Blood Levels of Long-Chain Polyunsaturated Fatty Acids, Aspirin, and the Risk of Colorectal Cancer
- Megan N. Hall1,2,
- Hannia Campos1,
- Haojie Li3,
- Howard D. Sesso4,
- Meir J. Stampfer1,2,3,4,
- Walter C. Willett1,2,3 and
- Jing Ma3
- Departments of 1Nutrition and 2Epidemiology, Harvard School of Public Health; 3Channing Laboratory and 4Division of Preventive Medicine, Department of Medicine, Harvard Medical School and Brigham and Women's Hospital, Boston, Massachusetts
- Requests for reprints:
Jing Ma, Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Room 336, Harvard Medical School, 181 Longwood Ave, Boston, MA 02115. Phone: 617-525-2708; Fax: 617-525-2008. E-mail: jing.ma{at}channing.harvard.edu
Abstract
Background: N-3 fatty acids may decrease risk of colorectal cancer by inhibiting the cyclooxygenase-2 enzyme and production of proinflammatory eicosanoids derived from arachidonic acid (20:4n-6). Aspirin also inhibits the cyclooxygenase-2 enzyme and may share with n-3 fatty acids a potential mechanism to decrease the risk of colorectal cancer.
Methods: We conducted a nested case-control analysis using blood samples collected from the Physicians' Health Study participants in 1982 to 1984. N-3 and n-6 fatty acid levels were measured using gas-liquid chromatography for 178 men who developed colorectal cancer through December 31, 1995 and 282 age- and smoking-matched controls. We used conditional logistic regression to examine associations. All statistical tests were two-sided.
Results: Total long-chain n-3 fatty acids were nonsignificantly inversely associated with colorectal cancer risk [relative risk (RR) for highest versus lowest quartile, 0.60; 95% confidence interval (95% CI), 0.32 to 1.11; Ptrend = 0.10], after adjustment for possible confounders. We observed potential interaction between randomized aspirin assignment and long-chain n-3 fatty acid levels (Pinteraction = 0.04). Among men not on aspirin, RRs (95% CI) for increasing quartiles of long-chain n-3 fatty acids were 1.00 (reference), 0.60 (0.28-1.28), 0.51 (0.22-1.17), and 0.34 (0.15-0.82), Ptrend = 0.006. For participants taking aspirin, there was no additional benefit of increasing n-3 fatty acid levels. The RR (95% CI) for the highest versus lowest quartile of n-6 fatty acids was 0.64 (0.35-1.17).
Conclusions: Blood levels of long-chain n-3 fatty acids were associated with decreased risk of colorectal cancer among men not using aspirin. N-6 fatty acids were nonsignificantly inversely associated with colorectal cancer risk. (Cancer Epidemiol Biomarkers Prev 2007;16(2):314–21)
Footnotes
-
↵3 Q. Sun, personal communication.
-
Grant support: R25 CA 098566, CA 34944, CA 40360, and CA 97193 from the National Cancer Institute, and grants HL 26490 and HL 34595 from the National Heart Lung, and Blood Institute, NIH, Bethesda, MD.
-
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
- Accepted November 14, 2006.
- Received April 28, 2006.
- Revision received November 1, 2006.
