Natural Fiber is Healthy, but What About Synthetic Fiber in Foods?

Is synthetic fiber in processed foods bad for you?

You enjoy fiber in abundance when you eat whole, plant-based foods, including fruits, vegetables, legumes, whole grains, and nuts. Unfortunately, most people don’t get their 5+ servings of plant-based foods daily. Instead, most get about half that amount – but why? These folks reach for processed and packaged foods. In their natural state, most processed foods are low in fiber.

But, knowing that Americans don’t get enough dietary fiber, processed foods manufacturers have taken to adding synthetic fiber to packaged foods, so they can claim that their items are high in fiber. You commonly find synthetic fiber in products like breakfast bars, margarine, salad dressings, and even yogurt and ice cream. These fibers add texture to foods as well.

But, is this a healthful addition? Does synthetic fiber have the same benefits as the natural fiber you get when you bite into an apple or eat a bowl of lentils? Surprisingly, there’s some concern that these synthetic forms of added fiber could be harmful.

What is Synthetic Fiber?

Synthetic fiber is also called functional fiber. Unlike natural fiber abundant in many plant-based foods, synthetic fiber is made in a laboratory by fusing fiber molecules together. The final product is composed of carbohydrates that your body doesn’t break down and that don’t cause a rise in blood sugar. In that respect, synthetic fiber is like natural fiber. Both have minimal impact on blood sugar and help to moderate the overall blood glucose response to a meal.

Two of the most common synthetic or functional fibers are inulin and xanthan gum. Like the natural fiber you find in plant-based foods, these functional fibers slow the rate at which food passes from the stomach into the intestinal tract. This leads to a greater feeling of fullness, satisfaction, and satiety.

But, there may be some downsides to consuming foods enriched with synthetic fiber, including inulin. Researchers at Georgia State University and the University of Toledo recently conducted a study in mice that raises questions about the addition of some forms of synthetic fiber to packaged foods. They were looking to see whether inulin would help ward off some of the complications associated with obesity. The good news? Inulin did seem to help the mice avoid obesity. The bad news? The mice that ate inulin in their diet develop liver cancer at a higher rate.

How might inulin potentially be linked with liver cancer? The researchers in the study believe that bacteria in the gut break inulin down into compounds that may have unrecognized effects on the digestive tract.

The inulin manufacturers add to processed foods is derived from chicory root, a plant that grows in the United States and Europe. Chicory root is commonly made into a type of herbal coffee for people who can’t tolerate the caffeine in regular coffee. But, the chicory root undergoes processing before manufacturers add it to products. The processing may alter it in such a way that is harmful. You also find inulin naturally in garlic, onions, bananas, and wheat. There’s no evidence that these foods are harmful with the exception of wheat in people who are wheat intolerant, so it may be the processing that synthetic inulin undergoes.

The mice that developed liver cancer in this study had altered and elevated gut bacteria, a condition known as dysbiosis. Intriguingly, the researchers observed no evidence of liver cancer in inulin-fed mice that were treated with broad-spectrum antibiotics to deplete gut bacteria.

It’s not clear whether inulin has the same impact on humans, but it certainly raises questions about whether functional fiber has the same benefits as natural fiber and whether it could also cause harm. At the current time, the FDA allows eight types of functional fiber to be included on nutrition labels, including inulin. So, when you look at the nutritional information on a packaged product and see X grams of dietary fiber, inulin or another form of synthetic fiber may what you’re consuming.

Inulin isn’t the only functional fiber manufacturers add to products, but it shows that most of these unnatural forms of fibers haven’t been adequately studied to ensure they’re safe. When you pick up that high-fiber bar to munch on, you don’t know if the fiber has the same benefits as the fiber you get when you bit into a crunchy, red apple.

Get Fiber from Natural Sources

The other drawback to eating packaged, high-fiber foods is these foods usually contain other additives along with sugar, salt, and unhealthy oils. Processed foods are altered in ways that destroy their flavor and texture and manufacturers have to add salt, sugar, oils, flavorings, and emulsifiers to give food products a crave-worthy texture and taste. We know that eating these foods, in general, isn’t a healthy option. In fact, another recent study raised a question as to whether emulsifiers in processed foods have a negative impact on the gut microbiome. It’s important to know as the gut microbiome and its bacterial residents play a key role in digestive and immune health. All in all, you’re better off reaching for fiber-rich foods in their natural state rather than a food product that’s been doctored up in a laboratory.

One thing is clear. Americans need more fiber. In fact, the average American only gets half the amount recommended for good health. Recommendations are that men get 38 grams daily and women should get 25 grams each day. We’re falling short!

The Bottom Line

We need more research into synthetic fiber. Since it’s processed and synthesized in a lab, it’s different than the fiber you find in nature. Be cautious about consuming it until we know more. Enjoy more whole, plant-based foods. They’re a natural and delicious source of fiber!



Ann Nutr Metab. 2016;68(1):26-34. doi: 10.1159/000441626.|
Nutrients 2015, 7(11), 8887-8896; doi:10.3390/nu7115441
WorldBakers.com. “Adding Refined Fiber To Processed Foods Could Have Serious Health Risks, Study Finds”
WebMD.com. “Chicory”
Nature. 2015 Mar 5;519(7541):92-6. doi: 10.1038/nature14232. Epub 2015 Feb 25.
Curr. Opin. Pharmacol. 2009; 9: 737-743.


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