What is fiber and why does the body need it?

What is fiber?

The human body absorbs many different substances from incoming food - fats, proteins, carbohydrates, microelements, etc. However, there are elements in the food that seem to be just ballast - but without them the gastrointestinal tract either does not work at all, or functions with impairments. And in first place among these substances is fiber. This term refers to fibers that are primarily found in foods of plant origin. They are not directly absorbed by the cells of the digestive system, but they perform two important functions:

1. They serve as food for beneficial intestinal microflora, which in turn are human symbiont organisms.
2. They create a “ballast load” on the intestines, ensuring its normal peristalsis.

Fiber is a collective term because it includes a number of different substances:

• Insoluble. This is primarily lignin, a substance that makes up the walls of plant cells. Also insoluble is cellulose, a polysaccharide that is also a component of plant cell walls.
• Soluble. These are various types of non-cellulosic polysaccharides. There are many varieties of them: hemicellulose of various forms, guar, mucus, gum, etc. Their main feature is that they form a gel-like mass that can undergo microbial fermentation in the large intestine.

What is dietary fiber?

Dietary fiber, or fiber, refers to carbohydrates in plants that your body cannot digest.
Once dietary fiber reaches your colon, it is either broken down by gut bacteria or passed out of your body in your stool ().

There are two main types of dietary fiber – soluble and insoluble. Most high fiber foods contain a combination of them, but they are usually richer in one type (,).

In the intestines, soluble dietary fiber absorbs water and becomes gel-like. This allows your gut bacteria to break them down easily. Chia seeds and oats are rich in soluble dietary fiber (, ,).

In contrast, insoluble dietary fiber has a more rigid microscopic structure and does not absorb water. Instead, they add bulk to the stool. Fruits and vegetables contain large amounts of insoluble dietary fiber (,).

You should aim to eat 14 grams of fiber for every 1,000 calories you consume per day. This is about 25 grams for women and 38 grams for men. Unfortunately, only about 5% of people reach this recommended amount ().

Not getting enough fiber can negatively impact your health. For example, diets low in fiber have been linked to digestive tract problems such as constipation and dysbiosis, which is the abnormal growth of harmful bacteria in the intestines (, , ).

Diets low in dietary fiber are also associated with an increased risk of obesity, colon cancer, and breast cancer (, , ).

Conclusion:

Dietary fiber, also known as fiber, refers to carbohydrates that your body cannot digest. Most people don't eat enough fiber. Recommendations suggest women should consume about 25 grams of fiber per day, while men should consume 38 grams.

Why is fiber needed?

Humans are not herbivores, and their gastrointestinal tract cannot directly absorb fiber. However, it performs a number of very important functions in nutrition:

1. It provides food volume. In order for peristalsis to occur normally, food must fill the intestinal lumen, putting pressure on its walls, which improves passage through the intestines and avoids constipation.
2. Fiber cleanses the intestines. To greatly simplify it, we can say that its particles work like a brush, cleaning out everything that has stuck to the walls of the gastrointestinal tract. Without this, “blockages” again begin, fecal stones (coprolites) form, etc.
3. Fiber slows down the absorption of sugars and other carbohydrates. Therefore, foods high in dietary fiber help normalize blood glucose levels. This allows you to avoid surges, reduces hunger and helps you avoid gaining excess weight.
4. Dietary fiber is not digestible by humans, but serves as food for the intestinal microflora. Some substances (such as lignin) are not used by microbes, but everything else completely or partially serves as food for them.

The benefits of fiber for the body

• quickly saturates, slows down the rate of food digestion, thus helping to control appetite, which helps normalize weight;
• regulates the absorption of micro- and macronutrients;
• reduces “bad” cholesterol and blood glucose levels;
• regulates intestinal motility;
• swelling in the intestines, it acquires the ability to absorb and remove metabolic products harmful to the body;
• has a beneficial effect on intestinal microflora;
• consuming sufficient amounts of dietary fiber prevents many diseases, including cardiovascular diseases (heart attacks, coronary heart disease), diabetes, obesity, certain types of cancer (primarily colon), gastrointestinal diseases, and reduces the risk of developing infections and inflammatory processes .

Fiber norm for humans

The amount of dietary fiber needed for a healthy diet varies depending on gender, age, the body's adaptation to different types of diet, and other factors. However, on average, we can assume that a person needs to take from 35 to 50 grams with food per day. fiber. Is this standard being observed?

Unfortunately no. As studies by nutritionists show, most people on average do not gain 15 grams per day. There are several reasons for this:

• Eating purified and refined foods. The absence of husks and impurities improves taste and quality - but leads to “starvation” for fiber.
• Boiling, frying and other types of processing also break down fiber.

What to do? After all, switching to eating raw plant foods is problematic. The solution is to eat foods that are so rich in fiber that cleaning and heat treatment does not harm this component.

Daily fiber intake

As we have already found out, fiber and dietary fiber are important for maintaining health.

A healthy adult should consume 25–35 g of fiber per day. That's quite a lot.

Insufficient consumption increases the risk of developing colon cancer, constipation, gallstones, diabetes, obesity, heart and vascular diseases.

The World Health Organization recommends consuming at least 400 g of fresh vegetables and fruits daily.

Where are the sources of fiber?

To gain the required amount of dietary fiber, you need to consider the following foods in your diet:

• Bread made from unrefined flour (whole grain).
• Bran.
• Cereal porridges - oatmeal, pearl barley, buckwheat, etc.
• Pasta, especially, oddly enough, gray - made from unrefined flour.
• Fresh fruits. Berries (blackberries, raspberries, etc.), pears and apples, as well as oranges and tangerines are especially useful.
• Vegetables – the leaders here are carrots (especially raw ones), pumpkin and broccoli.
• Nuts, especially almonds.
• Legumes - beans, peas, lentils and chickpeas.

How to take fiber correctly?

The daily value of dietary fiber is 20-30 grams []. At least half of them should be coarse dietary fiber, the rest should come in the form of soft fiber. Each type of dietary fiber performs its own functions in our body to improve health, improve the quality of life and performance, so different fiber representatives should be present in the menu.

Natural sources of fiber:

• fruits;
• vegetables;
• legumes;
• nuts;
• cereals and whole grains;
• seaweed and fresh herbs.

It is recommended to eat at least 400 g of fruits and vegetables per day []. They should be consumed mainly raw or stewed. By adding fresh or dried fruits and berries to porridge, you can increase the daily dose of dietary fiber by 2-5 grams [].

Bran is rich in fiber. They can be added to porridges, jelly, 2 tablespoons per day []. The dose of dietary fiber should be increased gradually, bringing it to the daily norm. For fiber to “work”, you need to drink enough water (up to 2.5 liters per day) [].

Diet balanced in fiber

There is no generally accepted diet that would contain all the necessary substances for each person - everything is individual here. However, for a healthy diet you should adhere to the following rules:

• Eat at least three fresh fruits a day (for example, three apples or pears).
• Have 3 servings of vegetable dishes in your daily diet (preferably from raw foods - for example, in the form of salads).
• There are four slices of whole grain bread.
• Be sure to consume oatmeal at least once every 2-3 days.
• Eat legumes at least 3-4 times a week.

IMPORTANT: When choosing a diet, you need to take into account the calorie content of dishes, individual tolerance, allergies, etc. If in doubt, consult your doctor.

Possible problems

Although fiber is beneficial, everything should be in moderation. If there is too much dietary fiber in the diet, gas formation (flatulence) may begin. It means that bacteria in the large intestine have actively entered the diet and have begun to break down fiber, simultaneously producing methane and other gases.

How to avoid these problems? There are several simple ways:

• Eat often, but little by little, gradually increasing the amount of fiber.
• Start your diet with morning oatmeal. It contains enough fiber, but does not stimulate flatulence.
• There are more fruits. You can replace desserts with them, add them to porridge, etc.
• Move actively. A sedentary lifestyle contributes to stagnation in the intestines, and the longer the fiber stays there, the stronger the gas formation.

Finally, you can use special fiber supplements. However, nutritionists insist: dietary fiber taken separately as a dietary supplement is not as effective as when it is mixed with the main food. Therefore, it is better to normalize your diet.

Types of fiber

• Soluble dietary fiber. They dissolve in water, forming a viscous gel. For example, the viscosity of oatmeal is related to this. Water-soluble fiber is found mainly in fruits and vegetables, legumes, and some grains. Although it is not digested or broken down in the small intestine, bacteria in the large intestine can ferment it. This type of fiber primarily provides longer-lasting satiety by delaying the passage of food through the gastrointestinal tract. It also slows down the absorption of glucose. Makes the rise and fall of glucose levels, and therefore insulin in the blood, smoother and slower.

Read also: Glycemic index. How spikes in glucose and insulin affect your life

• Insoluble fiber. They are the dense outer shells of plants. For example, apple peel, bran, etc. A lot of insoluble fiber is found in whole grains of wheat, rye, etc. These fibers do not dissolve in water and are practically not digested by bacteria. Therefore, they are sometimes called coarse fiber. They provide long lasting saturation. But, one of the main functions is to increase the volume of the stool. This is how dietary fiber helps with constipation.

In fact, this division is arbitrary, since almost all plant products contain both soluble and insoluble fiber, they are equally important for health.