What is a fiber?

Fiber is an extremely important of a healthy diet, and unfortunately many modern diets find themselves in short supply of this essential nutrient. Dietary fiber is found in plants and is indigestible, yet enables the body to eliminate waste and maintain homeostasis. It may seem strange to think that a high amount of dietary fiber can be found in a protein powder, but when you think about the source, you’ll understand how LENTEINTM Plus Powder provides both a punch of protein and is packed full of dietary fiber as well.

What Is Dietary Fiber?

Dietary fiber is the indigestible portion of a plant. It is categorized into two different groups: soluble and insoluble. Although there are two types of fiber, most plants contain both in varying degrees. Because the body is unable to digest these nutrients, they travel through the digestive system largely unaltered. This promotes the elimination of waste and can regulate the blood sugar. It is found in most fruits, vegetables, beans, grains, and legumes. Our bodies need both types of fiber to maintain health and wellness.

Soluble fiber absorbs water and fatty acids as it makes its way through the digestive tract and becomes gelatinous. It slows digestion and the emptying of the stomach which can regulate the rate at which sugars are absorbed by the blood through the intestines. This is beneficial for people of all health backgrounds but specifically for those who have a difficult time managing their blood sugar levels and cholesterol. Further it can become fermented by the bacteria in the digestive system which has shown to improve digestion and the function of the immune system. Foods that are high in soluble fiber include: apples, citrus, dark green veggies such as broccoli, spinach, and brussel sprouts, beans, and whole grains.

Insoluble Fiber

Insoluble fiber does not become altered in any way by the process of digestion. Because of this, its main function in our diets is to keep things moving along. It enables healthy elimination of waste from the intestines and colon. Healthy and regular elimination of waste promotes pH balance in the body as well as protects the colon from harmful microbes that can alter the DNA and cause colorectal cancers. Insoluble fiber can be found in the skins of many fruits and vegetables, whole grains, nuts, and seeds.

How Can You Tell If You’re Not Getting Enough Fiber

When food companies process foods like grains, fruits, and veggies they do so at the cost of fiber. The loss of this essential nutrient has many harmful effects. The first, and most uncomfortable, sign of a low-fiber diet is constipation. Because insoluble fiber’s main job is to move food and waste through our digestive system, it makes sense that the lack of it would cause slowing or stopping of elimination. Thankfully getting things started again can be as easy as eating an apple. The next symptom of a low-fiber diet is a constant feeling of hunger and unpredictable blood sugar levels. Soluble fiber keeps us feeling full and allows our body the time it needs to digest our foods properly. When we don’t eat enough soluble fiber we feel hungry more often, this leads to eating more food and causing spikes in blood sugar. Eating a bowl of oatmeal and an orange for breakfast can keep you feeling fuller longer and allow your body to digest at a proper pace. Finally, because fiber slows digestion while promoting the elimination of waste, it has been shown to lower cholesterol and promote heart health as well. It does this by acting as a sort of “magnet” for cholesterol as it passes through your digestive system.

Protein and Fiber

Many protein powders on the market are made from whey, which doesn’t contain any fiber to begin with, and the ones made from plants are often highly processed, which strips them of their fibrous nutrients. LENTEINTM Plus Powder is a unique plant-based protein powder that is created with a simple process that leaves fiber and other nutrients intact during processing. The water lentil is full of soluble and insoluble protein to begin with, during processing we do our best retain the integrity of every nutrient. This way we can provide you with a whole source of not only protein but the fiber, omega 3 fatty acids, and other plant compounds that keep your body healthy and well.

A healthy diet encomapasses all aspects of wellness. A mix of protein, fiber, water, and plant compounds are necessary for all of our vital functions. Ensuring you’re receiving high quality nutrients is easy when you trust the power of a whole, plant-based protein powder like LENTEINTM Plus Powder

Soluble Fiber

Foods rich in this type of fiber include oatmeal, nuts, beans, apples, and blueberries.

The health benefits include:

Heart protection: Inside your digestive system, soluble fiber attaches to cholesterol particles and takes them out of the body, helping to reduce overall cholesterol levels and the risk of heart disease. Oatmeal may offer the most heart protection.

Diabetes protection: Because soluble fiber isn’t well absorbed, it doesn’t contribute to the blood sugar spikes that can put you at risk for type 2 diabetes and heart disease. If you already have diabetes (either type 1 or type 2) soluble fiber can even help keep your condition under control.

Weight loss: Soluble fiber can also help you get to — or stay at — a healthy weight by keeping you feeling full without adding many calories to your diet.

Healthy bowel movements: Soluble fiber soaks up water as it passes through your system, which helps bulk up your stool and guard against constipation and diarrhea. In fact, most fiber supplements contain mostly soluble fiber.

Dietary fiber is a plant-based nutrient that is sometimes called roughage or bulk. It is a type of carbohydrate but, unlike other carbs, it cannot be broken down into digestible sugar molecules. Therefore, fiber passes through the intestinal tract relatively intact. However, on its journey, fiber does a lot of work.

The term “dietary fiber” refers to the indigestible parts of plant-based foods. In other contexts, “fiber” might refer to plant-based cloth, but when speaking of nutrition, the terms “fiber” and “dietary fiber” are often interchangeable.

Fiber is important to digestion and regularity, weight management, blood sugar regulation, cholesterol maintenance and more, according to Paige Smathers, a Utah-based dietitian. It has also been linked to longevity and decreasing the risk of cancer.

The Institute of Medicine has set a recommended daily amount (RDA) for fiber intake. Men ages 50 and younger should consume 38 grams of fiber per day, and men 51 and older should consume 30 grams. Women ages 50 and younger should consume 25 grams per day, while their older counterparts should have 21 grams. Most Americans do not consume enough fiber, according to the institute.

Soluble fiber vs. insoluble fiber

Fiber can be put into two categories: soluble and insoluble fiber, according to Colorado State University.

Simply put, Smathers said, soluble fiber, such as pectin, gum and mucilage, dissolves in water; insoluble fiber, such as hemicellulose, cellulose and lignin, does not. In the body, soluble fiber dissolves and becomes a gel-like substance. Insoluble fiber mostly retains its shape while in the body.

Both soluble and insoluble fibers have important benefits, according to Smathers. Soluble fiber is known to help decrease blood glucose (blood sugar) levels. It also helps lower blood cholesterol.

Insoluble fiber, on the other hand, speeds up the passage of food through the digestive system. This helps maintain regularity and prevent constipation. It also increases fecal bulk, which makes stools easier to pass.

Most plant-based foods contain both soluble and insoluble fiber, but the amounts of each vary in different foods, according to the Mayo Clinic. Good sources of soluble fiber include beans, lentils, oatmeal, peas, citrus fruits, blueberries, apples and barley. Good sources of insoluble fiber include foods with whole-wheat flour, wheat bran, brown rice, cauliflower, potatoes, tomatoes and cucumbers. Some foods, like nuts and carrots, are good sources of both types of fiber.

Benefits of fiber


“Dietary fiber aids in improving digestion by increasing stool bulk and regularity,” said Smathers. This is probably fiber’s best-known benefit. Bulkier, softer stools are easier to pass than hard or watery ones, which not only makes life more comfortable, but also helps maintain colorectal health. According to the Mayo Clinic, a high-fiber diet may help reduce the risk of hemorrhoids and diverticulitis (small, painful pouches on the colon).

Heart health

Fiber also helps lower cholesterol, said Kelly Toups, a registered dietitian with the Whole Grains Council. The digestive process requires bile acids, which are made partly with cholesterol. As your digestion improves, the liver pulls cholesterol from the blood to create more bile acid, thereby reducing the amount of LDL (bad) cholesterol.

Blood sugar regulation

A meta-analysis of studies regarding the relationship between fiber and blood glucose (blood sugar) levels published in The Journal of the American Board of Family Medicine found that increased fiber intake can reduce blood glucose levels during the standard fasting blood glucose test (a test of blood sugar levels after an overnight fast).

The article showed that levels of HbA1c also decreased with increased fiber. HbA1c refers to glycated haemoglobin, which occurs when proteins in the blood mix with blood sugar. It is associated with increased risk of diabetes complications. Soluble fiber is especially helpful in this regard.

Possible cancer prevention

The research has been mixed regarding the link between fiber and colorectal cancer prevention. While the National Cancer Institute asserts that a high-fiber diet does not reduce the risk to a clinically significant degree, a 2011 meta-analysis from the British Journal of Medicine found an association between cereal fiber and whole grain intake and reduced risk of colorectal cancer.

A more recent animal study suggested that fiber might only cause this benefit if a person possesses the right kind and amount of gut bacteria. Fiber naturally reacts with bacteria in the lower colon and can sometimes ferment into a chemical called butyrate, which may cause cancer cells to self-destruct. Some people naturally have more butyrate-producing bacteria than others, and a high-fiber diet can help encourage the bacteria’s growth.


According to some scientists, fiber could actually help people live longer. A meta-analysis of relevant studies published in the American Journal of Epidemiology concluded, “high dietary fiber intake may reduce the risk of total mortality.”

One recent study suggests that cereal fiber, from foods like whole-grain bread, cereal and pasta, is especially effective. Over a 14-year period, those who ate the most cereal fiber were 19 percent less likely to die than those who ate the least.

Food allergies and asthma

New research suggests that fiber could play a role in preventing food allergies, the existence of which has long puzzled scientists. Again, this theory comes down to the interaction between fiber and bacteria in the gut.

Scientists theorize that people are not producing the right gut bacteria to tackle foods commonly associated with allergies, like peanuts and shellfish. Without the right bacteria, particles of these foods can enter the bloodstream via the gut. Fiber helps produce a bacterium called Clostridia, which helps keep the gut secure.

The same reasoning explains why fiber might help people with asthma. Unwanted particles escaping the gut and entering the bloodstream can cause an autoimmune response like asthmatic inflammation. A 2013 animal study found that mice eating a high-fiber diet were less likely to experience asthmatic inflammation than mice on a low- or average-fiber diet.

High-fiber foods

“Fiber is found in whole grains, beans, fruits and vegetables,” Smathers said. It is often found in higher concentration in fruit and vegetable skins.

She suggested a diet incorporating the following high-fiber foods:

  • Lentils, which have 16 grams of fiber per cup, cooked
  • Bran flakes, which have 7 g of fiber per cup. Bran muffins are also a good choice
  • Berries like raspberries and blackberries, with around 7 g per cup
  • Apples with the skin on (4.4 g)
  • Pears with the skin on (5.5 g)
  • Split peas are full of fiber with 16.3 g per cup, cooked
  • Black beans, which have 15 g per cup, cooked
  • Lima beans bring in 13.2 g per cup, cooked
  • Pearled barley, with 6 g per cup, cooked
  • Popcorn’s 3.5 g per 3 cups make it a fiber-full snack
  • Artichokes: a medium one has more than 10 g of fiber
  • Broccoli has 5 g of fiber when boiled
  • Turnip greens have 5 g of fiber when boiled
  • Green peas have almost 9 g per cup, cooked

Fiber supplements

People struggling to get enough fiber in their diets often turn to supplements. While Smathers reported that supplements are not as good as fiber from whole foods, fiber supplements can be helpful for people looking to regulate their bowel movements or who suffer from constipation. They also have the same cholesterol-lowering and blood sugar stabilization effects — if you can get enough of them. A supplement does not carry nearly as much fiber as a fiber-rich food like lentils or peas, so merely sprinkling powder on your yogurt probably will not get you the fiber you need.

Furthermore, fiber-rich foods are wildly high in other vital nutrients, which you won’t get if you add supplements to nutritionally void foods.

Fiber supplements can interact with certain drugs, like aspirin, carbamazepine and warfarin, according to the Mayo Clinic. They can also cause bloating and gas — just like the real thing.

High-fiber diet

In order to get all the benefits of fiber, many people adopt a high-fiber diet. When incorporating more fiber into your diet, start slowly, adding 5 g a day for two weeks, the University of Michigan recommends. If consumed too fast or in excess, fiber can cause bloating, cramps and even diarrhea. Let your body get used to having more fiber.

The University of Michigan also advises balancing non-caffeinated drinks with caffeinated ones. Because caffeine is a diuretic that causes loss of fluids, adding excess caffeine to a high-fiber diet can cause constipation. Aim for two cups of non-caffeinated fluids for every cup of caffeinated ones.

Smathers recommended the following tips for a successful high-fiber diet:

  • Add fruit (especially berries) to every meal.
  • Start the day with bran cereal or oatmeal and berries.
  • Add beans or legumes to a lunchtime salad or soup, or have a bean or lentil burger rather than one with meat.
  • At dinner, add high-fiber vegetables like broccoli, corn and turnip greens to meat sauces. Combine with whole-wheat pasta or brown rice.

Low-fiber diet

Sometimes, medical situations require people to adopt a low-fiber diet, at least for a time. Those undergoing chemotherapy, radiation or surgery often need to give their intestinal tract a rest, according to the University of Pittsburgh Medical Center. People suffering from Crohn’s disease, diverticulitis, inflammatory bowel disease and ulcerative colitis often maintain a low-fiber diet for a longer time.

People on a low-fiber diet should avoid high-fiber foods that make the intestinal tract work harder, like legumes, beans, whole grains and many raw or fried vegetables and fruits, according to the National Institutes of Health (NIH). Refined grains, many cooked vegetables and ripe melons, peaches, plums, bananas and apricots are still okay. But also avoid spicy foods, fried foods, tough or processed meat, caffeine, cocoa from cocoa powder and nuts.

Additional resources

  • Colorado State University: Dietary Fiber
  • Mayo Clinic: Dietary Fiber – Essential for a Healthy Diet
  • NIH: Low-Fiber Diet


Since the early 1950s, various definitions of dietary fiber have been proposed by different countries and organizations (Table 1). In 1953, Hipsley defined dietary fiber as a term for nondigestible constituents that make up the plant cell wall, encompassing the “unavailable carbohydrate” that had been described much earlier by McCance and Lawrence (1929). This definition was expanded by Trowell (1972) based on: (1) a number of hypotheses relating dietary fiber to health (“dietary fiber hypothesis”) including prevention of diverticular disease and colon cancer (Burkitt et al., 1972; Trowell, 1972); (2) a concern for the adverse effects from consuming diets high in refined carbohydrates, termed The Saccharine Disease (Cleave and Campbell, 1966); and (3) the need to replace the term “crude fiber” (Trowell, 1972). Based on the above concerns, dietary fiber was defined as “the skeletal remains of plant cells that are resistant to digestion (hydrolysis) by enzymes of man” (Trowell, 1972).


Definitions of Dietary Fiber.

In 1976, Trowell and colleagues recognized the inadequacy of the 1972 definition because it was not known at the time of the first definition that components of the plant cell other than the cell wall, including mucilages, storage polysaccharides, and algal polysaccharides, were not hydrolyzed by the alimentary enzymes. Therefore, dietary fiber was redefined (Trowell et al., 1976) (Table 1). This definition is synonymous with the term “unavailable carbohydrate”, a component of food that was measured by Southgate (1969). Publication of the 1976 definition was the result of interest in the possible health benefits of non-digestible storage polysaccharides, notably guar gum of the cluster bean. This gum was shown to reduce serum cholesterol concentration (Jenkins et al., 1975) and flatten the postprandial glycemia (Gassull et al., 1976).

The 1976 Trowell definition was the basis for the definition set by the Expert Advisory Committee on Dietary Fibre of Health and Welfare Canada (Health and Welfare Canada, 1985) (Table 1). The Health and Welfare Canada definition was initially intended to define dietary fiber with a view to future health claims for fiber. The Committee sought a definition that was broad enough to accommodate the range of dietary fiber values obtained from a number of analytical techniques. The term “endogenous” was added to the definition to emphasize that indigestible materials formed during processing, such as Maillard reaction products or charred carbon, were not considered to be dietary fiber. In addition, water soluble components found in foods, including gums, mucilages, and pectic substances, as well as non-nutritive fiber-associated substances, such as phytates, were intended to be part of dietary fiber.

In 1984, New Zealand Food Regulations defined dietary fiber as the “edible plant material not hydrolysed by the endogenous enzymes of the human digestive tract”; it was to be measured by the first method of analysis (Prosky et al., 1985) accepted by AOAC (AOAC method 985.29).

In 1987, the U.S. Food and Drug Administration (FDA) adopted AOAC method 985.29 for regulatory purposes to identify dietary fiber as a mixture of nonstarch polysaccharides, lignin, and some resistant starch (USFDA, 1987) (Table 1). Related methods that isolated the same components as AOAC method 985.29 were developed independently (AOAC methods 991.42, 991.43, 992.16, 993.19, 993.21, and 994.13; see Table 2) and accepted by AOAC in subsequent years. These methods are also accepted by FDA. The 1976 Trowell definition was the basis for FDA accepting the AOAC methods for isolating dietary fiber. These methods exclude all oligosaccharides (3 to 9 degrees of polymerization) from the definition and include all polysaccharides, lignin, and some of the resistant starch that is resistant to the enzymes (protease, amylase, and amyloglucosidase) used in the AOAC methods. However, FDA did not and still does not have a written definition of dietary fiber for the purposes of food labeling and health claims.


Components Measured by the Various Methods of Fiber Analysis.

Similar to the United States, there is no official definition of dietary fiber in Japan. A standard method for measuring dietary fiber in Japan is based on AOAC method 985.29 plus a chromatographic method that isolates low molecular weight maltodextrins (Gordon and Ohkuma, in press) (Table 1). Dietary fibers can also be approved in Japan as effective ingredients in foods for specific health use; these include indigestible maltodextrin, hydrolyzed guar gum, chitosan, polydextrose, psyllium, wheat bran, and depolymerized sodium alginate (DeVries, 2001). For many Asian countries, dietary fiber intake tables have been based on AOAC methods 985.29 and 991.43, although the definition used by China since 1995 does not identify a specific method (Jian-xian, 1995) (Table 1).

The Expert Panel on Dietary Fiber of the Life Sciences Research Office (LSRO) proposed a definition of dietary fiber in 1987 similar to the one identified by Health and Welfare Canada in 1985. This definition included nonstarch polysaccharides and lignin and excluded fiber-associated substances found in the plant cell wall such as phytates, cutins, saponins, lectins, proteins, waxes, silicon, and other inorganic components (LSRO, 1987). Other substances not considered to be dietary fiber according to the LSRO definition include indigestible compounds formed during cooking or processing (e.g., resistant starch, Maillard reaction products), oligosaccharides and carbohydrate polymers of less than 50 to 60 degrees of polymerization that are not recovered in dietary fiber analysis, nonplant-derived compounds (e.g., chitin, chitosan), and synthetic carbohydrate polymers.

In 1988, Health Canada published guidelines for novel fiber sources and food products containing them that can be labeled as a source of fiber in addiion to those included in their 1985 definition (Health Canada, 1988) (Table 1). The rationale for these guidelines was that there were safety issues unique to novel sources of fiber, and if a product was represented as containing fiber, it should have the beneficial physiological effects associated with dietary fiber that the public expects. The guidelines indicate that both safety and efficacy of the fiber source have to be established in order for the product to be identified as a source of dietary fiber in Canada, and this has to be done through experiments using human subjects. Three measures of efficacy were identified: (1) laxation, (2) normalization of blood lipid levels, and (3) attenuation of blood glucose responses. Detailed guidelines were later produced for the clinical studies required to assess laxation effects, as this was the physiological function most often used by industry when seeking approval for a novel fiber source (Health Canada, 1997a).

In 1995, a definition for dietary fiber appeared in the Codex Alimentarius Guidelines on Nutrition Labelling (FAO/WHO, 1995) (Table 1). The Codex allows the analytical methods AOAC 985.29 and AOAC 991.43 (Table 2) for measurement of dietary fiber in special foods and infant formula. There have been recent attempts to revise the Codex definition; however, there has not been a consensus on the inclusion of animal and other chemically characterized substances (FAO/WHO, 2000).

Several countries in Europe published definitions for dietary fiber in the late 1980s and early 1990s, including Germany (Anonymous, 1989), Belgium (Anonymous, 1992), and Italy (Anonymous, 1993) (Table 1). For labeling purposes, Denmark, Finland, Norway, and Sweden have defined dietary fiber as edible material that cannot be degraded by human endogenous enzymes, as measured by AOAC method 985.29 (Table 1). The issue regarding inclusion or exclusion of inulin and fructooligosaccharides has been handled somewhat differently by these countries in the absence of European Union regulation. In Denmark and Norway, fructans have been allowed to be included as dietary fiber on the food labels since 1995 and 1998, respectively (i.e., before the approval of AOAC method 997.08). Sweden made a similar decision in 1999, specifying AOAC method 997.08. In 1998, the Food Administration of Finland recommended that inulin and oligofructose be labeled separately and not be included as dietary fiber. In 2001, however, AOAC method 997.08 was added to 985.29 for analysis of dietary fiber, implying that inulin and oligofructose can now be labeled as dietary fiber in the four Nordic countries (N-G Asp, Division of Applied Nutrition, Lund University, personal communication, February 22, 2001).

In 1998, the Committee on Medical Aspects of Food and Nutrition Policy (COMA) of the United Kingdom formally adopted the Englyst nonstarch polysaccharide method for defining dietary fiber (COMA, 1998) (Table 1). In September 2000, the U.K. Food Standards Agency recommended AOAC methods 991.43 and 997.08 (Table 2) to ensure consistent labeling of food products (Hignett, 2000) (Table 1). In November 2000, the U.K. Food Standards Agency acknowledged COMA’s definition of dietary fiber as nonstarch polysaccharides yet recognized that the “European rules preclude insistence on a national definition”. AOAC method 985.29 and the Englyst method (Englyst and Cummings, 1984) are cur rently accepted by the European Community to measure dietary fiber but there is no clearly written definition of the material that is measured by these methods.

In May 2000, the American Association of Cereal Chemists (AACC) adopted an updated definition of dietary fiber that was developed by a committee appointed to review, and if necessary, update the original AACC definition of dietary fiber (AACC, 2000) (Table 1). This definition is similar to the ANZFA definition. The AACC definition recognizes that the primary characteristics of dietary fiber are resistance to digestion and absorption in the small intestine and fermentation in the large intestine; the rationale for including these characteristics is that it recognizes the key physiological impacts of fiber demonstrated in the past 30 years of research (AACC, 2000).

In November 2000, the recently formed Australia New Zealand Food Authority (ANZFA) concluded that relying on a prescribed analytical method as the sole means of defining dietary fiber for regulatory purposes was unsatisfactory since analytical methods do not take into consideration the physiological impact of new food forms or food ingredients that are part of the diet (ANZFA, 2000). Thus, a definition has been proposed (Table 1) that includes the origin, chemistry, and physiology of dietary fiber, similar to the Codex Alimentarius Guidelines on Nutrition Labelling (FAO/WHO, 1995) and the earlier New Zealand Food Regulations definition (New Zealand, 1984). Furthermore, ANZFA has endorsed the use of AOAC method 985.29 or 991.43, and AOAC methods 997.08 or 999.03, which measure fructans (e.g., inulin) (Table 2).

In conclusion, a variety of definitions for dietary fiber have been promulgated by scientific and regulatory agencies worldwide. Some definitions specifically state a physiological definition of dietary fiber, whereas others rely on more prescribed analytical methods as the sole determinant of dietary fiber. The majority of accepted analytical methods for the measurement of dietary fiber are based on a variety of AOAC accepted methods.

Since many definitions are based on methods to analyze dietary fiber, the evolution of the methodologies to measure fiber were reviewed (see Appendix C). Nonstarch polysaccharides are recovered by all methods designed to measure all components of dietary fiber, and only those methods developed to measure a specific fiber component (e.g., resistant maltodextrins, inulin, polydextrose) do not recover nonstarch polysaccharides (Table 2). Most methods include the non-carbohydrate lignin as a component of dietary fiber. Only the methods of Englyst and the methods developed to measure a specific type of polysaccharide exclude lignin. In addition, the methods of Englyst and of Mongeau and Brassard, which were designed to measure all fiber components, do not include resistant starch as fiber.

Dependence on ethanol precipitation as a means of recovering polysaccharides excludes polydextrose, resistant maltodextrin, and oligosaccharides, and most inulin, which are soluble in ethanol. These saccharides also are lost if ethanol is used at the beginning of an analytical procedure to remove mono- and disaccharides. Measurement of polysaccharides from animal sources (e.g., chitin, chitosan, or chondroitin sulfate) has not been systematically studied, but methods developed to measure total fiber do recover a portion of these types of polysaccharides.


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Fiber is one of those good-for-you nutrients. But what exactly is it? Why do you need it and what food should you eat to get it?

What Is Fiber?

Fiber is a carbohydrate that the body can’t digest. It’s found in the plants we eat — fruits, vegetables, grains, and legumes.

Fiber can be soluble or insoluble:

  • Soluble fiber dissolves in water. It helps lower cholesterol and improve blood sugar control.
  • Insoluble fiber does not dissolve in water. It helps with constipation.

Both kinds of fiber are important parts of a healthy diet.

What Are the Benefits of Fiber?

A diet high in fiber:

  • helps prevent or relieve constipation
  • increases feelings of fullness, which may help with weight control
  • lowers cholesterol
  • helps prevent heart disease and diabetes
  • may lower the chances of getting some types of cancer

What Are Good Sources of Fiber?

Foods that are naturally high in fiber, include:

  • whole grains, such as 100% whole-wheat bread, brown rice, and oatmeal
  • cooked dried beans, such as black beans, lentils, and split peas
  • fruit and vegetables
  • nuts and seeds

Look for the fiber content of foods on the nutrition labels — it’s listed as part of the information given for “total carbohydrates.” A high-fiber food has 5 grams or more of fiber per serving and a good source of fiber is one that provides 2.5 to 4.9 grams per serving.

How Much Fiber Do I Need?

Teen girls (14–18 years old) should get 25 grams of fiber per day and teen guys (14–18 years old) should get 31 grams of fiber per day.

It’s best to get your fiber directly from foods rather than from pills or other supplements. The best sources are fresh fruits and vegetables, nuts and legumes, and whole-grain foods. If your doctor recommends a fiber supplement, take it as directed.

Other things to know:

  • Add fiber to your diet slowly over a few weeks. Adding too much fiber too quickly can cause bloating, gas, and/or cramps.
  • Drink plenty of water, which helps move fiber through the intestines.

Making Fiber Part of Your Diet

Here are some simple ways to make sure you get enough fiber.


  • Have a bowl of hot oatmeal.
  • Opt for whole-grain cereals that list ingredients such as whole wheat or oats as one of the first few items on the ingredient list.
  • Top fiber-rich cereal with apples, oranges, berries, or bananas. Add almonds to pack even more fiber punch.
  • Try bran or whole-grain waffles or pancakes topped with apples, berries, or raisins.
  • Enjoy whole-wheat bagels or English muffins instead of white toast.

Lunch and Dinner:

  • Make sandwiches with whole-grain breads (rye, oat, or wheat) instead of white.
  • Use whole-grain spaghetti and other pastas instead of white.
  • Try wild or brown rice with meals instead of white rice. Add beans (kidney, black, navy, and pinto) to rice dishes for even more fiber.
  • Spice up salads with berries and almonds, chickpeas, cooked artichokes, and beans (kidney, black, navy, or pinto).
  • Add lentils or whole-grain barley to your favorite soups.
  • Sweet potatoes, with the skins, are tasty side dishes.
  • Take fresh fruit when you pack lunch for school. Pears, apples, bananas, oranges, and berries are all high in fiber.

Snacks and Treats:

  • Top yogurt, cereal, or oatmeal with fruit and nuts.
  • Put veggies, like lettuce, tomato, or avocado, on sandwiches.
  • Add beans to soups and salads.
  • Add bran to baked goods.
  • Choose air-popped popcorn, whole-grain crackers, fruit, or vegetables as healthy snack options.

Reviewed by: Mary L. Gavin, MD Date reviewed: September 2019

Last Updated on October 3, 2019

It’s easy to spot media stories telling us to eat more fiber for a healthier life and better gut health.

We can see them pretty much every day, whether online, on TV or in the newspapers.

Also, there are dozens of studies vouching for the digestive health benefits of dietary fiber.

However, consuming any food compound in excess can be problematic, and fiber is no exception.

In fact, research shows that there are some side effects that consuming too much fiber can cause.

This article examines this issue in more detail.

Can You Have Too Much Fiber?

Just because fiber has benefits doesn’t mean we should eat as much of it as we can.

For one thing, it is possible to experience adverse effects if we consume too much, especially when supplementing.

Some possible symptoms of excessive fiber intake include stomach and digestive issues such as bloating, cramps, and gas.

But how much fiber is too much?

The “official” recommended daily fiber intake is set at around 30 grams depending on gender (1).

Anyone eating a standard whole-foods-based diet is unlikely to exceed this amount greatly.

However, those who go overboard on green smoothies, fiber supplements, and excessive amounts of grains might far exceed this figure.

More isn’t always better, and research shows that an excessive amount of fiber can cause problems.

Potential Problems Caused by Too Much Fiber

Here are a few signs, symptoms and problems that excessive fiber intake can cause.

1. Constipation

Usually thought of as a consequence of too little fiber, constipation may also result from an excessive intake. In fact, it can even be worse than on a low-fiber diet (2).

One study investigated fiber intake in 63 constipation patients who were currently on a high-fiber diet. The researchers split the participants into three groups; a no fiber, reduced fiber, and continuous high fiber diet plan.

Surprisingly, only the participants reducing their fiber intake saw a benefit. Participants who reduced their fiber intake had improvements in straining, gas, constipation, and anal bleeding (3).

The researchers explained that an over-consumption of fiber may cause constipation through a build-up of undigested matter in the digestive tract.

The risk is higher when first increasing fiber in the diet, so it’s important to increase fiber slowly if you plan on making any significant dietary change.

Lastly, a greater fiber intake increases the body’s water requirements, not drinking enough can cause dehydration and make the problem worse (4, 5).

Key Point: Evidence suggests that too much fiber can cause constipation. Studies also show that cutting down on fiber intake can be an effective remedy to relieve constipation.

2. Nutrient Malabsorption

In reality, most people already consume relatively low fiber diets. As a result, it’s rare to impede the absorption of nutrients through excessive fiber intake.

However, insoluble fiber—mainly found in whole grains—can reduce our absorption of certain nutrients.

Specifically, fiber can bind essential minerals including calcium, iron, magnesium, and zinc (6, 7).

For example, a recent randomized trial showed that a high intake of fiber causes a “slight but significant” reduction in calcium absorption (8).

Whole grain sources of fiber are also sources of antinutrients like phytic acid. While phytate can have some beneficial effects on our body, it’s also capable of binding minerals.

In particular, studies show that higher dietary phytate intake inhibits the absorption of iron, calcium, and zinc (9, 10).

Key Point: Dietary fiber decreases the bioavailability of some essential minerals. However, this effect is only slight for people with a reasonable fiber intake and would likely require excessive amounts of fiber to do harm.

3. Gas and Bloating

Gas and feeling bloated are two of the most common complaints against a high fiber diet plan.

Since we think it’s the healthy thing to do, many people go overboard and include too much fiber-rich food in each meal.

As the microbiota in our gut digest fiber, the process produces various gases. This gas can lead to belching, flatulence and abdominal bloating, causing a considerable amount of discomfort to sufferers (11, 12, 13).

If this is something that sounds familiar, then consider how much fiber you’re consuming.

This digestive distress is especially common when increasing fiber intake suddenly (14).

Foods such as beans and cruciferous vegetables like cabbage, kale, and sprouts are common culprits for gas production.

Key Point: Eating a few vegetables with a meal is perfectly healthy, but massive amounts is overkill. Too much fiber often causes gassiness and abdominal bloating.

4. Abdominal Cramping

Stomach cramps can be both painful and frustrating, and they can sometimes be a sign of excessive fiber intake.

The gases released by the breakdown of large amounts of fiber are the culprit, and studies show that reducing fiber intake can ease abdominal pain (15, 16).

In this case, it is a build-up of gases in the colon that causes the problem by exerting pressure on the colon walls.

A systematic review of randomized controlled trials demonstrates that fiber intake can relieve symptoms of irritable bowel syndrome – except for abdominal pain. This study found that “in some cases, insoluble fibers may worsen the outcome” (17).

While stomach cramping may be a sign of too much fiber, if it persists then seeing a doctor for an accurate diagnosis is important.

Key Point: Various studies show that too much fiber can lead to abdominal pain.

5. Intestinal Blockage

Fortunately, this condition is very rare and unlikely.

However, there are documented cases of gastrointestinal tract blockages, which are a serious medical emergency (18, 19).

Notably, too much fiber can increase the risk of a phytobezoar developing. This condition is a large, trapped mass in the digestive system which consists of fruit and vegetable fibers.

Coupled with inadequate chewing, a large intake of high-fiber food is one of the biggest risk factors for a phytobezoar (20).

A low-fiber diet is usually the default recommendation for those at risk of an intestinal blockage (21, 22).

Key Point: An intestinal blockage is pretty much the very worst case scenario, but a serious overload of fiber can lead to a bowel obstruction.

6. Dehydration

Dehydration as a result of excessive fiber depends on how much fluid the individual is consuming in the first place.

If it is an inadequate amount and fiber consumption increases, then it’s a possible cause of dehydration.

For larger amounts of dietary fiber, it’s important to ensure sufficient water intake.

The reason why is because soluble fiber absorbs water in the digestive tract, which increases the body’s hydration needs (23, 24).

You may have heard the “eight glasses per day” suggestion for water intake, but there isn’t much evidence behind this.

It’s incredibly difficult to ascertain how much water each individual needs, as this depends on so many different things. For example; the climate, physical activity, diet, and each person’s unique biology can all influence hydration levels.

With this in mind, judging water requirements by listening to thirst and urine color (ideally pale yellow) is ideal.

Key Point: An insufficient amount of water on a high-fiber diet will lead to dehydration.

7. Acid Reflux and GERD

Recently, evidence suggests that small intestinal bacterial overgrowth (SIBO) may cause some cases of acid reflux.

Acid reflux is otherwise known as gastroesophageal reflux disease (GERD), but you may know this best as heartburn.

Heartburn is a digestive disorder in which stomach acid leaks into the esophagus, and it may cause anything from mild discomfort to sharp, burning pain.

In cases of heartburn, gas from the bacterial fermentation of carbohydrates can rise upward. As a result, these gases put pressure on the LES valve (lower esophageal sphincter) which keeps acid in the stomach and out of the esophagus.

For this reason, lowering carbohydrate levels has been put forward as a potential therapeutic solution to GERD.

There appears to be strong evidence too.

For instance, a recent 16-week study of 144 obese women with GERD saw all symptoms resolve in all women on a low-carb, high-fat diet (25).

Key Point: Higher amounts of fermentable carbohydrate such as fiber may play a role in symptoms of GERD.

How to Counteract Too Much Fiber

What can you do if you overeat fiber?

If you have symptoms of consuming too much, then the most important ways to counteract them are;

  • STOP fiber intake until the condition subsides: consuming more fiber when there is a large amount still undigested will worsen the problem.
  • Drink lots of water – adequate hydration will help with the digestion process.
  • Do some light exercise such as walking: exercise and movement are known to help improve constipation and speed digestion up.

Final Thoughts

Like with many things in nutrition, there isn’t always a clear black and white.

Despite all the health claims we read about fiber, it’s important to be aware of the possibility of adverse effects at higher levels of consumption.

It’s also worth remembering that some fiber-containing foods are incredibly nutritious – avocados, raspberries, and cacao just to name a few.

Irritable bowel syndrome (IBS) is one of the most common and troublesome conditions for which individuals seek medical attention. Specific food practices may contribute to symptoms of constipation, diarrhea, bloating, gas, and abdominal pain. Adding fiber to your diet may help improve bowel function and decrease symptom severity.

Fiber is a double-edged sword for people with intestinal disorders. While fiber alleviates constipation, certain high fiber foods, such as bran, may increase gas production and bloating. However, it seems likely that most people with IBS will benefit from at least a moderate increase in dietary fiber intake.

While fiber may appear to be a simple solution, the typical Western diet for adults often fall below the current recommendation of 20–35gm per day. Adding too much fiber too fast can result in a worse condition than being on a low fiber diet. A gradual increase in dietary fiber can modify, improve and, in some people, eliminate the abnormal bowel habits and painful symptoms associated with IBS.

People who have difficulty obtaining the goal of 20–35gm per day through diet alone may find fiber supplementation helpful. With any dietary fiber, the guideline is to start low, go slow.

As an added benefit, consuming generous amounts of fiber in your everyday diet potentially can improve overall health. Fruits and vegetables appear to exert a strong healthy effect.

Gastrointestinal (GI) Health Benefits of Dietary Fiber

Dietary fiber has specific benefits for maintaining GI health. High fiber foods take longer to chew, which gives the brain a chance to register fullness, preventing overeating. High fiber foods also slow digestion, which prolongs this feeling of fullness.

Research in fiber and GI health took off in the 1970s when a link was first proposed between high fiber intake and low rates of some chronic diseases. While the use of dietary fiber in the treatment of certain GI disorders may be debatable, the evidence to at least consider fiber therapy is strong.

IBS patients who are prone to constipation appear to benefit the most from fiber treatment. Other people with various forms of GI disorders may benefit from a variety of treatments involving more than a little trial and error. Because these disorders have many components, the greatest challenge will be in identifying one or several strategies that prove effective.

Soluble and Insoluble Fiber

Dietary fiber can be classified as either soluble or insoluble. Soluble fiber (found in vegetables, fruits, and oat cereals for example) dissolves in water, becomes a soft gel, and is readily fermented. These include pectin, guar gum, and other gums.

Insoluble fiber does not dissolve or gel in water and is poorly fermented. Cellulose (found in legumes, seeds, root vegetables, and vegetables in the cabbage family), wheat bran, and corn bran are examples of insoluble fiber.

If you find that fiber seems to be a problem that causes you to feel bloating or pain, it is usually insoluble fiber that is the problem. Soluble fiber is less likely to be a problem. But the reaction is the opposite in some people, so trial and error may be the best option.

High fiber substances containing both soluble and insoluble fibers have the properties of both. They include oat bran, psyllium, and soy fiber. Methylcellulose is a semi-synthetic fiber. It is soluble and gel forming, but not fermentable.

Types of fiber differ in the speed and extent to which they are digested in the GI tract, and in the process of fermentation. There may be both good and bad aspects to fermentation, but there are certainly metabolic products produced by fermentation which contribute to colonic health. The solubility and fermentation of a particular fiber affects how it is handled in the GI tract.

Since the effect of identical fibers varies from person to person, individual response may vary. We encourage individuals try different types of fiber.

Specific Treatment Using Dietary Fiber

Despite some uncertainties about its use and effectiveness, fiber is a reasonable approach in treatment of GI disorders, particularly in IBS with constipation. Once a diagnosis of IBS is made, your physician may suggest the fibers listed below for treatment of various symptoms.

IBS Symptoms Fiber Treatment
Lower abdominal pain Methylcellulose or Psyllium
Upper abdominal pain Oatmeal, Oat bran, or Psyllium
Constipation Methylcellulose or Psyllium
Incomplete evacuation Methylcellulose or Psyllium
Diarrhea Psyllium or Oligofructose
Excessive gas Methylcellulose or Polycarbophil

Nutrition therapy, with an emphasis on dietary fiber modification, appears to be a safe and effective initial treatment of gastrointestinal disorders, particularly in constipation prone individuals. Fiber intake can be tailored to the symptoms most evident and can be fine-tuned in partnership with a medical care provider.

Tips for Adding Fiber to Your Diet

Making small, gradual changes can add up to a big difference in the nutritional value of your diet. Experiment with fresh foods and don’t be afraid to try new foods and recipes. Here are a few practical tips for adding fiber to your diet.


  • Cook in microwave to save time and nutrients
  • Cook only until tender-crisp to retain taste and nutrients


  • Replace the meat in salads and main dishes with presoaked dried beans and peas
  • Presoaking reduces the gas-producing potential of beans if you discard the soaking water and cook using fresh water
  • Use a slow cooker for bean soups and stews


  • Snack on fruit anytime, anywhere
  • Experiment with unusual fruits such as kiwi, pineapple, and mangos
  • Leave peelings on fruit whenever possible
  • Use fresh and dried fruit in muffins, pancakes, quick breads, and on top of frozen yogurt


  • Choose whole-grain varieties of breads, muffins, bagels, and English muffins
  • Try fresh pasta instead of dried
  • Mix barely cooked vegetables with pasta for a quick pasta salad

Did This Article Help You?

IFFGD is a nonprofit education and research organization. Our mission is to inform, assist, and support people affected by gastrointestinal disorders. If you found this article helpful, please consider supporting IFFGD with a small tax- deductible donation.

Adapted from IFFGD Publication #152 by James W. Anderson, MD, Professor of Medicine and Clinical Nutrition, University of Kentucky; Chief, Endocrine-Metabolic Section, VA Medical Center, Lexington, KY. Last modified on September 15, 2014 at 12:43:28 PM

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