Statistics Canada and the Canadian Cancer Society reported that colorectal cancer is the country’s second leading cause of death. In the same year, the U.S. Statistics National Cancer Institute stated that there were 106,000 new cases of colon cancer, and 40,870 cases of rectal cancer in America. Deaths from both diseases were 49,920.
Meanwhile in Europe, the International Aging for Research on Cancer reported, that the most common forms of cancer in that continent were lung, colorectal, and breast cancers.
How Folate and Vitamin B6 Inhibits Colon Cancer Risk
Because of their roles in the maintenance of intracellular normal DNA synthesis and methylation (the addition of a methyl group to a substrate which alters the way genes are expressed), folate and vitamin B6 have been hypothesized to reduce colorectal cancer risk.
Folate participates in the regeneration of methionine which is converted to S-adenosylmethionine – a methyl donor for DNA methylation, while vitamin B6 suppresses cell proliferation, oxidative stress, nitric oxide synthesis, and angiogenesis.
Abnormal DNA methylation patterns are frequently noted in colorectal tumors with wide areas of hypomethylation along the genome, accompanied by regional “hypermethylation” at specific sites, especially areas rich in cytosine-guanine (called “CpG”) islands. Folate and vitamin B6 function as co-enzymes in the synthesis of purines and thymidylate for DNA. Low levels of these two vitamins may result in the misincorporation of uracil into DNA leading to chromosome breaks and disruption of DNA repair.
Human Studies About Folate and Vitamin B6 Protective Effects Against Colorectal Cancer
Thirteen studies have been conducted investigating the association between folate and vitamin B6 on colon cancer. Each investigation indicated an inverse relationship between the vitamins and the disease.
The most recent study was a meta-analysis conducted by Larsson et al. In their investigation, they confirmed that high vitamin B6 intake and serum levels of pyridoxal 5′- phosphate (PLP) – the active form of vitamin B6 – were inversely associated with the risk of colorectal cancer. Their research was published in the Journal of the American Medical Association.
In earlier research, Zhang and colleagues discovered that high intakes of folate and vitamin B6 may reduce the risk of colon cancer in women. In this study, 37,916 women aged 45 y and older who were free of cancer and cardiovascular risk were recruited. During an average of 10.1 follow-up years, 220 colorectal adenocarcinoma cases were documented. It was noted that women who were not taking supplements or had low dietary folate and vitamin B6 had significant higher risk of colorectal cancer; while those with the highest dietary intakes of the vitamins had the lowest colorectal cancer risk. Additional studies reported similar inverse associations between the vitamins and the carcinoma.
Chief Functions of Folate, Significant Sources, and RDA
Folate: folacin, or folic acid in its primary form tetrahydrofolate (THF) and dihydrofolate (DHF) are used in DNA synthesis and are thus important in new cell formation. Fortified grains, leafy green vegetables, legumes, seeds, and liver are excellent sources of folate. It is heat and oxygen-sensitive. The RDA for healthy adults is 400 micrograms per day. The maximum or Upper Tolerable Level for adults is 1000 mcg/day.
Chief Functions of Vitamin B6, Significant Sources, and RDA
Vitamin B6 occurs in three forms: pyridoxal, pyridoxine, and pyridoxamine. It is part of coenzymes PLP (pyridoxal phosphate) and PMP (pyridoxamine phosphate) used in amino acid and fatty acid metabolism. It helps to convert tryptophan to niacin and to serotonin, and helps to make red blood cells. Meats, fish, poultry, potatoes, legumes, non-citrus fruits, liver, and soy products are excellent sources of vitamin B6. The daily RDA for healthy adults is 1.3 mg/day. The maximum or Upper Tolerable Level for adults is 100 mg/day.