A diet poor in folic acid appears to enhance the risk of colorectal cancer in laboratory mice which suggested that a similar deficiency could also be linked to colon cancer in humans, according to a study by Canadian researchers.
Scientists at McGill University in a one-year study of 137 mice, saw that animals that were fed a diet low in folic acid had a greater likelihood of developing colorectal cancer than rodents which were given a fully balanced diet containing adequate folate.
Geneticist Rima Rozen, scientific director of the Montreal Children's Hospital and the study's lead investigator said, "We found tumours in the mice that were on the low-folate diet and no tumors in mice that were on the regular diet."
The researchers observed that one in four mice that were given low-folate diets developed intestinal tumors, with some of the animals developing more than one each, said researchers.
The findings of the study was published on Wednesday in the journal Cancer Research.
Rozen asserted that several human studies have revealed that low intake of folic acid, found in leafy green vegetables and citrus fruits, might be associated with an increased risk of colon cancer. However such studies cannot pinpoint with any accuracy what factor or factors definitely lead to a person developing a certain cancer.
The use of mice in the study allowed researchers to carefully control possible contributing factors including environment and diet, she said, bringing them closer to a direct cause and effect.
Rozen said "What folate does, or the mechanism we propose in this study, is that lack of folate damages your DNA."
Folic acid importance to health is a well established fact. It is needed to help cells retain the integrity of DNA during division. In addition it has been shown to help prevent certain types of heart disease, and women who do not consume sufficient folic acid during pregnancy are at a risk of producing offspring with neural tube defects like spina bifida.
Rozen however stressed that she's not suggesting people start loading up on folic acid but rather make sure that they get the recommended daily allowance of 400 micrograms by eating foods such as broccoli, spinach and orange juice, or by taking a multivitamin.
She said, "I want to make sure people understand the value of recommended daily allowances. I don't want people to go out and take pharmacologic doses of anything . . . In moderation, folate is important."
The researchers also tested mice with a genetic mutation that impairs the body's ability to metabolize folic acid. It was found that rodents with the mutation and also fed a low-folate diet had more than double the incidence of intestinal tumours.
"It's sort of a double whammy in the sense that it's not only the low dietary folate, but it's the combination," Rozen said, noting that 10 per cent of humans are believed to carry a similar genetic mutation.
According to Dr. Andy Smith, a colorectal cancer surgeon at Sunnybrook Health Sciences Centre in Toronto, the study is important because it appears to confirm the long-held suspicion that inadequate folic acid plays a role in tumor formation.
He said, "It really helps tease out the actual mechanisms." While the mechanism found in mice cannot be though to be exactly the same as in humans, Smith said, "I think in this case it really resonates because of the observations made so clearly in humans that low folate is associated with the development of tumors."
However, Smith said he operates on many people with colorectal cancer who have "beautiful diets."
He said, "Even if you have a healthy diet, you still ought to be talking to your physician about whether you should be having a test to screen for colorectal cancer" recommending that Canadians aged 50 or older should have a fecal occult blood test or a colonoscopy.
Smith said, "Because while your risk may be reduced, it's not eliminated. And people who live very healthy lives are still vulnerable to colorectal cancer."
It has been estimated that by the end of the year an estimated 20,000 Canadians will have been diagnosed with colorectal cancer and about 8,500 is expected to die of the disease in 2006, making it the second most deadly cancer after lung cancer.
Dr. Sharlene Gill, a medical oncologist at the B.C. Cancer Agency said, "This does support the idea that a balanced, healthy diet that does include an appropriate intake of fruits and vegetables may contribute to a lower incidence of cancer.