Folic Acid Fights Off Colon Cancer

THURSDAY, March 14, 2002 (HealthDayNews) -- A daily multivitamin containing just 400 micrograms of folic acid may be all that's needed for women with a family history of colorectal cancer to dramatically cut their chances of developing the disease.

That's the key finding of a new study of 88,000 women, which appears in today's issue of the journal Cancer Epidemiology, Biomarkers and Prevention.

"The preventive effects were also seen in women who did not have a family history of colorectal cancer, but for those who did have a first-degree relative with this disease, the effects were truly dramatic," says lead author Dr. Charles S. Fuchs, a medical oncologist at Harvard's Dana Farber Cancer Institute, where some of the research took place.

Studies show the risk of colorectal cancer in men and women is about 6 percent. However, add in a close relative with the disease -- a parent or sibling -- and that risk doubles at minimum. The latest government statistics show colorectal cancer remains the second-leading cause of cancer death in the United States. The department of Health and Human Services (HHS) estimates that 90 million Americans are at risk for developing this disease, with men and women equally affected. This year, an estimated 148,300 people will be diagnosed with colorectal cancer, resulting in some 56,600 deaths.

The Harvard study used information from the Nurses Health Study -- a project begun by Brigham and Women's Hospital in 1976 to track the health of 121,700 women for at least 25 years. At the start of the study, the women filled out extensive dietary and lifestyle questionnaires, along with details of their personal and family health histories, all of which has been updated on a regular basis.

For this study, researchers relied on data from 88,000 women, 11,808 of whom had reported a family history of colorectal cancer by 1992.

Between 1976 and 1992, 535 cases of colorectal cancer were confirmed in the study group. Those who had a family history of colorectal cancer were twice as likely to develop the disease when compared with those who had no family history of this illness.

"There was no question that there was a genetic component, but since not everyone who has the genetic connection gets colorectal cancer, we suspected there was also an environmental factor affecting the risk," Fuchs says.

Based on previous analysis, he believed that factor was the nutrient folate, also known as folic acid. Thus, researchers divided the women into four groups, based on their reported total daily intake of folic acid, including food and vitamin supplements: under 200 micrograms; 201 to 300 micrograms; 301 to 400 micrograms; and over 400 micrograms.

A special study design let researchers factor out the benefits of folic acid from other nutrients in the multivitamin, or even other components found in foods high in folic acid. In addition, because the amino acid methionine, as well as alcohol consumption, were also thought to affect colorectal cancer risks, researchers formed subgroups of women to analyze those factors.

Women who took multivitamins containing 400 micrograms or more of folic acid daily reduced their inherited risk of colorectal cancer by nearly half -- restoring their chance of getting this disease to that of the general population.

Further, although results were seen within the first year of use, the folic acid protection increased as time went on. Those women who took the supplements at least five years experienced the most dramatic risk reduction: Their chance of getting colorectal cancer was also lowered to that of the general population, putting them on equal footing with women who had no family history of the disease.

While increased methionine intake also appeared to reduce cancer risks, that drop was not any greater than seen with folic acid, nor were risks further decreased when both nutrients were combined. And, since methionine was also found to increase levels of homocystine, a factor linked to heart disease, it was dismissed as a candidate for reducing colorectal cancer risks.

While reducing alcohol intake didn't appear to decrease risks, increasing to more than two drinks a day more than doubled the chances of developing colorectal cancer in women at high risk.

Doctors are calling the new study important, and say patients at risk for colorectal cancer should take the advice about folic acid to heart.

"I think the study was well done, and its results mesh with previous research showing nutrients may make an important difference in reducing risks of colorectal cancer," says Dr. Sidney Winawer, a gastroenterologist at Memorial Sloan-Kettering Cancer Center, where earlier research showed calcium was also beneficial in reducing colorectal cancer risks.

Although he suspects similar results could be obtained by eating foods high in folic acid -- like enriched grains and some vegetables -- Winawer says he recommends folic acid supplements.

"Most people don't eat a good diet, so it's very difficult to get this much folic acid from foods," he says.

For gastroenterologist Dr. Mark Pochapin, the finding is key: "Taking folic acid won't hurt you, and as this study shows, it may offer you important protection. For those at increased risk for colorectal cancer, it's an important way to take control of your health."

However, he adds, "a vitamin pill cannot replace the importance of a colorectal cancer screening, particularly if you do have a family history of this disease."

Fuchs agrees: "Our study showed that folic acid can modify risks, but not make them disappear. The average person still has a 6 percent chance of developing colorectal cancer, so regular screening remains an essential prevention tool."

Colorectal screening is considered so important that yesterday HHS Secretary Tommy G. Thompson urged all Americans over age 50 to talk to their doctor about one or more of the following colorectal cancer screening tests: