Adherence to French dietary guidelines is associated with a reduced risk of mortality in the E3N French prospective cohort.

Background: Diet is a modifiable risk factor for non-communicable diseases which are the major causes of death worldwide. French dietary guidelines, updated in 2017, provide recommendations for a healthier diet. We aimed to study the association between adherence to these dietary guidelines and mortality in the E3N (Etude Epidémiologique auprès de femmes de l'Education Nationale) French cohort. A secondary objective was to investigate the role of dietary exposure to chemical contaminants in this association.

Methods: We studied 72 585 women of the E3N prospective cohort, which completed a food frequency questionnaire in 1993. We estimated adherence to French dietary guidelines using the simplified "Programme National Nutrition Santé-guidelines score 2" (sPNNS-GS2, range -20.4 to 12.6). We estimated the association between sPNNS-GS2 and all-cause or cause-specific mortality using Cox proportional hazard models. Causes of death were coded and validated by the French Epidemiology Center on Medical Causes of Death (Inserm-CépiDc).

Results: During follow-up (1993-2014), we identified 6 441 deaths. The mean sPNNS-GS2 was 3.8 (SD 3.0). In the fully adjusted model, we found a non-linear association between sPNNS-GS2 and all-cause, all-cancer, breast cancer and lung cancer mortality (p-values for the overall association < 0.001), with a diminution of the risk as sPNNS-GS2 increases up to its median or 65 percentile (depending on the outcome), and then a plateau (for all-cause and breast cancer mortality) or an inversion of the trend (for all-cancer and lung cancer mortality). Furthermore, we identified a linear inverse association with cardiovascular diseases mortality (HR [95%CI]: 0.86 [0.76; 0.97]), and no association with colorectal cancer mortality. We observed similar results when additionally adjusting on dietary exposure to chemical contaminants.

Conclusions: This study conducted in a large prospective cohort following more than 70 000 women for over 20 years suggested that higher adherence to French dietary guidelines was associated with a reduced risk of mortality from all-cause, cardiovascular diseases, all-cancer, breast cancer, and lung cancer, except for high values of adherence for lung cancer mortality. These results contribute to informing on the importance of following the French nutritional recommendations.