From the Guidelines
Low fiber intake is associated with a significantly higher risk of cancer, particularly colorectal cancer, compared to high fiber intake, with a 10-13% reduction in risk for each 10g/d increment of total dietary fiber consumed. The evidence suggests that consuming high-fiber foods such as whole grains, fruits, vegetables, and legumes can reduce the risk of cancer, with the strongest protective effect observed for colorectal cancer 1. The mechanisms by which fiber exerts its protective effects include speeding transit time through the colon, reducing exposure to potential carcinogens, and producing beneficial short-chain fatty acids during fermentation that may inhibit cancer cell growth.
Some key points to consider when increasing fiber intake include:
- Consuming at least 25-30 grams of fiber daily from whole foods, rather than relying on supplements 1
- Gradually adding whole foods to the diet to allow the gut microbiome to adjust
- Drinking plenty of water to help fiber move through the digestive system effectively
- Choosing whole grain rice, bread, pasta, and cereals, and limiting consumption of refined carbohydrates 1
- Eating a variety of healthy foods, with an emphasis on plant sources, and limiting consumption of red and processed meats 1
The most recent and highest quality study on this topic, published in 2017, found that for each 10g/d increment of total dietary fiber consumed, the risk of colorectal cancer was decreased by 13% 1. This study provides strong evidence for the protective effects of fiber intake on cancer risk, and supports the recommendation to consume a high-fiber diet for cancer prevention. Therefore, increasing fiber intake to at least 25-30 grams per day from whole foods is recommended to reduce the risk of cancer, particularly colorectal cancer.
From the Research
Difference in Cancer Risk between Low and High Fibre Intake
The difference in cancer risk between low and high fibre intake can be understood by examining the relationship between dietary fibre consumption and the incidence of various types of cancer.
- Studies have shown that high fibre intake is associated with a reduced risk of several types of cancer, including colorectal, esophageal, gastric, breast, and ovarian cancers 2.
- A combined analysis of 13 case-control studies found that risk of colorectal cancer decreased as fibre intake increased, with a relative risk of 0.53 for the highest quintile of intake compared to the lowest quintile 3.
- A systematic review and meta-analysis found that dietary fibre intake had a protective role in reducing the risk of colon cancer, with a relative risk of 0.74 for the highest versus lowest consumption 4.
- An ecological analysis of the Seven Countries Study found that fibre intake was inversely associated with colorectal-cancer mortality, with a 33% lower risk for every 10g increase in daily fibre intake 5.
Comparison of Low and High Fibre Intake
Comparing low and high fibre intake, the evidence suggests that:
- Low fibre intake is associated with a higher risk of certain types of cancer, particularly colorectal cancer 3, 4, 5.
- High fibre intake is associated with a reduced risk of cancer, with a probable level of evidence for several types of cancer 2.
- The difference in cancer risk between low and high fibre intake can be substantial, with estimates suggesting that increasing fibre intake by 13g per day could reduce the risk of colorectal cancer by 31% 3.
Key Findings
Key findings from the studies include:
- Dietary fibre intake is inversely associated with the risk of colorectal cancer 3, 4, 5.
- High fibre intake is associated with a reduced risk of several types of cancer, including esophageal, gastric, and breast cancers 2.
- The protective effects of dietary fibre on cancer risk may vary depending on the type of cancer and the population being studied 2, 3, 4, 5.