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Vitamin supplements such as folic acid haven't been shown to prevent cancer.

Fortifying with folate - an open debate

by Lyndsey Gilpin
Jan 29, 2013

Most people accept the benefits of folic acid for pregnant women to reduce the risk of birth defects.

But use of the supplement, especially by men and women at risk or in treatment for cancer, shows no impact good or bad, according to Oxford researchers. 

High-dose folic acid supplements, or fortification, had no significant effect on site-specific cancers or overall cancer risks, according to Oxford researchers in a study published last week in the medical journal, Lancet.

“The results provided reassurance of the safety of folic acid for site-specific cancer report, but we adopted a cautious tone,” said Dr. Robert Clarke, reader of epidemiology and public medicine at the University of Oxford. “We can’t prove something is negative but we can report findings on the debate that has been around.”

The research, which took about 10 years, follows the release of two individual 2007 reports indicating a 69 percent increase in risk of cancer after seven years of folic acid therapy, according to Clarke.

The Lancet study looked at 18 different cancer sites, specifically focusing on colorectal cancer. About 50,000 participants, two-thirds of which were men, participated in 13 trials over five years. They were given a range of 0.5 to 5 milligrams of folic acid in most cases. One trial used 40 milligrams a day.

In the randomized study, participants took daily supplements of folic acid for up to five years, or the end of 2010. Some were taken in combination with other B vitamins. They were no more likely to develop cancer than those who took placebo. About 8 percent of new cases of cancer were reported in the folic acid group, while just over 7 percent were reported in the placebo group.

Nationally, one in two men and one in three women have a lifetime risk of developing cancer, according to the American Cancer Society.

“This [study] is novel in the number of people and it allowed the investigation of multiple cancers,” Clarke said. “It was much more reliable data than the individual trials that previously addressed this issue.”

Folic acid supplements are part of a holistic approach to wellness, do not offer as many benefits when taken alone, according to Dr. Holly Furlong, a chiropractic doctor, at the Chicago Institute of Natural Health.

She said she offers a B vitamin and folic acid supplementation when patients complain of extreme fatigue and have low levels of the vitamins in their blood.

“It depends on the diet the patient has,” Furlong said. “It’s optimal to get it from food, but it cooks off. Sometimes they can’t get enough with food.”

High dose vitamin supplements are common in patients undergoing cancer treatment, specifically chemotherapy, according to Furlong. Folic acid is also taken by some patients hoping to prevent cancer.

Preclinical work suggests that folate may have anticancer properties, said Dr. Virginia Kaklamani, an oncologist at Northwestern Memorial Hospital and co-director of the Cancer Genetics Program at Lurie Comprehensive Cancer Center.

However, she doesn’t recommend supplements as long as the individual consumes a well-balanced diet.

“No supplement has been shown to help prevent cancer,” she said. “Most studies on vitamins and minerals don’t show any reduction in cancer risk.”