Most of us know that fiber is good for us. It’s why we’re told to eat whole grains, load up on vegetables, and eat the skins of fruit. And there’s also growing evidence suggesting that a high-fiber diet may be protective against disease.
But even with an abundance of benefits, fiber still has a dark side—especially when in excess. Although meeting your daily intake recommendations for fiber is essential, exceeding them too much can be risky.
If you think more is better where fiber is concerned, we’re breaking down the details on how much fiber is too much, the potential side effects of high-fiber diets, and how to get the perfect dose.
Let’s get started.
What Is Fiber?
When you think about fiber, what’s the first thing that comes to mind? For many people, it’s bowel movements. Unlike most of the food we eat, the human body cannot digest dietary fiber. It’s a non-digestible carbohydrate that’s classified based on its solubility:
- Soluble fiber: Dissolves in water and is metabolized or digested by the beneficial bacteria in the gut; it attracts water and forms a gel-like substance.
- Insoluble fiber: Does not dissolve in water and travels intact mainly through the GI tract; this fiber helps to bulk up stool and make it easier to pass.
The type of fiber often dictates the benefits, but most foods contain small amounts of both soluble and insoluble fiber.
Top 3 Benefits Of Fiber
1. Supports gut health
One of the most notable roles of fiber is in supporting gut health (i.e., feeding the beneficial bacteria in the GI tract). Although this is not true of all bacteria residing in the gut, most offer a mutually beneficial role to the host—you provide them with food and safe habitat.
In return, they support various physiological functions you can’t do yourself. That’s things like weight management, blood sugar regulation, immune function, and even certain aspects of cognition 1-4.
But like everything else, bacteria need energy—and this comes in the form of dietary fiber. Humans don’t possess the necessary enzymes to digest fiber, so it travels through the digestive tract relatively intact. However, most bacteria can metabolize fiber, which provides them with food by serving as a “prebiotic” 5.
In this way, they support the growth of good gut bugs, which improves health outcomes and supports the production of short-chain fatty acids like acetate, propionate, and butyrate 6—these SCFAs feed colonocytes, which helps to reduce gut inflammation and improve digestion.
However, the fermentation of fiber can also lead to gas production, which is why people following a high-fiber diet often experience flatulence and minor stomach discomfort.
2. May support weight loss
Trying to lose a few pounds? Increasing your prebiotic fiber intake could be the key to better weight management. In fact, there is a link between the dietary fiber inulin and weight loss. Although nothing substitutes for hard work and consistency, dietary fiber is essential for increasing satiety and regulating your hormones.
Studies suggest that the viscosity-producing effects of certain types of fibers can enhance satiety and reduce overall energy intake 7. However, the average American intake of 15g/day will not cut it. To see any beneficial effects, you’ll need to aim for over 25g daily 8.
3. May reduce blood sugar fluctuations
Most people who don’t have diabetes don’t think twice about how their diet influences their blood sugar. Still, chronic and drastic glucose fluctuations can lead to various problems, including metabolic syndrome and pre-diabetes or diabetes.
The solution? Boost your fiber intake.
Maintaining a balanced diet is important to regulate glucose levels, but the high viscosity of soluble fibers may help to mitigate spikes after a high-carb meal by delaying glucose absorption 8, 9.
How Much Fiber Is Too Much? The Optimal Daily Dose
You can’t argue that getting enough fiber daily is critical to maintaining optimal health and well-being. And while it can be tempting to load up on fiber to reduce symptoms and improve health, don’t.
Too much fiber can be almost as problematic as too little, especially if you’re consuming a large amount in a short period.
Typically, exceeding 45–70 grams of fiber daily can lead to adverse effects. Here are some of the most common side effects of overeating fiber:
1. Changes in bowel movements
Too little fiber can cause constipation, but too much can also cause it—along with diarrhea. Fiber acts as a bulking agent and pulls water into the GI tract.
Not consuming enough fluids alongside fiber can lead to dehydration in the GI tract and make stools firm and hard to pass. This tends to be more problematic with foods high in soluble fiber, such as oatmeal, beans and legumes, apples, and strawberries.
On the other hand, too much fiber can also lead to diarrhea or loose stools, especially if you’re consuming high amounts of insoluble fiber from things like wheat, corn bran, leafy vegetables, and broccoli.
Because insoluble fiber travels undigested through the GI tract, it adds bulk to your stool and speeds up transit time, resulting in diarrhea 10. To avoid this, ensure you’re consuming sufficient soluble fiber alongside it.
Related Post: Best Probiotic for Constipation
2. Gas and bloating
Gas and bloating are two common side effects of too much fiber 11, 12. This often happens when large amounts are consumed quickly because the fiber isn’t digested or broken down, moving through the digestive tract.
As a result, bacteria that reside in the colon partially digest some of the fiber and release gas as a byproduct.
3. Abdominal pain or discomfort
Abdominal cramping can be another sign of too much fiber, which may result from excessive fiber causing digestion to slow too much.
4. Mineral deficiencies
Most people don’t know that too much fiber can cause mineral losses. This is because fiber binds to minerals 13; under normal circumstances, this isn’t an issue, but excessive amounts can interfere with mineral absorption and decrease stores.
This generally isn’t a problem for people who consume sufficient quantities of soluble and insoluble fiber. But too much insoluble fiber without soluble fiber can cause issues.
So, what’s the “ideal” dose of fiber?
The Institute of Medicine and the American Heart Association recommend the following daily intakes 14:
- Children 1–3 years old: 19 grams
- Children 4–8 years old: 25 grams
- Girls 9–18 years old: 26 grams
- Boys 9–13 years old: 31 grams
- Males between 14–50: 28 grams
- Females between 19–50: 25 grams
- Men over 50: 21 grams
- Women over 50: 30 grams
3 Tips For Getting Enough Fiber
1. Know your high-fiber foods
The best place to start if you want to increase your fiber intake is to know which foods are high in fiber and which aren’t.
Stay away from processed and refined foods devoid of nutrients and fiber, and load up on plant foods in their whole form. Here are some great picks:
- Beans and legumes (chickpeas, kidney, black, cannellini)
- Dark leafy green vegetables (kale, collards, spinach, arugula, chard)
- Root vegetables (carrots, turnip, parsnip, squash, beet)
- Avocado
- Fruits (pears, strawberries, apples, raspberries)
- Artichoke
- Asparagus
- Oats
- Nuts and seeds (almonds, chia seeds, sunflower seeds, pumpkin seeds)
2. Keep tabs on how much you’re consuming
Not sure if you’re consuming enough fiber? Track your food for a week and see! Although calorie counting isn’t the ideal long-term situation, writing down the type and amount of food you eat can help you calculate how much fiber you’re consuming daily and where you may need to make changes.
If you’re not consuming enough, try adding a new high-fiber food daily to hit your goals.
3. Choose a clean and quality supplement
Fiber supplements can be problematic for people looking to increase their fiber intake quickly, as excessive intake can lead to nasty side effects.
But if you’re looking for all the benefits of a conventional fiber supplement or a high-fiber diet without the drawbacks, we have something for you: Performance Lab Prebiotic.
It’s the world’s first 2-in-1 probiotic + soluble fiber supplement designed for peak microbiome performance.
Rather than adding in new colonies of bacteria, Prebiotic nourishes your existing colonies with Orafti® Synergy1 (Inulin-FOS from chicory root) for robust growth and health.
As a result, Prebiotic delivers more reliable, natural, and comfortable microbiome support. And the addition of soluble fiber supports better digestion, immune function, fat loss, and more that you wouldn’t usually get from traditional probiotic supplements.
Give it a try and you'll soon notice the difference!
References
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- Musso G, Gambino R, Cassader M. Obesity, diabetes, and gut microbiota: the hygiene hypothesis expanded?. Diabetes Care. 2010;33(10):2277-2284.
- Steinhoff U. Who controls the crowd? New findings and old questions about the intestinal microflora. Immunol Lett. 2005;99(1):12-16.
- Cryan JF, O’Mahony SM. The microbiome-gut-brain axis: from bowel to behavior. Neurogastroenterol Motil. 2011;23(3):187-192.
- Parnell JA, Reimer RA. Prebiotic fiber modulation of the gut microbiota improves risk factors for obesity and the metabolic syndrome. Gut Microbes. 2012;3(1):29-34.
- Wong JM, de Souza R, Kendall CW, Emam A, Jenkins DJ. Colonic health: fermentation and short chain fatty acids. J Clin Gastroenterol. 2006;40(3):235-243.
- Burton-Freeman B. Dietary fiber and energy regulation. J Nutr. 2000;130(2S Suppl):272S-275S.
- Howarth NC, Saltzman E, Roberts SB. Dietary fiber and weight regulation. Nutr Rev. 2001;59(5):129-139.
- McRorie JW Jr, McKeown NM. Understanding the Physics of Functional Fibers in the Gastrointestinal Tract: An Evidence-Based Approach to Resolving Enduring Misconceptions about Insoluble and Soluble Fiber. J Acad Nutr Diet. 2017;117(2):251-264.
- Pituch-Zdanowska A, Banaszkiewicz A, Albrecht P. The role of dietary fibre in inflammatory bowel disease. Prz Gastroenterol. 2015;10(3):135-141.
- Gonlachanvit S, Coleski R, Owyang C, Hasler W. Inhibitory actions of a high fibre diet on intestinal gas transit in healthy volunteers. Gut. 2004;53(11):1577-1582.
- Grabitske HA, Slavin JL. Gastrointestinal effects of low-digestible carbohydrates. Crit Rev Food Sci Nutr. 2009;49(4):327-360.
- Bergman CJ, Gualberto DG, Weber CW. Mineral binding capacity of dephytinized insoluble fiber from extruded wheat, oat and rice brans. Plant Foods Hum Nutr. 1997;51(4):295-310.
- Trumbo P, Schlicker S, Yates AA, Poos M; Food and Nutrition Board of the Institute of Medicine, The National Academies. Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein and amino acids .J Am Diet Assoc. 2002;102(11):1621-1630.
