Association of serum phospholipid fatty acids with breast cancer risk among postmenopausal cigarette smokers

Association of saturated fatty acids with cancer risk: a systematic review and meta-analysis

OBJECTIVE

Extensive research has explored the link between saturated fatty acids (SFAs) and cardiovascular diseases, alongside other biological dysfunctions. Yet, their association with cancer risk remains a topic of debate among scholars. The present study aimed to elucidate this association through a robust meta-analysis.

METHODS

PubMed, Embase, Cochrane Library, and Web of Science databases were searched systematically to identify relevant studies published until December 2023. The Newcastle-Ottawa Scale was used as the primary metric for evaluating the quality of the included studies. Further, fixed- or random-effects models were adopted to determine the ORs and the associated confidence intervals using the Stata15.1 software. The subsequent subgroup analysis revealed the source of detection and the cancer types, accompanied by sensitivity analyses and publication bias evaluations.

RESULTS

The meta-analysis incorporated 55 studies, comprising 38 case-control studies and 17 cohort studies. It revealed a significant positive correlation between elevated levels of total SFAs and the cancer risk (OR of 1.294; 95% CI: 1.182-1.416; P-value less than 0.001). Moreover, elevated levels of C14:0, C16:0, and C18:0 were implicated in the augmentation of the risk of cancer. However, no statistically significant correlation of the risk of cancer was observed with the elevated levels of C4:0, C6:0, C8:0, C10:0, C12:0, C15:0, C17:0, C20:0, C22:0, and C24:0. Subgroup analysis showed a significant relationship between excessive dietary SFA intake, elevated blood SFA levels, and heightened cancer risk. Increased total SFA levels correlated with higher risks of breast, prostate, and colorectal cancers, but not with lung, pancreatic, ovarian, or stomach cancers.

CONCLUSION

High total SFA levels were correlated with an increased cancer risk, particularly affecting breast, prostate, and colorectal cancers. Higher levels of specific SFA subtypes (C14:0, C16:0, and C18:0) are also linked to an increased cancer risk. The findings of the present study would assist in providing dietary recommendations for cancer prevention, thereby contributing to the development of potential strategies for clinical trials in which diet-related interventions would be used in combination with immunotherapy to alter the levels of SFAs in patients and thereby improve the outcomes in cancer patients. Nonetheless, further high-quality studies are warranted to confirm these associations.

Serum Saturated Fatty Acids including Very Long-Chain Saturated Fatty Acids and Colorectal Cancer Risk among Chinese Population

The association between circulating saturated fatty acids (SFAs) including very long-chain SFAs (VLCSFAs) and colorectal cancer (CRC) risk has not been clearly established. To investigate the association between serum SFAs and CRC risk in Chinese population, 680 CRC cases and 680 sex and age-matched (5-year interval) controls were recruited in our study. Serum levels of SFAs were detected by gas chromatography. Unconditional logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the association between serum SFAs and CRC risk. Results showed that total SFAs were positively associated with the risk of CRC (adjusted OR _{quartile 4 vs. 1} = 2.64, 95%CI: 1.47-4.74). However, VLCSFAs were inversely associated with CRC risk (adjusted OR _{quartile 4 vs. 1} = 0.51, 95%CI: 0.36-0.72). Specifically, lauric acid, myristic acid, palmitic acid, heptadecanoic acid, and arachidic acid were positively associated with CRC risk, while behenic acid and lignoceric acid were inversely associated with CRC risk. This study indicates that higher levels of total serum SFAs and lower levels of serum VLCSFAs were associated with an increased risk of CRC in Chinese population. To reduce the risk of CRC, we recommend reducing the intake of foods containing palmitic acid and heptadecanoic acid such as animal products and dairy products, and moderately increasing the intake of foods containing VLCSFAs such as peanuts and canola oil.

Circulating plasma phospholipid fatty acid levels and breast cancer risk in the Cancer Prevention Study-II Nutrition Cohort

Prospective studies that objectively measure circulating levels of fatty acids are needed to clarify their role in the etiology of breast cancer. Thirty-eight phospholipid fatty acids were measured using gas chromatograph in the plasma fraction of blood samples collected prospectively from 2718 postmenopausal women (905 breast cancer cases) enrolled in the Cancer Prevention Study II Nutrition Cohort. Associations of 28 fatty acids that passed quality control metrics (modeled as per 1-SD increase) with breast cancer risk were assessed using multiple variable conditional logistic regression models to compute odds ratios (OR) and 95% confidence intervals (CI). The false discovery rate (q value) was computed to account for multiple comparisons. Myristic acid levels were positively associated with breast cancer risk (OR, 1.17, 95% CI: 1.07-1.28; q value = 0.03). Borderline associations were also found for palmitoleic acid (OR, 1.14, 95% CI: 1.04-1.24) and desaturation index16 (OR, 1.10, 95% CI: 1.01-1.20) at nominal P values (<.03) (q values>0.05). These findings suggest that higher circulating levels of myristic acid, sourced from dietary intake of palm kernel oils along with increased de novo synthesis of fatty acids, may increase breast cancer risk. Additional studies are needed to investigate de novo synthesis of fatty acid in breast cancer tissues.

Omega-3 polyunsaturated fatty acid biomarkers and risk of type 2 diabetes, cardiovascular disease, cancer, and mortality

BACKGROUND & AIMS

Considerable attention has focused on the role of omega-3 polyunsaturated fatty acids (PUFA) in the prevention of cardiometabolic diseases, which has led to dietary recommendations to increase omega-3 fatty acid intake. A meta-analysis was conducted to summarize evidence from prospective studies regarding associations between omega-3 PUFA biomarkers and risk of developing major chronic diseases.

METHODS

Four electronic databases were searched for articles from inception to March 1, 2022. Random-effects model was used to estimate the pooled relative risk (RR) and 95% confidence intervals (CIs) for the association of omega-3 PUFAs, including α-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA), with risk of developing type 2 diabetes (T2D), cardiovascular disease (CVD), including coronary heart disease (CHD) and stroke, cancer, and mortality. The Grades of Recommendation, Assessment, Development and Evaluation assessment tool was used to rates the confidence in estimates.

RESULTS

A total of 67 prospective studies comprised of 310,955 participants were identified. Individual omega-3 PUFAs showed divergent associations with the study outcomes of interest. A significant inverse association with T2D risk was observed across categories of ALA (relative risk [RR]: 0.89, 95% confidence interval [CI]: 0.82-0.96), EPA (RR: 0.85, 95% CI: 0.72-0.99) and DPA (RR: 0.84, 95% CI: 0.73-0.96) biomarkers. The marine-origin omega-3 fatty acids biomarkers but not ALA was significantly associated with lower risks of total CVD, CHD, and overall mortality, with RRs ranging from 0.70 for DHA-CHD association to 0.85 for EPA-CHD association. A lower risk of colorectal cancer was observed at higher levels of DPA (RR: 0.76, 95% CI: 0.59-0.98) and DHA (RR: 0.80; 95% CI: 0.65-0.99), whereas no association was noted for other outcomes. In addition, a dose-response relationship was observed between an increasing level of EPA, DPA, or DHA biomarker and lower risk of CVD.

CONCLUSIONS

Higher concentrations of marine-derived omega-3 PUFA biomarkers were associated with a significantly reduced risk of total CVD, CHD, and total mortality. Levels of ALA were inversely associated with a lower risk of T2D but not CVD-related outcomes. These data support the dietary recommendations advocating the role of omega-3 PUFAs in maintaining an overall lower risk of developing cardiovascular disease and premature deaths.

Dietary trans-fatty acid intake in relation to cancer risk: a systematic review and meta-analysis

CONTEXT

Apart from ruminant fat, trans-fatty acids are produced during the partial hydrogenation of vegetable oils, (eg, in the production of ultraprocessed foods). Harmful cardiovascular effects of trans-fatty acids are already proven, but the link with cancer risk has not yet been summarized.

OBJECTIVE

A systematic review (following PRISMA guidelines) - including observational studies on the association of trans-fatty acid intake with any cancer risk - was conducted, with no limitations on population types.

DATA SOURCES

The electronic databases PubMed and Embase were searched to identify relevant studies.

DATA EXTRACTION

This systematic review included 46 articles. Quality was assessed via the Newcastle-Ottawa scale. Meta-analyses were conducted if at least 4 articles exploring the same transfat-cancer pairings were found.

DATA ANALYSIS

Nineteen cancer types have been researched in cohort and case-control studies on trans-fatty acids, with breast cancer (n = 17), prostate cancer (n = 11), and colorectal cancer (n = 9) as the most researched. The meta-analyses on total trans-fat showed a significant positive association for prostate cancer (odds ratio [OR] 1.49; 95%CI, 1.13-1.95) and colorectal cancer (OR 1.26; 95%CI, 1.08-1.46) but not for breast cancer (OR 1.12; 95%CI, 0.99-1.26), ovarian cancer (OR 1.10; 95%CI, 0.94-1.28), or non-Hodgkin lymphoma (OR 1.32; 95%CI, 0.99-1.76). Results were dependent on the fatty acid subtype, with even cancer-protective associations for some partially hydrogenated vegetable oils. Enhancing moderators in the positive transfat-cancer relation were gender (direction was cancer-site specific), European ancestry, menopause, older age, and overweight.

CONCLUSION

Despite heterogeneity, higher risk of prostate and colorectal cancer by high consumption of trans-fatty acids was found. Future studies need methodological improvements (eg, using long-term follow-up cancer data and intake biomarkers). Owing to the lack of studies testing trans-fatty acid subtypes in standardized ways, it is not clear which subtypes (eg, ruminant sources) are more carcinogenic.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42018105899.

A Prospective Analysis of Plasma Phospholipid Fatty Acids and Breast Cancer Risk in 2 Provinces in Canada

BACKGROUND

Studies suggest that fatty acid status influences breast cancer etiology, yet the roles of individual fatty acids in breast cancer risk are unclear, specifically when central adiposity and menopausal status are considered.

OBJECTIVES

This study examined the associations of fatty acid status with breast cancer risk including location, menopausal status, and waist-to-hip ratio as key variables.

METHODS

Prediagnostic plasma phospholipid fatty acids were measured in women with breast cancer (n = 393) and age-matched controls (n = 786) from a nested case-control prospective study within Alberta's Tomorrow Project (ATP) and British Columbia Generations Project (BCGP) cohorts. Binary logistic regression models were used to evaluate associations of fatty acids and breast cancer risk with subgroup analysis for menopausal status and waist-to-hip ratio.

RESULTS

Women from BCGP had a higher n-3 (ɷ-3) fatty acid status compared with the ATP (6.4% ± 0.08% vs. 5.3% ± 0.06%; P < 0.001), so subsequent analysis was blocked by cohort. Overall, fatty acids had inconsistent associations with risk. In the ATP among premenopausal women, total long-chain n-3 fatty acids (ORQ4vsQ1 = 1.78; 95% CI: 0.58, 5.43; P-trend = 0.007, P-interaction = 0.07) were positively associated with breast cancer risk, whereas in BCGP, DHA (ORQ4vsQ1 = 0.66; 95% CI: 0.28, 1.53; P-trend = 0.03, P-interaction = 0.05) and total long-chain n-3 fatty acids (ORQ4vsQ1 = 0.66; 95% CI: 0.28, 1.54; P-trend = 0.03) were associated with decreased cancer risk when the waist-to-hip ratio was <0.85.

CONCLUSIONS

Our findings suggest that regional variations in fatty acid status influence breast cancer risk, resulting in positive associations of total long-chain n-3 fatty acids in premenopausal ATP women and negative associations of these fatty acids in BCGP women with a waist-to-hip ratio below guidelines. This study highlights the complexity and difficulty in using fatty acid status to predict breast cancer risk in diverse populations without the consideration of other risk factors.

Serum Phospholipids Fatty Acids and Breast Cancer Risk by Pathological Subtype

This study evaluates whether serum phospholipids fatty acids (PL-FAs) and markers of their endogenous metabolism are associated with breast cancer (BC) subtypes. EpiGEICAM is a Spanish multicenter matched case-control study. A lifestyle and food frequency questionnaire was completed by 1017 BC cases and healthy women pairs. Serum PL-FA percentages were measured by gas chromatography-mass spectrometry. Conditional and multinomial logistic regression models were used to quantify the association of PL-FA tertiles with BC risk, overall and by pathological subtype (luminal, HER2+ and triple negative). Stratified analyses by body mass index and menopausal status were also performed. Serum PL-FAs were measured in 795 (78%) pairs. Women with high serum levels of stearic acid (odds ratio (OR)_T3vsT1 = 0.44; 95% confidence interval (CI) = 0.30–0.66), linoleic acid (OR_T3vsT1 = 0.66; 95% CI = 0.49–0.90) and arachidonic to dihomo-γ-linolenic acid ratio (OR _T3vsT1 = 0.64; 95% CI = 0.48–0.84) presented lower BC risk. Participants with high concentrations of palmitoleic acid (OR_T3vsT1 = 1.65; 95% CI = 1.20–2.26), trans-ruminant palmitelaidic acid (OR_T3vsT1 = 1.51; 95% CI = 1.12–2.02), trans-industrial elaidic acid (OR_T3vsT1 = 1.52; 95% CI = 1.14–2.03), and high oleic to stearic acid ratio (OR_T3vsT1 = 2.04; 95% CI = 1.45–2.87) showed higher risk. These associations were similar in all BC pathological subtypes. Our results emphasize the importance of analyzing fatty acids individually, as well as the desaturase activity indices.

N-6 Polyunsaturated Fatty Acids and Risk of Cancer: Accumulating Evidence from Prospective Studies

Previous studies on the association between polyunsaturated fatty acids (PUFAs) and cancer have focused on n-3 PUFAs. To investigate the association between intake or blood levels of n-6 PUFAs and cancer, we searched the PubMed and Embase databases up to March 2020 and conducted a meta-analysis. A total of 70 articles were identified. High blood levels of n-6 PUFAs were associated with an 8% lower risk of all cancers (relative risk (RR) = 0.92; 95% confidence interval (CI): 0.86-0.98) compared to low blood levels of n-6 PUFAs. In the subgroup analyses by cancer site, type of n-6 PUFAs, and sex, the inverse associations were strong for breast cancer (RR = 0.87; 95% CI: 0.77-0.98), linoleic acid (LA) (RR = 0.91; 95% CI: 0.82-1.00), and women (RR = 0.88; 95% CI: 0.79-0.97). In the dose-response analysis, a 2% and 3% decrease in the risk of cancer was observed with a 5% increase in blood levels of n-6 PUFAs and LA, respectively. Thus, there was no significant association between n-6 PUFA intake and the risk of cancer. The pooled RR of cancer for the highest versus lowest category of n-6 PUFA intake was 1.02 (95% CI: 0.99-1.05). Evidence from prospective studies indicated that intake of n-6 PUFAs was not significantly associated with risk of cancer, but blood levels of n-6 PUFAs were inversely associated with risk of cancer.

Erythrocyte membrane fatty acids and breast cancer risk by tumor tissue expression of immuno-inflammatory markers and fatty acid synthase: a nested case-control study

BACKGROUND

Previous studies of fatty acids and breast cancer risk have shown mixed results, which may be due in part to tumor heterogeneity. Prior research has also illustrated an important role of specific fatty acids in immune regulation, T cell function, and inflammation, indicating that the effects of specific fatty acids on breast cancer risk may vary by tumor expression of immuno-inflammatory markers. We therefore aimed to evaluate the relationships between prediagnostic erythrocyte membrane fatty acids and breast cancer risk by tumor tissue expression of immuno-inflammatory markers (CD4, CD8, CD20, CD163, COX-2) and fatty acid synthase (FAS).

METHODS

We conducted a matched case-control study nested within the Nurses' Health Study II (n = 235 cases and 235 controls). Blood samples were collected from 1996 to 1999. Tumor tissue blocks were collected for cases diagnosed after blood collection and through 2006. Unconditional nominal polytomous logistic regression adjusted for matching factors and potential confounders was used to assess whether associations between fatty acids and breast cancer risk varied by tumor expression subtype, ascertained via immunohistochemistry. Odds ratios (OR) and 95% confidence intervals (CI) were estimated separately by tumor expression subtype using unconditional logistic regression.

RESULTS

Associations between fatty acids and breast cancer risk did not vary substantially by tumor CD4, CD20, CD163, or COX-2. However, n-3 polyunsaturated fatty acids (PUFAs) were inversely associated with CD8^low but not CD8^high cancers (CD8^low OR_{T3 vs T1} = 0.45, 95% CI 0.23-0.87, P_trend = 0.02; CD8^high OR_{T3 vs T1} = 1.19, 95% CI 0.62-2.26, P_trend = 0.62; P_het = 0.04). n-6 PUFAs were suggestively inversely associated with CD8^high but not CD8^low cancers (CD8^high OR_{T3 vs T1} = 0.61, 95% CI 0.32-1.14, P_trend = 0.11; CD8^low OR_{T3 vs T1} = 1.63, 95% CI 0.87-3.04, P_trend = 0.12; P_het = 0.02). Trans fatty acids were positively associated with FAS^high but not FAS^low tumors (FAS^high OR_{T3 vs T1} = 2.94, 95% CI 1.46-5.91, P_trend = 0.002; FAS^low OR_{T3 vs T1} = 0.99, 95% CI 0.52-1.92, P_trend = 0.97; P_het = 0.01).

CONCLUSION

Results indicate that the effects of n-3 PUFAs, n-6 PUFAs, and trans fatty acids on breast cancer risk may vary by tumor tissue expression subtypes. Findings suggest potential immuno-modulatory and FAS-mediated mechanisms.

Association of Dietary Intake Ratio of n-3/n-6 Polyunsaturated Fatty Acids with Breast Cancer Risk in Western and Asian Countries: A Meta-Analysis

Objective:

This systematic review and meta-analysis were performed to determine association of dietary intake ratio of n-3/n-6 polyunsaturated fatty acids with breast cancer risk in Western and Asian countries.

Methods:

The authors conducted a meta-analysis of published research articles on association of dietary intake ratio of n-3/n-6 polyunsaturated fatty acids (PUFAs) with breast cancer risk in Western and Asian countries published between January 2000 and February 2019 in online article databases of PubMed, ProQuest and EBSCO. Pooled risk ratios (RR) were calculated using fixed and random-effect models. Publication bias was visually evaluated by performing funnel plots and statistically assessed by Egger’s and Begg’s tests. Data were processed by using Stata version 14.2 (Stata Corporation).

Results:

This study reviewed 913 articles. There were 13 studies included in systematic review continued by meta-analysis of relevant data with total number of samples: 275,264 patients. The results showed dietary intake ratio of n-3/n-6 PUFAs with breast cancer risk in Western and Asian countries (RR = 0.99; 95%CI: 0.92-1.07). Dietary intake ratio of n-3/n-6 PUFAs with breast cancer risk in Western countries reached (RR = 0.98; 95%CI: 0.91-1.06) and there was any significant publication bias for studies included. Dietary intake ratio of n-3/n-6 PUFAs with breast cancer risk in Asian countries reached (RR = 1.18; 95%CI: 0.94-1.47) and there was not any significant publication bias for studies included.

Conclusion:

This analysis confirmed association of dietary intake ratio of n-3/n-6 PUFAs with breast cancer risk in Western and Asian countries. Higher dietary intake ratio is associated with lower risk of breast cancer in Asian countries rather than Western countries. This study suggests increasing dietary intake ratio n-3/n-6 PUFAs will provide benefit for breast cancer prevention.

Dietary intake and serum levels of trans fatty acids and risk of breast cancer: A systematic review and dose-response meta-analysis of prospective studies

BACKGROUND & AIMS

Although the relationship between dietary intake and serum levels of trans fatty acids and risk of breast cancer has been investigated extensively, findings are inconsistent. To summarize earlier findings on the association of dietary intake and serum levels of trans fatty acids with risk of breast cancer through a dose-response meta-analysis.

METHODS

The online databases of PubMed, ISI Web of Science, Scopus, ProQuest, Science Direct and Embase were searched for relevant publications up to June 2018, using MeSH and non-MeSH keywords. In total, 7 prospective studies [6 cohort studies and one nested case-control study] were included on total dietary trans fat intake, and five studies [1 cohort study and 4 nested case-control studies] were included about serum trans fatty acids. Assessment of study quality was conducted using the Newcastle-Ottawa scale. Study-specific RRs were combined via fixed-effects model to compute overall RRs.

RESULTS

Participants were apparently healthy aged 26 years or older. We observed no significant relationship between dietary intake of total trans fatty acids and risk of breast cancer (pooled effect size: 1.02, 95% CI: 0.95-1.10, P = 0.403). Combining 3 effect sizes from 2 prospective and one nested case-control study, no significant relation was seen between dietary intake of CLA and risk of breast cancer (pooled effect size: 1.05, 95% CI: 0.95-1.17, P = 0.513). Based on 5 effect sizes, each additional 1 g/day dietary intake of total trans fats was not significantly associated with risk of breast cancer (RR = 1.00; 95% CI = 0.99-1.01). In addition, it seems that serum levels of trans fats might be associated with an increased risk of breast cancer only among postmenopausal women (Pooled effect size: 1.37, 95% CI: 1.04-1.81, P = 0.02).

CONCLUSIONS

In conclusion, dietary intake of trans fatty acids was not associated with risk of breast cancer; however, a significant positive association was seen between serum trans fats and risk of breast cancer in postmenopausal women.

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.

Erythrocyte membrane fatty acids and breast cancer risk: a prospective analysis in the nurses' health study II

The roles of specific fatty acids in breast cancer etiology are unclear, particularly among premenopausal women. We examined 34 individual fatty acids, measured in blood erythrocytes collected between 1996 and 1999, and breast cancer risk in a nested case-control study of primarily premenopausal women in the Nurses' Health Study II. Breast cancer cases diagnosed after blood collection and before June 2010 (n = 794) were matched to controls and conditional logistic regression was used to estimate OR's (95% CI's) for associations of fatty acids with breast cancer; unconditional logistic regression was used for stratified analyses. Fatty acids were not significantly associated with breast cancer risk overall; however, heterogeneity by body mass index (BMI) was observed. Among overweight/obese women (BMI ≥ 25), several odd-chain saturated (SFA, e.g. 17:0, OR_Q4vsQ1 (95% CI) =1.85 (1.18-2.88), p_trend =0.006 p_int <0.001), trans (TFA, e.g. 18:1, OR_Q4vsQ1 (95% CI) =2.33 (1.45-3.77), p_trend <0.001, p_int =0.007) and dairy-derived fatty acids (SFA 15:0 + 17:0 + TFA 16:1n-7t; OR_Q4vsQ1 (95% CI) =1.83(1.16-2.89), p_trend =0.005, p_int <0.001) were positively associated, and n-3 polyunsaturated fatty acids (n-3 PUFA, e.g. alpha-linolenic acid; OR_Q4vsQ1 (95% CI) =0.57 (0.36-0.89), p_trend =0.017, p_int =0.03) were inversely associated with breast cancer. Total SFA were inversely associated with breast cancer among women with BMI < 25 (OR_Q4vsQ1 (95% CI) =0.68 (0.46-0.98), p_trend =0.05, p_int =0.01). Thus, while specific fatty acids were not associated with breast cancer overall, our findings suggest positive associations of several SFA, TFA and dairy-derived fatty acids and inverse associations of n-3 PUFA with breast cancer among overweight/obese women. Given these fatty acids are influenced by diet, and therefore are potentially modifiable, further investigation of these associations among overweight/obese women is warranted.

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

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

Linoleic acid and breast cancer risk: a meta-analysis

Objective

Prior studies on linoleic acid, the predominant n-6 fatty acid, and breast cancer risk have generated inconsistent results. We performed a meta-analysis to summarize the evidence regarding the relationship of dietary and serum linoleic acid with breast cancer risk.

Design

Pertinent studies were identified by a search of PubMed and EMBASE. The fixed- or random-effect pooled measure was selected based on between-study heterogeneity.

Results

Eight prospective cohort studies and four prospective nested case–control studies, involving 10 410 breast cancer events from 358 955 adult females across different countries, were included in present study. Compared with the lowest level of linoleic acid, the pooled relative risk (RR; 95 % CI) of breast cancer was 0·98 (0·93, 1·04) for the highest level of linoleic acid. The pooled RR (95 % CI) for dietary and serum linoleic acid were 0·99 (0·92, 1·06) and 0·98 (0·88, 1·08), respectively. The RR (95 % CI) of breast cancer was 0·97 (0·91, 1·04), 0·95 (0·85, 1·07), 0·96 (0·86, 1·07), 0·98 (0·87, 1·10) and 0·99 (0·85, 1·14) for linoleic acid intake of 5, 10, 15, 20 and 25 g/d, respectively. The risk of breast cancer decreased by 1 % (RR=0·99; 95 % CI 0·93, 1·05) for every 10 g/d increment in linoleic acid intake.

Conclusions

This meta-analysis indicated that both dietary linoleic acid intake and serum linoleic acid level were associated with decreased risk of breast cancer, although none of the associations were statistically significant. Further investigations are warranted.

Associations of erythrocyte ω-3 fatty acids with biomarkers of ω-3 fatty acids and inflammation in breast tissue

There is increasing evidence that chronic inflammation is associated with increased breast cancer risk. Long-chain omega-3 polyunsaturated fatty acids (LCω-3PUFA) may reduce circulating biomarkers of inflammation; however associations of blood LCω-3PUFA with breast tissue LCω-3PUFA and breast tissue biomarkers of inflammation are not well understood. We conducted a cross-sectional analysis of breast tissue and blood samples from n = 85 women with no history of breast cancer, who underwent breast reduction surgery. Fatty acids of erythrocytes and undissected breast tissues were analyzed by gas chromatography; C-reactive protein (CRP), interleukin (IL)-6 and IL-8 in plasma and tissue were measured by ELISA. Multivariable-adjusted regression models were used to estimate associations between erythrocyte LCω-3PUFA and breast tissue biomarkers. Women in the highest erythrocyte LCω-3PUFA tertile had LCω-3PUFA concentrations in the breast 73% (95% CI: 31-128%; p trend < 0.0001) higher than women in the lowest tertile. Associations for each individual LCω-3PUFA were similar in magnitude. No significant association was found for the shorter ω-3 PUFA, α-linolenic acid. Although compatible with no association, women in the highest tertile of erythrocyte eicosapentaenoic acid had a nonsignificant 32% (95% CI: -23 to 62%) reduced breast tissue CRP. No correlation was observed between erythrocyte ω-3 PUFA and tissue IL-6 or IL-8 concentrations. Our findings provide evidence that erythrocyte ω-3 fatty acids are valid measures of breast tissue concentrations, and limited evidence that inverse associations from prospective epidemiologic studies of blood LCω-3PUFA and breast cancer risk may be partly explained by reductions in breast tissue inflammation; however, these findings require replication.

α-Linolenic Acid Reduces Growth of Both Triple Negative and Luminal Breast Cancer Cells in High and Low Estrogen Environments

Flaxseed, rich in α-linolenic acid (ALA), is a complementary breast cancer (BC) therapy; however ALA effectiveness and mechanism are unclear. Variation in cellular expression of estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and estrogen (E2) levels may alter ALA effectiveness. This research determined the effect of ALA on growth, apoptosis, and phospholipid fatty acids of 4 BC cell lines with varying receptor expression ± E2. MCF-7 (ER+/PR+/HER2-), BT-474 (ER+/PR+/HER2+), MDA-MB-231 (ER-/PR-/HER2-) and MDA-MB-468 (ER-/PR-/HER2-) cells were incubated with ALA (50-200 μM) ± 1 nM E2 for 48-72 h. ALA dose-dependently reduced growth, measured by trypan blue exclusion, of all cells (55-80% with 75 μM), and this effect was not altered by E2. ALA (75 μM)+E2 induced apoptosis, measured by flow cytometry (up to 111.2%). Decreased growth and increased apoptosis is related to increased cell phospholipid % ALA (up to 25.1%), measured by gas chromatography. ALA is shown for the first time to reduce cell growth and induce apoptosis regardless of receptor expression and E2 environment, by incorporating into BC phospholipids, supporting the use of ALA and ALA-rich foods as a safe, inexpensive complementary therapy for a wide range of BC.

Omega-3 and omega-6 Fatty acids in blood and breast tissue of high-risk women and association with atypical cytomorphology

The ratio of omega-3 to omega-6 fatty acids, especially the long-chain eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) to arachidonic acid (AA) ratio, is inversely associated with breast cancer risk. We measured the association between cytologic atypia, a biomarker for short-term risk of breast cancer development, and omega-3 and omega-6 fatty acid intake and levels in blood and breast tissue. Blood and benign breast tissue, sampled by random periareolar fine-needle aspiration (RPFNA), was obtained from 70 women at elevated risk for breast cancer. Self-reported dietary intake was assessed by the NCI's Food Frequency Questionnaire. The fatty acid composition of five lipid compartments, red blood cell, plasma and breast phospholipids, and plasma and breast triaclyglycerides (TAG), was analyzed by gas chromatography as weight percent. Median daily intakes of EPA+DHA and total omega-3 fatty acids were 80 mg and 1.1 g, respectively. The median total omega-3:6 intake ratio was 1:10. Compared with women without atypia, those with cytologic atypia had lower total omega-3 fatty acids in red blood cell and plasma phospholipids and lower omega-3:6 ratios in plasma TAGs and breast TAGs (P < 0.05). The EPA+DHA:AA ratio in plasma TAGs was also lower among women with atypia. This is the first report of associations between tissue levels of omega-3 and omega-6 fatty acids and a reversible tissue biomarker of breast cancer risk. RPFNA cytomorphology could serve as a surrogate endpoint for breast cancer prevention trials of omega-3 fatty acid supplementation.

Prospective associations between plasma saturated, monounsaturated and polyunsaturated fatty acids and overall and breast cancer risk - modulation by antioxidants: a nested case-control study

BACKGROUND

Mechanistic data suggest that different types of fatty acids play a role in carcinogenesis and that antioxidants may modulate this relationship but epidemiologic evidence is lacking. Our aim was to investigate the association between plasma saturated, monounsaturated and polyunsaturated fatty acids (SFAs, MUFAs and PUFAs) and overall and breast cancer risk and to evaluate the potential modulatory effect of an antioxidant supplementation on these relationships.

METHODS

A nested case-control study included all first incident cancer cases diagnosed in the SU.VI.MAX study between 1994 and 2002 (n=250 cases, one matched control/case). Participants to the SU.VI.MAX randomized controlled trial received either vitamin/mineral antioxidants or placebo during this intervention period. Baseline fatty acid composition of plasma total lipids was measured by gas chromatography. Conditional logistic regression was performed overall and stratified by intervention group.

RESULTS

Dihomo-γ-linolenic acid (Ptrend=0.002), the dihomo-γ-linolenic/linoleic acids ratio (Ptrend=0.001), mead acid (Ptrend=0.0004), and palmitoleic acid (Ptrend=0.02) were inversely associated with overall cancer risk. The arachidonic/dihomo-γ-linolenic acids ratio (Ptrend=0.02) and linoleic acid (Ptrend=0.02) were directly associated with overall cancer risk. Similar results were observed for breast cancer specifically. In stratified analyses, associations were only observed in the placebo group. Notably, total PUFAs were directly associated with overall (Ptrend=0.02) and breast cancer risk in the placebo group only.

CONCLUSION

Specific SFAs, MUFAs and PUFAs were prospectively differentially associated with cancer risk. In addition, this study suggests that antioxidants may modulate these associations by counteracting the potential effects of these fatty acids on carcinogenesis.

Ratio of n-3/n-6 PUFAs and risk of breast cancer: a meta-analysis of 274135 adult females from 11 independent prospective studies

Background

Increased ratio of n-3/n-6 polyunsaturated fatty acids (PUFAs) in diet or serum may have a protective effect on the risk of breast cancer (BC); however, the conclusions from prospective studies are still controversial. The purpose of this study is to ascertain the relationship between intake ratio of n-3/n-6 PUFAs and the risk of BC, and estimate the potential summarized dose–response trend.

Methods

Relevant English-language studies were identified through Cochrane Library, PubMed and EMBASE database till April 2013. Eligible prospective studies reporting the multivariate adjusted risk ratios (RRs) for association of n-3/n-6 PUFAs ratio in diet or serum with BC risk. Data extraction was conducted independently by 2 investigators; disagreements were reconciled by consensus. Study quality was assessed using the Newcastle-Ottawa scale. Study-specific RRs were combined via a random-effects model.

Results

Six prospective nested case–control and 5 cohort studies, involving 8,331 BC events from 274,135 adult females across different countries, were included in present study. Subjects with higher dietary intake ratio of n-3/n-6 PUFAs have a significantly lower risk of BC among study populations (pooled RR = 0.90; 95% CI: 0.82, 0.99), and per 1/10 increment of ratio in diet was associated with a 6% reduction of BC risk (pooled RR = 0.94; 95% CI: 0.90, 0.99; P for linear trend = 0.012). USA subjects with higher ratio of n-3/n-6 in serum phospholipids (PL) have a significantly lower risk of BC (pooled RR = 0.62; 95% CI: 0.39, 0.97; I² = 0.00%; P for metaregression = 0.103; P for a permutation test = 0.100), and per 1/10 increment of ratio in serum PL was associated with 27% reduction of BC risk (pooled RR = 0.73; 95% CI: 0.59, 0.91; P for linear trend = 0.004; P for metaregression = 0.082; P for a permutation test = 0.116).

Conclusions

Higher intake ratio of n-3/n-6 PUFAs is associated with lower risk of BC among females, which implies an important evidence for BC prevention and treatment is by increasing dietary intake ratio of n-3/n-6 PUFA. No firm conclusions from USA populations could be obtained, due to the limited numbers of USA studies.

Carcinogenesis alters fatty acid profile in breast tissue

Cancerogenesis is associated with cell membrane changes. The aim of this study was to investigate whether breast tissues with different degrees of cancer involvement have different fatty acid profiles. Fourteen breast cancer patients with a mean age of 61 years were recruited. Morphological features of the tumoral specimens were characterized. Approximately 60 % of patients had invasive ductal carcinoma, and 80 % were ER positive; 65 % were PR positive; and 65 % were HER2 negative. The segments with confirmed cancer had significantly less amounts of total lipids as compared with the corresponding grossly normal or interface tissues. The fatty acid profile in cancer tissue was significantly different from that in other tissues. Fatty acid composition of five classes of phospholipids revealed the variations between cancer tissue and the other two segments. A transition of changes in fatty acid composition in these fractions of phospholipids was observed. The interface tissue had intermediate amounts of several fatty acids including palmitic acid, stearic acid, and arachidonic acid. Interestingly, we observed significantly higher amounts of the n-3 fatty acid DHA in cancer tissue as compared to the other two tissues. Data from this study will provide evidence that biochemical changes particularly phospholipid composition may take place well in advance prior to morphological changes. Should this theory be confirmed by larger studies, deviation of phospholipid composition from normal values can be used as markers of susceptibility of tissue to cancer development.

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

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

Dietary polyunsaturated fatty acids and breast cancer risk in Chinese women: a prospective cohort study

Breast cancer is the most common cancer in women. Controversy exists regarding the role of dietary fat in breast cancer etiology. We investigated the association of dietary polyunsaturated fatty acids (PUFAs) and the ratio of n-6 PUFAs to marine-derived n-3 PUFAs with breast cancer risk in the Shanghai Women's Health Study, a prospective cohort study including 72,571 cancer-free participants at baseline. Dietary fatty acid intake was determined using food frequency questionnaires. We used Cox proportional hazards analysis to estimate the relative risks (RRs) and 95% confidence intervals (CIs) for the association of breast cancer risk with dietary fatty acids consumption. In 583,998 person-years of follow-up, we identified 712 breast cancer cases. We found no association of breast cancer risk to dietary intake of linoleic acid, arachidonic acid, α-linolenic acid or marine-derived n-3 PUFA. We found a statistically significant interaction between n-6 PUFA intake, marine-derived n-3 PUFA intake and breast cancer risk (p = 0.008). Women with lower intake (the lowest tertile) of marine-derived n-3 PUFA and higher intake (the highest tertile) of n-6 PUFA had an increase risk for breast cancer (RR = 2.06; 95% CI = 1.27-3.34) compared to women with higher intake (the highest tertile) of marine-derived n-3 PUFAs and lower intake (the lowest tertile) of n-6 PUFAs after adjusting for potential confounders. The relative amounts of n-6 PUFA to marine-derived n-3 PUFAs may be more important for breast cancer risk than individual dietary amounts of these fatty acids.