We’ve all heard that eating a diet high in fiber is linked with lower risk of disease. But, there’s something that feels off about high-fiber toaster pastries or other foods like yogurt, which normally don’t contain fiber. New research suggests that adding highly-processed fiber to already processed foods may impact human health in a negative way, including increasing the risk for liver cancer. This assertion is based on research completed at Georgia State University and the University of Toledo (1).There’s plenty of proof that eating foods that are naturally high in fiber is good for our health. Fiber from the skins and flesh of plant-based foods (whole grains, fruits, vegetables, beans, nuts, and seeds) has been found to aid weight management and cholesterol and blood sugar reduction. It has also been linked to a reduced risk for certain types of cancer. Fiber even aids in feeding the microbiota (good bacteria) in our bowels, which keeps our immune systems humming (2). As health-conscious consumers recognize that their diets aren’t cutting the mustard as far as fiber goes, the food industry is enriching foods with refined soluble fibers like inulin. A recent US FDA ruling has allowed foods with supplemental fiber to be marketed as healthful. Serious concerns about the safety of these added fibers have come to light in this study.The initial research was undertaken to evaluate a diet enriched with refined inulin on obesity-associated risks in mice. Placed on a diet containing inulin to help reduce obesity risk, the mice began developing jaundice and after 6 months, many developed liver cancer.Dr. Matam Vijay-Kumar, the senior author of the study from the University of Toledo, found the results surprising, but continued to research the health impact of processed soluble fiber. Despite the study being conducted in mice, it has potential ramifications for human health, indicating against enriching processed foods with refined, fermentable fiber.According to Dr. Andrew Gewirtz, one of the study’s authors and professor at the Institute for Biomedical Sciences at Georgia State, the research suggests that adding purified fibers to processed foods does not have the same health benefits as eating fruits and vegetables that are naturally high in soluble fiber. In fact, it may cause serious, life-altering conditions like liver cancer in some people. He believes that the FDA rule change, which has encouraged marketing fiber-fortified food as healthful, is careless and should be better scrutinized.In this study, chicory root, a form of inulin that we normally don’t consume, was used. The fiber goes through an extraction and chemical process. Rodents that developed liver cancer in the study were found to have previous dysbiosis or altered intestinal microbiota. This was suggested to play a vital role in the development of liver cancer.This research suggests a need for further studies evaluating the effects of refined fiber, in particular on liver health.The authors concluded that their research identified refined soluble fiber, while normally beneficial to good health, as possibly harmful, leading to diseases like liver cancer. Fiber in general should not be seen as “bad,” as the research sheds light on fortified foods instead of natural foods and this type of fiber may be detrimental in some individuals with gut bacterial dysbiosis.If you’re concerned about which fibers may be added to your foods, the following fibers  are FDA-approved and considered safe...

1. Beta-glucan soluble fiber, also called oat bran fiber
2. Psyllium husk: a soluble fiber that may relieve constipation and help with diarrhea
3. Cellulose: a non-soluble fiber that helps you to feel full, so you eat less
4. Guar gum: a soluble fiber that is often used as a thickener in foods
5. Pectin: a water-soluble fiber often added to jams and jellies
6. Locust bean gum: also known as carob gum, a thickening agent found in sauces and cereals
7. Hydroxypropylmethylcellulose: a soluble fiber that is found in some gluten-free foods

References:

1. Vishal Singh, Beng San Yeoh, Benoit Chassaing, Xia Xiao, Piu Saha, Rodrigo Aguilera Olvera, John D. Lapek, Limin Zhang, Wei-Bei Wang, Sijie Hao, Michael D. Flythe, David J. Gonzalez, Patrice D. Cani, Jose R. Conejo-Garcia, Na Xiong, Mary J. Kennett, Bina Joe, Andrew D. Patterson, Andrew T. Gewirtz, Matam Vijay-Kumar. Dysregulated Microbial Fermentation of Soluble Fiber Induces Cholestatic Liver Cancer. Cell, 2018; 175 (3): 679 DOI: 10.1016/j.cell.2018.09.004Slavin, J. Fiber and prebiotics: Mechanisms and health benefits. Nutrients. 2013 Apr; 5(4): 1417–1435.
2. https://www.verywellfit.com/natural-vs-added-fiber-4155913

Submitted by Lisa Andrews, MEd, RD, LD