Not all fibres are created equal

The consumption of whole foods naturally rich in fibre confers an array of health benefits is pretty much a given. It is widely accepted that dietary fibre is important for digestive health, bowel regularity and feelings of satiety. It is thought that adequate fibre consumption can improve cholesterol and blood sugar levels and can assist in preventing some diseases such as diabetes, heart disease and bowel cancer.

The benefits of fibre are so recognised that the US Food and Drug Administration rules allow foods containing supplemented fibres to be marketed as health-promoting. The food industry has been enriching processed foods with highly refined soluble fibres, such as inulin, to benefit from the healthy fibre halo.

However, a new study by researchers at Georgia State University and the University of Toledo is raising serious concerns about the safety of adding refined fibre to processed foods.

The researchers set out to test the idea that a diet enriched with refined inulin might help combat obesity-associated complications in mice. While such an inulin-containing diet did stave off obesity, some of the mice started to develop jaundice. After six months, many of these mice developed liver cancer.

“Such a finding was really surprising,” said Dr Matam Vijay-Kumar of the University of Toledo and senior author of the study, “but at the same time we recognised their potential importance and accepted the challenge of exploring how processed dietary soluble fibre was inducing liver cancer.”

Although this study was performed in mice, it has potential implications for human health, particularly cautioning against enriching processed foods with highly refined, fermentable fibre.

“These findings indicate that enriching foods with purified fibres may not recapitulate the benefits of eating fruits and vegetables naturally rich in soluble fibre,” said Dr Andrew Gewirtz, professor at the Institute for Biomedical Sciences at Georgia State.

“Moreover, it may result in serious, life-threatening liver cancer in some individuals. Hence, we think the recent FDA rule change that has effectively encouraged marketing of fibre-fortified food as health-promoting is ill-conceived and should be reconsidered.”

“The inulin used in this study is coming from chicory root, not a food we would normally eat. In addition, during the extraction and processing of the fibre, it goes through a chemical process,” said Vishal Singh, a postdoctoral fellow from The University of Toledo and one of the lead researchers in the study.

Mice that developed liver cancer in this study had pre-existing dysbiosis, meaning an altered intestinal microbiota composition, which was found to play a central role in the promotion of liver cancer.

These findings highlight the need for more studies looking at the effects of purified diet consumption in humans, and especially on liver health.

“We importantly demonstrated that soluble fibre, while it generally beneficially impacts health, can also become detrimental, leading to diseases as severe as liver cancer,” said Dr Benoit Chassaing, assistant professor at the Neuroscience Institute at Georgia State. “However, we do not want to promote that fibre is bad. Rather, our research highlights that fortifying processed foods with fibre may not be safe to certain individuals with gut bacterial dysbiosis, in whom consumption of purified fibre may lead to liver cancer.”

These findings were published in the biological journal Cell.

Image credit: ©stock.adobe.com/au/marilyn barbone