A study of diet and breast cancer

Comparison between the effects of dietary fat level and of calorie intake on methylnitrosourea-induced mammary carcinogenesis in female SD rats

The aim of this study was to separate the effects of calorie intake on tumorigenesis from those of fat content and fat composition in an animal model. Our principal observations were the following. Decreasing the calorie level by 30% significantly inhibited tumor development in any observed parameter of tumorigenesis, independently of the level of fat. The fat content of semi-synthetic diets, although varying by 44.4%, did not significantly influence mammary tumorigenesis; in fact, carcinogenic expression was discontinuously related to the fat level. A plateau of tumor incidence was observed at the level of 35 energy percentage of fat. Fat composition did not influence tumorigenesis or body weight gain. The role of caloric restriction is thus stressed in relation to possible dietary prevention of cancer.

Dietary fat and the risk of breast cancer

Dietary fat has been suggested as a risk factor for breast cancer in women, but the available data on humans are sparse and inconsistent. In 1980, 89,538 U.S. registered nurses who were 34 to 59 years of age and had no history of cancer completed a previously validated dietary questionnaire designed to measure individual consumption of total fat, saturated fat, linoleic acid, and cholesterol, as well as other nutrients. In a subsample of 173 participants studied in detail, those in the highest quintile of fat intake consumed a mean of 44 percent of calories from fat, as compared with 32 percent for those in the lowest quintile. During four years of follow-up, 601 cases of breast cancer were diagnosed among the 89,538 nurses in the study. After adjustment for known determinants in multivariate analyses, the relative risk of breast cancer among women in the highest quintile of calorie-adjusted total fat intake, as compared with women in the lowest quintile, was 0.82 (95 percent confidence limits, 0.64 and 1.05). The corresponding relative risks were 0.84 (confidence limits, 0.66 and 1.08) for saturated fat, 0.88 (0.69 and 1.12) for linoleic acid, and 0.91 (0.70 and 1.18) for cholesterol intake. Similar results were found for both postmenopausal and premenopausal women. These data are based on a limited period of follow-up and do not exclude a possible influence of fat intake before adulthood or at levels lower than 30 percent of calories. They suggest, however, that a moderate reduction in fat intake by adult women is unlikely to result in a substantial reduction in the incidence of breast cancer.

Dietary factors and the risk of breast cancer

We evaluated the risk of breast cancer in relation to the frequency of consumption of a few selected dietary items. Data were used from a case-control study of 1,108 histologically confirmed breast cancer patients and 1,281 control subjects who were in the hospital for acute conditions unrelated to any of the established or suspected risk factors for breast cancer. Moderately elevated risk estimates were associated with higher levels of fat consumption in seasonings [butter, margarine, and oil, relative risk (RR) = 1.34, 95% confidence interval (CI) = 1.06-1.71] and meat (RR = 1.36, 95% CI = 1.12-1.65), whereas a reduced risk (RR = 0.42, 95% CI = 0.34-0.51) was associated with a more frequent green vegetable consumption. It was not possible to show that these associations were incidental, because allowance for several identified potential confounding factors, including the major identified or potential risk factors for breast cancer, did not materially modify the risk estimates. Further, no appreciable interaction emerged with age or menopausal status, because the diet-related risk estimates were similar in pre- or postmenopausal women. However, the implications of these findings in terms of specific micronutrients (e.g., retinol or beta-carotene) and biological correlates are still unclear. Alcohol consumption was significantly greater among breast cancer cases, with a multivariate risk estimate of 2.92 for the highest level. Thus, the present findings confirm that various aspects of diet may influence the risk of breast cancer, although the small amount of available knowledge does introduce serious uncertainties in any discussion of the potential implications in terms of prevention on a public health scale.

Caloric intake, body weight, and cancer: a review

The literature is reviewed for evidence concerning the relation between caloric intake, body weight, and cancer. Convincing experimental data regarding caloric intake and benign and malignant tumor incidence have been available since the 1940s and demonstrate that caloric restriction significantly reduces tumor incidence for a variety of tumor types in several animal models. Some epidemiological investigations provide evidence for a positive calorie-cancer association in humans, although it is difficult (in these studies) to separate the effects of calories per se from those of dietary fat. A larger number of investigations have evaluated body weight alone, and high relative body weight or high caloric intake has been associated with increased risk of cancer of the breast, colon, rectum, prostate, endometrium, kidney, cervix, ovary, thyroid, and gallbladder. In contrast, lung, bladder, and stomach cancers appear to be inversely associated with body weight, and some prospective studies of men demonstrate greater total cancer mortality among lean individuals. However, in their analyses, few of these latter investigations considered the effects of cigarette smoking, antecedent illness, or competing causes of death. While the relations between caloric intake, other dietary macronutrients (e.g., fat), and body weight are complex and require further investigation, a complete review of the data suggests that reducing caloric intake and relative body weight may lead to a considerable decrease in cancer risk in humans.

Diet and breast cancer: a case-control study in Greece

A case-control study of the role of diet in the etiology of breast cancer was conducted in Athens, Greece. There are reasons to believe that the diet of the Greek population is characterized by greater heterogeneity than that in most countries where such studies have been undertaken. The case series consisted of 120 consecutive patients with histologically confirmed breast cancer admitted to either of two teaching hospitals over a 12-month period. The controls were 120 patients admitted to a teaching hospital for trauma and orthopedic conditions during the same period. Dietary histories concerning the frequency of consumption of 120 foods and drinks were obtained by interview. Cases reported significantly less frequent consumption of vegetables as a group and, within that group, specifically of cucumber, lettuce and raw carrot. After adjustment for potential external confounding variables and for confounding between food categories, the odds ratio for persons in the highest quintile of vegetable consumers, relative to those in the lowest quintile, was 0.09 with 95% confidence limits 0.03-0.30. That is to say, the lowest quintile of vegetable consumers had about 10 times the breast cancer risk of the highest quintile. For a score based on consumption of only the 3 specified salad items the odds ratio over the extreme quartiles was 0.12 (0.05-0.32). There was no association with consumption of fats and oils, alcohol or coffee, and no significant association with any other major food category (including alcohol and coffee) after adjustment for confounding variables.

Plasma lipids and prolactin in patients with breast cancer

In a comparative study of pre- and postmenopausal women with benign and malignant breast disease, a number of differences were observed in circulating plasma prolactin and lipid concentrations. Plasma lipids, phospholipids, triglycerides, cholesterol and free fatty acids were all higher in blood obtained from breast cancer patients prior to surgery. HDL-Cholesterol levels were significantly lower in these patients. These differences remained when the patient groups were sub-divided according to menopausal status. Plasma prolactin concentrations were also found to be higher in cancer compared with non-cancer patients, this effect being more marked in premenopausal than in postmenopausal patients. Premenopausal patients with invasive or poorly differentiated disease had significantly higher prolactin levels than those with non-invasive disease. No correlations were found between plasma prolactin and any of the lipid fractions.

Studies of nutrients and their relationship to cancer in the multiethnic population of Hawaii

Because of the many ethnic cultures in Hawaii, there is great dietary variation in the population, even within individual ethnic groups. Epidemiologic studies in this setting are providing useful information on the role of macro- and micronutrients in the risk for certain cancers. The results of several recent and ongoing case-control studies are described, especially with regard to the influence of dietary fat, vitamin A, and vitamin C. The degree of consistency of the findings with other reports in the literature is discussed.

Height, weight, and risk of breast cancer relapse

The records of 231 patients with primary breast cancer and 85 patients with metastatic breast cancer were reviewed to determine whether indices of body weight were associated with prognosis. Results support previous reports that indices of body weight are relatively weak, but real, prognostic factors.

The use of polytomous dual response data to increase power in case-control studies: an application to the association between dietary fat and breast cancer

Computer simulation has been used to compare various methods for analyzing data from case-control studies when two response variables are available to measure a risk factor. When such variables are continuous or polytomous, and a dose-response relationship exists, it is concluded that power may be increased by including individuals who are discordant on their responses. Failure to use the most appropriate method can lead to a substantial loss in power. The results are illustrated by reanalysis of data from an earlier case-control study of diet and breast cancer. This reanalysis has strengthened the evidence for a positive association between saturated fat intake and risk of breast cancer, with some suggestion that this association is limited to premenopausal women, in whom the increase in risk may be substantial.

Premalignant diseases of the breast

The importance of identifying women at increased risk for developing breast cancer is obvious. Environmental and host factors as well as breast histology are reviewed in this article.

Social factors, diet and breast cancer in a northern Italian population

The relation of breast cancer to social and dietary variables was evaluated in a case-control study of 368 women with breast cancer admitted to the General Hospital of Pordenone (a town in the eastern side of Northern Italy) and 373 age-matched controls. Occupation was related to the risk of breast cancer, housewives and non-manual workers (teachers and other professionals, clerical workers, etc.) showing relative risks of 1.7 and 2.4 respectively when compared to women occupied in agriculture. The role of education was apparently less important, and not statistically significant. The risk was higher in women who were obese, the trend of increasing risk with increasing body mass index being confined to post-menopausal women. When indicators of dietary fat intake were analysed, a significantly increased risk was found with more frequent consumption of milk and dairy products but the risk estimates were only slightly above unity with reference to meat consumption. Women who drank alcoholic beverages showed a relative risk of 2.5 compared to women who had never drunk, when allowance was made for all identified potential confounding factors. The association between alcohol and breast cancer was not explained by the other dietary variables considered, and the risk estimates were higher for women who drank more wine, or more than one type of alcoholic beverage. Thus, the findings of the present study give evidence in favour of the hypothesis that alcohol consumption is related to the risk of breast cancer.

Do hormones cause breast cancer?

The evidence that various endogenous and exogenous sex hormones play a role in the etiology of breast cancer is reviewed. It is hypothesized that prolonged exposure to normal levels of ovarian estrogens and cyclic progesterone resulting from early menarche and late menopause, and primarily willful nulliparity and late childbearing, act at an early stage in the development of breast cancer by promoting excessive proliferation of normal epithelial stem cells. Excess endogenous or exogenous estrogens can enhance risk by stimulating proliferation of epithelial cells that have undergone partial malignant transformation. The breast, however, is much less responsive to the tumor-promoting effects of estrogens than the endometrium, and estrogens probably play a less important role in the later stages of mammary than endometrial carcinogenesis.

Diet and the epidemiology of human breast cancer

There are substantial data on breast tumorigenesis in animals that suggest that diet may be an important factor in human breast cancer etiology. The promotional effects of dietary fat, and, in particular, unsaturated fats, on mammary tumors in rodents is well established. The geographic distribution of breast cancer in humans correlates with international differences in average fat intake. Differences in dietary habits among populations in the United States and their breast cancer risk also have been observed. In the United States, the trend has been toward increased total fat consumption and increased use of polyunsaturated fats. However, breast cancer incidence among white women in the United States has changed very little. Case-control studies of dietary intake and breast cancer risk have shown inconsistent results, and prospective studies of breast cancer mortality and serum cholesterol and serum lipids show no differences in risk between women with high levels of cholesterol and serum lipids compared with women with low levels. Laboratory studies also suggest the possibility that natural inhibitors of breast cancer may occur in the diet as well. Antioxidants, inducers of microsomal enzyme activity, and retinoids, all have been implicated in the metabolic epidemiology of breast cancer. Research results at Roswell Park memorial Institute have associated lower levels of intake of dietary vitamin A with a slightly elevated risk of breast cancer. To date, the epidemiologic data do not indicate with confidence that any specific dietary risk factor may be associated with breast cancer risk in the United States population. Additional epidemiologic studies on inhibition or promotion of breast cancer following the leads of previous laboratory research may clarify the nature and practical significance of the relationship between diet and breast cancer.

Use of dual responses to increase validity of case-control studies

It has been demonstrated that randomly distributed inaccuracy of dichotomous reports in case-control studies biases estimates of the effects of exposure toward one. We show that a simple procedure involving the use of dual exposure reports may lessen this bias. The use of this procedure is illustrated with a data set in which the actual relative risk associated with dichotomous exposure is 4.0. We observe that, if exposure is reported with 60% accuracy and the observed relative risk is approximately 1.3, an additional set of equally accurate exposure reports can be used to uncover an assessed relative risk as high as 1.7. The supplementing of exposure reports with 90% accuracy by an additional set of equally accurate reports can be used to uncover an assessed relative risk as as high as 1.7. The supplementing of exposure reports with 90% accuracy by an additional set of equally accurate exposure reports can increase the observed relative risk from 3.0 to as high as 3.9. We conclude that using dual reports could be valuable in strengthening the inference of case-control studies assessing the effects of dietary, occupational, or other exposures.

Estrogen and progesterone receptors in breast cancer in Black Americans: Correlation of receptor data with tumor differentiation

It has been observed that 60-70% of breast cancer patients have estrogen receptors (ER) and that nearly two-thirds of such patients respond favorably to endocrine therapy. Cytosolic ER and progesterone receptors (PgR) have been evaluated in the current study, among 146 black women with breast cancer in order to determine whether the distribution of ER and PgR differs from the national norm. The results showed following trends that were similar to reports from other institutions: (1) postmenopausal patients and primary tumors showed higher ER positivity than premenopausal patients and metastatic sites, respectively; (2) a significant correlation between the ER positivity and tumor grade; and (3) a higher PgR positivity in ER-positive patients than in ER-negative patients. However, statistically significant differences were observed in three parameters when compared to reports from other institutions on white patients: (1) a low incidence of ER-positive (46%) and high incidence of ER-negative (42%) tumors; (2) a higher incidence of poorly differentiated (55.5%) and a lower incidence of well differentiated (5.5%) tumors; tumor grade was independent of age, menopausal status, histopathology and stage; and (3) a higher percentage of patients discovered at a more advanced stage of the disease. The clinical implications of these results in explaining the relatively poorer survival of black women with breast cancer compared to whites is discussed. Whether this high incidence of PD tumors and thus a high incidence of ER negativity is due to ethnic differences and/or environmental and other factors remains to be elucidated.

Meat and fat consumption and cancer mortality: A study of strict religious orders in Britain

The close correlations between mortality from breast and colorectal cancers and the per-caput consumption of meat or fat in different countries suggest that these dietary items may be involved in the aetiology of the neoplasms. To investigate further these possible relations a study has been conducted of cancer mortality between 1911 and 1978 in two groups of enclosed religious orders for women: one of 1769 nuns who eat no meat and one of 1044 nuns who eat little meat. Mortality from breast and colorectal cancer was not significantly lower in either group than in the general population. It is difficult to evaluate the small reduction in breast cancer mortality in the no-meat group because of the wide confidence limits. An unexpected finding was an excess mortality from oesophageal cancer in both groups. These findings concern women who reduced their meat consumption in adult life: it is suggested that they are compatible with the evidence put forward to support a role for fat or meat intake in causation of breast cancer if dietary influences in pre-adult life are important. The findings on colorectal cancer point to the aetiological importance in this disease of aspects of diet other than fat or meat intake.

The natural history of neoplastic development: the relation of experimental models to human cancer

The natural history of the development of neoplasia in experimental systems may be separated into at least three different stages, those of initiation, promotion and progression. Evidence for such distinct stages has been demonstrated in at least half a dozen different experimental systems. The stage of promotion is that stage most easily modulated. The actions of promoting agents are reversible and only effective above certain threshold levels of the promoting agent. This is in contrast to the stage of initiation, which can be induced at any dose of the carcinogenic agent in an irreversible manner. Agents exhibiting both initiating and promoting activities are termed complete carcinogens while incomplete carcinogens are those capable only of initiation. Promoting agents do not initiate but may promote cells initiated by ambient environmental means, giving the appearance of complete carcinogens in standard bioassay procedures. The stages of initiation and promotion have been extensively studied in skin and liver carcinogenesis and show almost identical characteristics. A variety of promoting agents in the human environment have been demonstrated both by experimental and epidemiologic methodologies. The importance of an understanding of tumor promotion in relation to the prevention of human cancer is emphasized.

Nutrient intake and hormonal status of premenopausal vegetarian Seventh-day Adventists and premenopausal nonvegetarians

The relationship between dietary nutrients and plasma estrone, estradiol-17 beta, estriol, dehydroepiandrosterone sulfate, and prolactin levels was investigated in 14 premenopausal Seventh-day Adventist vegetarian (SV) women and 9 premenopausal non-Seventh-day Adventist nonvegetarian (NV) women. The SV subjects consumed less fat, especially saturated fat, and used significantly less fried food than the NV subjects. Plasma levels of estrone and estradiol-17 beta in the SV subjects were significantly lower than in the NV subjects. SV estradiol-17 beta and estriol levels were positively correlated with linoleic acid and protein intake, while NV prolactin levels were significantly correlated with intakes of oleic and linoleic acids and total fat. The data suggest that specific dietary nutrients were related to the hormonal milieu of these SV and NV subjects.

Stage-specific breast-cancer incidence rates by age among Japanese and Caucasian women in Hawaii, 1960-1979

We have analysed the age- and stage-specific breast-cancer incidence rates of Japanese and Caucasian women in Hawaii for a 20-year period. A comparison of the 1192 Japanese and 1531 Caucasian patients by stage at diagnosis showed that Japanese women were likely to have breast cancer diagnosed at an earlier stage than Caucasian women, but this difference was statistically significant only after the menopause (ages 55+). We further found that for age 50-74, the age-specific ratios of Caucasian to Japanese incidence rates were least for in situ breast cancer, and successively greater for localized, regional and distant breast cancer. We interpreted this latter finding to be an indication that postmenopausal breast cancers in Japanese women have slower average growth rates than in Caucasian women. Such slower growth rates may explain the better breast-cancer survival among Japanese women after allowing for differences in stage, tumour size, histology, or treatment.

Dietary factors and breast cancer risk

As part of a case-control study in northern Alberta, Canada, 577 women aged 30-80 with breast cancer diagnosed during 1976-77 and a population-based age-stratified random sample of 826 disease-free female controls were questioned about certain aspects of their diet. Computing relative risks (RRs) by tertiles, significant increasing trends were found with more frequent consumption of beef (RRs of 1.0, 2.3, 1.5; test for trends, p less than 0.001), pork (RRs of 1.0, 1.6, 2.2; test for trend, p less than 0.001), and sweet desserts (RRs of 1.0, 1.3, 1.5; test for trend, p = 0.01). Elevated risks were also noted for use of butter at the table and for frying with butter or margarine, as opposed to vegetable oils. The association of total beef and pork consumption with breast cancer was not materially affected by controlling for age at first birth, family history of breast cancer, previous benign breast biopsy or socioeconomic status. Nor was the association reduced by controlling for ages of menarche and menopause, even though within the control series the intake of beef and pork reported in adult life was higher among those with a lower age at menarche or a older age at natural menopause.

Cholesterol and obesity as prognostic factors in breast cancer

Analysis of disease-free survival rates in 374 women with operable breast cancer revealed that preoperative weight, particularly in combination with serum cholesterol, is a significant prognostic determinant. Overall, women weighing under 150 pounds had a significantly higher cumulative five-year disease-free survival rate (67%) compared with women weighing more (49%) (z = 2.2298, P = 0.026). Women with low serum cholesterol levels had better cumulative five-year disease-free survival (67%) than women with high serum cholesterol levels (58%) (z = 1.1008, P = 0.27). The combination of high weight and high serum cholesterol levels was associated with an extremely poor cumulative five-year disease-free survival (32%) compared with that observed for women in whom values of either, or both, variables were low (68%) (z = 3.7843, P = 0.0004). These patterns in disease-free survival persisted even after controlling for tumor stage. The findings indicate that weight and cholesterol, in addition to their previously reported effect on the risk of breast cancer development, influence significantly the subsequent course of the disease.

Breast Cancer

The pre-eminence of breast cancer as a significant cause of premature mortality and as the most prevalent cancer of women in North America justifies a major thrust in prevention. In the past, a number of hormonal risk factors were identified. Increasingly, evidence is being obtained to support the role of dietary risk factors and most particularly the total level of dietary fat. Overweight as a risk factor in postmenopausal women also points to the importance of dietary factors. It is concluded that the time is ripe for an active program of evaluating the effect of reduction in the consumption of total fat, particularly in adolescent, early adult and premenopausal women, and in reducing overweight in postmenopausal women, both as aspects of national policy and as special investigations in defined population groups.

The role of a high-fat diet in enhancing the development of mammary tumors in ovariectomized rats

The incidences of mammary tumors in female Sprague-Dawley rats injected with 7,12-dimethylbenz-(a)anthracene (DMBA) on day 50, ovariectomized 80 days later, and then maintained for 40 weeks on semipurified high-fat (20%) and low-fat (0.5%) high-fat diets, were 57% and 25%, respectively. In addition, the group exhibited significantly higher tumor multiplicities than the low-fat group (0.78 vs 0.25 tumors/total rats at risk). The weight gains of the HF and LF groups were similar, indicating that the differences in tumor yields were due to the fat content of the diet per se and not to caloric insufficiency or obesity. These results indicate that a high-fat diet has a tumor-enhancing effect in the absence of normal periodic ovarian secretions. Extragonadal estrogen production stimulated by high dietary fat intake may play a role, possibly by inducing secretion of the tumor-promoting hormone prolactin. The etiological, preventive, and therapeutic implications of these results with regard to human breast cancer are discussed.

Breast cancer in Greenland--selected epidemiological, clinical, and histological features

Fifty-seven breast cancers were diagnosed among indigenous Greenlandic women from 1950 to 1974. An additional 22 cases registered between 1975 and 1979 represent a minimum number and were only used as basis for minimum incidence rates. Changes in age-adjusted rate, age-specific incidence pattern, and relative risk were consistent with an upward shift from a population of low risk between 1950 and 1969 to one of intermediate risk from 1970 onward, a finding that relates well to increased urbanization and westernization. The risk of breast cancer in Greenland may be associated with consumption of saturated fats but is seemingly not correlated to total fat intake which has always been on a par with high-risk Danish levels. An association with diet may in reality have been stronger than suggested but weakened by a counterbalancing effect of high fertility, especially in the youngest age groups. Evaluation of histological features and survival did not suggest differences which could favorably compare with findings in white population groups contrary to reported results from the population of Japan, also one of low risk and of mongoloid origin. Further studies should consider dietary intakes, endocrine variations, and breast fluid secretion with special attention to girls at the age of menarche.

Is diet an essential risk factor for coronary heart disease?

Cigarette smoking, hypertension and diet each play a major role in the development of coronary heart attacks in most industrialized nations. In some countries where cigarette smoking and hypertension are prevalent there is a low risk of coronary heart disease (CHD). Hyperlipidaemia resulting from national food habits appears to be the essential factor in the high rates of CHD in developed countries.

Significance of protein-energy malnutrition in dentistry: some suggestions for the profession

A sound nutritional state is extremely important for the maintenance of healthy oral tissues as well as the body in general. Dentistry is, by nature, related to nutrition and dental practitioners should inform their patients and the public of its importance. For this reason, dentists should have a much broader background in nutrition and food sciences.

Breast cancer in black American women

A case-control study of breast cancer among Black American women was conducted in seven hospitals in New York City from 1969 to 1975. Results are reported for 127 cases and 317 controls. Compared to women with a first birth before age 19, those with a first birth after 25 had a relative incidence rate for breast cancer of 3.8 and 2.2 for the pre- and postmenopausal age-groups, respectively. Compared to nulliparous women, parous women had a relative incidence rate of 0.6 for premenopausal and 0.7 for postmenopausal women. The incidence rate of breast cancer for women with a menopause after age 49 was estimated to be 3.1 times that of women with a menopause before age 45. Thus, the known risk factors for breast cancer among Whites are also related to the etiology of the disease among Blacks. The incidence rate of breast cancer has increased among younger Blacks since 1947 and is now similar to that among younger Whites. However, among older women, the incidence rate is still appreciably higher for Whites. The most likely explanation of this pattern is that Black women born since about 1925 are being exposed at the same frequency as White women to the causes of breast cancer.