A cohort study of fat intake and risk of breast cancer

Macronutrient composition of plant-based diets and breast cancer risk: the E3N prospective cohort study

PURPOSE

Recent evidence suggests that plant-based diets may reduce the risk of breast cancer (BC). However, the macronutrient composition of plant-based diets and its potential impact on BC risk has not been well explored. This analysis investigated the association of macronutrient composition with BC risk across a spectrum of plant-based diet indexes using a multidimensional approach.

DESIGN

This study followed 64,655 participants from the Etude Epidémiologique auprès de femmes de la Mutuelle Générale de l'Education Nationale (E3N) cohort from 1993 to 2014. Diets were evaluated using validated 208-item diet history questionnaires at baseline (1993) and follow-up (2005), to calculate adherence to the overall plant-based diet (PDI), healthful plant-based diet (hPDI), and unhealthful plant-based diet (uPDI). The association of macronutrient composition with BC risk was assessed via generalized additive time-dependent Cox models across different levels of these indexes. Response surfaces were generated to visualize compositional associations at the 25th, 50th, and 75th percentile of each index (low, moderate, and high).

RESULTS

A total of 3,932 incident BC cases were identified during the 21-year follow-up. There was a significant association between macronutrient composition and BC risk for hPDI, uPDI, and PDI (all P < 0.001). Akaike information criterion favored the hPDI model for characterizing the association between macronutrients and BC. BC risk was highest for individuals with a lower hPDI score who also consumed a diet containing lower protein (10%), lower carbohydrate (35%), and higher fat (55%). The lowest risk of BC was observed in those with higher hPDI scores with the lowest intake of protein (10%). At higher PDI and uPDI, diets containing higher protein (30%) and fat (45%) had the highest BC risk.

CONCLUSION

These results demonstrate a complex relationship between macronutrient composition, plant-based diet quality, and BC risk. Further research is needed to examine specific foods that may be driving these associations.

REGISTRY

The protocol is registered at clinicaltrials.gov as NCT03285230.

Developing dietary interventions as therapy for cancer

Cancer cells acquire distinct metabolic preferences based on their tissue of origin, genetic alterations and degree of interaction with systemic hormones and metabolites. These adaptations support the increased nutrient demand required for increased growth and proliferation. Diet is the major source of nutrients for tumours, yet dietary interventions lack robust evidence and are rarely prescribed by clinicians for the treatment of cancer. Well-controlled diet studies in patients with cancer are rare, and existing studies have been limited by nonspecific enrolment criteria that inappropriately grouped together subjects with disparate tumour and host metabolic profiles. This imprecision may have masked the efficacy of the intervention for appropriate candidates. Here, we review the metabolic alterations and key vulnerabilities that occur across multiple types of cancer. We describe how these vulnerabilities could potentially be targeted using dietary therapies including energy or macronutrient restriction and intermittent fasting regimens. We also discuss recent trials that highlight how dietary strategies may be combined with pharmacological therapies to treat some cancers, potentially ushering a path towards precision nutrition for cancer.

Dietary Fat and Sugar in Promoting Cancer Development and Progression

The uncontrolled cellular growth that characterizes tumor formation requires a constant delivery of nutrients. Since the 1970s, researchers have wondered if the supply of nutrients from the diet could impact tumor development. Numerous studies have assessed the impact of dietary components, specifically sugar and fat, to increased cancer risk. For the most part, data from these trials have been inconclusive; however, this does not indicate that dietary factors do not contribute to cancer progression. Rather, the dietary contribution may be dependent on tumor, patient, and context, making it difficult to detect in the setting of large trials. In this review, we combine data from prospective cohort trials with mechanistic studies in mice to argue that fat and sugar can play a role in tumorigenesis and disease progression. We find that certain tumors may respond directly to dietary sugar (colorectal and endometrial cancers) and fat (prostate cancer) or indirectly to the obese state (breast cancer).

Dietary total fat and fatty acids intake, serum fatty acids and risk of breast cancer: A meta-analysis of prospective cohort studies

Results from prospective cohort studies on the association between dietary total fat and fatty acids intake and risk of breast cancer remain controversial. Pertinent prospective cohort studies were identified by a search of Embase and PubMed from inception to September 2015. Study-specific relative risks (RRs) with 95% confidence intervals were pooled using a random-effect model. Between-study heterogeneity and publication bias were assessed, and sensitivity analysis was conducted. Twenty-four independent studies on dietary total fat and fatty acids intake and seven studies on serum fatty acids were included. The pooled RR of breast cancer for the highest vs. lowest category of dietary total fat intake was 1.10 (1.02-1.19); however, no association was observed in studies adjusting for traditional risk factors of breast cancer. No association was observed between animal fat, vegetable fat, saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), n-3 PUFA, n-6 PUFA, eicosapentaenoic acid, docosahexaenoic acid, alpha-linolenic acid, oleic acid, linoleic acid and arachidonic acid and risk of breast cancer. The pooled RRs of breast cancer for the highest vs. lowest category of serum SFA, MUFA, PUFA, n-3 PUFA and n-6 PUFA were 1.00 (0.78-1.28), 1.41 (0.99-2.03), 0.59 (0.27-1.30), 0.81 (0.60-1.10) and 0.84 (0.60-1.18), respectively. Results from this meta-analysis suggested that dietary total fat and fatty acids might be not associated with risk of breast cancer.

Meta-Analysis of Saturated Fatty Acid Intake and Breast Cancer Risk

The associations between saturated fatty acid (SFA) consumption and risk of breast cancer (BC) remains inconclusive. Therefore, we conducted this meta-analysis to determine the quantitative relations between dietary SFA intake and incidence of BC.Literatures published up to April 2015 were systematically screened through Pubmed and Web of Science. Relevant publication quality was evaluated by conducting the Newcastle-Ottawa scale. We used fixed effects models or random effect models to calculate the summary relative risks (RRs) and odds ratios (ORs), and conducted sensitivity analyses and evaluated the publication bias.We identified a total of 52 studies (24 cohort studies and 28 case-control studies), with over 50,000 females diagnosed with BC. The associations between dietary SFA intake and risk of BC were 1.18 for case-control studies (high vs low intake, 95% confidence interval [CI] = 1.03-1.34) and 1.04 for cohort studies (95% CI = 0.97-1.11). When restricted analyses to population-based studies, positive associations were observed for both cohort (RR [95% CI] = 1.11 [1.01-1.21]) and case-control studies (OR [95% CI] = 1.26 [1.03-1.53]). Additionally, for case-control studies, significant positive associations between higher SFA intake and BC risk were observed for Asian (OR [95% CI] = 1.17 [1.02-1.34]) and Caucasian (OR [95% CI] = 1.19 [1.00-1.41]), as well as for postmenopausal women (OR = 1.33, 95% CI: 1.02-1.73). In contrast, higher dietary SFA intake was not associated with risk of BC among premenopausal women, in cohort studies or hospital-based studies.A positive association between higher dietary SFA intake and postmenopausal BC risk was observed in case-control but not in cohort studies. More studies are warranted to confirm these findings.

Total energy intake and breast cancer risk in sisters: the Breast Cancer Family Registry

Energy restriction inhibits mammary tumor development in animal models. Epidemiologic studies in humans generally do not support an association between dietary energy intake and breast cancer risk, although some studies suggest a more complex interplay between measures of energy intake, physical activity, and body size. We examined the association between total energy intake jointly with physical activity and body mass index (BMI) and the risk of breast cancer among 1,775 women diagnosed with breast cancer between 1995 and 2006 and 2,529 of their unaffected sisters, enrolled in the Breast Cancer Family Registry. We collected dietary data using the Hawaii-Los Angeles Multiethnic Cohort food frequency questionnaire. Using conditional logistic regression to estimate the odds ratios (OR) and 95 % confidence intervals (CI) associated with total energy intake, we observed an overall 60-70 % increased risk of breast cancer among women in the highest quartile of total energy intake compared to those in the lowest quartile (Q4 vs. Q1: OR = 1.6, 95 % CI: 1.3-2.0; P (trend) < 0.0001); these associations were limited to pre-menopausal women or women with hormone receptor-positive cancers. Although the associations were slightly stronger among women with a higher BMI or lower level of average lifetime physical activity, we observed a positive association between total energy intake and breast cancer risk across different strata of physical activity and BMI. Our results suggest that within sisters, high energy intake may increase the risk of breast cancer independent of physical activity and body size. If replicated in prospective studies, then these findings suggest that reductions in total energy intake may help in modifying breast cancer risk.

Dietary intake of specific fatty acids and breast cancer risk among postmenopausal women in the VITAL cohort

Studies of dietary fat intake and breast cancer have been inconsistent and few have examined specific fatty acids. We examined the association between specific monounsaturated (MUFA), polyunsaturated (PUFA), saturated (SFA), and trans-fatty acids (TFA) and breast cancer risk. Participants, 50-76 yr, were female members of the VITamins And Lifestyle (VITAL) Cohort, who were postmenopausal at baseline. In 2000-2002, participants completed a food frequency questionnaire. Seven hundred seventy-two incident, primary breast cancer cases were identified using a population-based cancer registry. Cox proportional hazard models estimated hazard ratios (HR) and 95% confidence intervals (95% CI) for the association between fatty acid intake and breast cancer risk. Intake of total MUFAs (highest vs. lowest quintile: HR = 1.61, 95% CI: 1.08-2.38, P trend = 0.02), particularly myristoleic and erucic acids, was associated with increased breast cancer risk. Whereas total SFA was suggestive of an increased risk (HR = 1.47, 95% CI: 1.00-2.15, P trend = 0.09), strong associations were observed for palmitic, margaric, and stearic acids. Total TFA and PUFA intake were not associated with breast cancer. However, among TFAs, linolelaidic acid was positively associated with risk; among PUFAs, intake of eicosapentaenoic and docosahexaenoic acids were inversely associated with risk. Our findings show that fatty acids are heterogeneous in their association with postmenopausal breast cancer risk.

Summary and meta-analysis of prospective studies of animal fat intake and breast cancer

The objective of the present review was to examine the potential association between animal fat intake and breast cancer. We conducted a meta-analysis and review of epidemiological cohort studies, including data reported in the Pooling Project publication of Prospective Studies of Diet and Cancer. Random- and fixed-effects models were utilised to generate summary relative risk estimates (SRRE), and sensitivity and influence analyses were conducted. In the meta-analysis that included data reported in the Pooling Project publication of prospective cohorts (n 8) and subsequent publications of cohort studies (n 3), no significant association was observed comparing the highest category of animal fat intake with the lowest (SRRE 1.03; 95 % CI: 0.76, 1.40). Similarly, no significant association between a 5 % increment of energy from animal fat intake and breast cancer (SRRE 1.02; 95 % CI 0.97, 1.07) was observed in the meta-analysis of these studies. In conclusion, the results of the present quantitative assessment are not supportive of a positive independent association between consumption of animal fat and breast cancer, although findings may be sensitive to the type of dietary instrument used in cohort studies.

Dietary fat and breast cancer risk in the European Prospective Investigation into Cancer and Nutrition

BACKGROUND

Epidemiologic studies have produced conflicting results with respect to an association of dietary fat with breast cancer.

OBJECTIVE

We aimed to investigate the association between fat consumption and breast cancer.

DESIGN

We prospectively investigated fat consumption in a large (n = 319,826), geographically and culturally heterogeneous cohort of European women enrolled in the European Prospective Investigation into Cancer and Nutrition who completed a dietary questionnaire. After a mean of 8.8 y of follow-up, 7119 women developed breast cancer. Cox proportional hazard models, stratified by age and center and adjusted for energy intake and confounders, were used to estimate hazard ratios (HRs) for breast cancer.

RESULTS

An association between high saturated fat intake and greater breast cancer risk was found [HR = 1.13 (95% CI: 1.00, 1.27; P for trend = 0.038) for the highest quintile of saturated fat intake compared with the lowest quintile: 1.02 (1.00, 1.04) for a 20% increase in saturated fat consumption (continuous variable)]. No significant association of breast cancer with total, monounsaturated, or polyunsaturated fat was found, although trends were for a direct association of risk with monounsaturated fat and an inverse association with polyunsaturated fat. In menopausal women, the positive association with saturated fat was confined to nonusers of hormone therapy at baseline [1.21 (0.99, 1.48) for the highest quintile compared with the lowest quintile; P for trend = 0.044; and 1.03 (1.00, 1.07) for a 20% increase in saturated fat as a continuous variable].

CONCLUSIONS

Evidence indicates a weak positive association between saturated fat intake and breast cancer risk. This association was more pronounced for postmenopausal women who never used hormone therapy.

Diet and breast cancer: a review of the prospective observational studies

The role of diet for the risk of breast cancer is of great interest as a potentially modifiable risk factor. The evidence from prospective observational studies was reviewed and summarized on selected dietary factors, gene-diet interactions, and breast cancer incidence. Dietary factors were considered that, based on their nutritional constituents, are of particular interest in the context of breast cancer: fat intake, biomarkers of fat intake, fruit and vegetable consumption, antioxidant vitamins (vitamins A, C, E, and beta-carotene), serum antioxidants, carbohydrate intake, glycemic index and glycemic load, dairy consumption (including vitamin D), consumption of soy products and isoflavones, green tea, heterocyclic amines, and adolescent diet. The PubMed database was searched for all prospective studies that relate these dietary items to the incidence of breast cancer or consider gene-diet interactions. Among the prospective epidemiologic studies conducted on diet and breast cancer incidence and gene-diet interactions and breast cancer incidence, to date there is no association that is consistent, strong, and statistically significant, with the exception of alcohol intake, overweight, and weight gain. The apparent lack of association between diet and breast cancer may reflect a true absence of association between diet and breast cancer incidence or may be due to measurement error exceeding the variation in the diet studied, lack of sufficient follow-up, and focus on an age range of low susceptibility. The risk of breast cancer can be reduced by avoidance of weight gain in adulthood and limiting the consumption of alcohol.

Meat consumption and risk of breast cancer in the UK Women's Cohort Study

We performed a survival analysis to assess the effect of meat consumption and meat type on the risk of breast cancer in the UK Women's Cohort Study. Between 1995 and 1998 a cohort of 35 372 women was recruited, aged between 35 and 69 years with a wide range of dietary intakes, assessed by a 217-item food frequency questionnaire. Hazard ratios (HRs) were estimated using Cox regression adjusted for known confounders. High consumption of total meat compared with none was associated with premenopausal breast cancer, HR=1.20 (95% CI: 0.86-1.68), and high non-processed meat intake compared with none, HR=1.20 (95% CI: 0.86-1.68). Larger effect sizes were found in postmenopausal women for all meat types, with significant associations with total, processed and red meat consumption. Processed meat showed the strongest HR=1.64 (95% CI: 1.14-2.37) for high consumption compared with none. Women, both pre- and postmenopausal, who consumed the most meat had the highest risk of breast cancer.

The Canadian Study of Diet, Lifestyle, and Health: design and characteristics of a new cohort study of cancer risk

BACKGROUND

We have established a new cohort study, the Canadian Study of Diet, Lifestyle, and Health, to investigate the relationship between diet, lifestyle factors, molecular markers, and cancer incidence in Canada.

METHODS

The cohort was established predominantly by recruiting alumni from the Universities of Alberta, Toronto, and Western Ontario between 1995 and 1998, but also includes a small contingent recruited mostly in 1992 through the Canadian Cancer Society. Participants completed baseline lifestyle and food frequency questionnaires, measured waist and hip circumferences, and provided hair and toenail specimens.

RESULTS

Seventy-three thousand nine hundred and nine individuals (34,291 males and 39,618 females) were recruited, with representation from all Canadian provinces and territories; 97% provided biological specimens. The mean (S.D.) ages of the male and female participants at recruitment were 51.6 (15.6) and 46.1 (15.2) years, respectively. Data from a random sample of the study subjects at baseline show that approximately one-half of the males and one-third of the females were overweight (BMI>or=25kg/m(2)), and approximately one-quarter of all participants reported that they walked at least 4h/week. Mean (S.D.) daily caloric intake was 2341 (697)kcal for males and 2091 (612)kcal for females.

CONCLUSIONS

Given the rich repository of questionnaire and biological data, and an average follow-up time for cohort members of 10.4 years, the study is poised to make a major Canadian contribution towards understanding the roles of diet, lifestyle factors, and molecular markers in influencing cancer risk.

Diet and breast cancer

Clarification of the role of diet in breast cancer pathogenesis is important in order to identify modifiable risk factors on which to focus prevention efforts. Excess weight and weight gain in adult life are related to higher risk of postmenopausal breast cancer, and weight loss after menopause is associated with substantially reduced risk. Even moderate alcohol consumption contributes considerably to excess breast cancer risk, which can likely be mitigated with adequate folate intake. Diet during early life may play a substantial role in later cancer risk, but data are limited. In addition, physical activity and the prevention of weight gain can improve survival after a breast cancer diagnosis.

Association of energy intake and energy balance with postmenopausal breast cancer in the prostate, lung, colorectal, and ovarian cancer screening trial

Energy restriction remains one of the most effective ways known to prevent breast cancer in animal models. However, energy intake has not been consistently associated with risk of breast cancer in humans. In a prospective study, we assessed whether energy intake, body size, and physical activity each independently influence breast cancer risk in postmenopausal women and estimated the joint effect of combinations of these individual factors. As part of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, 38,660 women, ages 55 to 74 years and recruited from 10 centers in the United States during 1993 to 2001, were randomized to the screening arm of the trial. At baseline, the women completed a self-administered questionnaire, including a food frequency questionnaire. During follow-up from 1993 to 2003, 764 incident breast cancer cases were ascertained. Women in the highest quartile of energy intake (> or = 2,084 kcal/d) compared with those in the lowest quartile (<1,316 kcal/d) had a significantly increased risk for breast cancer [multivariate relative risk (RR), 1.25; 95% confidence interval (95% CI), 1.02-1.53; P(trend continuous) = 0.03]. Current body mass index (BMI) was also positively and significantly associated with risk (multivariate RR comparing >30 kg/m2 with <22.5 kg/m2, 1.35; 95% CI, 1.06-1.70; P(trend) = 0.01). Women with > or = 4 hours/wk of vigorous recreational physical activity had a significantly reduced risk of breast cancer compared with those who reported no recreational physical activity (multivariate RR, 0.78; 95% CI, 0.60-0.99; P(trend) = 0.15). None of these associations with individual energy balance measures was substantially confounded by the other two measures. When we estimated the joint effect of all three variables, women with the most unfavorable energy balance (the highest energy intake, highest BMI, and least physical activity) had twice the risk (RR, 2.10; 95% CI, 1.27-3.45) of women with the most favorable energy balance (the lowest energy intake, lowest BMI, and most physical activity). Although our estimates of absolute energy intake, based on a food frequency questionnaire, are imperfect, these results suggest that energy intake, in addition to BMI and physical activity may be independently associated with breast cancer risk. In addition, these three aspects of energy balance may act jointly in determining breast cancer risk.

Lipídio: fator de risco e prevenção do câncer de mama

A hipótese de que uma dieta rica em gordura promova o desenvolvimento do câncer de mama na menopausa é fortalecida por estudos caso-controle, que mostram forte associação positiva entre uma dieta rica em lipídios e as taxas de incidência de câncer de mama. Por outro lado, a ingestão dietética de gordura não parece estar relacionada com o risco de câncer de mama em estudos de coorte. Em vista desses achados conflitantes, tem sido difícil propor qualquer recomendação nutricional para a prevenção do câncer de mama. Estudos com animais e observações recentes em humanos, entretanto, têm mostrado evidências de que a dieta rica em ácido graxo linoléico estimula vários estágios no desenvolvimento de câncer mamário. Alguns estudos ainda mostram que o óleo de peixe, constituído de ácidos graxos ômega-3, parece prevenir o câncer pela influência sobre a atividade de enzimas e proteínas relacionadas à proliferação celular. Assim, são necessários estudos epidemiológicos que integrem as interações de ácidos graxos específicos com o catabolismo hormonal, fatores nutricionais protetores e de risco relacionados com o câncer de mama. Nesse trabalho, abordaremos os fatores protetores, de risco e as implicações quali e quantitativas dos ácidos graxos da dieta sobre o câncer de mama.

Prophylaxis approach to a-symptomatic post-menopausal women: Breast cancer

Breast cancer is the most common cancer of women worldwide. Its frequency increases throughout the female lifespan. Epidemiological research has clearly identified important reproductive risk factors for breast cancer, including age at menarche, age at menopause, age at first-term pregnancy and nulliparity, which provide important clues to the hormonal origin of this disease. The widespread use of exogenous sex steroids as contraceptive agents and as hormonal replacement therapy has been a source of concern and generates discussion about their effects on breast health. Lifestyle changes, exercise or diet could play a role in primary prevention of breast cancer. Regular exercise, ingestion of adequate amounts of fruit and vegetables, limiting alcohol consumption, avoidance of obesity in post-menopausal women, and perhaps the use of olive oil, may all have a protective effect and should be considered by women. There is insufficient scientific evidence of the role played by phyto-oestrogens on breast cancer risk. Other preventive measures that include the use of drugs such as statins or aspirin should not be recommended until we have more information about their effects on the breast. Especially for high-risk women, all the aforementioned measures may be not enough, and chemo-prevention should be considered. The use of selective oestrogen receptor modulators (SERMs) to reduce breast cancer risk is still being evaluated. Tamoxifen was the first SERM approved for the reduction of breast cancer incidence in women at high risk. However its use has limitations, due to significant side effects. Raloxifene has been approved for the prevention and treatment of post-menopausal osteoporosis and has provided excellent indications of breast cancer risk reduction, with a more favourable profile than tamoxifen.

Dietary fat and risk of breast cancer

BACKGROUND

Breast cancer is one of the major public health problems among women worldwide. A number of epidemiological studies have been carried out to find the role of dietary fat and the risk of breast cancer. The main objective of the present communication is to summarize the evidence from various case-control and cohort studies on the consumption of fat and its subtypes and their effect on the development of breast cancer.

METHODS

A Pubmed search for literature on the consumption of dietary fat and risk of breast cancer published from January 1990 through December 2003 was carried out.

RESULTS

Increased consumption of total fat and saturated fat were found to be positively associated with the development of breast cancer. Even though an equivocal association was observed for the consumption of total monounsaturated fatty acids (MUFA) and the risk of breast cancer, there exists an inverse association in the case of oleic acid, the most abundant MUFA. A moderate inverse association between consumption of n-3 fatty acids and breast cancer risk and a moderate positive association between n-6 fatty acids and breast cancer risk were observed.

CONCLUSION

Even though all epidemiological studies do not provide a strong positive association between the consumption of certain types of dietary fat and breast cancer risk, at least a moderate association does seem to exist and this has a number of implications in view of the fact that breast cancer is an increasing public health concern.

Nutritional fats and the risk of type 2 diabetes and cancer

Dietary factors are important predictors for the risk of diabetes type 2. Increased consumption of fibre-rich foods, fruits and vegetables as well as limited amounts of total and saturated fats are essential elements in the prevention of diabetes type 2. The association between these dietary factors and the appearance of diabetes was not only present in cohort studies but were also major elements in the dietary part of the two large diabetes prevention trials (Finnish Diabetes Prevention Study, Diabetes Prevention Program). There is also strong evidence for a relation between obesity and total fat intake and the incidence of certain types of cancers. There is a significant correlation between total fat intake and the risk of cancer; however, it is much weaker than that of the effect of red meat. Recommendations to decrease red meat intake, particularly processed meat, may decrease the risk of colorectal and prostate cancer and may have beneficial effects on breast cancer as well, although this evidence is less compelling. Overall, recommendations focused on controlling or reducing body weight by regular physical activity and avoidance of excessive energy intake from all sources, particularly from fat and saturated fats, by increasing consumption of fibre-rich carbohydrates, vegetables and fruits are effective in decreasing the risk for type 2 diabetes by more than 50% in high-risk individuals. Similar dietary patterns are likely to diminish the manifestation of certain forms of cancers. These conclusions are in agreement with current recommendations for cancer prevention as propagated by the American Cancer Society.

Baseline data and design for a randomized intervention study of dietary change in religious organizations

BACKGROUND

Reducing dietary fat has been identified as a potential means of preventing chronic disease. Several studies have identified methods of changing dietary fat consumption in small, intensive intervention settings. Fewer studies have examined how to improve dietary habits of individuals in the general public.

METHODS

The Eating for a Healthy Life (EHL) project was a randomized trial [n = 40 religious organizations (ROs) and 2175 individuals, 1099 in intervention]. The study tested an intervention package of self-help books, motivational messages, and social interactions designed to change dietary behaviors (lowering fat, increasing fruit and vegetable consumption) among members of religious organizations aged 18 and over. The primary outcomes are fat- and fruit- or vegetable-related behaviors measured using the Fat and Fiber Behavior (FFB) Questionnaire.

RESULTS

Religious organizations and their members participated fully in the initial study activities.

CONCLUSIONS

This study will support a rigorous test of the intervention package.

Consumption of dairy products and the risk of breast cancer: a review of the literature

Differences in eating patterns and breast cancer rates across countries suggest that several dietary components, including dairy products, could affect breast cancer risk. However, dairy products are a diverse food group in terms of the factors that could potentially influence risk. Some dairy products, such as whole milk and many types of cheese, have a relatively high saturated fat content, which may increase risk. Moreover, milk products may contain contaminants such as pesticides, which have carcinogenic potential, and growth factors such as insulin-like growth factor I, which have been shown to promote breast cancer cell growth. In contrast, the calcium and vitamin D contents of dairy products have been hypothesized to reduce breast cancer risk. We reviewed the current epidemiologic literature on the relation between dairy product intakes and breast cancer risk, focusing primarily on the results of cohort and case-control studies. Most of the studies reviewed showed no consistent pattern of increased or decreased breast cancer risk with a high consumption of dairy products as a whole or when broken down into high-fat and low-fat dairy products, milk, cheese, or butter. Measurement error may have attenuated any modest association with dairy products. The available epidemiologic evidence does not support a strong association between the consumption of milk or other dairy products and breast cancer risk.

Does diet affect breast cancer risk?

The role of specific dietary factors in breast cancer causation is not completely resolved. Results from prospective studies do not support the concept that fat intake in middle life has a major relation to breast cancer risk. However, weight gain in middle life contributes substantially to breast cancer risk. Alcohol is the best established dietary risk factor, probably by increasing endogenous estrogen levels. Hypotheses relating diet during youth to risk decades later will be difficult to test. Nevertheless, available evidence is strong that breast cancer risk can be reduced by avoiding weight gain during adult years, and by limiting alcohol consumption.

The Role of Nutrition in the Prevention of Breast Cancer

Nutrition has been widely studied as a leading environmental factor in the prevention of breast cancer (BC). Despite the challenges in relating consumption of specific nutrients to BC risk, particularly in the context of a total diet, many investigators have contributed valuable information. Dietary fat has received the most attention and also created the most uncertainty. Specific types of fat, particularly monounsaturated fat and the ratio of omega-3 to omega-6 fatty acids, demonstrate more potential to influence BC risk. A wide variety of other dietary factors have been studied in relation to BC including total energy, dietary fiber, alcohol, micronutrients, phytochemicals, specific foods, and food constituents. Results of epidemiological studies relating consumption of these dietary factors to BC have increased the knowledge base that provides rationale for various nutritional strategies to contribute to BC prevention.

Dietary fat and breast cancer risk revisited: a meta-analysis of the published literature

Animal experiments and human ecological studies suggest that dietary fat intake is associated with a risk of breast cancer, but individual-based studies have given contradictory results. We have carried out a meta-analysis of this association to include all papers published up to July 2003. Case–control and cohort studies that examined the association of dietary fat, or fat-containing foods, with risk of breast cancer were identified. A total of 45 risk estimates for total fat intake were obtained. Descriptive data from each study were extracted with an estimate of relative risk and its associated 95% confidence interval (CI), and were analysed using the random effects model of DerSimonian and Laird. The summary relative risk, comparing the highest and lowest levels of intake of total fat, was 1.13 (95% CI: 1.03–1.25). Cohort studies (N=14) had a summary relative risk of 1.11 (95% CI: 0.99–1.25) and case–control studies (N=31) had a relative risk of 1.14 (95% CI 0.99–1.32). Significant summary relative risks were also found for saturated fat (RR, 1.19; 95% CI: 1.06–1.35) and meat intake (RR, 1.17; 95% CI 1.06–1.29). Combined estimates of risk for total and saturated fat intake, and for meat intake, all indicate an association between higher intakes and an increased risk of breast cancer. Case–control and cohort studies gave similar results.

Preventing cancer: dietary lifestyle or clinical intervention?

In Australia, colorectal, prostate and breast cancers are the most frequently occurring cancers in our society, a pattern that is quite different from that of underdeveloped countries. While diet is largely responsible for these differences, technological advances mean that the solutions can be viewed as systematic, financial, lifestyle or technological. They range from those that require self-discipline and care for personal well-being through to those that are seemingly a quick technological fix that will work in spite of an unhealthy lifestyle. There are three main approaches available for prevention of these cancers: dietary lifestyle, chemoprevention and screening. It has been estimated that the potential for prevention by a healthy dietary lifestyle is excellent and might reduce the burden of breast, prostate and colorectal cancer by 33-55%, 10-20% and 66-75%, respectively. This should be safe and inexpensive and have collateral benefit such as reduced cardiovascular disease and osteoporosis. But, population compliance with more plant-based, less calorie dense foods is uncertain, the most healthy are likely to be the most compliant and evidence for effectiveness when interventional programs are undertaken is disappointing. It is not clear how dependable the dietary approach would be where inherited genetic factors determine risk for one of these cancers. Chemoprevention, the administration of natural or synthetic agents that delay, slow down or inhibit the process of tumorigenesis, are still under development and study. Hormone receptor modulators for breast and derivatives of non-steroidal anti-inflammatory drugs for colorectal cancers seem to have most promise and may reduce tumour incidence or death by as much as 50%. These agents are simpler to comply with than changing dietary lifestyle and they are more potent, hence they may be of particular value in high-risk settings. But they are likely to be more costly and run the risk of adverse effects with few collateral benefits. Screening, or the testing of an individual for a disease when that individual does not have any symptoms or signs suggesting that the disease is present, aims to prevent or delay the development of the cancer. Screening impacts on mortality more so than on incidence, reducing colorectal cancer mortality in the range 15-60% and breast cancer mortality by 23-37%. Screening has the advantage of being effective in high-risk as well as average-risk groups and is an 'easy' solution for the person who elects not to follow a healthy dietary lifestyle. Nonetheless, it is expensive, demanding on resources, provides no collateral benefits and does not have the same potential to reduce incidence of disease as does the dietary approach. With these Western cancers, we are fortunate that there are options for prevention. At least choices are available and some will suite certain circumstances and personalities more than others.

Intake of fruits, vegetables and selected micronutrients in relation to the risk of breast cancer

High fruit and vegetable intake has been linked with a reduced risk of breast cancer, but evidence is not consistent. We investigated the associations of breast cancer risk with vegetables, fruits and related micronutrient intake in a population-based case-control study among Chinese women in Shanghai, where dietary patterns differ substantially from other study populations. Included in the study were 1,459 incident breast cancer cases and 1,556 frequency-matched controls. Usual dietary habits were assessed by in-person interviews. Logistic regression was used to compute adjusted odds ratios (ORs) and 95% confidence intervals (CIs) to measure strength of the associations. There was no association between breast cancer risk and total vegetable intake. The risk of breast cancer declined, however, with increasing intake of dark yellow-orange vegetables (trend test, p = 0.02), Chinese white turnips (trend test, p </= 0.001), and certain dark green vegetables (trend test, p </= 0.001) with adjusted OR in the highest quintile being 0.79 (95% CI = 0.60-0.98), 0.67 (95% CI = 0.53-0.85) and 0.65 (95% CI = 0.51-0.83) respectively. Intake of fruits, except watermelons and apples, was inversely associated with breast cancer risk (p-values for trend tests </=0.05). Our study suggests that high intake of certain vegetables and fruits may be associated with a reduced risk of breast cancer.

Comparison of adipose tissue fatty acids with dietary fatty acids as measured by 24-hour recall and food frequency questionnaire in Black and White Adventists: the Adventist Health Study

PURPOSE

To calibrate and compare intake of different fats and individual fatty acids as assessed with a food frequency questionnaire (FFQ) against that estimated with (i) a series of dietary recalls and; (ii) the relative fat concentration in an adipose tissue biopsy. The FFQ was specially designed for use in a cohort of Seventh-day Adventists. In preparation for a large cohort study investigating the effect of diet on risk of colon, prostate and breast cancer.

METHODS

The association of adipose tissue fatty acids and dietary fat intake was assessed in 49 black and 72 white Seventh-day Adventists subjects using 8 different 24-hour recalls, a 200-item food frequency questionnaire (FFQ) and adipose tissue biopsies from each subject.

RESULTS

Pearson correlation between fatty acids in adipose tissue and dietary intake as assessed by multiple 24-hour recalls were as follows: Linoleic acid: 0.77 in black and 0.71 in white subjects, respectively; Linolenic acid: 0.68 (blacks) and 0.62 (whites); Total Polyunsaturated fat (PUFA): 0.78 (blacks) and 0.70 (whites); Total Monounsaturated fat (MUFA): 0.35 (blacks) and 0.03 (whites); Total Saturated fat (SFA): 0.46 (blacks) and 0.56 (whites). Correlations between fatty acids in adipose tissue and dietary intake as assessed by FFQ were: Linoleic acid: 0.61 (blacks) and 0.52 (whites), respectively; Linolenic acid: 0.29 (blacks) and 0.49 (whites); PUFA: 0.62 (blacks) and 0.53 (whites); MUFA: 0.07 (blacks) and 0.31 (whites), SFA: 0.21 (blacks) and 0.31 (whites).

CONCLUSIONS

Our study confirms findings of others that 24-hour recalls are valid for assessing dietary intake of different types of fat. The FFQ we developed and used in this study gave reasonably valid measures of fatty acid intake in our population and is thus suitable for use in large cohort studies. It had validity comparable to that observed for other FFQs.

Fat and protein intake and subsequent breast cancer risk in postmenopausal women

The role of diet in the etiology of breast cancer has been extensively evaluated. Case-control studies generally support an association, while cohort studies have produced inconsistent results. This study, carried out on the ORDET cohort, is the first prospective Italian study to address the relation between diet and breast cancer. Female volunteers were recruited from 1987 to 1992 among residents of Varese Province, Northern Italy, an area covered by a cancer registry. A semiquantitative self-administered food questionnaire was completed by participants. After a mean 5.5 yr of follow-up, 56 cases of invasive breast cancer were identified among the 3,367 postmenopausal members; 214 controls were randomly chosen from the cohort, matched to cases for age, menopausal status at recruitment, recruitment center, and recruitment period. The adjusted odds ratios for the highest tertile of intake vs. the lowest were 3.47 [95% confidence interval (CI) = 1.43-8.44] for total fat, 3.78 (95% CI = 0.95-15.0) for animal protein, and 0.42 (95% CI = 0.18-0.95) for total carbohydrates. These findings indicate a significant positive association between total fat and animal protein and risk of breast cancer and an inverse association with carbohydrates and constitute new evidence for a role of diet in the etiology of breast cancer.

Dietary fat and cancer

Based on current epidemiologic knowledge, public health recommendations to decrease total fat intake for the prevention of cancer appear largely unwarranted. Recommendations to decrease red meat intake, particularly processed meat or beef intake, may, on the other hand, decrease the risk of colorectal cancer and prostate cancer; it may have a beneficial effect on breast cancer as well, although the evidence is much less compelling in this regard. There appears to be no particular benefit regarding cancer prevention that would accrue from reducing fat intake from vegetable sources, and in the case of breast cancer, there is some suggestive but preliminary evidence that olive oil or other sources of monounsaturated fatty acids may modestly decrease risk. Overall, recommendations focused on controlling weight by regular physical activity and avoidance of excessive energy intake from all sources; increasing plant food intake; consuming a variety of whole grains, vegetables, and fruits; and decreasing red meat intake are likely to be more effective in decreasing risk of breast, colorectal, and prostate cancer than decreasing total fat intake. This conclusion is consistent with current recommendations for cancer prevention as promulgated by the American Cancer Society.

Dietary interventions to prevent disease

Changing dietary behaviors to prevent chronic disease has been an important research focus for the last 25 years. Here we present a review of published articles on the results of research to identify methods to change key dietary habits: fat intake, fiber intake, and consumption of fruits and vegetables. We divided the research reviewed into sections, based on the channel through which the intervention activities were delivered. We conclude that the field is making progress in identifying successful dietary change strategies, but that more can be learned. Particularly, we need to transfer some of the knowledge from the individual-based trials to community-level interventions. Also, more research with rigorous methodology must be done to test current and future intervention options.

Assessment of questionnaire validity for measuring total fat intake using plasma lipid levels as criteria

The validation of dietary total fat measurements has been elusive because no specific biomarker exists. In metabolic studies with controlled diets, plasma fasting triglyceride levels are reduced with higher fat intake and can thus serve as an "alloyed gold" standard. Participants in this cross-sectional analysis were 269 men aged 47-83 years from the Health Professionals Follow-up Study who completed a semiquantitative food frequency questionnaire and provided fasting blood specimens in 1994. In a multiple regression analysis adjusted for age; smoking; alcohol consumption; physical activity; body mass index; and intakes of protein, dietary fiber, and total energy, total fat intake was inversely associated with fasting triglycerides (for a fat increase of 1% of energy, triglyceride levels were lower by 2.5% (95% confidence interval: -3.7 to -1.3%, p = 0.0002)). For reported fat intakes of 20% or less of energy, the geometric mean fasting triglyceride level was 179, and for more than 40% of energy, it was 102 mg/dl. In addition, as predicted by metabolic studies, the inverse association between dietary fat and fasting triglyceride level was much stronger among overweight men than among men with a BMI of less than 25. These data provide additional evidence that informative measurements of dietary fat can be obtained by carefully constructed food frequency questionnaires.

Types of dietary fat and breast cancer: a pooled analysis of cohort studies

Recently, there has been interest in whether intakes of specific types of fat are associated with breast cancer risk independently of other types of fat, but results have been inconsistent. We identified 8 prospective studies that met predefined criteria and analyzed their primary data using a standardized approach. Holding total energy intake constant, we calculated relative risks for increments of 5% of energy for each type of fat compared with an equivalent amount of energy from carbohydrates or from other types of fat. We combined study-specific relative risks using a random effects model. In the pooled database, 7,329 incident invasive breast cancer cases occurred among 351,821 women. The pooled relative risks (95% confidence intervals [CI]) for an increment of 5% of energy were 1.09 (1.00-1.19) for saturated, 0.93 (0.84-1.03) for monounsaturated and 1.05 (0.96-1.16) for polyunsaturated fat compared with equivalent energy intake from carbohydrates. For a 5% of energy increment, the relative risks were 1.18 (95% CI 0.99-1.42) for substituting saturated for monounsaturated fat, 0.98 (95% CI 0.85-1.12) for substituting saturated for polyunsaturated fat and 0.87 (95% CI 0.73-1.02) for substituting monounsaturated for polyunsaturated fat. No associations were observed for animal or vegetable fat intakes. These associations were not modified by menopausal status. These data are suggestive of only a weak positive association with substitution of saturated fat for carbohydrate consumption; none of the other types of fat examined was significantly associated with breast cancer risk relative to an equivalent reduction in carbohydrate consumption.

Dietary fat and breast cancer

One of the most often studied associations in epidemiology is dietary fat and breast cancer risk. That migrants from low-risk countries increase their risk on immigrating to higher-risk countries suggests that some modifiable lifestyle or environmental factor is responsible for the development of breast cancer. Although early international correlational studies and experimental animals studies support dietary fat as a risk factor for breast cancer, more recent data from case-control studies and cohort studies have been equivocal, thus the analytical data do not support a strong positive association. The conflicting results from analytic studies may be due to methodologic issues associated with study design, dietary assessment tools, measurement error, improper statistical analyses, and a lack of heterogeneity in fat intake among the study population. Moreover, current dietary questionnaires may be inadequate in capturing true dietary intakes or capturing the risk with exposure during earlier periods of a woman's life. Although two large clinical trials investigating the fat/breast cancer relationships issue are underway, researchers are generally skeptical at their ability to detect an independent association between fat and breast cancer risk. Further epidemiologic studies using current methodology may not prove to be fruitful in generating definitive answers to shed light on this controversial issue. In addition, rather than concentrating on dietary fat, researchers should focus on diets that are not only low in saturated fat, but also high in fruit and vegetable consumption. Researchers should take advantage of advances in molecular and genetic technology for a different perspective in examining the issue. For example, markers of susceptibility to breast cancer that can detect women at higher risk for breast cancer may be helpful in clarifying the role of dietary fat. More comprehensive and multiple approaches to studying dietary factors and breast cancer are recommended.

Dietary fat and adult diseases and the implications for childhood nutrition: an epidemiologic approach

Reducing dietary saturated fat by 7% of energy, a realistic target, would reduce serum cholesterol by 10% and mortality from ischemic heart disease by 25-30%. Randomized trials show that this mortality reduction is attained rapidly, usually by the third year after initial reduction of dietary saturated fat intake. Dietary change in adulthood may therefore reverse the adverse health effects of a high-fat diet in childhood. In the absence of such change, however, dietary fat in childhood may increase the risk of cardiovascular disease in adult life because of a longer duration of exposure to a high-fat diet. Assessing the effects of diet on cancer risk is more difficult. The intermediary markers of risk that are analogous to serum cholesterol are less satisfactory and there are negligible trial data. Cohort studies of diet and cancer, although subject to bias, do not favor a direct causal relation between dietary fat and cancer. But a reduction in risk is likely when dietary fat is reduced as part of a general change toward a healthier diet. The trend toward increased energy intake and body size in childhood and relatively low dietary fiber contribute to the decreasing age at menarche, which is associated with an increased risk of breast cancer. Low dietary fiber, low fruit and vegetable consumption, and high red meat consumption are associated with colon cancer and other cancers, and important causal effects of diet on cancer are likely. As with cardiovascular disease, this dietary trend that is commenced in childhood is likely to increase age-specific rates of colon cancer in adult life, but the risk may be reversed with later dietary change.

Dietary fat, fat subtypes, and breast cancer in postmenopausal women: a prospective cohort study

BACKGROUND

The intake of total dietary fat and of certain fat subtypes has been shown to be strongly associated with breast cancer in international comparisons and in animal experiments. However, observational epidemiologic studies have generally reported either weak positive or no associations. To extend the prospective epidemiologic evidence on this question, we examined the association between adult dietary intake of fat, fat subtypes, and breast cancer in a large, prospective cohort of postmenopausal women.

METHODS

Participants were selected from a national breast cancer mammography screening program conducted from 1973 through 1981 at 29 centers throughout the United States. From 1987 through 1989, 40022 postmenopausal women satisfactorily completed a mailed, self-administered questionnaire that included a 60-item National Cancer Institute/Block food-frequency questionnaire. Women were then followed for an average of 5.3 years; 996 women developed breast cancer. Risk was assessed by use of Cox proportional hazard regression, with age as the underlying time metric. All statistical tests were two-sided.

RESULTS

Compared with women in the lowest quintile (Q1) of percentage of energy from total fat, the adjusted risk ratio (RR) and 95% confidence interval (CI) for women in the highest quintile (Q5) was 1.07 (95% CI = 0.86-1.32). In analyses stratified by history of benign breast disease (BBD), a positive association was observed among only women with no history of BBD (RR (Q5 versus Q1) = 2.20; 95% CI = 1.41-3.42; test for trend, P =.0003). The increased risk in these women appeared to be attributable to unsaturated fat intake and oleic acid in particular.

CONCLUSIONS

In this study, there was no overall association between fat intake during adulthood and breast cancer risk; however, among women with no history of BBD, there appeared to be a positive association between total and unsaturated fat intake and breast cancer risk.

Pancreatic cancer: any prospects for prevention?

Primary prevention of pancreatic cancer and public health measures to reduce its incidence are dependent on data from epidemiological studies. Currently, the only definite risk factor is smoking, although a diet rich in fruit and vegetables may be protective. The K-ras mutation may have a role in diagnosis and screening.

Understanding meta-analysis in cancer epidemiology: dietary fat and breast cancer

Meta-analyses of the relationship between dietary fat and breast cancer risk using different methodologies have reported conflicting results. This investigation compares methodologic aspects of meta-analyses of patient data (MAP) with meta-analyses of data from the literature (MAL), and computes relative risk (RR) estimates from a random effects model using 28 published studies of dietary fat and breast cancer. MAP and MAL results compare closely when homogeneity is verified. When statistical homogeneity is rejected, a random effects model adjusting for study design and location is appropriate. The highest RR was found for case-control studies of European women (RR: 1.46), followed by North American case-control studies (RR: 1.25), case-control studies of women on other continents (RR: 1.23), cohort studies in Europe (RR: 1.20), and cohort studies in North America (RR: 1.02). The overall risk estimate in a MAL with heterogeneous studies should be interpreted only in a conditional model.

Garlic, onion and cereal fibre as protective factors for breast cancer: a French case-control study

The role of diet on breast cancer risk was investigated in a case-control study of 345 patients diagnosed with primary breast carcinoma between 1986 and 1989 in the north-east of France (Lorraine). For each case, one control was matched for age (+/-3 years) and socio-economic status. The dietary history questionnaire consisted of a self-administered food frequency questionnaire, a 6-day food diary and an energy expenditure record. It also elicited personal characteristics and medical history. While taking into account total caloric intake and established risk factors, breast cancer risk was shown to decrease as consumption of fibre (p value for trend = 0.03), and garlic and onions (p value for trend <10(-6)) increased. This study also supports the epidemiologic evidence that saturated fat intake and breast cancer risk are associated in post-menopausal women (p value for trend = 0.03). Conversely, it suggests that unsaturated fat intake could lower the risk in the same subgroup (p value for trend = 0.03). Our findings on protective factors of breast cancer could induce effective preventive measures and warrant further experimental investigations to isolate specific subfractions.

Interactions between hormones and chemicals in breast cancer

Development of breast cancer in women is dependent on diverse factors, including genetic predisposition, exposure to both exogenous and endogenous chemicals, which can modulate initiation, promotion and progression of this disease, and the timing of exposure to these agents. Several compounds--including 16 alpha-hydroxyestrone (16 alpha-OHE1), catecholestrogens, and aromatic amines--have been proposed as initiators of mammary carcinogenesis in humans; however, their role as genotoxins is unconfirmed. Lifetime exposure to estrogens has been established as an important risk factor for breast cancer, and it has been suggested that xenoestrogens may directly add to the hormonal risk or indirectly increase risk by decreasing 2-hydroxyestrone (2-OHE1)/16 alpha-OHE1 metabolite ratios. Results of recent studies suggest that chemical-induced modulation of 2-OHE1/16 alpha-OHE1 metabolite ratios is not predictive of xenoestrogens or mammary carcinogens. Moreover, based on current known dietary intakes of natural and xenoestrogenic/antiestrogenic chemicals, it is unlikely that xenoestrogens contribute significantly to a woman's overall lifetime exposure to estrogens. More information is required on the identities and serum levels of both natural and xenoendocrine active compounds, their concentrations in serum, and the mammary gland and levels of these compounds at critical periods of exposure.

Essential fatty acids and breast cancer: a case-control study in Uruguay

The relationship between frequency of intake of different types of fat and breast cancer was investigated in a case-control study conducted in Montevideo, Uruguay, during the time period 1994-1996. Our study comprised 365 cases and 397 controls. A moderate and non-significant increase in risk of breast cancer, associated with total fat intake, was found. Saturated and monounsaturated fat intake were not associated to an increased risk of this malignancy, whereas polyunsaturated fat and linoleic acid were associated with a significantly reduced risk (OR 0.26, 95% CI 0.13-0.53). On the contrary, both alpha-linolenic acid and cholesterol intakes were associated with an increased risk of breast cancer (OR for the upper quartile of intake of alpha-linolenic acid 3.79, 95% CI 1.53-9.40). When alpha-linolenic was examined at different levels of intake, the OR's were significantly higher at low levels of linoleic acid intake (OR 7.5, 95% CI 1.9-28.8).

Differential modulation by dietary n-6 or n-9 unsaturated fatty acids on the development of two murine mammary gland tumors having different metastatic capabilities

It is widely known that dietary lipids can modify the ability of different cancers to grow up and metastasize, especially mammary gland tumors. However, it is still unclear whether n-6 fatty acids behave as tumor promoters in this gland cell population. The effect of different nutritional polyunsaturated fatty acids (PUFAs) on tumor growth parameters of two transplantable murine mammary gland adenocarcinomas of low and high metastatic ability was tested on hosts fed diets with corn oil (CO) rich in 18:2n-6, evening primrose oil (EPO) containing 18:3n-6 (GLA) and a third formula supplemented with olein (O) 18:1n-9, which induces an essential fatty acid deficiency (EFAD). Tumor growth parameters were not adversely affected in the corn oil group with respect to stock-fed controls. Furthermore, metastatic spreading diminished in this group. EPO showed a moderate antitumor activity whereas the n-9-enriched diet showed no clear-cut effects. In both mammary gland tumors, n-6 fatty acid-rich lipids formulae, containing GLA and linoleic acid, were not tumor promoters. On the contrary, both exhibited anticancer activity.