Adding highly refined fiber to processed foods could have negative effects on human health, such as promoting liver cancer, according to a new study by researchers at Georgia State University and the University of Toledo.
Accumulating evidence demonstrates consumption of whole foods naturally rich in fiber confers an array of health benefits.
This, combined with an appreciation by many health-conscious consumers that their diets are lacking in such fibers, has led to the food industry enriching foods with highly refined soluble fibers, such as inulin.
Recently, changes in U.S. Food and Drug Administration rules allow foods containing supplemented fibers to be marketed as health-promoting.
This study raises serious concerns about the safety of adding refined fiber 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.
Inulins are a group of naturally occurring polysaccharides produced by many types of plants,industrially most often extracted from chicory.
The inulins belong to a class of dietary fibers known as fructans. Inulin is used by some plants as a means of storing energy and is typically found in roots or rhizomes.
Most plants that synthesize and store inulin do not store other forms of carbohydrate such as starch. In the United States in 2018, the Food and Drug Administration approved inulin as a dietary fiber ingredient used to improve the nutritional value of manufactured food products.
Using inulin to measure kidney function is the “gold standard” for comparison with other means of estimating creatinine clearance.
Inulin and its analog sinistrin are used to help measure kidney function by determining the glomerular filtration rate (GFR), which is the volume of fluid filtered from the renal (kidney) glomerular capillaries into the Bowman’s capsule per unit time.
Inulin is of particular use as it is not secreted or reabsorbed in any appreciable amount at the nephron, allowing GFR to be calculated. However, due to clinical limitations, inulin and sinistrin, although characterised by better handling features, are rarely used for this purpose and creatinine values are the standard for determining an approximate GFR.
Inulin enhances the growth and activities of bacteria or inhibits growth or activities of certain pathogenic bacteria.
A 2017 systematic review of clinical trial results showed that dietary supplementation with inulin reduced biomarkers of metabolic syndrome.
Diet and side effects
The side effects of inulin dietary fiber diet, which may occur in sensitive persons, are:
- Intestinal discomfort, including flatulence, bloating, stomach noises, belching, and cramping
- Anaphylactic allergic reaction (rare) – inulin is used for GFR testing, and in some isolated cases has resulted in an allergic reaction, possibly linked to a food allergy response.
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 recognized their potential importance and accepted the challenge of exploring how processed dietary soluble fiber 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 fiber.
“These findings indicate that enriching foods with purified fibers may not recapitulate the benefits of eating fruits and vegetables naturally rich in soluble fiber,” said Dr. Andrew Gewirtz, professor in the Institute for Biomedical Sciences at Georgia State and one of the study’s authors.
“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 fiber-fortified food as health-promoting is ill-conceived and should be reconsidered.”
These findings were published in the Oct. 18 issue of Cell, one of the world’s leading biological journals.
“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 fiber, 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 preexisting 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 fiber, while it generally beneficially impacts health, can also become detrimental, leading to diseases as severe as liver cancer,” said Dr. Benoit Chassaing, assistant professor in the Neuroscience Institute at Georgia State.
“However, we do not want to promote that fiber is bad.
Rather, our research highlights that fortifying processed foods with fiber may not be safe to certain individuals with gut bacterial dysbiosis, in whom consumption of purified fiber may lead to liver cancer.”
More information: Vishal Singh et al. Dysregulated Microbial Fermentation of Soluble Fiber Induces Cholestatic Liver Cancer, Cell (2018). DOI: 10.1016/j.cell.2018.09.004
Journal reference: Cell search and more info website
Provided by: Georgia State University