According to a new study of 500,000 middle-aged adults, people whose diets contain plenty of folate have a lower risk of colon and rectal cancers.
In addition, the study did not find any extra cancer-related danger at very high levels of folate -- as some researchers have worried based on previous study findings.
In the late 1990s, the U.S. and Canadian governments began requiring that folic acid (a synthetic form of folate) be added to white flour, white pasta and corn meal in order to prevent certain birth defects that had been linked to low folate levels in pregnant women.
While previous studies have generally suggested that a diet rich in folate decreases the risk of colorectal cancer as well, most of those were done before fortification started. To see if the government mandate affected that link, the current study used data from a diet survey started in 1995.
At the start of the study, participants filled out a questionnaire about their normal eating habits and any supplements they took regularly. From that, the researchers were able to calculate how much folate they got on a typical day before and after fortification started.
After 10 years of follow up, people who consumed the highest amount of folate each day (at least 900 micrograms including fortified foods) were 30% less likely to get colorectal cancer than those who got less than 200 micrograms each day. That was after taking into account weight, smoking, physical activity, and certain other aspects of diet.
The recommended daily allowance for folate is 400 micrograms for most adults and 600 micrograms for pregnant women. Excellent sources of folate include cooked lentils and beans, edamame (young green soybeans), cooked spinach, broccoli, asparagus, avocado and orange juice.
As a result of fortification, the average person's folate intake through foods increased by about 100 micrograms per day.
The study did not find any increase in cancer rates at folate levels far above that recommended daily allowance. Concern over the possibility that too much folate could raise cancer risk had mostly come from studies in animals..
Those studies suggested that in healthy cells, folate or folic acid helps ensure DNA replicates and cells are grow properly. But once cells are pre-cancerous, giving extra folic acid can increase the progression of cancer cells.
In other words, it's possible that if someone already had cell changes that are precursors of colorectal cancer, too much folate could make the cancer grow faster.
The current findings suggest that fortifying grains with folate did not seem to lead to a spike in colorectal cancers. However, there's still a concern that people taking really high levels of folic acid (in supplements) may be detrimental.
To be safe, people who do have colon cancer should not take extra folic acid.
The study was published in the American Journal of Clinical Nutrition.
All research on this web site is the property of Leslie Beck Nutrition Consulting Inc. and is protected by copyright. Keep in mind that research on these matters continues daily and is subject to change. The information presented is not intended as a substitute for medical treatment. It is intended to provide ongoing support of your healthy lifestyle practices.