The study “The Interaction between Dietary Fiber and Fat and Risk of Colorectal Cancer in the Women’s Health Initiative” by Navarro et al. explored possible associations between fiber (soluble, pectins, insoluble) and fatty acids (omega-3, DHA+EPA, and omega-6) and the risk of colorectal cancer (CRC).
Researchers extrapolated data from the women’s health initiative (WHI), a large prospective study aimed at examining major chronic diseases in postmenopausal women (50-79 years old). CRC diagnoses were updated every year from initiation (1993-1998) until 2010 with a mean follow-up of 11.7 years. Dietary intakes were reported at baseline and assessed using a food frequency questionnaire (FFQ). Intakes of fiber and fat were then divided into quintiles for comparison and all statistical models were adjusted for CRC risk factors including: age, family history of CRC, red and processed meat consumption, body mass index, leisure physical activity, smoking, alcohol use, current use of non-steroidal anti-inflammatory drugs, folate, calcium, total energy intake, history of screening for colonoscopy, education level, and use of menopausal hormone.
Researchers noted the following results:
- Of the 134,017 women included in the study, 1,952 developed CRC.
- Women with CRC were less likely to have ever used hormone therapy and consumed less calcium.
- Total soluble and insoluble fiber intakes were not associated with significant changes in CRC risk.
- Associations of total fat, omega-6 PUFA, omega-3 PUFA, and EPA+DHA with CRC risk were null.
- The interaction between DHA+EPA and soluble fiber was statistically significant with a significant decreased risk of CRC with increasing DHA+EPA intake among those with the lowest quintile of soluble fiber intake.
Researchers conclude that the results “do not support the results obtained in preclinical studies demonstrating that combinations of higher fiber and fat subtypes are associated with reduced risk of CRC.” However, it should be noted that the dietary intakes of fiber were low overall, where only a portion of the participants in the highest quintile achieving the recommended daily intake of 21g/day. Similarly, intakes of omega-3 PUFA and EPA+DHA were substantially lower than levels used in experimental diets.