Two groups from INSERM and Institut Gustave Roussy collaborated to conduct an epidemiologic study on a cohort of French women members of the Mutuelle générale de l'Education nationale (E3N). The scientists showed that the risk of breast cancer was doubled in women having higher serum levels of trans fatty acids. The trans fatty acids studied are those from industrial sources (processed foods, processed bread, processed pastries, cakes, potato chips, pizza dough, etc.).
Unlike Asian countries, where the protective effect of omega-3 fatty acids from fish on breast cancer risk was clearly demonstrated, a protective effect against breast cancer was not found in this study.
These results are published in the American Journal of Epidemiology
The E3N cohort is the French part of EPIC, a large European study coordinated by the International Agency for Research on Cancer (IARC), and involving 500 000 Europeans in 10 countries.
The unhealthy effects of trans fatty acids on cardiovascular risk have been well established since the early 1990s, yet their impact on breast cancer risk remained to be elucidated. The teams of scientists from INSERM and Institut Gustave Roussy sought to evaluate the role of various types of fatty acids on breast cancer development, using blood samples collected between 1995 and 1998, amongst 25 000 of the 100 000 women followed up within the E3N study.
In order to assess the health effects of human diet, scientists assayed various biomarkers of diet in the blood, and particularly fatty acid levels. Data on 363 women diagnosed with breast cancer after blood sampling were analysed. Their serum fatty acid levels were then compared with those of breast cancer-free women controls. Two controls were matched to each breast cancer case, for a total of 702 women.
Near-doubling of risk
The analysis of trans and cis fatty acids showed that breast cancer risk increases with the increase in trans fatty acid level, reflecting processed food consumption. These results show that women with elevated serum levels of trans fatty acid have almost twice the risk of developing breast cancer, compared to women with the lowest levels. "At this stage, we can only recommend limiting the consumption of processed foods, the source of industrially-produced trans fatty acid. Particularly, industrial processes generating trans fatty acids (partially hydrogenated vegetable oils) still in use should be curbed, as this has been undertaken in Denmark for a few years. As far as regulations on labeling of processed products, the content in trans fatty acids should be clearly indicated", the report concluded.
Protective effect of omega-3 fatty acids for breast cancer not universal
Also, the authors of the study confirmed the results of other studies conducted in North American and European countries concerning the absence of association between omega-3 fatty acid serum levels, for which the main dietary source is the intake of fish, and risk of breast cancer. While a protective effect of omega-3 fatty acids on breast cancer risk was clearly demonstrated in Asian countries, where fish consumption is much higher than in Europe or in North America, this protective effect could not be measured in this highly-powered French study, probably due to considerably lower per-capita consumption of fish.
In industrialised countries, breast cancer is the most common cancer in women. According to the authors of the study, among the risk factors that may lend themselves to primary prevention, diet shows strong potential, as a single but consistent change in dietary habits could lower the risk of breast cancer, subject to clear identification of responsible nutrients. Among those, dietary lipids could play a major role. Further analysis from the EPIC study will therefore test the hypothesis of a role for trans fatty acids in carcinogenesis in a population with wide variations in the intake of those fatty acids, among other lipids.
THE E3N STUDY
E3N, an epidemiologic study conducted on women members of the MGEN (French National Education workers complementary medical insurance scheme) led by Dr Françoise Clavel-Cahpelon (INSERM-Gustave Roussy), is a prospective cohort study of about 100 000 volunteer French women born between 1925 and 1950, and followed up since 1990.
Data on their lifestyle factors (diet, hormonal treatments, etc.) and their health status were collected by self-administered questionnaire every other year since 1990. These data were complemented by biological measurements, obtained for 25 000 volunteers, from a blood specimen taken for later analysis (case-control studies nested within the cohort). E3N gives primary consideration to breast and colorectal cancers, due to their high incidence rates.
For more information:
V. Chajès; A. C.M. Thiébaut; M. Rotival; E. Gauthier ; V. Maillard; M.C. Boutron-Ruault; V. Joulin; G. M. Lenoir ; F. Clavel-Chapelon. Serum trans-monounsaturated fatty acids are associated with an increased risk of breast cancer in the E3N-EPIC Study. Am. J. Epidemiol. 2008 (DOI: 10.1093/aje/kwn069)
Unité mixte de recherche CNRS -IGR-Université Paris Sud FRE 2939 "Stabilité génétique et oncogenèse"
Tel : +33 (0) 142 115 414
Responsable de l'Etude E3N
Directrice de Recherche Inserm, Equipe ERI 20, Institut Gustave Roussy.
Tel : +33 (0) 142 114 148