In Reply: We agree with Dr Lu that blood PLP levels are not identical to dietary vitamin B6 intake. Blood PLP level is a more accurate and direct measure of PLP exposure. That is indeed one of the reasons why we chose to investigate blood PLP levels in relation to risk of colorectal cancer. As Lu points out, the conclusion in the Abstract could have been made more accurate by stating that blood PLP level but not vitamin B6 intake had a statistically significant inverse association with risk of colorectal cancer in this meta-analysis.
Larsson SC, Wolk A. Vitamin B6, Blood PLP Level, and Risk of Colorectal Cancer—Reply. JAMA. 2010;303(22):2251-2252. doi:10.1001/jama.2010.736