Breast cancer risk and fatty acids in the breast and abdominal adipose tissues

Fatty acid profiles and Delta9 desaturase (stearoyl-CoA desaturase; SCD 1) expression in adipose tissue surrounding benign and malignant breast tumors

The progression of tumors occurs through interactions between the tumor and the stroma. Understanding the role of adipose tissue (AT), as the main component of the breast tumor microenvironment (TME) in the development of cancer, is crucial for the early detection of breast cancer (BC). This study compared the FA profiles, desaturase index (DI), and stearoyl CoA desaturase 1 (SCD1) mRNA levels in the AT that surrounds tumors in women with BC and benign breast disease (BBD). Specimens were collected from 40 Iranian women who had undergone breast surgery. These women were age- and BMI-matched and were divided into two groups: BC (n = 20) and BBD (n = 20). Gas chromatography and quantitative real-time PCR were used to analyze the FA profiles and SCD1 mRNA levels, respectively. The DI was calculated by dividing the amounts of monounsaturated FAs by the amount of saturated FA. There were no significant differences in age and BMI between women with BC and BBD. The FA profiles and DI were also similar in both groups. However, mRNA levels of SCD1 were found to be 5 times higher in the breast AT of BC than in the breast AT of BBD (p < 0.0001). We showed that SCD1 was significantly upregulated in the AT surrounding BC tumors, even though the DI and FA profiles were unchanged compared to those in the AT of BBD patients. It is important to note that the breast AT of women with BBD has previously been overlooked and warrants further studies.

Breast cancer and dietary fat quality indices in Iranian women: A case-control study

Background

The association between breast cancer (BC) and different indices of dietary fats has not been well-studied. Thus, this study aimed to investigate the association between BC and dietary fat quality (DFQ) indices in Iranian women.

Methods

This case-control study was conducted on 120 women with breast cancer and 240 healthy women in Tehran, Iran. Food Frequency Questionnaire and nutritionist IV software were used to assess the intake of dietary fats and to calculate the DFQ indices.

Results

The patients with BC had a higher total fat (TF) (P < 0.01) and a lower ratio of polyunsaturated fatty acids (PUFAs) omega-3 to PUFAs omega-6 (ω-3/ω-6) compared with the controls (P < 0.001). TF had a significant association with BC risk (OR: 1.16; 95% CI: 1.01-1.33, P < 0.001). No significant association was found between BC and PUFA/saturated fatty acid ratio or the ω-3/ω-6 ratio.

Conclusion

The patients with BC had a lower ω-3/ω-6 ratio and a higher total dietary fat intake than the healthy women. Total dietary fat intake was also directly associated with the risk of BC. Thus, low-fat diets may have beneficial effects for BC prevention. Further longitudinal studies are warranted.

Bilateral gradient-echo spectroscopic imaging with correction of frequency variations for measurement of fatty acid composition in mammary adipose tissue

PURPOSE

To develop a simultaneous dual-slab three-dimensional gradient-echo spectroscopic imaging (GSI) technique with frequency drift compensation for rapid (<6 min) bilateral measurement of fatty acid composition (FAC) in mammary adipose tissue.

METHODS

A bilateral GSI sequence was developed using a simultaneous dual-slab excitation followed by 128 monopolar echoes. A short train of navigator echoes without phase or partition encoding was included at the beginning of each pulse repetition time period to correct for frequency variation caused by respiration and heating of the cryostat. Voxel-wise spectral fitting was applied to measure the areas of the lipid spectral peaks to estimate the number of double-bond (ndb), number of methylene-interrupted double-bond (nmidb), and chain length (cl). The proposed method was tested in an oil phantom and 10 postmenopausal women to assess the influence of the frequency variation on FAC estimation.

RESULTS

The frequency drift observed over 5:27 min during the phantom scan was about 10 Hz. Phase correction based on the navigator reduced the median error of ndb, nmidb, and cl from 9.7%, 17.6%, and 3.2% to 2.1%, 9.5%, and 2.8%, respectively. The in vivo data showed a mean ± standard deviation frequency drift of 17.4 ± 2.5 Hz, with ripples at 0.3 ± 0.1 Hz. Our reconstruction algorithm successfully separated signals from the left and right breasts with negligible residual aliasing. Phase correction reduced the interquartile range within each subject's adipose tissue of ndb, nmidb, and cl by 18.4 ± 10.6%, 18.5 ± 13.9%, and 18.4 ± 10.6%, respectively.

CONCLUSION

This study shows the feasibility of obtaining bilateral spectroscopic imaging data in the breast and that incorporation of a frequency navigator improves the estimation of FAC.

Fatty acid composition in mammary adipose tissue measured by Gradient-echo Spectroscopic MRI and its association with breast cancers

PURPOSE

To assess the association of fatty acid levels in mammary adipose tissue of postmenopausal women with the presence of breast cancer using the Gradient-echo Spectroscopic Imaging (GSI).

MATERIALS AND METHODS

Unilateral GSI was performed at 3 T in 61 postmenopausal women undergoing breast MRI exams. The study included 19 women with breast cancer, 23 women with benign/high risk lesions, and 19 women with a history of cancer. Voxel-wise spectral analysis of fatty acids was conducted to measure relative portions of monounsaturated (MUFA), polyunsaturated (PUFA), and saturated fatty acids (SFA) in each voxel. The voxels within mammary adipose tissue were automatically selected and their median fatty acid fractions were used for quantitative analysis. Statistical analyses were performed using χ² test, one-way analysis of variance (ANOVA) with Tukey-Kramer multiple comparison tests, and linear regression.

RESULTS

Postmenopausal women with malignancies had significantly higher SFA (0.336 ± 0.038) in mammary adipose tissue compared to those with benign disease (0.283 ± 0.046, p = 0.0008) and to those with a history of breast cancer (0.287 ± 0.050, p = 0.0038). Postmenopausal women with malignant lesions had significantly lower MUFA (0.352 ± 0.041) compared to those with benign disease (0.401 ± 0.043, p = 0.0032) and with history of breast cancer (0.388 ± 0.055, p = 0.0484). The history of cancer group had a significant correlation (r = 0.60, p = 0.006) between SFA and BMI, and the cancer group had a significant correlation (r = 0.57, p = 0.010) between PUFA and BMI.

CONCLUSIONS

Fatty acid composition of mammary adipose tissue, particularly higher SFA and lower MUFA, may be associated with breast cancer. The GSI method utilizes an automated voxel-based analysis to measure fatty acid composition, and may be used to assess the role of mammary adipose tissue in cancer development and progress.

Some biochemical studies on trans fatty acid-containing diet

trans fatty acids (TFA's) are unsaturated fatty acid which have one or more double bond, they are present naturally and most of it is artificial, fried, baked food and margarine are major sources of TFA, there are several biological effects of TFAs on body health, various study showed that dietary TFA associated with various health disorders such as Diabetes, cardiovascular disease (CVD), Obesity, breast cancer, prostatic cancer infertility, and coronary artery disease (CAD). The World Health Organization (WHO) in 2015 encourages eliminations of trans fatty acids. The diet which related to non-communicable diseases include TFA should be eliminated, WHO's European Food and Nutrition Action Plan 2015-2020 suggested that TFAs should be less than 1% of the daily energy intake include natural origin. So the aim of this review, to know more than about trans acids, their nature, sources, and their different effect on health and how can analysis it.

Biomarker of long-chain n-3 fatty acid intake and breast cancer: Accumulative evidence from an updated meta-analysis of epidemiological studies

Objective: We aimed to summarize the up-to-date epidemiology evidence on biomarkers of long-chain (LC) n-3 fatty acid (FA) intake in relation to breast cancer (BC).Methods: Epidemiology studies determining FA levels in biospecimen (circulating blood or adipose tissue (AT)) were identified from PubMed, EMBASE, and Cochrane Library databases until March 2018. Multivariate-adjusted risk ratios (RRs) with 95% confidence intervals (CIs) were pooled using a random-effect model. Difference in biospecimen proportions of LC n-3 FA between BC cases and non-cases were analyzed as a standardized mean difference (SMD).Results: Thirteen cohort and eleven case-control studies were eligible for the present meta-analysis. The estimated SMD was -0.14 (95% CI: -0.27, -0.11) for LC n-3 FA and -0.27 (95% CI: -0.42, -0.11) for LC n-3/n-6 FA ratio. When comparing the top tertiles with the bottom baseline levels, circulating LC n-3 FA was significantly associated with a lower risk of BC (RR: 0.84, 95% CI: 0.74, 0.96), but not AT (RR: 1.02, 95% CI: 0.70, 1.48). Significant inverse dose-response associations were observed for each 1% increment of circulating 20:5n-3 and 22:6n-3.Conclusion: This meta-analysis highlights that circulating LC n-3 FA as a biomarker of intake may be an independent predictive factor for BC, especially 20:5n-3 and 22:6n-3.

Evaluation of Breast Lipid Composition in Patients with Benign Tissue and Cancer by Using Multiple Gradient-Echo MR Imaging

Purpose To demonstrate the feasibility of the use of a rapid, noninvasive, in vivo imaging method to measure fatty acid fractions of breast adipose tissue during diagnostic breast magnetic resonance (MR) examinations and to investigate associations between fatty acid fractions in breast adipose tissue and breast cancer status by using this method. Materials and Methods The institutional review board approved this retrospective HIPAA-compliant study and informed consent was waived. Between July 2013 and September 2014, multiple-echo three-dimensional gradient-echo data were acquired for 89 women. Spectra were generated and used to estimate fractions of monounsaturated fatty acid (MUFA), polyunsaturated fatty acid (PUFA), and saturated fatty acid (SFA) in the breast adipose tissue. Analysis of covariance and exact Mann-Whitney tests were used to compare groups and the Spearman rank correlation coefficient was used to characterize the association of each imaging measure with each attribute. Results For postmenopausal women, MUFA was lower (0.38 ± 0.06 vs 0.46 ± 0.10; P < .05) and SFA was higher (0.31 ± 0.07 vs 0.19 ± 0.11; P < .05) for women with invasive ductal carcinoma than for those with benign tissue. No correlation was found between body mass index (BMI) and fatty acid fractions in breast adipose tissue. In women with benign tissue, postmenopausal women had a higher PUFA (0.35 ± 0.06 vs 0.27 ± 0.05; P < .01) and lower SFA (0.19 ± 0.11 vs 0.30 ± 0.12; P < .05) than premenopausal women. Conclusion There is a possible link between the presence of invasive ductal carcinoma and fatty acid fractions in breast adipose tissue for postmenopausal women in whom BMI values are not correlated with the fatty acid fractions. (©) RSNA, 2016 Online supplemental material is available for this article.

Arachidonic acid and cancer risk: a systematic review of observational studies

Background

An n-6 essential fatty acid, arachidonic acid (ARA) is converted into prostaglandin E₂, which is involved in tumour extension. However, it is unclear whether dietary ARA intake leads to cancer in humans. We thus systematically evaluated available observational studies on the relationship between ARA exposure and the risk of colorectal, skin, breast, prostate, lung, and stomach cancers.

Methods

We searched the PubMed database for articles published up to May 17, 2010. 126 potentially relevant articles from the initial search and 49,670 bibliographies were scrutinised to identify eligible publications by using predefined inclusion criteria. A comprehensive literature search yielded 52 eligible articles, and their reporting quality and methodological quality was assessed. Information on the strength of the association between ARA exposure and cancer risk, the dose-response relationship, and methodological limitations was collected and evaluated with respect to consistency and study design.

Results

For colorectal, skin, breast, and prostate cancer, 17, 3, 18, and 16 studies, respectively, were identified. We could not obtain eligible reports for lung and stomach cancer. Studies used cohort (n = 4), nested case-control (n = 12), case-control (n = 26), and cross-sectional (n = 12) designs. The number of subjects (n = 15 - 88,795), ARA exposure assessment method (dietary intake or biomarker), cancer diagnosis and patient recruitment procedure (histological diagnosis, cancer registries, or self-reported information) varied among studies. The relationship between ARA exposure and colorectal cancer was inconsistent based on ARA exposure assessment methodology (dietary intake or biomarker). Conversely, there was no strong positive association or dose-response relationship for breast or prostate cancer. There were limited numbers of studies on skin cancer to draw any conclusions from the results.

Conclusions

The available epidemiologic evidence is weak because of the limited number of studies and their methodological limitations, but nonetheless, the results suggest that ARA exposure is not associated with increased breast and prostate cancer risk. Further evidence from well-designed observational studies is required to confirm or refute the association between ARA exposure and risk of cancer.

In vivo determination of human breast fat composition by ¹H magnetic resonance spectroscopy at 7 T

The role of diet and fat consumption in the pathogenesis of breast cancer is an important subject. We report a method for noninvasive determination of lipid composition in human breast by proton magnetic resonance spectroscopy (MRS) at 7 T. Two respiratory-triggered TE-averaged stimulated echo acquisition mode (STEAM) acquisitions were performed on the adipose tissue of 10 healthy volunteers where the second acquisition had all gradients inverted. This acquisition protocol allows the suppression of modulation sidebands that complicate spectral analysis at the short TE(avg) = 24.5 ms. The entire acquisition takes ∼10 min. Ten lipid peaks were typically resolved. T(1) and T(2) were also measured and used to correct the peak intensities. The calculated average lipid composition for saturated was 28.7 ± 8.4%, monounsaturated, 48.5 ± 7.9%, and polyunsaturated, 22.7 ± 3.1%, in close agreement with reported values from subcutaneous adipose measurements. Intrasubject variability was 2.0, 1.6, and 3.6% for the saturated, monounsaturated, and polyunsaturated fractions, respectively. In conclusion, we have shown that a chemical analysis of lipids in breast tissue can be determined quite simply, quickly, and noninvasively by proton MRS at 7 T.

Omega-3 fatty acid supplements in women at high risk of breast cancer have dose-dependent effects on breast adipose tissue fatty acid composition

BACKGROUND

Preclinical evidence of the preventive benefits of omega-3 (n-3) polyunsaturated fatty acids (PUFAs) in breast cancer continues to fuel interest in the potential role of dietary fat content in reducing breast cancer risk. The dose of fish-oil/omega-3 PUFAs needed to achieve maximal target tissue effects for breast cancer prevention remains undefined.

OBJECTIVE

To determine the dose effects of omega-3 fatty acids on breast adipose tissue fatty acid profiles, we conducted a study of 4 doses of omega-3 PUFAs in women at high risk of breast cancer.

DESIGN

In this 6-mo randomized open-label study, 48 women with increased breast cancer risk received 1, 3, 6, or 9 capsules/d of an omega-3 PUFA supplement that provided 0.84, 2.52, 5.04, and 7.56 g docosahexaenoic acid (DHA) + eicosapentaenoic acid (EPA) daily, respectively. Subjects made monthly visits, at which time pill counts were made and fasting blood samples were collected to determine fatty acid profiles; anthropometric measurements were made, breast adipose tissue samples were collected, and laboratory tests of toxicity (alanine aminotransferase, LDL cholesterol, and platelet function) were made at baseline and at 3 and 6 mo.

RESULTS

All doses led to increased serum and breast adipose tissue EPA and DHA concentrations, but the response to 0.84 g DHA+EPA/d was less than the maximum possible response with > or = 2.52 g/d. Body mass index attenuated the dose response for serum tissue DHA and EPA (P = 0.015 and 0.027, respectively) and breast adipose tissue DHA (P = 0.0022) in all of the treatment groups. The incremental increase in DHA and EPA correlated inversely with baseline fat and serum values. Compliance over 6 mo was 92.9 +/- 9.2% and was unaffected by treatment arm. No severe or serious toxicities were reported.

CONCLUSIONS

Daily doses up to 7.56 g DHA+EPA were well tolerated with excellent compliance in this cohort at high risk of breast cancer. Body mass index and baseline fatty acid concentrations modulated the dose-response effects of omega-3 PUFA supplements on serum EPA and DHA and breast adipose tissue DHA.

Trans-fatty acids and cancer: a mini-review

The association between trans-fatty acids (TFA) and cancer risk is poorly understood and remains controversial. It is recognised that unique biological effects are associated with specific isoforms within families of fatty acids such as those belonging to the n-3 fatty acids. Furthermore, the interactions between diet and genetic polymorphisms are increasingly recognised for their potential risk-modifying effects on human health and disease. Therefore, the aim of the present review is to evaluate whether specific TFA isomers and genetic polymorphisms differentially modify cancer risk in prostate, colon and breast cancers in animal and human models. Potential mechanisms of action by which TFA may affect cancer development are also reviewed. Overall, across a number of experimental models and human studies, there is insufficient and inconsistent evidence linking specific TFA isomers to cancers of the prostate, colon and breast. A number of methodological limitations and experimental considerations were identified which may explain the inconsistencies observed across these studies. Therefore, further research is warranted to accurately assess the relationship between TFA and cancer risk.

Trans-fatty acids and cancer: the evidence reviewed

The present review comes from the authors of the recent Scientific Advisory Committee on Nutrition (SACN) review Update on Trans Fatty Acids and Health, and focuses on assessing the strength of the evidence for a link between trans-fatty acid (trans-FA) intake and cancer. It evaluates a range of human ecological, case-control and prospective studies with trans-FA exposure assessed using either dietary assessment methods or trans-FA levels in tissues. Relevant animal studies are also presented in order to elucidate potential mechanisms. It concludes that there is weak and inconsistent evidence for a relationship between trans-FA and breast or colorectal cancer. Evidence for an association between trans-FA and prostate cancer is limited, but a recent large case-control study has shown a strong interaction between risk and trans-FA intake for the RNASEL QQ/RQ genotype that is present in about 35 % of the population. This potential association requires further investigation. The single study on non-Hodgkin's lymphoma reported a strong positive association, but only used a single assessment of dietary trans-FA made at the start of the study in 1980, and the significant changes in trans-FA intakes between then and the end of follow-up in 1994 limit the reliability of this observation. There is insufficient evidence to allow any differentiation between the effects of trans-FA from animal or vegetable origin on cancer risk.

The lipidome as a composite biomarker of the modifiable part of the risk of breast cancer

The potential for dietary fat to prevent breast cancer makes identification of defined molecules a mandatory step. In order to circumvent the limitations and/or bias of dietary exposure assessment tools, we have used the fatty acid composition of white adipose tissue as biomarker of past lipid intake. When considered separately, candidate fatty acids identified as favourable on the basis of their association with breast cancer risk have usually led to inconsistent results in dietary intervention studies carried out in rats. This inconsistency indicates that any approach based on a single fatty acid should be abandoned for an integrated view over the complex lipid interactions, which finally determines the lipidome, the lipid profile that is found in individuals. We reappraised the role of the complete lipid profile through a comprehensive study of adipose tissue fatty acids obtained in patients with benign or malignant breast tumors. Rather than a single fatty acid, a composite indicator combining elevated monounsaturates and low n-6/n-3 fatty acid ratio was associated with decreased breast cancer risk. The lipidome may provide the opportunity to quantify the modifiable part of the risk of breast cancer. The lipidome may be used as a template for designing proper dietary modifications in order to delay the occurrence of breast cancer. Which dietary modifications should be undertaken in order to bring a pertinent change to the lipidome with respect to the risk of breast cancer is currently unknown. The lipidome may allow the individualization of a high risk population of women, who may be targeted for a dietary prevention of breast cancer. The setting and validation of a high-throughput lipidomic station with analytical capabilities fitted to the need of mass screening is required. These two locks must be resolved before a primary prevention of breast cancer by diet could be contemplated.

Association between serum trans-monounsaturated fatty acids and breast cancer risk in the E3N-EPIC Study

The authors assessed the association between serum phospholipid fatty acids as biomarkers of fatty acid intake and breast cancer risk among women in the E3N Study (1989-2002), the French component of the European Prospective Investigation into Cancer and Nutrition. During an average of 7 years of follow-up, 363 cases of incident invasive breast cancer were documented among 19,934 women who, at baseline (1995-1998), had completed a diet history questionnaire and provided serum samples. Controls were randomly matched to cases by age, menopausal status at blood collection, fasting status at blood collection, date, and collection center. Serum phospholipid fatty acid composition was assessed by gas chromatography. Adjusted odds ratios for risk of breast cancer with increasing levels of fatty acids were calculated using conditional logistic regression. An increased risk of breast cancer was associated with increasing levels of the trans-monounsaturated fatty acids palmitoleic acid and elaidic acid (highest quintile vs. lowest: odds ratio = 1.75, 95% confidence interval: 1.08, 2.83; p-trend = 0.018). cis-Monounsaturated fatty acids were unrelated to breast cancer risk. A high serum level of trans-monounsaturated fatty acids, presumably reflecting a high intake of industrially processed foods, is probably one factor contributing to increased risk of invasive breast cancer in women.

Lipid peroxidation, oxidative stress genes and dietary factors in breast cancer protection: a hypothesis

We have recently proposed that lipid peroxidation may be a common mechanistic pathway by which obesity and hypertension lead to increased renal cell cancer risk. During this exercise, we noted a risk factor swap between breast and kidney cancer (oophorectomy and increased parity, detrimental for kidney, beneficial for breast; high blood pressure, detrimental for kidney, beneficial for breast when it occurs during pregnancy; alcohol, beneficial for kidney, detrimental for breast, and so on). We have subsequently proposed the hypothesis that lipid peroxidation represents a protective mechanism in breast cancer, and reviewed the evidence of the role of lipid peroxidation on established hormonal and non-hormonal factors for breast cancer. Here, we review the evidence in support of lipid peroxidation playing a role in the relationships between dietary factors and breast cancer. Available evidence implicates increased lipid peroxidation products in the anti-carcinogenic effect of suspected protective factors for breast cancer, including soy, marine n-3 fatty acids, green tea, isothiocyanates, and vitamin D and calcium. We also review the epidemiological evidence supporting a modifying effect of oxidative stress genes in dietary factor-breast cancer relationships.

Biomarkers of dietary fatty acid intake and the risk of breast cancer: a meta-analysis

The use of the fatty acid composition of adipose tissue, erythrocyte membranes, serum and plasma as biological markers of fatty acid intake was recently introduced in epidemiological studies. The biomarkers of fatty acid intake have the advantage of providing quantitative measurement independent of energy intake and of the subject's memory. We performed a meta-analysis of published results of epidemiological studies of the composition of fatty acids in biological samples and breast cancer risk. The analysis was based on 3 cohort and 7 case-control studies including 2,031 cases and 2,334 controls. The summary statistic used was the average of the relative risk estimated for each level of the fatty acid on study, weighted by the inverse of its variance. Random effect models were assumed when the test for heterogeneity was significant. Overall relative risks were estimated for studies including pre- and post-menopausal breast cancer and separately for post-menopausal women. In cohort studies, a significant protective effect was found for total n-3 polyunsaturated fatty acids, while total monounsaturated fatty acids, oleic acid (C18:1 n-9c) and palmitic acid (C16:0) were significantly associated with an increase of breast cancer risk. Total saturated fatty acids were significantly associated with breast cancer risk in cohort studies only in postmenopausal women. For case-control studies, the only finding was for alpha linolenic acid (C18:3, n-3), which showed an inverse association bordering on statistical significance. The findings of cohort studies fit well with hypotheses derived from experimental animal studies. More epidemiological cohort studies that integrate biological markers of dietary fatty acid intake are needed in order to determine the contribution of different types of fatty acids in the etiology of breast cancer.

Serum fatty acids and breast cancer incidence

Fatty acid composition of the diet may be essential to the development of breast cancer. We studied the ability of several fatty acids of serum total lipids to predict breast cancer incidence in a case-control study nested within a longitudinal population study. The proportions of fatty acids in serum total lipids were determined from stored serum samples collected at baseline for 127 incident breast cancer cases and 242 matched controls. Women with a higher proportion of total polyunsaturated fatty acids (PUFAs) in serum had a reduced risk of breast cancer. The odds ratio (OR) between the highest and lowest tertiles of serum PUFA was 0.31 (95% confidence interval, CI = 0.12-0.77). This association was mainly due to n-6 PUFAs and especially to linoleic acid. The ORs were 0.35 (CI = 0.14-0.84) and 0.29 (CI = 0.12-0.73), respectively. Of the monounsaturated fatty acids (MUFAs), higher trans-11-18:1 levels were related to an increased breast cancer risk (OR = 3.69, CI = 1.35-10.06). The association was stronger in postmenopausal than in premenopausal women. The present study suggests that higher serum proportions of the n-6 PUFA linoleic acid and lower proportions of the MUFA trans-11-18:1 fatty acid predict a reduced incidence of breast cancer.

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.

Opposing effects of dietary n-3 and n-6 fatty acids on mammary carcinogenesis: The Singapore Chinese Health Study

We investigated the effects of individual fatty acids on breast cancer in a prospective study of 35 298 Singapore Chinese women aged 45–74 years, who were enrolled during April 1993 to December 1998 (The Singapore Chinese Health Study). At recruitment, each study subject was administered, in-person, a validated, semiquantitative food frequency questionnaire consisting of 165 food and beverage items. As of December 31, 2000, 314 incident cases of breast cancer had occurred. We used the Cox regression methods to examine individual fatty acids in relation to breast cancer risk, with adjustment for age at baseline interview, year of interview, dialect group, level of education, daily alcohol drinking, number of live births, age when menstrual periods became regular, and family history of breast cancer. Consumption of saturated, monounsaturated or polyunsaturated fat overall was unrelated to risk. On the other hand, high levels of dietary n-3 fatty acids from fish/shellfish (marine n-3 fatty acids) were significantly associated with reduced risk. Relative to the lowest quartile of intake, individuals in the higher three quartiles exhibited a 26% reduction in risk (relative risk (RR)=0.74, 95% confidence interval (CI)=0.58, 0.94)); RRs were similar across the top three quartiles of intake (0.75, 0.75, 0.72, respectively). Overall, there was no association between n-6 fatty acids and breast cancer risk. However, among subjects who consumed low levels of marine n-3 fatty acids (lowest quartile of intake), a statistically significant increase in risk was observed in individuals belonging to the highest vs the lowest quartile of n-6 fatty acid consumption (RR=1.87, 95% CI=1.06–3.27); the corresponding RR for advanced breast cancer was 2.45 (95% CI=1.20–4.97, P for trend=0.01). To our knowledge, these are the first prospective findings linking the intake of marine n-3 fatty acids to breast cancer protection.

Intakes of fish and marine fatty acids and the risks of cancers of the breast and prostate and of other hormone-related cancers: a review of the epidemiologic evidence

Marine fatty acids, particularly the long-chain eicosapentaenoic and docosahexaenoic acids, have been consistently shown to inhibit the proliferation of breast and prostate cancer cell lines in vitro and to reduce the risk and progression of these tumors in animal experiments. However, whether a high consumption of marine fatty acids can reduce the risk of these cancers or other hormone-dependent cancers in human populations is unclear. Focusing primarily on the results of cohort and case-control studies, we reviewed the current epidemiologic literature on the intake of fish and marine fatty acids in relation to the major hormone-dependent cancers. Despite the many epidemiologic studies that have been published, the evidence from those studies remains unclear. Most of the studies did not show an association between fish consumption or marine fatty acid intake and the risk of hormone-related cancers. Future epidemiologic studies will probably benefit from the assessment of specific fatty acids in the diet, including eicosapentaenoic and docosahexaenoic acids, and of the ratio of these to n-6 fatty acids, dietary constituents that have not been examined individually very often.

Long-chain n-3-to-n-6 polyunsaturated fatty acid ratios in breast adipose tissue from women with and without breast cancer

Animal studies suggest that dietary polyunsaturated fatty acids (PUFAs) of the n-6 class, found in corn and safflower oils, may be precursors of intermediates involved in the development of mammary tumors, whereas long-chain (LC) n-3 PUFAs, found in fish oil, can inhibit these effects. This case-control study was designed to examine the relationship between the PUFA composition of breast adipose tissue and the risk of breast cancer. Using fatty acid levels in breast adipose tissue as a biomarker of past qualitative dietary intake of fatty acids, we examined the hypothesis that breast cancer risk is negatively associated with specific LC n-3 PUFAs (eicosapentaenoic acid and docosahexaenoic acid) and positively associated with n-6 PUFAs (linoleic acid and arachidonic acid). Breast adipose tissue was collected from 73 breast cancer patients and 74 controls with macromastia. The fatty acid levels were determined by gas-liquid chromatography. A logistic regression model was used to obtain odds ratio estimates while adjusting for age. The age-adjusted n-6 PUFA (linoleic acid and arachidonic acid) content was significantly higher in cases than in controls (P = 0.02). There was a trend in the age-adjusted data suggesting that, at a given level of n-6 PUFA, LC n-3 PUFAs (eicosapentaenoic acid and docosahexaenoic acid) may have a protective effect (P = 0.06). A similar inverse relationship was observed with LC n-3-to-n-6 ratio when the data were adjusted for age (P = 0.09). We conclude that total n-6 PUFAs may be contributing to the high risk of breast cancer in the United States and that LC n-3 PUFAs, derived from fish oils, may have a protective effect.

Intake of conjugated linoleic acid, fat, and other fatty acids in relation to postmenopausal breast cancer: the Netherlands Cohort Study on Diet and Cancer

BACKGROUND

Conjugated linoleic acid (CLA), which is present in milk products and meat from ruminants, appears to have anticarcinogenic activity against breast cancer in animal and in vitro experiments. To date, few epidemiologic data are available in humans.

OBJECTIVE

This study evaluated the relation between intakes of CLA and other fatty acids and breast cancer incidence in the Netherlands Cohort Study.

DESIGN

Intake data derived from a validated 150-item food-frequency questionnaire were linked to an existing database with analytic data on specific fatty acids in European foods (the TRANSFAIR study). With 6.3 y of follow-up and 941 incident cases of breast cancer, multivariate rate ratios and 95% CIs were calculated for energy-adjusted intakes of fatty acids and CLA-containing food groups (eg, butter, cheese, milk, other milk products, and meat).

RESULTS

CLA intake showed a weak, positive relation with breast cancer incidence (rate ratio for highest compared with lowest quintile: 1.24, 95% CI: 0.91, 1.69; P for trend = 0.02). Statistically significant positive associations were found with total trans fatty acids and (borderline) with saturated fatty acids. Significant inverse associations were found with monounsaturated and cis unsaturated fatty acids, whereas total fat and energy intake of CLA-containing food groups were not related to breast cancer incidence.

CONCLUSION

The suggested anticarcinogenic property of CLA in animal and tissue culture models could not be confirmed in this epidemiologic study in humans.

N-3 and N-6 fatty acids in breast adipose tissue and relative risk of breast cancer in a case-control study in Tours, France

Experimental studies have indicated that n-3 fatty acids, including alpha-linolenic acid (18:3 n-3) and long-chain n-3 polyunsaturated fatty acids inhibit mammary tumor growth and metastasis. Earlier epidemiological studies have given inconclusive results about a potential protective effect of dietary n-3 polyunsaturated fatty acids on breast cancer risk, possibly because of methodological issues inherent to nutritional epidemiology. To evaluate the hypothesis that n-3 fatty acids protect against breast cancer, we examined the fatty acid composition in adipose tissue from 241 patients with invasive, nonmetastatic breast carcinoma and from 88 patients with benign breast disease, in a case-control study in Tours, central France. Fatty acid composition in breast adipose tissue was used as a qualitative biomarker of past dietary intake of fatty acids. Biopsies of adipose tissue were obtained at the time of surgery. Individual fatty acids were measured as a percentage of total fatty acids, using capillary gas chromatography. Unconditional logistic regression modeling was used to obtain odds ratio estimates while adjusting for age, height, menopausal status and body mass index. We found inverse associations between breast cancer-risk and n-3 fatty acid levels in breast adipose tissue. Women in the highest tertile of alpha-linolenic acid (18:3 n-3) had an odds ratio of 0.39 (95% confidence intervals [CI] = 0.19-0.78) compared to women in the lowest tertile (trend p = 0.01). In a similar way, women in the highest tertile of docosahexaenoic acid (22:6 n-3) had an odds ratio of 0.31 (95% CI = 0.13-0.75) compared to women in the lowest tertile (trend p = 0.016). Women in the highest tertile of the long-chain n-3/total n-6 ratio had an odds ratio of 0.33 (95% confidence interval = 0.17-0.66) compared to women in the lowest tertile (trend p = 0.0002). In conclusion, our data based on fatty acids levels in breast adipose tissue suggest a protective effect of n-3 fatty acids on breast cancer risk and support the hypothesis that the balance between n-3 and n-6 fatty acids plays a role in breast cancer.

Dietary fats and cancer

The present review addresses the evidence for a possible link between dietary fat and cancer. International comparisons suggest that a high-fat diet may increase cancer risk, and this hypothesis is supported by animal experiments. However, epidemiological studies within populations show little or inconsistent associations. Taken together, the available evidence for a relation between dietary fat and cancer is weak.

Effect of an alpha-linolenic acid-rich diet on rat mammary tumor growth depends on the dietary oxidative status

To investigate whether the oxidative status of an 18:3(n-3) polyunsaturated fatty acid (PUFA)-enriched diet could modulate the growth of chemically induced rat mammary tumors, three independent experiments were performed. Experiments I and II examined the variation of tumor growth by addition of antioxidant (vitamin E) or a prooxidant system (sodium ascorbate/2-methyl-1,4-naphthoquinone) to a 15% linseed oil diet rich in 18:3(n-3). Experiment III addressed the role of PUFA in the tumor growth modulation by vitamin E. For this purpose, we compared the effect of vitamin E in 15% fat diets containing a high level of 18:3(n-3) (linseed oil, high-PUFA diet) or devoid of 18:3(n-3) (hydrogenated palm/sunflower oil, low-PUFA diet). In Experiments I-III, tumor growth increased in the presence of vitamin E compared with control (without vitamin E). Furthermore, it decreased when prooxidant was added. In contrast, no difference was observed when the diet was low in PUFA, suggesting that sensitivity of PUFA to peroxidation may interfere with tumor growth. This observation was supported by growth kinetic parameter analysis, which indicated that tumor growth resulted from variations in cell loss but not from changes in cell proliferation. These data show that, in vivo, PUFA effects on tumor growth are highly dependent on diet oxidative status.

Low alpha-linolenic acid content of adipose breast tissue is associated with an increased risk of breast cancer

Data derived from experimental studies suggest that alpha-linolenic acid may have a protective effect in breast cancer. Observations obtained from epidemiological studies have not allowed conclusions to be drawn about a potential protective effect of dietary alpha-linolenic acid on breast cancer, possibly because of methodological issues. This case-control study conducted in an homogeneous population from a central area in France was designed to explore the hypothesis that alpha-linolenic acid inhibits breast cancer, using fatty acid levels in adipose breast tissue as a biomarker of past qualitative dietary intake of fatty acids. Biopsies of adipose breast tissue at the time of diagnosis were obtained from 123 women with invasive non-metastatic breast carcinoma. 59 women with benign breast disease served as controls. Individual fatty acids were analysed by capillary gas chromatography. An unconditional logistic regression model was used to obtain odds ratio estimates whilst adjusting for age, menopausal status and body mass index (BMI). No association was found between fatty acids (saturates, monounsaturates, long-chain polyunsaturates n-6 or n-3) and the disease, except for alpha-linolenic acid which showed an inverse association with the risk of breast cancer. The relative risk of breast cancer for women in the highest quartile of adipose breast tissue alpha-linolenic acid level was 0.36 (95% confidence interval=0.12-1.02) compared with those in the lowest quartile (P trend=0.026), suggesting a protective effect of alpha-linolenic acid in the risk of breast cancer. The effects of dietary alpha-linolenic on the risk of breast cancer warrant further study.

Serum n-3 fatty acids, fish consumption and cancer mortality in six Japanese populations in Japan and Brazil

Japanese people consume significant amounts of long chain n-3 polyunsaturated fatty acids (PUFAs) derived from fish, but the association of PUFAs with cancer mortality has not been fully investigated. To study geographic differences in n-3 PUFAs intake, we compared serum fatty acid and dietary fish intake among various Japanese populations having different rates of cancer mortality. The subjects were 50 men from each of five regions in Japan and 47 Japanese men from Sao Paulo, Brazil. All were randomly selected and aged 40 to 49 years. Serum fatty acids were measured by gas chromatography and the frequency of fish intake was obtained by a food frequency questionnaire. Significant geographic differences in serum fatty acid levels (% of total fatty acids) and fish intake (days/4 weeks) were observed. The percentages of serum total PUFA were similar in the six regions, though there was an almost three-fold difference in n-3 PUFAs content between Brazil (3.9%) and Akita (10.9%). The frequency of total fish intake corresponded to serum n-3 PUFAs composition. The relationship between cancer mortality and serum n-3 PUFAs levels was not clear, though an inverse association between prostate cancer and serum n-3 PUFAs levels appeared to exist. The results suggest that although serum n-3 PUFAs varied significantly, the observed geographic difference did not account for the different cancer risks at the population level.

Dietary fat and carcinogenesis

Epidemiologic investigations have suggested a relationship between dietary fat intake and various types of cancer incidences. Furthermore, epidemiologic studies as well as studies with animal models have demonstrated that not only the amount but also the type of fat consumed is important. At present, the mechanism by which dietary fat modulates carcinogenesis has not been elucidated. The effects of dietary fat on the development of tumours have been summarized in the present review with emphasis on colorectal, pancreas, breast and prostate cancer. It is concluded that influence on synthesis of prostaglandins and leukotrienes may be the universal mechanism by which dietary fats modulate carcinogenesis.

Adipose fatty acids and cancers of the breast, prostate and colon: an ecological study. EURAMIC Study Group

Animal and ecological studies suggest that linoleic acid intake is related to breast-cancer incidence. Analytical epidemiologic studies, however, do not support such findings. The primary objective of our ecological study was to investigate the association between breast-cancer incidence and linoleic acid status across European countries. In addition, other fatty acids and cancer sites were studied. Mean fatty acid composition of adipose tissue samples in 11 centres from 8 European countries and Israel served as indicators of exposure of the population. Figures on cancer incidence for the respective or comparable regions were obtained from published data. N-6 fatty acids in adipose tissue ranged from 10.4 in Helsinki to 24.6 g/100 g fatty acids in Jerusalem. N-6 fatty acids were not associated significantly with breast, colon or prostate cancer. Cancers of the breast and colon were associated negatively with cis-mono-unsaturated fatty acids and positively with trans fatty acids. Despite a large range in intake, we found no evidence of a positive association between n-6 fatty acid status and breast cancer, but associations were observed between other fatty acids and cancer. Differences in linoleic acid intake cannot explain risk differences in breast-cancer incidence between affluent countries, while associations of other fatty acids with cancer rates may reflect cultural differences.

Dietary modulation of omega-3/omega-6 polyunsaturated fatty acid ratios in patients with breast cancer

BACKGROUND

Polyunsaturated fatty acids of the omega-6 (omega-6) class, as found in corn and safflower oils, can act as precursors for intermediates involved in the growth of mammary tumors when fed to animals, whereas polyunsaturated fatty acids of the omega-3 (omega-3) class, as found in fish oil, can inhibit these effects. The effects of dietary intervention on the ratios of these fatty acids in breast and other adipose tissues have not previously been prospectively studied.

PURPOSE

The present investigation was conducted to study the impact on the ratio of omega-3 and omega-6 polyunsaturated fatty acid in plasma and in adipose tissue of the breast and buttocks when women with breast cancer consume a low-fat diet and fish oil supplements.

METHODS

Twenty-five women with high-risk localized breast cancer were enrolled in a dietary intervention program that required them to eat a low-fat diet and take a daily fish oil supplement throughout a 3-month period. Breast and gluteal fat biopsy specimens were obtained from each woman before and after dietary intervention. The fatty acid compositions of specimens of plasma, breast fat, and gluteal fat were determined by gas-liquid chromatography. Statistical analysis involved use of a two-sided paired t test.

RESULTS

After dietary intervention, a reduction in the level of total omega-6 polyunsaturated fatty acids in the plasma was observed (P<.0003); moreover, total omega-3 polyunsaturated fatty acids increased approximately three-fold (P<.0001) and the omega-3/omega-6 polyunsaturated fatty acids ratio increased approximately fourfold (i.e., mean values increased from 0.09 to 0.41; P = .0001). An increase in total omega-3 polyunsaturated fatty acids in breast adipose tissue was observed following dietary intervention (P = .04); the omega-3/omega-6 polyunsaturated fatty acid ratio increased from a mean value of 0.05 to 0.07 (P = .0001). An increase in total omega-3 polyunsaturated fatty acids was observed in gluteal adipose tissue following the intervention (P = .05); however, the ratio of omega-3 to omega-6 polyunsaturated fatty acids (mean ratio values of 0.036-0.045; P = .06) was unchanged.

CONCLUSION

Short-term dietary intervention can lead to statistically significant increases in omega-3/omega-6 polyunsaturated fatty acid ratios in plasma and breast adipose tissue. Breast adipose tissue changed more rapidly than gluteal adipose tissue in response to the dietary modification tested in this study. Therefore, gluteal adipose tissue may not be a useful surrogate to study the effect of diet on breast adipose tissue.

Trans fatty acids and cancer

Despite a general lack of evidence for the carcinogenic effects of trans fatty acids, some recent research and popular media have suggested a possible association. The available scientific data do not support this relationship and are reviewed so as to put this issue in perspective.

Essential fatty acid consumption and risk of breast cancer

Animal and ecological studies of essential fatty acids suggest that omega-3 fatty acids found in fish oils and omega-6 fatty acids found in vegetable oils may be playing a role in the etiology of breast cancer. Essential fatty acids may modulate breast cancer risk by interacting with prostaglandins, which have immunosuppressive and platelet aggregative capabilities. The fatty acid composition of adipose tissue reflects the dietary consumption of essential fatty acids over a period of years. Biochemical techniques have been used in epidemiological studies to accurately estimate fatty acid consumption. However, analytical epidemiology studies that have used biochemical measurements of adipose tissue fatty acid composition, have not supported a relationship between consumption of these essential fatty acids and breast cancer risk.

Time-course study of adipose tissue fatty acid composition during mammary tumor growth in rats with controlled fat intake

Previous work in breast cancer patients has indicated an inverse relationship between the risk of relapse and the alpha-linolenic acid (18:3n-3) level in adipose breast tissue. To determine whether low alpha-linolenic levels in patients with aggressive breast cancer resulted from lower 18:3n-3 dietary intake and/or increased metabolism of stored 18:3n-3, we analyzed the fatty acid composition of mammary adipose tissue during tumor growth in a rat model of mammary carcinogenesis. Rats were fed a diet containing 10% fat as rapeseed oil (in which 9% of total fatty acids is 18:3n-3). one-half of the rats received an injection of nitrosomethylurea (NMU) to initiate mammary tumors. In control and NMU-treated groups, three to five animals were sacrificed every three weeks during the five-month experimental time. tumor growth was followed by weekly palpation of the animals and by the measure of total tumor mass and number in sacrificed rats. Mammary tumor and adipose tissues were sampled in sacrificed rats. We found that although mammary adipose tissue fatty acid profile changed throughout the experiment, there was no difference in fatty acid profile between control and NMU-treated rats of the same age. In the NMU-treated group, 18:3n-3 level remained identical throughout the experimental period, irrespective of tumor burden. These data show that, in this model, mammary tumor growth does not modify stored fatty acid levels, including 18:3n-3. this suggests that decreased 18:3n-3 level in patients with poor prognosis is not a consequence of tumor burden but more likely depends on decreased dietary intake.

Developing Yoshida sarcoma does not influence the fatty acid composition of adipose tissues in the rat

The potential involvement of individual fatty acids from diet or from adipose tissue in the outcome of cancer emphasizes the need for more insight into the relationship between fatty acids and tumor growth. The main objective of the present study was to examine whether rapid tumor growth would induce changes in the fatty acid composition of adipose tissue, indicating selective use and thus deposition of dietary fatty acids and/or selective removal of stored fatty acids from adipose tissue. We used a rodent model of transplanted solid tumor (Yoshida sarcoma) and measured the fatty acid composition from different adipose sites in the absence and in the presence of tumor but at the same intake of dietary fatty acids. We found that Yoshida sarcoma could grow rapidly without significantly altering the fatty acid composition of adipose tissue, irrespective of its location. These results do not favor the hypothesis of a selective removal of fatty acids from adipose tissue by growing tumors. They moreover indicate that tumors do not modify the storage of individual dietary fatty acids.

Diet and breast cancer: trial and error?

The risk of developing breast cancer in females is determined by characteristics of hormone- and pregnancy-related tissue growth and development and mechanistic interactions between carcinogens and molecular targets and clonal selection of cell lines. Animal models have substantiated the idea that breast tissue may have periods of increased sensitivity to carcinogens and that dietary fat, and particularly energy intake, affect cancer risk. In epidemiological research, ecological studies clearly demonstrated positive associations between dietary fat and breast cancer risk, but individual-based case-control studies and cohort studies did not support a causal interpretation. The debate is now whether the ecological fallacy or biases in analytical epidemiology account for the apparent discrepancy, and the character of the debate is mainly of a methodological nature. Ecological and analytical studies, however, are fundamentally different with respect to the time- and age-axes considered. The lack of association in analytical studies addressing late-stage carcinogenesis may be attributed to exposures being relevant earlier in life. Analytical studies that integrate insights relating to periods of increased tissue susceptibility and mechanistic models of carcinogenic action may be fruitful in producing new outlooks for breast cancer prevention.