B vitamins may help to reduce colorectal cancer risk

According to a new study increased intakes of vitamin B2 and B6 are associated with a 20% reduction in the risk of colorectal cancer.

In the observational study, the potential association between B vitamin intakes and cases of colorectal cancer (CRC) was investigated in 88,045 postmenopausal US women for up to 16 years (1). The study results showed that participants with the highest average intakes of vitamin B2 (over 3.97 milligrams of riboflavin per day) had a 20% lower risk of CRC, compared to women with the lowest average intakes (less than 1.8 mg per day). In addition, women with the highest average intakes of vitamin B6 (over 3.88 mg per day) had a 20% lowerCRC risk, compared to women with the lowest average intakes (less than 1.52 mg per day). These associations were particularly strong among women who consumed alcohol infrequently (less than 13 grams of alcohol per week). Dietary, supplemental, and total folate intake were not associated with overall CRC risk. However, the results indicated that women who were exposed to the initial period of the mandatory folic acid fortification program (introduced in the US in 1998) for between three and nine years may have had a transient increase in CRC risk.

The researchers concluded that increased intakes of the vitamins B2 and B6 may support colorectal health as a suboptimal status of the vitamins can lead to the accumulation of homocysteine, which has been linked to elevatedCRC risk. The scientists noted that an explanation for the observed transient increased CRC risk is that in the early phase after initiation of food fortification with folic acid, total folate content of several forti-fied foods initially exceeded the amount specified by federal regulations (2). Mean folate content was repor-ted to have been reduced early after the fortification program had stared between the period of 2000 to 2003, e.g., in cereal-grain products (3). An earlier observational study with 525,488 men and women (re-cruited in a similar time frame and age range) indicated that increased intakes of total, dietary folate and supplemental folic acid may reduce CRC risk (4).

The finding that higher B vitamin intakes were associated with reduced CRC incidence particularly in alcohol drinkers is plausible, the researchers added, because alcohol disturbs folate absorption and metabolism. Therefore, drinkers have a higher folate requirement, and reduced CRC risks are more likely to be observed among those with high folate intake. However, moderate to heavy amounts of alcohol intake could complete-ly nullify the beneficial association of folate intake with CRC risk.

1. Zschäbitz S. et al. B vitamin intakes and incidence of colorectal cancer: results from the Women’s Health Initiative Observational Study cohort. Am J Clin Nutr. Published online January 2013.
2. Rader J. I. et al. Total folate in enriched cereal-grain products in the United States following fortification. Food Chem. 2000; 70:275–289.
3. Johnston K. E. and Tamura T. Folate content in commercial white and whole wheat sandwich breads.
   J Agric Food Chem. 2004; 52:6338–6340.
4. Gibson T. M. et al. Pre- and postfortification intake of folate and risk of colorectal cancer in a large prospective cohort study in the United States. Am J Clin Nutr. 2011; 94:1053–1062.