A new study published on bmj.com demonstrates that eating high- fiber diet, particularly cereal and whole grains, is linked to a reduced risk of colorectal cancer. Worldwide, colorectal cancer is the third most common cancer, with 1.2 million new cases diagnosed every year.

Although it is known that eating dietary fiber and whole grains helps to protect against cardiovascular disease, its link to colorectal cancer risk is less apparent. Researchers have toyed with the idea that the risk of colorectal cancer could be reduced through dietary fiber for nearly 40 years now, yet studies attempting to explain the link have so far only produced inconsistent results.

As part of the World Cancer Research Fund/American Institute for Cancer Research’s Continuous Update Project (CUP), a team of UK and Dutch researchers decided to examine the link between intake of dietary fiber and whole grains and risk of colorectal cancer.

Findings of the new study provide further support for public health recommendations to increase fiber intake, in particular cereal fiber and whole grains, such as breads, cereals, oatmeal, brown rice and porridge to help prevent colorectal cancer. The authors stress however, that further studies are needed to clarify outcomes for different fiber types and sub-sites within the colorectum, and in populations with different lifestyles and dietary characteristics.

The researchers evaluated results of 25 prospective studies with nearly two million participants, accounting for study design and quality to minimize bias. The findings demonstrated a clear gradient in risk linked to the amount of dietary fiber intake, despite of the overall risk reduction of colorectal cancer being small.

The found that each 10 g/day increase in intake of total dietary fiber and cereal fiber was linked to a 10% reduction in risk of colorectal cancer compared with the lowest levels of fiber intake. By adding three servings (90 g/day) of whole grains the linked risk of colorectal cancer was lowered by 20%. The study showed no substantial evidence for a link between fruit or vegetable fiber and the risk of colorectal cancer, although according to the researchers an earlier analysis showed a reduction in risk with high intake of fruit and vegetables, suggesting the potential role of components other than fiber in fruits and vegetables in explaining this result. In addition researchers discovered that increasing the intake of dietary fiber and whole grains could also reduce the risk of cardiovascular disease, overweight, type 2 diabetes, obesity, and perhaps overall mortality. Therefore increasing fiber intake and replacing refined grains with whole grains provides several health benefits.

The authors suggest that further studies should report more detailed results to be included in future analyses and conclude: ”In summary, our meta-analysis suggests that a high intake of dietary fiber, particularly from cereal and whole grains, is associated with a reduced risk of colorectal cancer.”

Professor Anne Tjønneland from the Danish Cancer Society says in an accompanying editorial that this analysis supports current evidence of the many health effects of whole grains. She supports the author’s view that research is still needed to explain details of the biological mechanisms responsible for the beneficial effects of these foods and to investigate barriers to increasing the intake of wholegrain products.

Written by: Petra Rattue