The effect of B vitamins on the risk of colorectal cancer may depend on their dietary intakes.  A study in Nutrition and Cancer suggests that low methionine and high folate can help prevent colon cancer while high methionine and high folate may increase the risk of developing colon cancer.

K. Julie and colleagues conducted the study and found a U-shaped relationship between the risk of colon cancer and dietary intake of vitamin B6 and an inverse U shaped relationship between the risk of rectal cancer and the dietary intake of B12.

Specifically for colon cancer, a 37% reduction in the risk was associated with low methionine and high folate and a 37% increase in the risk was associated with high methionine and high folate.

Methinione is a sulfur containing amino acid found rich in foods such as eggs.  Methionine may also be available as a dietary supplement.  Folate or its acid folic acid is often added to processed foods to prevent birth defects.   High folate has been associated with cancer.

Early studies show B vitamins are involved in one-carbon metabolism, which is important for DNA replication, DNA repair and gene expression.   Recent research suggests folate and vitamin B6 intakes reduced risk of colorectal cancer.

The current study involved 14,645 men and 22,467 women who were followed up for 15 years on average during which 910 incident colorectal cancers were recorded.  Dietary intakes of vitamins were estimated using a food frequency questionnaire.

The study concluded "Our study suggests a U-shaped association between colon cancer risk and vitamin B6 intake and an inverse U-shaped association between rectal cancer risk and vitamin B12."

And it also suggests that adequate folate intake might prevent colon cancer in men and women with low methionine intake.

The best thing to do to prevent colorectal cancer may be have high intake of dietary fiber.  That is, eating a high amount of fiber-rich green vegetables, beans, and whole grains may help protect against colorectal cancer.  B vitamins except for b12 are found high in plant-derived foods. (David Liu, PHD)