Folates and cancer prevention
TORONTO, CANADA. Folates (derivatives of folic acid) play a key role in the synthesis, repair, and methylation of DNA. It is therefore not surprising that a deficiency in this essential B vitamin has been implicated in Alzheimer’s disease, atherosclerosis, heart attack, stroke, osteoporosis, depression, dementia, cleft lip and palate, hearing loss, Raynaud’s phenomenon, and of course, neural tube defects.
There is now also evidence that a folate deficiency may be involved in the development of certain cancers. Dr. Young-In Kim, MD of the University of Toronto presents an overview of the current knowledge regarding the role of folates in cancer prevention. Some 20 studies have been published regarding the association between colorectal cancer (cancer of the colon or rectum) and folate status. Collectively, these studies suggest that people with a high intake of folates can reduce their risk of developing colorectal cancer by about 40 per cent when compared to people with low intakes. A study involving almost 90,000 American female nurses concluded that nurses who had been supplementing with 400 micrograms/day or more of folic acid for 15 years or more had a 75 per cent reduction in the risk of colorectal cancer when compared to people who did not supplement. The evidence concerning folates and breast cancer is not quite as clear. Studies have shown that even moderate alcohol consumption increases the risk of breast cancer and that this risk can be counteracted by supplementing with folic acid. The jury is still out on whether folate supplementation reduces the risk among non-drinkers although one study did show that postmenopausal women could decrease their risk of developing breast cancer by supplementing with folic acid. Another study involving 300 premenopausal women found a 50 per cent lower risk among women whose intake exceeded 304 micrograms/day. Other studies, however, have failed to confirm this effect.
A major study involving over 29,000 male, Finnish smokers found that those who developed pancreatic cancer had a significantly lower blood serum level of folate than did those who did not. A baseline serum folate level above 4.45 ng/mL was associated with a 55 per cent risk reduction when compared to levels below 3.33 ng/mL. An Australian study found a 64 per cent difference in risk between men with the highest folate intake and those with the lowest intake.
Dr. Kim concludes that a moderate increase in folate intake can materially help reduce the risk of certain cancers, but cautions that people who already have cancer should not increase their folate intake as there is evidence that high folate levels may accelerate the growth of existing tumours.
Kim, Young-In. Folate and cancer prevention: a new medical application of folate beyond hyperhomocysteinemia and neural tube defects. Nutrition Reviews, Vol. 57, October 1999, pp. 314- 21