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The #1 Worst Mistake You're Making With This Popular Supplement, New Study Finds

You could be taking the wrong supplement for your body.
FACT CHECKED BY Kristen Warfield

When it comes to supplements, it can be hard to tell which products are going to be good for your body and which could be doing some damage. There's a lot of misinformation out there, and even if you're taking something that's had benefits for a lot of people, it might not necessarily be the right supplement for your body. When it comes to fiber, for instance, there are a lot of different options out there.

Now, a new study finds that, for some people, taking too much of the prebiotic fiber inulin can cause inflammation.

In the study, published in the journal Cell Host & Microbe, researchers examined a group of 18 participants who had their diets supplemented with two different kinds of soluble fiber, arabinoxylan (found in whole grains) and long-chain inulin (present in onions and chicory root, among other foods). They found that high doses of inulin caused inflammation in some participants, while arabinoxylan was linked with a reduction in "bad" cholesterol.

fiber capsules
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However, there was a fair amount of variation from participant to participant. Study author Michael P. Snyder, Ph.D., Stanford W. Ascherman professor of genetics at the Stanford University School of Medicine, explains to Eat This, Not That! that, while some patterns may emerge in the research, the best thing you can do is pay attention to how your own, individual body responds to different foods.

"Although most people respond positively to arabinoxylan, not everyone does," he says, "and everyone's response to fibers is different. It's important to map your own response."

Plus, this was a study with a small sample size, which means that it's not a great idea to change your behavior just in response to these findings.

"It's important to put studies in the proper context," says Christine Byrne, MPH, RD, LDN, a Raleigh, North Carolina-based private practice dietitian. "This one was conducted on just 18 people, and the participants were on each type of fiber supplement for just three weeks each. That means that this is preliminary research—interesting enough to warrant further, larger studies, but far too small to draw any conclusions from."

In general, you probably don't need to worry too much about eating too much of any kind of fiber, unless you're eating a lot of processed foods with fiber added in. Melissa Groves Azzaro, RDN, LD, of The Hormone Dietitian notes that most of us are not getting the recommended amount of fiber each day, much less overdoing it with any one kind of fiber.

"While high doses (30 g) of inulin were found to increase inflammation and liver enzymes in three participants, the dose of inulin linked to these negative effects would be unlikely to be consumed by the average person," she says.

To make sure you're getting the nutrient from naturally high-fiber foods, check out these 43 Best High-Fiber Foods For a Healthy Diet.

Clara Olshansky
Clara Olshansky (they/she) is a Brooklyn-based writer and comic whose web content has appeared in Food & Wine, Harper’s Magazine, Men's Health, and Reductress. Read more