Association of Mediterranean diet with survival after breast cancer diagnosis in women from nine European countries: results from the EPIC cohort study

BACKGROUND

The Mediterranean diet has been associated with lower risk of breast cancer (BC) but evidence from prospective studies on the role of Mediterranean diet on BC survival remains sparse and conflicting. We aimed to investigate whether adherence to Mediterranean diet prior to diagnosis is associated with overall and BC-specific mortality.

METHODS

A total of 13,270 incident breast cancer cases were identified from an initial sample of 318,686 women in 9 countries from the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Adherence to Mediterranean diet was estimated through the adapted relative Mediterranean diet (arMED), a 16-point score that includes 8 key components of the Mediterranean diet and excludes alcohol. The degree of adherence to arMED was classified as low (score 0-5), medium (score 6-8), and high (score 9-16). Multivariable Cox proportional hazards models were used to analyze the association between the arMED score and overall mortality, and Fine-Gray competing risks models were applied for BC-specific mortality.

RESULTS

After a mean follow-up of 8.6 years from diagnosis, 2340 women died, including 1475 from breast cancer. Among all BC survivors, low compared to medium adherence to arMED score was associated with a 13% higher risk of all-cause mortality (HR 1.13, 95%CI 1.01-1.26). High compared to medium adherence to arMED showed a non-statistically significant association (HR 0.94; 95% CI 0.84-1.05). With no statistically significant departures from linearity, on a continuous scale, a 3-unit increase in the arMED score was associated with an 8% reduced risk of overall mortality (HR3-unit 0.92, 95% CI: 0.87-0.97). This result sustained when restricted to postmenopausal women and was stronger among metastatic BC cases (HR3-unit 0.81, 95% CI: 0.72-0.91).

CONCLUSIONS

Consuming a Mediterranean diet before BC diagnosis may improve long-term prognosis, particularly after menopause and in cases of metastatic breast cancer. Well-designed dietary interventions are needed to confirm these findings and define specific dietary recommendations.

Palaeolithic diet score and risk of breast cancer among postmenopausal women overall and by hormone receptor and histologic subtypes

BACKGROUND

The Palaeolithic diet (PD) has gained popularity globally. There is emerging evidence of its putative health benefits as short-term effects on chronic diseases have been reported. We evaluated the association between long-term adherence to the PD and breast cancer (BC) risk among postmenopausal women.

METHODS

65,574 women from the Etude Epidémiologique auprès de femmes de la Mutuelle Générale de l'Education Nationale (E3N) cohort were followed from 1993 to 2014. Incident BC cases were identified and validated. The PD score was calculated using dietary intake self-reported at baseline (1993) and follow-up (2005) or baseline only if censored before follow-up. Multivariable Cox proportional hazards regression models were used to estimate BC hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

Over a mean follow-up of 20 years, 3968 incident BC cases occurred. An increase of 1 standard deviation in the PD score was associated with an 8% lower BC risk, fully-adjusted model: HR1-SD 0.92, 95% CI; 0.89, 0.95. Compared to women with low adherence to the PD, women with high adherence had a 17% lower BC risk, HRQ5 vs Q1 0.83, 95% CI; 0.75, 0.92, Ptrend < 0.01. When considering BC subtypes, we observed the same pattern of association (Pheterogeneity > 0.10 for all).

CONCLUSIONS

High adherence to a PD characterised by fruit, vegetables, nuts, fish, and lean meat and limited in dairy, grains, legumes, refined sugar, and alcohol was associated with a lower BC risk. The lack of heterogeneity according to BC subtypes could indicate the involvement of non-hormonal mechanisms. The protocol is registered at clinicaltrials.gov as NCT03285230.

REGISTRY

The protocol is registered at clinicaltrials.gov as NCT03285230.

Dietary Inflammatory Index and risk of breast cancer: evidence from a prospective cohort of 67,879 women followed for 20 years in France

BACKGROUND

Inflammation is implicated in breast cancer development, and diet is one of the modifiable risk factors involved in the regulation of chronic inflammation. Previous studies on the association between breast cancer risk and Dietary Inflammatory Indexes (DII) derived from food frequency questionnaires and data on inflammatory potential of dietary components have reported inconsistent results.

OBJECTIVE

To investigate the association between the DII and the risk of breast cancer using data from a large population-based cohort study.

DESIGN

A total of 67,879 women from the E3N cohort were followed from 1993 to 2014. A total of 5686 breast cancer cases were diagnosed during the follow-up. The food frequency questionnaire administered at baseline in 1993 was used to calculate an adapted DII. Cox proportional hazard models using age as the time scale were used to estimate hazard ratios (HR) and 95% confidence intervals (CI). Spline regression was used to determine any dose-response relationship. We also evaluated effect modification by menopausal status, body mass index, smoking status and alcohol consumption.

RESULTS

The median DII score of the study population was slightly pro-inflammatory (DII = + 0.39); ranged from - 4.68 in the lowest quintile to + 4.29 in the highest quintile. The HR increased linearly with the DII (HR per 1SD = 1.04 [95% CI: 1.01, 1.07]), and reached 1.13 [95% CI: 1.04, 1.23] in the 5th quintile group as compared to the first. A positive linear dose-response relationship was also observed when modeling DII with spline functions. Slightly higher HRs were observed in non-smokers (HR _{for 1-SD increase} 1.06 [95% CI: 1.02, 1.10]; p trend = 0.001) and in low-alcohol consumers (≤ 1 glass/day) (HR _{for 1-SD increase} 1.05 [95% CI: 1.01, 1.08]; p trend = 0.002).

CONCLUSION

Our results suggest a positive association between DII and breast cancer risk. Consequently, the promotion of anti-inflammatory diet may contribute to breast cancer prevention.

Adapted dietary inflammatory index and differentiated thyroid carcinoma risk in two French population-based case-control studies

PURPOSE

Thyroid cancer is the most common endocrine cancer and its etiology is still not well understood. The aim of the present study was to assess the association between an adapted dietary inflammatory index and differentiated thyroid cancer (DTC) risk in two population-based case-control studies (CATHY and YOUNG-THYR) conducted in France.

METHODS

These studies included a total of 1321 DTC cases and 1502 controls, for which an adapted dietary inflammatory index (ADII) was computed based on food frequency questionnaires in each study separately. The association between ADII and thyroid cancer risk was assessed using logistic regression models controlling for potential confounders.

RESULTS

Higher ADII scores, corresponding to a higher pro-inflammatory potential of the diet, were associated with higher DTC risk (odds ratio (OR) for 1 standard deviation (SD) increase: 1.09, 95% confidence interval (CI): 1.01, 1.18, P: 0.03). Associations were stronger in analyses restricted to women (OR for 1-SD increase: 1.14, 95% CI 1.04, 1.25, P: 0.005), as well as in women with lower education level, current smoking, or high body mass index.

CONCLUSION

Our study suggests that a pro-inflammatory diet is associated with an increased risk of DTC, especially when combined with other inflammatory conditions such as tobacco smoking or overweight. Our findings will help better understand the role of diet-induced inflammation in DTC etiology.

A case-control study in France showing that a pro-inflammatory diet is associated with a higher risk of breast cancer

Dietary regimens promoting inflammatory conditions have been implicated in breast cancer development, but studies on the association between pro-inflammatory diet and breast cancer risk have reported inconsistent results. We investigated the association between the inflammatory potential of diet and breast cancer risk in a case-control study in France including 872 breast cancer cases and 966 population controls. All women completed a food frequency questionnaire that was used to compute a Dietary Inflammatory Index (DII) based on the inflammatory weight of 33 dietary components. The DII ranged from a median of - 3.22 in the lowest quartile (anti-inflammatory) to + 2.96 in the highest quartile (pro-inflammatory). The odds ratio contrasting quartile 4 to quartile 1 was 1.31 (95% CI 1.00, 1.73; p-trend = 0.02). Slightly higher odds ratios were observed in post-menopausal women, particularly those with body mass index > 25 kg/m2 (odds ratio 1.62; 95% CI 0.92, 2.83; p-trend = 0.02), and among ever smokers (odds ratio 1.71; 95% CI 1.11, 2.65; p-trend 0.01). The analyses by breast cancer subtype showed that the DII was associated with breast tumors that expressed either the estrogen (ER) or progesterone (PR) hormone receptors or the Human Epidermal Growth Factor Receptor-2 (HER2), but no association was seen for the triple negative breast tumor subtype. Our results add further evidence that a pro-inflammatory diet is associated with breast cancer risk with possible effect variation according to tumor subtype.

Dietary inflammatory index and type 2 diabetes risk in a prospective cohort of 70,991 women followed for 20 years: the mediating role of BMI

AIMS/HYPOTHESIS

Diet is one of the main lifestyle-related factors that can modulate the inflammatory process. Surprisingly the dietary inflammatory index (DII) has been little investigated in relation to type 2 diabetes, and the role of BMI in this relationship is not well established. We studied this association and the role of BMI in the inflammatory process in a large population-based observational study.

METHODS

A total of 70,991 women from the E3N (Etude Epidémiologique auprès de femmes de la Mutuelle Générale de l'Education Nationale) cohort study were followed for 20 years. Incident type 2 diabetes cases were identified using diabetes-specific questionnaires and drug reimbursement insurance databases, and 3292 incident cases were validated. The DII was derived from a validated food frequency questionnaire. Multivariable Cox regression models estimated HRs and 95% CIs between DII and incident type 2 diabetes. Interactions were tested between DII and BMI on incident type 2 diabetes and a mediation analysis of BMI was performed.

RESULTS

Higher DII scores, corresponding to a higher anti-inflammatory potential of the diet, were associated with a lower risk of type 2 diabetes. Compared with the 1st quintile group, women from the 2nd quintile group (HR 0.85 [95% CI 0.77, 0.94]) up to the 5th quintile group (HR 0.77 [95% CI 0.69, 0.85]) had a lower risk of type 2 diabetes before adjustment for BMI. There was an interaction between DII and BMI on type 2 diabetes risk (p_Interaction < 0.0001). The overall association was partly mediated by BMI (58%).

CONCLUSIONS/INTERPRETATION

Our findings suggest that a higher anti-inflammatory potential of the diet is associated with a lower risk of type 2 diabetes, and the association may be mediated by BMI. These results may improve our understanding of the mechanisms underlying the role of diet-related anti-inflammation in the pathogenesis of type 2 diabetes in women. Further studies are warranted to validate our results and evaluate whether the results are similar in men.