The Downsides of Fiber Supplements

Fiber supplements were at one point the avocado toast of its time—everyone, everywhere wouldn’t stop talking about it.


We all know why a fiber supplement craze began: researchers, doctors and dietitians all championed dietary fiber as an important nutrient and Americans weren’t eating enough. Labeled as a “nutrient of public health concern” by the 2015-2020 Dietary Guidelines for Americans, dietary fiber has a recommended 25g for daily consumption, and yet, most Americans ate only an average of 16.2g (1).


However healthy a fiber-rich diet can be, if the fiber is solely from fiber supplements, it is hard to say whether or not that fiber-rich diet is truly beneficial. After all, based on a 2000 calorie diet, the FDA recommends 25g of fiber per day from foods, not supplements. More specifically, the Institute of Medicine recommends women under the age of 50 to consume 25g and men under the age of 50 to consume 38g of fiber (2).


So how did we all become obsessed with supplements?

  • Marketing
  • We all fall prey to the power of marketing, especially in the dietary supplements industry. With health claims and promises thrown left and right, the industry has amassed an enormous consumer base, boasting an expected value of 216.2 billion USD by 2026 (3). This industry markets and brands its products in novel ways that could never work with actual foods: it’s more exciting to market a pill and give it a fancy name, such as the “radiant youth” pill, compared to rebranding healthy foods, such as oatmeal that looks boring to many people. While health claims and promises aren’t unjust, it is the style of marketing that makes supplements appear more effective and attractive to consumers.

  • Company incentives
  • This is a simple supply and demand concept: supplements are a high profit margin business with a rapidly growing consumer base. So, as more and more consumers demand dietary supplements, more and more companies emerge with supply to fulfill that demand. Not only does this benefit the consumer with a more diverse selection of pills, but also the company with the high profitability that this industry is known for. Company incentives, therefore, partly drive the obsession with supplements.

  • Convenience
  • A 2019 survey on American cooking habits showed that only 37% of those living in the U.S. cook between three to five times per week (4). This statistic goes to show the high percentage of Americans who don’t cook and for those who do, we don’t know if it’s a fully home-cooked meal or a pre-packaged frozen meal. Whether it’s the lack of time, energy, or skills to prepare home-cooked meals, it seems that many Americans opt for dining out, take-out, or microwaveable frozen foods because of its convenience. Similarly, it is more convenient to pop a pill than to cook a high fiber meal. 

  • Lack of nutrition education
  • Our school curriculums desperately lack basic nutrition education, and even medical doctors only spend less than 25 hours over four years learning about nutrition (though that is now changing) (5). With a lack of nutrition education and awareness in our societies, it is easy to consider dietary supplements equivalent to eating nourishing, nutritious foods. 


    So why are fiber supplements potentially harmful? What are the downsides?


  • Excessive fiber intake
  • Imagine you are eating chocolate chip cookies. We all know that cookies contain lots of processed sugars, but it’s so easy to overeat cookies--they taste so good! Now imagine eating sugars from strawberries and trying to reach that same amount of sugar consumption as with your chocolate chip cookies. Obviously, it won’t be as easy. This scenario rings true for fiber supplements vs. natural sources of fiber: it is easier to go overboard with fiber consumption through processed pills and supplements than natural foods.

    Many fiber supplements and pills in the market contain fiber sources that are more prone to bloating and gastrointestinal discomfort. For instance, many fiber pills contain inulin or chicory root fiber, which are highly fermentable fibers. Highly fermentable fibers are, as usual, fermented by gut bacteria but creates an excess of gas, hence the bloat and discomfort (5). Also, many studies on glucomannan, a soluble dietary fiber, made sure to conduct its studies using a low dosage of fiber (7,8) because of its “high viscosity” (7) and instructed its participants to take fiber supplements along with 8 oz of water (8). 

    Excess fiber, especially with pills that commonly contain highly fermentable fibers, can create the opposite of fiber’s desired effects. Thus, dietary fiber is recommended to be consumed through natural foods that will not only help to reach your daily fiber intake in appropriate amounts but also to reach a gradual sense of satiety that won’t lead to excess fiber consumption.


  • Supplemental fiber lacks the holistic benefits of fiber-rich foods
  • While it is true that fiber supplements and pills help reach the recommended intake, dietary fiber is recommended over functional fiber. Functional fiber is what we call fiber that provides just the functions of dietary fiber, lacking holistic health benefits generally associated with dietary fiber. 

    For example, dietary fiber’s beneficial effects on cardiovascular disease is well established (9,10). Its ability to lower LDL (“bad”) cholesterol is a prime example (11). This form of dietary fiber is from whole, unprocessed foods that provide health benefits beyond just fiber—for instance, chia seeds are both high in fiber and healthy fats (12), which will lower LDL cholesterol and prevent heart disease (11). Thus, what happens when you take fiber supplements? You won’t be reaping all the benefits that dietary fiber from whole foods can provide. Therefore, dietary fiber is recommended over functional fiber (supplements).


  • Promoting a healthy and diverse gut microbiome
  • The importance of a healthy gut microbiome should not be overlooked.

    The gut microbiome is made up of microbes (single-celled microorganisms) in our gastrointestinal tract (13). Numerous studies have recently stressed its significance on our overall health and disease prevention, including “human metabolism, nutrition, physiology, and immune function.” And, of course, fiber is amazing in that it can remarkably improve the gut microbial balance and increase its diversity (14).

    When it comes to supplements, one single type of fiber pill taken over and over again may not be as beneficial to our gut microbiome as many perceive it to be, especially for our gut microbiome diversity. Although the science behind gut microbiomes are relatively new and future research is necessary, current studies state that not all fibers are created equal; certain fibers affect our gut microbiome differently than others (15, 16). This impacts our gut microbiome diversity, and stresses the importance of a diverse source of dietary fiber (from many different fruits, grains, and vegetables), not just from one pill. Therefore, to promote a diverse and healthy gut microbiome, it is best to reach for the fresh fruits, vegetables, and grains, not the bottle of pills.


    A look into Blue Zones and other diets (Ornish and F-Factor diets)

    You might be wondering: if a natural high-fiber diet is so crucial to our health, what are some examples of such success?

    An exemplary diet would be any of the Blue Zone diets from around the world. Blue Zones are longevity hotspots in which people live longer and healthier lives.

    And what does their diet consist of?

    Whole, unprocessed foods that are naturally high in fiber. Their predominantly plant-based diets explain their high consumption of fiber (17).

    For example, the residents of Sardinia, Italy are known to consume beans, garden vegetables, chickpeas, fruits, barleys, and fennels, which all make up a high-fiber diet (18). Also, in Loma Linda, CA, USA, residents regularly eat leafy greens, nuts, legumes, oatmeal, and dates (18).

    Thus, a major commonality and success factor among the Blue Zone centenarians are their high-fiber diets from whole, natural foods.


    Similarly, the Ornish diet, named after physician and researcher Dean Ornish, is a naturally high-fiber, low-fat, high-carb, vegetarian dietary lifestyle that specifically targets heart disease (19). Although it was later met with some controversy over its low-fat, fairly restrictive diet plan, one thing is clear: a high-fiber diet is a significant factor behind its success (20). Needless to say, the high-complex carb component of this diet makes it naturally high in fiber, and has been shown to lower blood pressure and type-2 diabetes, both of which significantly increase the risk of heart disease.


    On the other hand, there are diets such as the F-Factor diet that does not embody the whole, natural, high-fiber diet that is highly esteemed in the nutrition field. The diet, recommended by registered dietitians who work at F-Factor (a nutrition private practice), relies on fiber and protein to promise a healthy but dramatic weight-loss. Yet, it has also been called calorie-restrictive (21). Besides the calorie-restrictive diet itself, it also promotes its product line of high-fiber, high-protein bars, and uses all artificial, unnatural ingredients. Their products not only show an obvious conflict of interest from the F-Factor dietitians, but were also met with heavy disapproval from dietitians who had no conflict of interest with F-Factor. Furthermore, the disapproval also came from customers; they complained of a variety of health issues, including “painful bloating” (22). Thus, the significance of dietary fiber from whole foods, not supplements, could not be stressed enough.


    Is it ever okay to take fiber supplements? 

    Yes! It is important to note that fiber additives and fiber pills can still be helpful in meeting the recommended intake of fiber. In appropriate amounts, they are a convenient, problem-free source of fiber for everyone to enjoy. However, fiber pills are extremely concentrated and users can easily go over the recommended intake, leading to a fiber overdose, of sorts. Also, they lack the holistic benefits that natural sources of high-fiber foods can provide, along with its health benefits for the gut microbiome.

    Thus, as long as it is taken with caution (take a look at the serving sizes of the pill and take with a full glass of water), no harm should be done.


    The magic weight loss pill?

    Fiber supplements have wrongly been marketed, believed, and used as weight loss treatment. While it is true that some studies point out that glucomannan pills, fiber extracted from the konjac root, “beneficially affect” (23) and “may promote weight loss” (7), most studies (24,8) claim that weight loss effects of most fiber supplementation is “not convincing” (24) enough to be considered an appropriate weight loss treatment. What the majority of studies state is that fiber supplements alone can’t provide the full extent of weight loss that is associated with dietary fiber. For example, dietary fiber increases satiety, which can promote weight loss (25). If taken straight from whole, unprocessed foods, dietary fiber can significantly increase a meal’s satiety and satisfaction over a single pill and a glass of water. Although extensive research hasn’t been conducted on the practicality of fiber supplements as an effective weight loss pill, the existing research recommends that dietary fiber from whole, unprocessed foods is the way to go.


    Author: Haekyeung Kang, BS, Nutrition and Dietetics, NYU, 2017-2021



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