Abstract Background Dietary trans fatty acids (TFAs) are either natural (from ruminant sources) or generated through industrial processes by partial hydrogenation of vegetable oils. Extended evidence demonstrated their role as cardiovascular risk factors. In contrast, their involvement in cancer etiology is suspected, but epidemiological evidence remains limited. Objectives Our objective was to investigate associations between TFA intake of different types (total, rumninant [rTFAs], industrial [iTFAs], and corresponding specific isomers) and the risk of cancer (overall and main cancer sites) in the NutriNet-Santé prospective cohort (2009-2020). Methods Overall, 104,909 participants were included. Usual TFA intake was estimated from validated repeated 24-h dietary records matched with detailed composition table. Associations between sex-specific quartiles of TFA intake and cancer risk were assessed using multi-adjusted Cox proportional hazard models. Results A total of 3,374 incident cancer cases occured during follow-up (among which 982 breast and 405 prostate cancers). Dietary intake of total TFAs was associated with higher prostate cancer risk (HRfor quartile 4 versus 1: 1.27, 1.11-1.77 Ptrend=0.005). rTFAs were associated with increased overall cancer risk (1.16, 1.02-1.32 Ptrend=0.07), in particular the conjugated linoleic acid isomers (CLA) (1.19, 1.04-1.36 Ptrend=0.04). These associations were specifically observed for breast cancer (rTFAs: 1.35, 1.06-1.72 Ptrend=0.01; CLA: 1.29, 1.00-1.66 Ptrend=0.048), in particular before menopause (rTFAs: 1.68, 1.06-2.67 Ptrend=0.02; CLA: 2.013, 1.25-3.23 Ptrend=0.003). Several iTFAs were associated with overall (1.18, 1.06-1.31 Ptrend=0.02 for transdocosenoic acid), breast (isomer 18:2t: 1.30, 1.06-1.58 Ptrend=0.01; hexadecenoic acid: 1.28, 1.05-1.56 Ptrend=0.02) and prostate (transdocosenoic acid: 1.52, 1.09-2.12 Ptrend=0.07) cancer risks. Conclusion In this large prospective study, several types of TFAs were associated with increased overall, breast and prostate cancer risks. Although further studies are needed to better understand underlying mechanisms, these results support the WHO's goal of achieving industrially produced TFAs elimination from food supplies. Meanwhile, the consumption of food products containing partially-hydrogenated oils should be avoided. Citation Format: Gaëlle Wendeu-Foyet, Véronique Chajes, Inge Huybrechts, Jean-Marie Bard, Charlotte Debras, Eloi Chazelas, Bernard Srour, Laurent Zelek, Chantal Julia, Emmanuelle Kesse-Guyot, Cédric Agaësse, Nathalie Druesne-Pecollo, Pilar Galan, Serge Hercberg, Mélanie Deschasaux-Tanguy, Mathilde Touvier. Industrial and ruminant trans fatty acid intakes and cancer risk: Results from the NutriNet-Santé cohort [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-12-35.
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