Vitamin B(6) may lower risk of colorectal cancer by preventing aberrations in one-carbon metabolism or by anti-inflammatory effects.
We prospectively evaluated the association between plasma levels of pyridoxal 5'-phosphate (PLP; the active form of vitamin B(6)) and risk of colorectal cancer in a nested case-control study within the Physicians' Health Study [Initiated in 1982 by Brigham and Women's Hospital and Harvard Medical School, Boston to track and test the health effects of diet, it is “one of the largest and longest-running observational cohort studies in America.”]
Among 14,916 men who provided blood specimens in 1982 to 1984, we identified 197 incident colorectal cancer cases through 2000 and individually matched them to 371 controls by age and smoking status.
Plasma PLP levels were positively correlated with cold cereal intake and plasma levels of folate and vitamin B(12) (age- and smoking-adjusted partial correction r = 0.28-0.48) and slightly inversely correlated with body mass index (r = -0.11) and plasma levels of homocysteine, C-reactive protein, tumor necrosis factor-alpha receptor 2, and interleukin-6 (r = -0.23 to -0.14).
With control for these factors and known risk factors for colorectal cancer, plasma PLP levels were significantly inversely associated with risk of colorectal cancer; compared with men in the lowest quartile, those with PLP in quartiles 2 to 4 had relative risks (95% confidence interval) of 0.92 (0.55-1.56), 0.42 (0.23-0.75), and 0.49 (0.26-0.92; P(trend) = 0.01), respectively. [Note: an RR of 1.0 would indicate no difference in average risk. An RR of 0.42 for example, indicates a 58% lower risk.]
In conclusion, vitamin B(6) may protect against colorectal cancer independent of other one-carbon metabolites and inflammatory biomarkers.
Source: Cancer epidemiology, Biomarkers, and Prevention, Apr 2009;18(4):1197-202. PMID: 19336555, by Lee JE, Li H, Giovannucci E, Lee IM, Selhub J, Stampfer M, Ma J. Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA. [E-mail: firstname.lastname@example.org]