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Surprising Side Effects of Eating Too Much Fiber, Say Dietitians

You need fiber for many health-related things, but eating too much can cause a lot of discomfort.

It's always possible to have too much of a good thing. For example, even though protein is a necessary nutrient to have on a daily basis, consuming too much of it can lead to brain fog, bloating, and weight gain. There are also vitamins like vitamin D that can cause irritability, exhaustion, or nausea.

Fiber is no exception to this rule. Fiber is necessary for a healthy digestive tract, as well as a healthy heart, gut microbiome, and management of your weight, blood pressure, and cholesterol. But what happens if you eat too much fiber? We talked with a few expert dietitians to learn about the possible side effects of eating too much fiber on a regular basis.

Then, for more healthy eating tips, check out Popular Foods with More Fiber Than Oatmeal.

How much fiber is too much?

fiber foods

Fiber is a necessary component of any diet and can help contribute to overall health. People across the globe who have the highest rates of longevity eat plenty of fiber on a daily basis, but many people in the United States don't get nearly enough.

"While adequate intake of fiber has been associated with gut health and has shown to play a role in improving various disease risks, studies have shown that only about 5% of Americans meet their daily fiber requirement," says Kristi Ruth RD, LDN at Carrots & Cookies.

So how much fiber should you be getting every day? According to Trista Best, MPH, RD, LD at Balance One Supplements, "women are encouraged to consume 21 to 25 grams of fiber a day, while men are encouraged to consume 30 to 38 grams a day."

You may actually become more constipated.

stomach ache

This may come as a surprise, but too much fiber can actually constipate you. This is contrary to what many people expect because you can also become constipated when you don't have enough fiber!

"Many people focus on increasing their intake of soluble fiber to help lower cholesterol and/or improve blood sugar control," says Ruth. "Little do they know that increasing intake of soluble fiber may actually be constipating, especially without drinking adequate amounts of water. This likely comes as a surprise to those who start increasing their fiber intake to help treat constipation. Fiber and water work together to bulk stool and help keep it moving through the digestive tract. Without water, stools will form but they will have a hard time moving through. In the end, if you increase your fiber intake, you should also increase your fluid intake. Or, at least ensure you are drinking enough fluid every day."

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But it can also cause diarrhea.

stomach pain

Although fiber is meant to help you go to the bathroom, too much fiber could actually constipate you or cause diarrhea. According to dietitians, a lot of this has to do with not only how much you eat but also the specific type.

"Interestingly, if you increase your fiber intake too quickly, you may experience diarrhea," says Ruth. "This is because fiber (specifically insoluble fiber) softens stool and has somewhat of a laxative effect. So in the end, understand the types of fiber and the reason why you are increasing them. Also, consider gradually increasing your intake of fiber so your digestive system has time to adjust. And, last, try to get a good balance of both soluble and insoluble fiber."

You may experience uncomfortable gas or bloating.

woman bloated stomach

Too much fiber can also quickly derail your day with some extreme stomach discomfort as well.

"Eating too much fiber might lead to bloating or gas, especially when you eat too much fiber too quickly," says Paulina Lee, MSHS, RD, LD, functional dietitian and founder of Savvy Stummy. "It's normal for our gut bacteria to create some gas by-product as it digests the food and fibers we consume, but when the gas and bloating becomes uncomfortable, that's when you might need to re-evaluate your fiber consumption."

Samantha Boesch
Samantha was born and raised in Orlando, Florida and now works as a writer in Brooklyn, NY. Read more about Samantha