Dietary fiber has long been known to be highly beneficial for gastrointestinal health, exerting a regulatory effect on digestive processes such as absorption, transit time, and stool formation, as well as having important microbial effects.
Unfortunately, modern diets in the Western industrialized world are notoriously low in fiber, with this deficiency linked to an array of gut and metabolic diseases. Some consumer research suggests the public is aware of the benefits of fiber, and that most people believe they consume enough. However, national consumption surveys indicate that only about 5% of the population meets recommendations, and inadequate intake of fiber has been called a public health concern.
But now, a new trend on social media may be changing the way people view and consume fiber. Called “Fibermaxxing,” it is being promoted by wellness content creators and being enthusiastically endorsed by some dietitians as “good for digestion, stable energy, and even a happier mood.” Other influencers suggest it can help with weight loss. A recent article in The New York Times quotes a 25-year-old wellness creator whose videos of herself consuming large quantities of fiber in the form of food such as chia seed puddings have garnered more than 10 million views.
Jennifer Chapler, MS, RD, CDN
“But is this really a new trend, or is it merely recycling an older version of the high-fiber diet?” muses Jennifer Chapler, MS, RD, CDN, a dietitian at Nutrition Transformations in Bergen County, New Jersey. “And is it a healthy trend to follow, or is it simply another fad diet that will disappear?”
The answer, according to Chapler, is both: Increasing the consumption of fiber is indeed beneficial, especially given the paucity of fiber in the standard Western diet. The question is how should you increase fiber intake, what type of fiber should you be consuming, and how much?
Evidence-Based Health Benefits of Fiber
An impressive number of studies have found that for each increase in dietary fiber intake of 7 g/d, there is a statistically significant reduction in the risk for cardiovascular disease, stroke, colorectal cancer, rectal cancer, and diabetes. A 2019 meta-analysis of 185 epidemiologic studies (encompassing close to 135 million person-years) found that high fiber intake (25-29 g/d) was associated with a reduced risk for all-cause mortality, as well as mortality from coronary heart disease and cancer, and a lower risk for stroke, diabetes, and colorectal cancer compared with lower fiber intake.
And, according to a review by Samantha K. Gill and coauthors, increasing dietary fiber can be regarded as a potential therapeutic intervention for disorders of the gastrointestinal tract, including irritable bowel syndrome, inflammatory bowel disease, and diverticular disease, as well as management of specific gastrointestinal symptoms such as constipation. The therapeutic benefits of fiber derive from its impact on nutrient digestion and absorption, improvement in glycemic and lipidemic responses, regulation of plasma cholesterol through limiting bile salt resorption, influencing gut transit, and promoting microbiota growth and metabolism, Gill and coauthors explained.
Dietary fiber consists of carbohydrates and lignins that are not hydrolyzed or absorbed in the upper part of the gastrointestinal tract. It includes many complex substances, each having a unique chemical structure and physical properties, and is commonly classified according to solubility in water. Total dietary fiber can be divided into two groups: “water soluble” (viscous substances such as pectin, gums, and mucilage) and water insoluble (nonviscous substances, such as cellulose, hemicellulose, and lignin). Unlike insoluble fibers, which remain discrete particles, soluble fibers have a “high affinity for water.”
“Through the process of digestion, soluble fiber from food mixes with water in the digestive track, forming a gel-like substance,” Chapler explained. “As this substance moves from the small intestine into the colon, it contacts the gut microbiota, which break it down through fermentation.”
The end result is short-chain fatty acids (SCFAs), which play a number of “key roles” in the gastrointestinal tract, wrote Gill and coauthors. In animal studies, SCFAs were shown to affect gastrointestinal motility; bridge communication between mucosal microbiota and the mucosal immune system, suggesting potential anti-inflammatory and immunomodulatory effects; maintain intestinal barrier integrity; and regulate appetite. They also indirectly help maintain gastrointestinal homeostasis through reducing luminal pH.
Insoluble fiber prevents constipation by adding bulk to the stool and clears the gut of harmful toxins, potentially contributing to the prevention of colorectal cancer, Chapler said. By improving gut transit time, it can contribute to controlling diverticulitis, and by increasing the sense of satiety following meals, it may potentially play a role in reducing overeating and assisting with weight loss.
Too Much of a Good Thing?
The wellness influencers advocating for “fibermaxxing” typically recommend basically healthy foods, Chapler noted. Their guidance is generally on the right track, she said, including recommending whole-food carbohydrate sources of fiber, such as whole grains, fruits, and vegetables; berries and apples; and beans, lentils, nuts, oatmeal, and chia seeds. These can be incorporated into the diet in creative ways, such as sprinkling chia into smoothies, yogurt, puddings, stir-fries, and oatmeal.
But “fibermaxxing” influencers often encourage people not only to meet but also to exceed daily recommendations, she said. Recommended daily fiber intake is 25 grams for women and 38 grams for men, according to the USDA, and 30 grams for all adults in the UK, but some influencers are encouraging people to eat 50 grams or even 100 grams of fiber a day.
“It’s not good to overdo anything, including fiber,” she emphasized. Instead, it’s better to “eat a variety of foods, including protein, complex carbohydrates, fruits and vegetables, and leafy greens — the more colorful the plate, the more nutrients the food will contain.”
Excessive consumption of fiber can cause bloating and flatulence and can even interfere with the absorption of nutrients from food, she said. “Eating fiber all day can also cause internal irritation and can interfere with absorption of medications.”
Fazia Mir, MD, DABOM, a gastroenterologist who practices in Albuquerque, New Mexico, and is affiliated with Presbyterian Hospital, agreed. She does not recommend fibermaxxing to her patients. In fact, consuming large amounts of fiber — more than 40-50 grams — can not only cause bloating but also actually cause constipation, she told Medscape Medical News. And the sense of fullness can prevent people from eating other varieties of food, leading to nutritional deficiencies. “Just adhere to the recommended daily intake,” advised Mir, who is a spokesperson for the American Gastroenterological Association.
It’s also important to increase fiber intake slowly rather than rapidly incorporating large quantities into one’s diet. This allows the gastrointestinal tract to adjust, Chaplin said. It’s equally important to drink sufficient fluids. “Fiber absorbs fluid as it moves through the digestive tract, so insufficient fluid intake can cause constipation, hard, dry stools, bloating, flatulence, and abdominal discomfort.”
The Role of Supplements
Yakira Escott Berkowitz, RD, a registered dietitian with a private practice in Bergen County, said that many of the clients who come to her seek advice about whether to use a fiber supplement.
Yakira Escott Berkowitz, RD
Taking a supplement can be “helpful and is better than nothing for people whose diet is deficient in fiber,” she told Medscape Medical News. “But I prefer people get their fiber from foods.”
If that’s not possible, she recommends products that are third-party tested. “I advise patients to look for the letters ‘NSF’ on any supplements.” This means they have been tested by the National Sanitation Foundation, an independent nongovernmental organization focused on public health and safety standards.
Chapler also thinks that getting fiber from food is preferable to getting it from a supplement. She recommends Fiber One cereal. “It’s a food, not a supplement, but it’s almost like taking a supplement. For patients really struggling with constipation, I’ll recommend they eat it twice daily.”
If patients require a supplement, psyllium — a bulking agent frequently used for treating constipation — can be recommended. It has established benefits, both for gastrointestinal and cardiometabolic health. Additionally, adding psyllium to a normal diet has been shown to improve body composition, lipids, glucose, and insulin in patients who have overweight or obesity. The combination of a healthy diet plus fiber supplementation yields the greatest improvements.
When Is Fibermaxxing Contraindicated?
There are several gastrointestinal diseases, such as Crohn’s disease and intestinal obstruction, in which fiber intake should be limited and increased only under medical supervision. Patients with malabsorption issues or those who have undergone bowel surgery should consume fiber with caution, also under medical supervision.
Chapler and Berkowitz both recommend that patients work in conjunction with a physician if they have any type of gastrointestinal condition or are taking medications because fiber can affect the absorption of several drugs. For example, large quantities of fiber can lower blood levels of metformin and can affect levothyroxine, digoxin, penicillin, and amoxicillin absorption. Consumption of pectin or oat bran together with lovastatin can reduce the medication’s absorption, and fiber should not be taken at the same time as antiarrhythmic drugs.
Constipation is common in people taking opioids, and the first approach to treatment is typically to encourage lifestyle changes and ensure adequate daily intake of water and fiber, together with avoiding heavy meals and highly fatty foods and evacuating as soon as the urge to defecate arises. Because opioid drugs inhibit intestinal motility, excess fiber could lead to bloating, flatulence, and fecalomas, so daily intake of fiber should not exceed 20 grams.
All the experts agreed that increased fiber intake should be part of an overall health plan that includes well-balanced, nutritious eating; sufficient intake of fluids; adequate amounts of physical exercise; and controlling calories and portion sizes.
Chapler also emphasizes the importance of mindful eating and chewing food well, which enhances utilization of fiber in the gastrointestinal tract. A review of 71 studies found that chewing is an important contributor to the swallowing process and physiologic/pathologic processes in the gastrointestinal tract. However, some fiber-rich foods are difficult to chew — a problem that particularly affects older adults who are often partially or fully edentulous who may then exclude high-fiber foods from their diet.
It is important for this population to work closely with a dietitian who can help them maximize nutritional intake in general, and fiber intake in particular, as there are many fiber-rich foods that are not difficult to chew, Chapler said.
On balance, she believes that the new focus on fiber due to the “fibermaxxing” trend can be a positive development, and that clinicians should encourage and support patients in their efforts to responsibly increase their consumption of this very important nutrient.
Chapler, Berkowitz, and Mir reported having no relevant financial relationships.
Batya Swift Yasgur, MA, LSW, is a freelance writer with a counseling practice in Teaneck, New Jersey. She is a regular contributor to numerous medical publications, including Medscape Medical News and WebMD, and is the author of several consumer-oriented health books, as well as Behind the Burqa: Our Lives in Afghanistan and How We Escaped to Freedom (the memoir of two brave Afghan sisters who told her their story).