES was increased with probable parental exposure to wood dusts during their usual occupation post pregnancy (odds ration [OR] = 3.2; 95% confidence interval [CI] = 1.1-9.2). Other exposures, including a priori suspected risk factors such as exposure to pesticides and farm animals, were not significantly associated with ES. A history of household pesticide extermination was associated with ES among boys aged 15 or younger (OR = 3.0; 95% CI = 1.1-8.1), but not among girls or older boys. Our results suggest that earlier reports of associations of ES with parental farm employment may have been describing risks associated with organic dusts encountered when working on a farm, rather than agricultural exposures or other farming related exposures.

Raw and Cooked Vegetables, Fruits, Selected Micronutrients, and Breast Cancer Risk: A Case-Control Study in Germany

In 1998-2000, a case-control study of breast cancer was conducted in Heidelberg, Germany. Three hundred ten consecutively recruited cases with primary breast cancer were matched according to 10-yr age groups to 353 controls with conditions unrelated to diet or endocrine disorders. Intake of raw vegetables, total vegetables, and whole-grain products was inversely associated with breast cancer risk (highest vs. lowest quartile adjusted odds ratio [OR] 0.51, 95% confidence interval [CI] 0.31-0.84; OR = 0.62, 95% CI = 0.38-1.02; and OR = 0.57; 95% CI = 0.34-0.95, respectively). Also, high intake of some selected vitamins and minerals possessing putative DNA-stabilizing properties displayed significant inverse risk associations. Adjusted ORs were as follows: vitamin C (OR = 0.49, 95% CI = 0.2-0.88), folate equivalents (OR = 0.47, 95% CI = 0.25-0.88), b-carotene (OR = 0.46, 95% CI = 0.27-0.80), zinc (OR = 0.35, 95% CI = 0.15-0.78), and copper (OR = 0.51, 95% CI = 0.31-1.03). In contrast, no significant association with risk was seen for an increased intake of fruits, cooked vegetables, fiber, calcium, manganese, or iron. In this population of German women, components of raw vegetables and some micronutrients appear to decrease breast cancer risk.

Methodologic and statistical considerations regarding use of biomarkers of nutritional exposure in epidemiology

In nutritional epidemiology, accurate quantification of nutritional exposure is critical. Even moderate flaws in measurement can lead to sizeable distortions in estimations of the effects of exposure. In many situations, this will lead to inaccurate direct estimation of exposure effects. In others, it will make it difficult to control for the confounding effects of nutritional exposure. Biomarkers offer important opportunities to advance research in nutritional epidemiology; their objectivity and potentially greater accuracy give them the potential to substantially lessen distortions that might result from imperfect measurements. Clearly, the accuracy of biomarkers as indicators of nutritional exposure is critical to their value. It is likely that establishing the accuracy of biomarkers will require some reference to self-reports, even if those reports are not as accurate as the biomarkers they are used to test. The goal of this paper is to describe aspects of accuracy-reproducibility, reliability and validity-as they apply to biomarkers in nutritional epidemiology.

A comparison of responses to a health and lifestyle questionnaire completed before and then after blood pressure screening

Changes over a 2-week period in self-reported health and lifestyle information were examined and related to medical feedback provided prior to the second self-report. The study group consisted of 128 females and 73 males ranging in age from 35 to 85 with a mean age of 55.5 years. On two occasions subjects completed self-assessment questionnaires including 52 items covering symptomatology and various lifestyle behaviours. Before the second self-assessment, subjects were classified as cases if their blood pressure was borderline or hypertensive according to World Health Organization guidelines or as controls otherwise. Subjects were informed of this classification. Across questions, the percentage disagreement between reports ranged from 0.0% to 44.1% with a median of 17.5% and with case-control differences significant at the 10% level for four questions. The mean difference between responses was significantly different from 0 at the 10% level for 15 questions with case-control differences significant at the 10% level for 6 questions. For 2 questions, the significance level of the association of response with case-control status changed from a value greater than 20% based on responses before feedback to a value less than 5% based on responses after feedback. Some evidence of recall bias was found.

Does lack of tocopherols and tocotrienols put women at increased risk of breast cancer?

Breast cancer is the leading site of new cancers in women and the second leading cause (after lung cancer) of cancer mortality in women. Observational studies that have collected data for dietary exposure to alpha-tocopherol with or without the other related tocopherols and tocotrienols have suggested that vitamin E from dietary sources may provide women with modest protection from breast cancer. However, there is no evidence that vitamin E supplements confer any protection whatever against breast cancer. Observational studies that have assessed exposure to vitamin E by plasma or adipose tissue concentrations of alpha-tocopherol have failed to provide consistent support for the idea that alpha-tocopherol provides any protection against breast cancer. In addition, evidence from studies in experimental animals suggest that alpha-tocopherol supplementation alone has little effect on mammary tumors. In contrast, studies in breast cancer cells indicate that alpha- gamma-, and delta-tocotrienol, and to a lesser extent delta-tocopherol, have potent antiproliferative and proapoptotic effects that would be expected to reduce risk of breast cancer. Many vegetable sources of alpha-tocopherol also contain other tocopherols or tocotrienols. Thus, it seems plausible that the modest protection from breast cancer associated with dietary vitamin E may be due to the effects of the other tocopherols and the tocotrienols in the diet. Additional studies will be required to determine whether this may be the case, and to identify the most active tocopherol/tocotrienol.

Evidence of recall bias in volunteered vs. prompted responses about occupational exposures

BACKGROUND

Recall bias remains a concern in case-control studies, although few investigations have found evidence of differential recall. This study examined whether differences in occupational exposure reporting occur in volunteered vs. prompted questionnaire responses.

METHODS

In a large, population-based, case-control study of a childhood cancer, neuroblastoma, we calculated odds ratios for broad occupational exposure groups on the assumption that in the absence of recall bias, risk estimates for such broad groupings should be close to the null value.

RESULTS

Prompted exposures and work activities showed little evidence of differential recall by parents of cases and controls (all OR < 1.2), but case parents were more likely to volunteer information about other exposures or activities (ORs: 1.35-1.71). Case mothers were also more likely than control mothers to report activities involving indirect exposure (OR = 1.41).

CONCLUSIONS

These findings suggest that prompted exposure questions are less likely to be subject to recall bias than open-ended questions.

Study design and hypothesis testing: issues in the evaluation of evidence from research in nutritional epidemiology

In addressing questions about the relations of dietary factors to disease in human populations, epidemiologic studies must account for the complexity of dietary habits, the intercorrelations among dietary habits, and the correlations of those habits with other behaviors. Furthermore, for studies of chronic disease, relevant dietary exposures may occur over decades. The classic epidemiologic study designs have been used to examine the associations between diet and disease; the strengths and weaknesses of those designs must be considered. Concerns have been raised regarding the validity of the measures of diet, the differential recall of diet by diseased individuals in case-control studies, and confounding by other related factors in both case-control and cohort studies. In clinical trials there may be difficulties in effecting the necessary dietary changes, especially for macronutrients, and there are also concerns about those circumstances in which participants cannot be blinded to their treatment. For case-control and cohort studies and for some clinical trials, intercorrelations among nutrients are a concern in the identification of factors that are important in the etiology of disease. It is important to understand these considerations when interpreting nutritional epidemiologic studies for the purpose of setting public policy. No one study can be considered definitive in the understanding of a diet-disease relation. However, epidemiologic findings from multiple studies taken together can contribute significantly to our understanding of diet in relation to disease in humans.

Diet and the risk of breast cancer in a case-control study: does the threat of disease have an influence on recall bias?

It has been suggested that recall bias may explain the discrepant results between case-control and cohort studies on diet and the risk of breast cancer. Two control groups were used for this case-control study of 25 to 75-year-old breast cancer cases (n = 310). The first group consisted of population controls drawn from the Finnish National Population Register (n = 454). The second group consisted of women who were referred to the same examinations as were the cases because of clinical suspicion of breast disease but who were later diagnosed as healthy (referral controls; n = 506). Because the diagnosis was unknown at the time of interview, it was possible to assess by comparing the two control groups whether the self-reporting of diet changed under the threat of disease. Dietary habits were examined using a validated, self-administered food-frequency questionnaire. Premenopausal women misreported their consumption of liquid milk products, tea, and sugar. Reporting bias was also associated with the intake of fat and vitamins. Postmenopausal women misreported consumption of milk products. When recall bias was taken into consideration, milk was associated with increased risk of premenopausal breast cancer, whereas high consumption of poultry or high intake of monounsaturated fatty acids, n-3 fatty acids, n-6 fatty acids, and vitamin E were related to lower risk. The study suggested that oil, milk, cheese, coffee and beta-carotene may act as protective factors in postmenopausal women, whereas butter and cream may be risk factors for breast cancer. In summary, it is possible that some food items may be overreported or underreported under the threat of disease in health-conscious population. However, most of the results in this study were not modified by recall bias.

Case-control study of breast cancer in south east England: nutritional factors

OBJECTIVES

To explore dietary risk factors, in particular fat intake, for breast cancer, using an approach to reduce recall bias of subjects and so provide a more reliable estimate of dietary intake than previous similar studies.

DESIGN

A case-control study of women aged 50-65 years attending the breast assessment clinics of the breast screening programme in Southampton and Portsmouth, southern England. Data were analysed for all women requiring further clinical procedures; all women recalled to have an early rescreen; and a random sample of women found to be normal and referred for a routine rescreening appointment (standard recall).

MEASUREMENTS

An interview obtained information on various lifestyle characteristics including smoking and alcohol intake, weight, waist, and hip measurements were also taken at the clinic. Women were given a detailed questionnaire on food intake to complete at home and return by post.

RESULTS

1577 women were included in the study: 220 with breast cancer (cases); 179 with benign breast disease; 353 early rescreen and 825 given a standard recall appointment. There were few differences in nutritional intake between the four groups. Logistic regression analyses were carried out comparing the dietary intake of cases with that of each control group adjusting for important demographic and reproductive factors. Results for the case and standard recall comparison are presented. The only non-calorific nutrient to reach significance was iron, which was negatively associated with risk (p = 0.03). For fat intake, the odds decreased with increasing polyunsaturated fat (p = 0.15), showed no trend with monounsaturated fat (p = 0.37) and increased (p = 0.10) with increasing saturated fat. No pattern was clear for the other calorie providing nutrients.

CONCLUSIONS

In line with recent cohort studies, this study has shown no evidence to support the hypothesis that dietary fat is an important contributor to breast cancer rates. Biases should have been reduced by studying subjects from the screening programme who were at an early stage of disease.

Diet and premenopausal bilateral breast cancer: a case-control study

We investigated associations between diet and premenopausal bilateral breast cancer in a familial matched case-control study. We studied 140 cases from population-based registries in Los Angeles County (California) and Connecticut, and from the major hospitals in the southern parts of the Province of Quebec. Unaffected sisters of the cases served as matched controls (222 total). Dietary intake were assessed with a food frequency questionnaire. Total fat, monounsaturated fat, polyunsaturated fat, oleic acid, and linoleic acid intake was inversely associated with premenopausal bilateral breast cancer risk. Consumption of carbohydrates (and sweetened beverages) was associated with an increased risk. We observed no associations for dietary fiber, antioxidants, or major food groupings, but we did observe inverse associations for intake of low fat dairy products and tofu. These findings suggest that monounsaturated and polyunsaturated fats, as well as soy foods, might reduce the risk of premenopausal bilateral breast cancer.

Intake of selected micronutrients and the risk of breast cancer

To investigate the relation between selected micronutrients and breast cancer risk, we conducted a case-control study of breast cancer between June 1991 and April 1994 in 6 Italian areas. The study included 2569 women admitted to the major teaching and general hospitals of the study areas with histologically confirmed incident breast cancer and 2588 control women with no history of cancer, who were admitted to hospitals in the same catchment areas for acute, non-neoplastic, nongynecological conditions unrelated to hormonal or digestive tract diseases or to long-term modifications of the diet. Dietary habits, including alcoholic beverage consumption, were investigated using a validated food frequency questionnaire, including 78 foods or food groups, several types of alcoholic beverages, some "fat intake pattern" questions and some open sections for foods consumed frequently by the subject and not reported in the questionnaire. To control for potential confounding factors, several multiple logistic regression models were used. When major correlates, energy intake and the mutual confounding effect of the various micronutrients were taken into account, beta-carotene, vitamin E and calcium showed a significant inverse association with breast cancer risk. The estimated odds ratios of the 5th quintile compared to the lowest one were 0.84 for beta-carotene, 0.75 for vitamin E and 0.81 for calcium. No significant association emerged for retinol, vitamin C, thiamin, riboflavin, iron and potassium. Our results suggest that a diet rich in several micronutrients, particularly beta-carotene, vitamin E and calcium, may be protective against breast cancer.

Interaction of family history of breast cancer and dietary antioxidants with breast cancer risk (New York, United States)

We sought to determine if specific dietary antioxidants may be particularly effective in reducing breast cancer risk for women reporting family history (FH) of breast cancer in a first-degree relative. Interviews regarding usual diet, health, and family histories were conducted with 262 premenopausal and 371 postmenopausal women with incident, primary breast cancer from western New York (United States). These women were frequency-matched by age and county of residence with community controls. Among premenopausal women, there was a significant interaction between FH and alpha-tocopherol; alpha-tocopherol was associated with significantly decreased risk among FH+ women (adjusted fourth-quartile odds ratio [OR] = 0.01, 95 percent confidence interval [CI] = 0.0-0.3). This association was much weaker for FH- women [OR = 0.7, CI = 0.4-1.2]. For FH- women, a significant inverse association was observed between beta-carotene and premenopausal breast-cancer risk (OR = 0.4, CI = 0.3-0.5), but not for FH+ women (OR = 0.5, CI = 0.1-4.0). Similar relationships, although not as strong, were noted among postmenopausal women. Although limited by small numbers, these results suggest that biologic mechanisms of tumorigenesis may differ in FH+ and FH- women, and that alpha-tocopherol may be a potential chemopreventive agent for women with a family history of breast cancer, particularly premenopausal women.

Fermented dairy products, dietary calcium and colon cancer: a case-control study in The Netherlands

To examine whether the consumption of fermented dairy products or the dietary intake of calcium decreases colon cancer risk, a case-control study was conducted in the The Netherlands. Dietary patterns were assessed in detail (for cases before diagnosis or symptoms occurred) using a structured dietary history questionnaire. After adjustment for potential confounding variables, consumption of fermented dairy products, hard cheese and unfermented dairy products was not significantly associated with risk of colon cancer: an odds ratio (OR) of 1.1 was found for individuals consuming more than one serving of fermented dairy products per day as compared to those consuming less than 10% of one serving a day. Adjustment for dietary calcium attenuated the associations. Total dietary calcium was positively but non-significantly associated with colon cancer risk after adjustment for age, gender, urbanization level and total energy intake. Additional adjustment for a positive family history of colorectal cancer, cholecystectomy and energy-adjusted intake of total fat, dietary fibre, vitamin C and alcohol increased the association. No differences were observed between calcium from fermented and from unfermented dairy sources. The observed associations for fermented dairy products and dietary calcium differed between men and women: positive significant associations were observed in men, while in women non-significant inverse associations were found. Our results do not support the hypothesis that an increased intake of commercially available, commonly used fermented dairy products or dietary calcium decreases the risk of colon cancer.