Processed Fiber May Increase Risk Of Liver Cancer

It can be hard to follow dietary recommendations, and dietary needs can be different for each person, meaning that diets need to be diverse and tailored to the individual needs and health risks of a person. 

But fiber is fiber, right? Nope. Fiber is a carb that helps provide certain health benefits with few calories. Whole food sources of dietary fiber are an important part of a healthy diet that can be a great aid in disease prevention. This kind of fiber occurs naturally in whole foods, and there are different types including insoluble and insoluble fiber. However, fermentable fiber is a type of fiber that gut bacteria can ferment and break down that is sometimes highly refined and added to processed foods such as convenience foods like snacks and cereals by their manufacturers. 

Liver cancer accounts for over 700,000 deaths around the world annually, according to the American Cancer Society, and it is projected to be the third deadliest cancer within this decade. This study suggests that foods containing fermentable fiber may not be a healthy choice for everyone, specifically those in certain subgroups and those who are at risk for liver cancer. It may be best to be cautious about diets that are high in fermentable fiber if you are at risk.

This study found the risk of developing liver cancer in mice with a specific congenital defect (portosystemic shunt which impacts blood flow and exchange between the liver and rest of the body) was substantial when on a diet that was enriched with fermentable fiber, these mice also had bile acid content in their blood related to the portosystemic shunts. Cholesterol is used by the liver to make bile acids which help the body to digest and absorb fat. 

Finding suggests that screening for bile acid levels may help to predict the risk of liver cancer, and it was theorized that a diet rich in fermentable fiber could have contributed to a suppressed immune system. 

According to the researchers, it was difficult to study portosystemic shunts in humans, but they were able to examine bile acid levels, looking at bile acid levels in men who developed liver cancer and matching them with controls. Bile acid levels were found to be double for those who developed liver cancer later in life, indicating the potential of using this screening to be helpful in the prediction of liver cancer. High fiber intake was associated with an increased risk of developing liver cancer among men with high bile acid levels by the researchers. 

“The findings are that in the setting of congenital portosystemic shunts in mice, fermented fiber-rich diets increase the chance of developing liver cancer. In humans, congenital portosystemic shunts are not common, but shunts develop in patients with cirrhosis. The findings in the study could help patients with liver disease and decrease their chances of developing liver cancer by diet modifications or other interventions,” said  Dr. Yiing Lin, Ph.D., a liver surgeon with Siteman Cancer Center at Washington University in St. Louis, not involved in the study.

“The greater our understanding of the biochemistry involved in the breakdown of dietary fiber and its impact on health such as liver cancer, the closer we get to developing new, effective treatments. In the current study, the work puts our finger on the molecular basis for the link between fiber and liver cancer risk. But it does need care in interpretation. Especially when trying to apply evidence from mice to humans,” noted Brian Power, RD, nutrition expert and registered dietician who was also not involved in the study.

“The effects of a modified diet in humans with liver disease will need to be confirmed. These are challenging studies since liver cancer develops in subsets of people with liver disease, and the effects of diet modifications have to be tracked over long periods of time and can be a challenge to control. However, these are important questions to address since metabolic syndrome and its association with liver cancer are significant problems in the U.S,” said Lin.