Dietary Fat and Postmenopausal Invasive Breast Cancer in the National Institutes of Health-AARP Diet and Health Study Cohort

Lifestyle Interventions in the Prevention and Treatment of Cancer

Despite evidence that cancer death rates in the United States are declining, the absolute number of new cancers and cancer deaths continues to increase, and there is clear evidence that certain human behaviors are influencing these increases. The 4 major factors of lifestyle that continue to be causally related to certain cancers—tobacco use, an unhealthy diet, inadequate exercise, and excessive exposure to ultraviolet radiation—are each independently important in their effects on the genetic and molecular processes that result in the malignant transformation of human cells. There is both irrefutable and otherwise strong evidence that 4 common cancers that occur in the United States—lung cancer, colon/rectal cancer, breast cancer, and prostate cancer—and a less common cancer, malignant melanoma, have etiologic factors that are lifestyle based and therefore controllable through alterations in human behavior. These cancers and the evidence that lifestyle is important in the causation and/or prevention of the disease are the subjects of this review.

Meat intake and mortality: a prospective study of over half a million people

BACKGROUND

High intakes of red or processed meat may increase the risk of mortality. Our objective was to determine the relations of red, white, and processed meat intakes to risk for total and cause-specific mortality.

METHODS

The study population included the National Institutes of Health-AARP (formerly known as the American Association of Retired Persons) Diet and Health Study cohort of half a million people aged 50 to 71 years at baseline. Meat intake was estimated from a food frequency questionnaire administered at baseline. Cox proportional hazards regression models estimated hazard ratios (HRs) and 95% confidence intervals (CIs) within quintiles of meat intake. The covariates included in the models were age, education, marital status, family history of cancer (yes/no) (cancer mortality only), race, body mass index, 31-level smoking history, physical activity, energy intake, alcohol intake, vitamin supplement use, fruit consumption, vegetable consumption, and menopausal hormone therapy among women. Main outcome measures included total mortality and deaths due to cancer, cardiovascular disease, injuries and sudden deaths, and all other causes.

RESULTS

There were 47 976 male deaths and 23 276 female deaths during 10 years of follow-up. Men and women in the highest vs lowest quintile of red (HR, 1.31 [95% CI, 1.27-1.35], and HR, 1.36 [95% CI, 1.30-1.43], respectively) and processed meat (HR, 1.16 [95% CI, 1.12-1.20], and HR, 1.25 [95% CI, 1.20-1.31], respectively) intakes had elevated risks for overall mortality. Regarding cause-specific mortality, men and women had elevated risks for cancer mortality for red (HR, 1.22 [95% CI, 1.16-1.29], and HR, 1.20 [95% CI, 1.12-1.30], respectively) and processed meat (HR, 1.12 [95% CI, 1.06-1.19], and HR, 1.11 [95% CI 1.04-1.19], respectively) intakes. Furthermore, cardiovascular disease risk was elevated for men and women in the highest quintile of red (HR, 1.27 [95% CI, 1.20-1.35], and HR, 1.50 [95% CI, 1.37-1.65], respectively) and processed meat (HR, 1.09 [95% CI, 1.03-1.15], and HR, 1.38 [95% CI, 1.26-1.51], respectively) intakes. When comparing the highest with the lowest quintile of white meat intake, there was an inverse association for total mortality and cancer mortality, as well as all other deaths for both men and women.

CONCLUSION

Red and processed meat intakes were associated with modest increases in total mortality, cancer mortality, and cardiovascular disease mortality.

Dietary patterns and breast cancer risk in Asian American women

BACKGROUND

The role of diet as a cause of breast cancer in Asian Americans has not been adequately studied.

OBJECTIVE

We investigated the association between dietary patterns and breast cancer risk in Asian Americans.

DESIGN

This population-based case-control study in Los Angeles County compared dietary patterns between 1248 Asian American women with incident breast cancer and 1148 age-, ethnicity-, and neighborhood-matched controls. The relation between dietary patterns and serum concentrations of estrogens, androgens, and sex hormone-binding globulin (SHBG) was investigated in 2172 postmenopausal control women.

RESULTS

We used a scoring method proposed by Trichopoulou et al (1) and found that adherence to a Mediterranean diet was inversely associated with risk; the odds ratio (OR) was 0.65 (95% CI: 0.44, 0.95) in women with the highest scores (> or = 8; most adherent) compared with those with the lowest scores (0-3; P for trend = 0.009), after adjustment for key covariates. We also used factor analysis and identified 3 dietary patterns (Western-meat/starch, ethnic-meat/starch, and vegetables/soy). In a combined index of the 3 patterns, women who were high consumers of Western and ethnic meat/starch and low consumers of the vegetables/soy diets showed the highest risk (OR: 2.19; 95% CI: 1.40, 3.42; P for trend = 0.0005). SHBG concentrations were 23% lower in women with a high intake of the meat/starch pattern and a low intake of the vegetables/soy pattern than in those with a low intake of the meat/starch pattern and a high intake of the vegetables/soy pattern (P for trend = 0.069).

CONCLUSION

Our results suggest that a diet characterized by a low intake of meat/starches and a high intake of legumes is associated with a reduced risk of breast cancer in Asian Americans.

Observational epidemiologic studies of nutrition and cancer: the next generation (with better observation)

It would be of enormous public health importance if diet and physical activity, both modifiable behavioral factors, were causally related to cancer. Nevertheless, the nutritional epidemiology of cancer remains problematic, in part because of persistent concerns that standard questionnaires measure diet and physical activity with too much error. We present a new strategy for addressing this measurement error problem. First, as background, we note that food frequency and physical activity questionnaires require respondents to report "typical" diet or activity over the previous year or longer. Multiple 24-hour recalls (24HR), based on reporting only the previous day's behavior, offer potential cognitive advantages over the questionnaires, and biomarker evidence suggests the 24-hour dietary recall is more accurate than the food frequency questionnaire. The expense involved in administering multiple 24 HRs in large epidemiologic studies, however, has up to now been prohibitive. In that context, we suggest that Internet-based 24 HRs, for both diet and physical activity, represent a practical and cost-effective approach for incorporating multiple recalls in large epidemiologic studies. We discuss (1) recent efforts to develop such Internet-based instruments and their accompanying software support systems; (2) ongoing studies to evaluate the feasibility of using these new instruments in cohort studies; (3) additional investigations to gauge the accuracy of the Internet-based recalls vis-à-vis standard instruments and biomarkers; and (4) new statistical approaches for combining the new instruments with standard assessment tools and biomarkers The incorporation of Internet-based 24 HRs into large epidemiologic studies may help advance our understanding of the nutritional determinants of cancer.

Marine n-3 and saturated fatty acids in relation to risk of colorectal cancer in Singapore Chinese: a prospective study

Experimental data support multiple roles for fatty acids in colorectal carcinogenesis. We examined dietary fatty acids and incidence of colorectal cancer, and evaluated effect modification by sex and stage of disease among a population-based cohort of 61,321 Singapore Chinese that was established between 1993 and 1998. As of December 31, 2005, 961 incident colorectal cancers were diagnosed. Presented hazard ratios (HRs) are for highest versus lowest quartiles with adjustment for potential confounders. Among women, we observed a dose-dependent, positive association between saturated fat and localized colorectal cancer (Dukes A or B) [(HR=1.69, 95% confidence interval (CI)=1.08-2.63, p for trend=0.01)]. No such associations were noted in men (p for interaction by sex=0.04). Marine n-3 polyunsaturated fatty acid (PUFA) intake was positively associated with advanced disease (Dukes C or D) (HR=1.33, 95% CI=1.05-1.70, p for trend=0.01), regardless of sex. The association with marine n-3 PUFAs was strongest among those with the shortest (<or=5 years) duration of follow-up (HR=1.49, 95% CI=1.00-2.21, p for trend=0.04). In contrast, we observed a small, albeit imprecise, inverse association with marine n-3 PUFAs for localized colorectal cancer among those with the longest duration of follow-up (>10 years) (HR=0.62, 95% CI=0.29-1.34, p for trend=0.55). Our findings suggest that subtypes of fatty acids may differentially influence risk of colorectal cancer of a specified stage.

Diet and expression of estrogen alpha and progesterone receptors in the normal mammary gland

OBJECTIVE

It has been recently reported that expression of estrogen alpha (ER-alpha) and progesterone (PR) receptors in the normal mammary gland is inversely associated with breast cancer risk among postmenopausal women. We investigated whether dietary intakes are associated with the expression of ER-alpha and PR receptors in the apparently normal, as opposed to pathological, mammary tissue.

METHODS

In a study in Greece, we examined associations of dietary intakes with ER-alpha and PR expression in the adjacent-to-pathological apparently normal mammary tissue of 562 women with either breast cancer (267 women) or BBD (299 women). Diet was assessed through an extensive food frequency questionnaire and results were analyzed using multiple logistic regression.

RESULTS

Monounsaturated (p = 0.03) and, to a lesser extent, polyunsaturated lipids (p = 0.08) were positively associated with ER-alpha expression. Cereals and starchy roots were inversely associated with ER-alpha (p = 0.01), whereas milk and dairy products were inversely associated with PR expression (p = 0.02). Ethanol intake was non-significantly inversely associated with ER-alpha expression (p = 0.07).

CONCLUSIONS

Our findings suggest that the weak associations of diet with breast cancer risk could be explained, to some extent, by effects of diet on receptor expression in the normal mammary gland.

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.

Methods of epidemiology: evaluating the fat-breast cancer hypothesis--comparing dietary instruments and other developments

Results from several large cohort studies that were reported 10 to 20 years ago seemed to indicate that the hypothesized link between dietary fat intake and breast cancer risk was illusory. In this article, we review several strands of more recent evidence that have emerged. These include two studies comparing the performance of dietary instruments used to investigate the dietary fat- breast cancer hypothesis, a large randomized disease prevention trial, a more recent meta-analysis of nutritional cohort studies, and a very large nutritional cohort study. Each of the studies discussed in this article suggests that a modest but real association between fat intake and breast cancer is likely. If the association is causative, it would have important implications for public health strategies in reducing breast cancer incidence. The evidence is not yet conclusive, but additional follow-up in the randomized trial, as well as efforts to improve dietary assessment methodology for cohort studies, may be sufficient to provide a convincing answer.

Do both heterocyclic amines and omega-6 polyunsaturated fatty acids contribute to the incidence of breast cancer in postmenopausal women of the Malmö diet and cancer cohort?

Heterocyclic amines (HAs), formed when meat and fish are cooked at high temperatures, have been linked to mammary gland cancer in rats, and some epidemiological studies indicate increased breast cancer risk by consumption of well-done meat. The epidemiological evidence linking HAs per se to breast cancer is however sparse, especially from prospective studies. Moreover, high-fat diets rich in omega-6 polyunsaturated fatty acids (PUFAs) have produced higher frequencies of HA-induced mammary gland tumors in rats compared to those fed low-fat diets. The aim was to evaluate prospectively if intake of HAs is associated with breast cancer incidence, and if the association is independent of omega-6 PUFA intakes. Among women 50 years or older at baseline from the population-based prospective Malmö Diet and Cancer cohort (n = 11,699), 430 women were diagnosed with incident invasive breast cancer during a mean follow-up of 10.4 years. Information on dietary habits was collected by a modified diet history method. Cox proportional hazards regression estimated hazard ratios (HRs) and 95% confidence intervals (CIs) of breast cancer associated with energy-adjusted intakes of HAs and omega-6 PUFA. Intakes of HAs were not associated with breast cancer incidence (HR, 0.94; 95% CI, 0.69-1.28, for highest compared to lowest quintile). In individuals with low HA intakes, a significant increased risk was observed among those with high intakes of omega-6 PUFAs. In conclusion, intakes of HAs are not associated with breast cancer incidence in this Swedish cohort, but dietary patterns very high in omega-6 PUFA may promote breast cancer development.

Low-fat dietary pattern and risk of benign proliferative breast disease: a randomized, controlled dietary modification trial

Modifiable factors, including diet, might alter breast cancer risk. We used the Women's Health Initiative Dietary Modification trial to test the effect of the intervention on risk of benign proliferative breast disease, a condition associated with increased risk of, and considered to be on the pathway to, invasive breast cancer. The Women's Health Initiative Dietary Modification trial was a randomized, controlled, primary prevention trial conducted in 40 U.S. clinical centers from 1993 to 2005. A total of 48,835 postmenopausal women, ages 50 to 79 years, without prior breast cancer, were enrolled. Participants were randomly assigned to the dietary modification intervention group or to the comparison group. The intervention was designed to reduce total dietary fat intake to 20% of total energy intake, and to increase fruit and vegetable intake to > or =5 servings/d and intake of grain products to > or =6 servings/d, but resulted in smaller, albeit significant, changes in practice. Participants had biennial mammograms and regular clinical breast exams. We identified women who reported breast biopsies free of cancer, obtained the histologic sections, and subjected them to standardized central review. During follow-up (average, 7.7 years), 570 incident cases of benign proliferative breast disease were ascertained in the intervention group and 793 in the comparison group. The hazard ratio for the association between dietary modification and benign proliferative breast disease was 1.09 (95% confidence interval, 0.98-1.23). Risk varied by levels of baseline total vitamin D intake but it varied little by levels of other baseline variables. These results suggest that a modest reduction in fat intake and increase in fruit, vegetable, and grain intake do not alter the risk of benign proliferative breast disease.

The role of dietary measurement error in investigating the hypothesized link between dietary fat intake and breast cancer--a story with twists and turns

The association between dietary fat and breast cancer is one of the most controversial hypotheses in nutritional epidemiology. In this editorial, the authors review the evidence from animal and human studies, including international correlation, case-control, cohort studies, intervention trials, and studies comparing dietary assessment instruments. The authors emphasize the importance of the role played by measurement error arising from assessing dietary habits using self-reported questionnaires, as it can distort estimated associations, not necessarily towards the absence of an association. They describe the twists and turns of the dietary fat and breast cancer debate that have revolved around this issue.

Early life events and conditions and breast cancer risk: from epidemiology to etiology

Risk factors for breast cancer--documented by intensive epidemiological investigations and viewed in the context of general principles of carcinogenesis--can be integrated to an etiologic model comprising 3 principal components: the likelihood of breast cancer occurrence depends on the number of mammary tissue-specific stem cells, which is determined in early life; all growth-enhancing mammotropic hormones affect the rate of expansion of initiated clones; and while a pregnancy stimulates the replication of already initiated cells, it conveys long-term protection through differentiation of mammary tissue-specific stem cells. This perspective accommodates much of what is known about the epidemiology and natural history of breast cancer and highlights the role of early life in the origin of this cancer.

A prospective study of red and processed meat intake in relation to cancer risk

BACKGROUND

Red meat and processed meat have been associated with carcinogenesis at several anatomic sites, but no prospective study has examined meat intake in relation to a range of malignancies. We investigated whether red or processed meat intake increases cancer risk at a variety of sites.

METHODS AND FINDINGS

The National Institutes of Health (NIH)-AARP (formerly the American Association for Retired Persons) Diet and Health Study is a cohort of approximately 500,000 people aged 50-71 y at baseline (1995-1996). Meat intake was estimated from a food frequency questionnaire administered at baseline. Cox proportional hazards regression was used to estimate hazard ratios and 95% confidence intervals within quintiles of red and processed meat intake. During up to 8.2 y of follow-up, 53,396 incident cancers were ascertained. Statistically significant elevated risks (ranging from 20% to 60%) were evident for esophageal, colorectal, liver, and lung cancer, comparing individuals in the highest with those in the lowest quintile of red meat intake. Furthermore, individuals in the highest quintile of processed meat intake had a 20% elevated risk for colorectal and a 16% elevated risk for lung cancer.

CONCLUSIONS

Both red and processed meat intakes were positively associated with cancers of the colorectum and lung; furthermore, red meat intake was associated with an elevated risk for cancers of the esophagus and liver.

PPARalpha and PPARbeta are differentially affected by ethanol and the ethanol metabolite acetaldehyde in the MCF-7 breast cancer cell line

The activity and/or the level of the peroxisome proliferator-activated receptors (PPARs) in liver and oligodendrocytes are regulated by ethanol. Despite the association between ethanol consumption and breast cancer risk, and the increasing evidence for an involvement of PPARs in some cancers, there have been no studies on the effect of ethanol or its metabolite acetaldehyde on PPARs in breast cancer. Using the MCF-7 breast cancer cell line, we examined the relationship between ethanol and its metabolite acetaldehyde on PPARalpha and PPARbeta transactivation. Ethanol (20 mM) reduced the potency of the PPARbeta ligand GW0742, evident by a rightward shift in the GW0742 dose-response curve, whereas for PPARalpha activation by GW7647, ethanol mediated its effects primarily through reducing efficacy as evidenced by a reduction in maximal response. Using the enzyme inhibitors 4-methylpyrazole and cyanamide and the metabolite acetaldehyde, we showed that PPARalpha and PPARbeta are differentially modulated by ethanol and acetaldehyde. While acetaldehyde is responsible for the inhibition of PPARalpha ligand inhibition with a concentration that inhibits 50% of activity (IC50) of 111 nM, acetaldehyde has no effect on PPARbeta or its ligand activation. Instead, inhibition of PPARbeta transactivation is mediated directly by ethanol. The differential effect of ethanol and acetaldehyde on PPARalpha and PPARbeta further underscores the differences between these receptors and may indicate the relevance of PPARs in the effects of ethanol in the human breast.

Dietary fat and breast cancer risk in the Swedish women's lifestyle and health cohort

We investigated whether dietary intakes of total fat, monounsaturated fat (MUFA), polyunsaturated fat (PUFA) and saturated fat (SFA) were associated with breast cancer risk in a prospective cohort of 49 261 Swedish women (30–49 years at enrolment), which yielded 974 breast cancer cases by December 2005. Further, we evaluated if associations differed by oestrogen and/or progesterone receptor tumour status. Total fat, MUFA, PUFA or SFA were not associated with risk overall. However, women in the highest MUFA and PUFA quintile intake had a reduced breast cancer risk after age 50 years (hazard ratios: 95% confidence interval=0.45: 0.25–0.99 and 0.54: 0.35–0.85, respectively) compared to women in the lowest quintile. The associations did not differ by oestrogen or progesterone receptor status. Despite the negative findings, type of fat during premenopausal years may have later differential effects on risk.