Researchers from Sweden have reported: “Vitamin B6 intake and blood PLP (pyridoxal phosphate, the active form of vitamin B6) levels were inversely associated with the risk of colorectal cancer in this meta-analysis.” The details of this study were published in the March 17, 2010 issue of the Journal of the American Medical Association.[1]

Vitamin B6 is a water-soluble vitamin. Pyridoxal phosphate is the active form and is a cofactor in amino acid metabolism. Pyridoxal phosphate is necessary for the enzymatic reaction governing the release of glucose from glycogen, in neurotransmitter synthesis, hemoglobin synthesis, and gene expression. B6 is metabolized in the liver.

Vitamin B6 is widely distributed in foods such as meats, whole grains, vegetables, and nuts. Cooking can destroy up to 50% of vitamin B6. Classic B6 deficiency is a skin disease; a dermatitis with ulceration, chelitis, conjunctivitis, and neurologic symptoms. Absolute deficiency of B6 is rare and is often associated with other B vitamin deficiencies. Deficiencies are most notable in the elderly and alcoholics. The best indicator of deficiency is plasma PLP level.

The current study looked at nine prospective studies evaluating the effect of vitamin B intake and PLP levels on the risk of developing colorectal cancer. They observed considerably variability in vitamin B6 intake but not in PLP levels. These authors reported that persons with the highest intake of vitamin B6 had a 10% lower risk of developing colorectal cancer compared with persons with the lowest intake. They observed a 48% reduced incidence of colorectal cancer in persons with the highest PLP levels compared with persons with the lowest levels. “The risk of colorectal cancer decreased by 49% for every 100-pmol/ml increase (approximately 2SDs) in blood PLP levels (RR, 0.51; 95% CI, 0.38-0.69).”

Comments: This study is provocative and suggests that adhering to a “healthy” diet with lots of fruits and vegetables should maximize PLP levels. Whether or not the average person would need supplementation is questionable, as vitamin supplementation studies—other than vitamin D—have been negative for cancer prevention.

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