Intake of trans fatty acids from partially hydrogenated vegetable and fish oils and ruminant fat in relation to cancer risk.

Intake of trans fatty acids (TFA) may influence systemic inflammation, insulin resistance and adiposity, but whether TFA intake influences cancer risk is insufficiently studied. We examined the association between TFA intake from partially hydrogenated vegetable oils (PHVO-TFA), partially hydrogenated fish oils (PHFO-TFA), and ruminant fat (rTFA) and cancer risk in the Norwegian counties study, a large cohort study with a participation rate >80%. TFA intake was assessed three times in 1974-1988 by questionnaire. A total of 77,568 men and women were followed up through 2007, during which time 12,004 cancer cases occurred. Hazard ratios (HRs) and confidence intervals (CIs) were estimated with Cox regression for cancer sites with ≥150 cases during follow-up. Significantly increased or decreased risks were found when comparing the highest and lowest intake categories (HRs, 95% CIs) for PHVO-TFA and pancreatic cancer in men (0.52, 0.31-0.87) and non-Hodgkin lymphoma (NHL) in both genders (0.70, 0.50-0.98); PHFO-TFA and rectal cancer (1.43, 1.09-1.88), prostate cancer (0.82, 0.69-0.96), and multiple myeloma (2.02, 1.24-3.28); and rTFA and all cancers (1.09, 1.02-1.16), cancer of the mouth/pharynx (1.59, 1.08-2.35), NHL (1.47, 1.06-2.04) and multiple myeloma (0.45, 0.24-0.84). Furthermore, positive trends were found for PHFO-TFA and stomach cancer (p(trend) = 0.01) and rTFA and postmenopausal breast cancer (p(trend) = 0.03). Inverse trends were found for PHVO-TFA and all cancers (p(trend) = 0.006) and cancer of the central nervous system in women (p(trend) = 0.005). PHFO-TFA, but not PHVO-TFA, seemed to increase cancer risk. The increased risks observed for rTFA may be linked to saturated fat.