High fiber foods have several health benefits. Dietary fibers are components of food that are resistant to digestive enzymes and are found mainly in cereals, fruits, and vegetables.

Dietary fiber is indigestible in the human small intestine and digested completely or partially fermented in the large intestine. That’s why dietary fiber is examined in two groups: water-soluble and water insoluble organic compounds.

Dietary fibers include celluloses, Hemicelluloses, polysaccharides, oligosaccharides, Lignin, and various other plant-associated substances.

Dietary fibers have a protective effect against certain gastrointestinal diseases, constipation, piles, gastroesophageal reflux disease, colon cancer,  duodenal ulcer, obesity, diabetes, diverticulitis stroke, hypertension, and cardiovascular diseases (1)(2).  

Types of Dietary fiber:

Dietary fibers are classified into two different types; water-soluble and water-insoluble dietary fibers and each type possesses its own benefits and functions.

Soluble Dietary Fiber:

As the name indicates, this type of fiber can dissolve in water to make gel-like material. They are well-fermented fibers. pectin, gums, and mucilages are included in this type of fiber.(3)

One of its main functions is lowering bad cholesterol (LDL) and stabilizing sugar levels in the blood. This form of fiber is mostly found in vegetables, oats, fruits, soy products, and legumes.(4)

Insoluble dietary fiber:

 They are water-insoluble and less fermented dietary fibers. Insoluble types of fibers do not dissolve in fluids. But they absorb the fluids and then stick to other materials for example to make a stool.

This causes the formation of a much softer and bulk mass of stool which is their major function. Some of the sources of insoluble fiber include nuts, seeds, fruits, whole grains and beans. cellulose, hemicellulose, lignin includes In this type of dietary fiber. ( 5)

Resistant Starch:

Resistant starch is not traditionally considered as a type of fiber but it acts in the same way to perform its functions. Like other types of fiber, it is also indigestible in the small intestine and moves to the large intestine without being digested.

The gut microbial convert this starch into short-chain fatty acids which provide protection against cancer.

The sources of resistant starch include unripe bananas, undercooked pasta, cooked rice, and potatoes (6).

Health Benefits of High Fibers Foods

Many types of research show that intake of dietary fibers provides many health benefits however many types of research show that the average intake of dietary fibers for US adults and children is less than the recommended level due to bad eating habits. ( 7)

Individuals with high intakes of dietary fiber appear to be at lower risk for developing coronary heart disease, obesity, hypertension, stroke, diabetes,and certain gastrointestinal diseases. Increase intake of dietary fibers lowers the serum cholesterol level and blood pressure. Increased intake of soluble dietary fiber improves insulin sensitivity and glycemia in diabetic and non-diabetic individuals. (8)

For Weight Control

Many studies show that 30g of dietary fiber helps in weight loss. The intake of Dietary fiber prevents from obesity (9)

Obesity has become a major health issue in developed countries and many developing countries because it is the root cause of many metabolic disorders. Along with exercise and physical activities, dietary fiber provides another solution for obesity and weight control management( 10).

 Many studies show that the use of soluble and insoluble forms of dietary fibers helps in weight control. Dietary fibers and foods having dietary fiber possess very low caloric amounts.
 They yield almost 2-3 calories per gram, So a high fiber diet is being recommended in obesity management for lowering weight (11).

Dietary fibers control the weight in the following ways

• Foods rich in fiber take more chewing time than other normal foods
• Soluble dietary fibers absorb more water and produce a form of viscous gel. This gel formation increases stomach distention.
• Along with increasing the satiety level, fibers affect the fat oxidation process, lead to decreased energy intake and lowering the fat content of the body.
• Fibres slow down the gastric emptying process and produce a feeling of satisfaction and this feeling decrease the serum insulin secretion and causing less food intake  (12)

May Prevent From Diabetes:

Diabetes is a metabolic disorder which is characterized by high blood sugar levels. Dietary fiber has an effective role in maintaining the blood glucose (sugar) level in the body. A soluble form of fiber causes a delay in the digestion process and a delay in the absorption of glucose into the blood.

Most specifically a diet consisting of carbohydrates and rich in dietary fiber such as those of legumes, fruits, cereals, and vegetables, is useful in the treatment of diabetes (13). 

Glycemic Index (GI) is the measurement of the rate at which food is converted to glucose in the bloodstream.  

Foods rich in dietary fibers show a low glycemic index (GI). Foods with high GI value, cause a sharp and rapid increase in the blood glucose level which contributes towards the disturbed function of insulin. This can even lead to the onset of type 2 diabetes. While fibers show low GI value which means that they release glucose slowly in the blood. Resultantly causing decreased insulin secretion and maintaining the normal sugar value ( 14).

High Fiber Foods Maintaining a healthy gut/digestive tract:

Dietary fiber is important for maintaining a healthy gut function. Both types of fiber either soluble or insoluble have health benefits with their effect on the digestive system.
 Use of dietary fiber can:

• Prevent and relieve constipation
• Help the smooth removal of waste products from the body
• Promote regular bowel movement
• Reduction of that waste spends in the human intestine
• Encourages the healthy gut microbes
• Insoluble form of fiber take the water from the system and increase the softness of stool in the intestine, making its elimination from the body easier
• The increased fiber content of diet leads to increased fecal energy excretion (mainly in the form of fat and nitrogen) (15)

Maintain cholesterol level in the body:

The individuals who consume fibers as an important part of their diet report reduced risk of coronary heart diseases and reduced risk of having a stroke, which in turn reduce the overall rate of morbidity and mortality among patients of coronary heart diseases by a level of 17 to 28%.

Dietary fiber supplementation such as those of β-glucan and Psyllium fiber causes a reduction in the level of LDL cholesterol concentrations. β-glucan is a type of water-soluble dietary fiber, which is derived from barley and oats

Psyllium is a water-soluble, gel-forming type of functional fiber which is derived from the seed husk of Plantago Ovata  (16).

Dietary fibers controls the cholesterol level in the body by the following three possible ways:

1. The use of fiber for reducing serum cholesterol levels is linked to the ability of chelating soluble dietary fibers. The fibers chelate with the cholesterol present in the lumen of the small intestine and thus reducing the absorption of cholesterol in the intestine. 
2. A soluble form of fibers also causes an increase in the fecal excretion of bile acids. This causes bile acid production from hepatic cholesterol. This reduces the level of circulating plasma LDL cholesterol because this plasma LDL is taken up by the liver in order to replenish the cholesterol level in the body. 
3. There are fibers that are freely fermented by colonic bacteria into short-chain fatty acids like acetic acid, propionic acid, and butyric acid. This propionic acid is absorbed and inhibits the function of the enzyme HMG-CoA reductase. This enzyme had to function at the rate-limiting step of the liver’s cholesterol synthesis. Blockage of this enzyme function by fibers causes a reduction in the level of cholesterol (17).

High Fiber Foods Reduces The Risk Of Cancer:

Scientific evidence has suggested that a diet low in fiber content is linked to colorectal cancer throughout the world. A high dietary fiber intake is associated with a low risk of colorectal cancer.   

As mentioned earlier, the fermentation of dietary fibers by intestinal microbes produces short-chain fatty acids. These acids provide protection against colorectal cancer. Fibers, fruits, and vegetables have antioxidants, vitamins, phytoestrogens, and phenolic acids which are protective against cancer ( 18)

Dietary fiber reduces the risks of cancer in the following  ways:

• Fibers produce stool more often, increase the bulk size, softens and dilute the stool. So, harmful chemicals including carcinogens spend less time in the bowel reducing the cancer risk.
• Microbes in the intestine produce butyrate from dietary fiber. This butyrate makes our bowel cells healthy reducing the risk of tumors development ( 19)

List of 24 highest fibers foods

For some decades, the food trend has been shifted towards food rich in fat while the use of food with high fiber content has been decreased. However, still, dietary fiber intake is an important part of the diet.

• Soluble dietary fiber is naturally found in different fruits, legumes, whole grains, and vegetables.
• An insoluble fiber consisting of cellulose and hemicellulose is mostly found in whole grains.

In addition, fiber supplementation is also used to increase the fiber content of different foods coming from cereals like wheat, oats, and corn. Followings are some of the sources of food rich in dietary fiber (20)

1. Barley:

Barley is the rich source of a soluble fiber called beta-glucan. Barley lessens hunger because of its high fiber content.

According to U.S Department of Agriculture, 100 grams of barley contains 14.6g of dietary fibers.(21) Soluble fibers usually form a gel-like substance in the human gut and this slows down the digestion process and also the absorption of nutrients. And this produces the feeling of fullness. (22)

2. Corn:

Corn is mostly yellow and comes in a variety of different colors like orange, white, black, and red. According to the U.S Department of Agriculture, 100 grams of corn contains 7.3g of dietary fibers. (23)

 Corn is a healthy cereal grain and is rich in fiber content, vitamins, and anti-oxidants.

The major components of fiber in corn are lignin, hemicellulose and cellulose. (24)

3. Oats:

Oats contain high fiber content and protein when compared to other whole grains. According to the U.S Department of Agriculture, 100 grams of oats contains 10 g of dietary fibers.(25)

 They consist of some unique constituents like beta-glucan and antioxidants named avenanthramides. Oats are gluten-free and pose various health benefits like weight loss, low blood sugar level, etc. (26)

4. Rice:

Dry rice and cooked rice contain varying amounts of fiber content with 1.3g and 0.7g fiber content respectively. Also when compared, brown rice possesses more dietary fiber content as compared to white one which is about 1.6g per 100g. This is because due to the processing of white rice, it losses seed coat which constitutes most of the fiber content. ( 27)

5. Wheat:

Whole wheat is a rich source of fiber. According to the U.S Department of Agriculture, 100 grams of wheat contains 13.1 g of dietary fiber.(28)

Processing of fiber removes the bran and causes the loss of fiber content. The main fiber component in wheat is arabinoxylan which is a type of cellulose while the rest of the component is of cellulose nature. (29)

6. Green beans:

Although the body needs some amount of cholesterol green beans contains no amount of cholesterol. According to the U.S Department of Agriculture, One cup 1/2’’ pieces (116g) of green beans contain 3.94g of dietary fibers (30).

The soluble form of fiber will be helpful in lowering LDL/bad cholesterol (31).

7. Soy:

Soybeans offer a fair value of both soluble and insoluble forms of fiber. The insoluble form of fiber in Soy is alpha-galactosides and it can cause diarrhea in some of the sensitive individuals.

Despite being offering some unhealthy side effects, soluble fibers present in Soy are generally considered healthy. 

Soybeans are utilized in the making of different products like tempeh, tofu, and miso. They are also used as an alternative of dietary replacement for meat and dairy products (32).

According to U.S Department of Agriculture, 18g of soy contains 0.144g of dietary fibers (33).

8. Raw Lentils:

Lentils are a powerful source of vitamin B, Iron, zinc, magnesium, plant-based proteins and fiber. Eating lentils can increase stool bulk and maintain a healthy gut. According to the U.S Department of Agriculture, 30g serving of lentils contains 0.99g of dietary fiber (34).

Lentils cannot be eaten in raw form because they have lectin in them. Lectin is a protein that can bind to the digestive tract and causes a number of various toxic reactions like vomiting and diarrhea. So, lentils should always use in the cooked form before eating. (35)

10. Kidney beans:

Like various other types of legumes, kidney beans are also a rich source of dietary fiber, proteins, and many other nutrients. . According to the U.S Department of Agriculture, 130g serving of kidney beans contains 8.06g of dietary fibers (36).

 They have a considerable amount of resistant starch in them which offers a significant role in weight management.

Despite that, nutritionists recommend beans, including kidney beans as part of a healthy diet because of their high protein source and their use as vegetables (37).

11. Carrots:

Carrot possesses a number of health benefits like weight control management. They also reduce cholesterol levels and are beneficial to improve eye health (38).

 According to the U.S Department of Agriculture, 100g of carrots contains 2.6g of dietary fibers.(39)

12. Chia Seeds:

These are a type of tiny black seeds and are considered a popular nutritious source among the health community. According to the U.S Department of Agriculture, 28g serving of chia seeds contains 10g of dietary fibers.(40)

 They contain a high amount of fiber, magnesium, calcium, and phosphorous.  They can be mixed into homemade jams for use. (41)

13. Buckwheat:

Irrespective of its name, buckwheat is not a grain but it is a form of seed. According to the U.S Department of Agriculture,  100g of buckwheat contains 5.6g of dietary fibers. (42)

These are seeds like grain that belong to a tree that is similar to rhubarb. These are rich sources of magnesium and zinc and they didn’t have gluten in them.

Being gluten-free in nature, they provide an alternative to flour for baking and cooking purposes. They can be used in breakfast cereals too.(43)

14. Quinoa:

Quinoa is an edible seed and pseudocereal as well. According to the U.S Department of Agriculture,  140g (1 cup) of quinoa contains 2.94g of dietary fibers.(44)

It is rich in magnesium, copper, folate and in antioxidants. It is also a source of vitamins like vitamins B1, B2, and B6. It provides a replacement for persons who are sensitive to gluten and it is used in the baking industry and for breakfast cereals.(45)

15. Almonds:

Almond is a popular and healthy type of tree nut. They are also a source of vitamin E and dietary fiber. According to the U.S Department of Agriculture, 36g serving of Almonds contains 4g of dietary fibers.(46)

They are rich in healthy fats and many nutrients like manganese and magnesium.  They can be eaten directly in raw form or for baking purposes can be converted to almond flour form.(47)

16. Beetroots:

The beetroot plant is loaded with various important nutrients like iron, copper, potassium, folate, and manganese. These are high in fiber and help in promoting the growth of good bacteria in the intestine. This increased growth of good microbes improves the function of the digestive system and boosts the immune system to fight against diseases. (48)

 According to the U.S Department of Agriculture, 100g of beetroot contains 10.5g of dietary fibers. (49)

17. Broccoli:

Broccoli is said to be the most nutritious food which is a rich source of various elements and nutrients. According to the U.S Department of Agriculture, 100g of broccoli contains 3.5g of dietary fiber.(50)

These include vitamin K, vitamin C, folate, vitamin B, potassium, iron, manganese, and various other nutrient elements that help to fight against cancer. The protein content in broccoli is also relatively high than other vegetables and their fiber content is also reasonable. (51)

18. Artichoke:

Artichoke is not such a popular one and most people do not know about it but it is the source of many nutrients and also provides a considerably high amount of dietary fiber and antioxidants. According to the U.S Department of Agriculture, 60g serving of Artichoke contains 1.02g of dietary fibers.(52)

Artichoke is fat-free and low sodium which has many nutrients like folate, potassium, vitamin C, magnesium, and fibers. It also shows anti-inflammatory properties and assists in improving digestive tract function.(53)

19. Chick Pea

Chickpeas are the type of legume plant with the source of various minerals and proteins. They can be used as vegetables, can be used in salads, and in many other ways. They are especially rich in a type of soluble fiber named raffinose which is broken down by gut microbes and helps in making bowel movements easier and regular.(54)

According to the U.S Department of Agriculture, 100g serving of chick peas contains 4.5g of dietary fibres.(55)

20. Split peas:

Split peas are used in soup and contain a rich amount of fiber. According to the U.S Department of Agriculture, 240g serving of split peas contains 1.44g of dietary fibers.(56)

They are made from seeds of peas that have been dried, split, and peeled. Besides fiber, they are also a good source of various nutrients like amino acids, potassium, manganese, and copper. They are also low in fats and beneficial for health. (57)

21. Avocado

Avocado is rich in healthy fats and it is also a rich source of potassium, magnesium, vitamin B, vitamin C, and vitamin E. They are unique in a sense as they contain high fiber and fats instead of carbohydrates. (58)

According to the U.S Department of Agriculture, 100g serving of Avocado contains 7.7g of dietary fibers. (59)

22. Strawberries:

Strawberries are a delicious and rich source of Vitamin C, manganese, and some other powerful antioxidants and dietary fibers. According to the U.S Department of Agriculture, 142g serving of strawberries contains 2.98g of dietary fibers. (60)

Fibers constitute about 26% of the carbohydrate content of strawberries serving both soluble and insoluble forms of fibers. These improve the function of gut bacteria by feeding them and maintaining the health of the digestive tract.(61)

23. Bananas:

Bananas are the source of vitamin B6, potassium, and vitamin C. According to the U.S Department of Agriculture, 100g serving of bananas contains 9.9g of dietary fibers.(62)

The unripe form of banana which is green in color contains a considerable amount of resistant starch also. This is resistant to digestion and performs the functions like fiber. (63)

24. Apples:

Apples are sweet and tasty food that is eaten in fresh form and also use in various salads. They are high in fiber content. According to the U.S Department of Agriculture,100g of Apple contains 2.5g of dietary fibers.(64)

Apple packs a bundle of various vitamins, minerals, and soluble types of fiber. The peel of the apple contains a high fiber amount so make sure to eat it too without peeling the apple.

Also, the pectin present in apples poses many health benefits like improving gut function and reducing the risk of coronary diseases. (65)