Dietary fiber: Types, Sources and Health benefits

Dietary fiber

Dietary fiber is a fundamental part of a healthy diet, which is not digested or absorbed into your body. It’s is a type of carbohydrate and is also known as roughage.

Fiber is found in abundance in vegetables, whole grain, fruits, and legumes. It is very important to keep your body healthy. Since dietary fiber cannot digest in the stomach, it ends up in your colon. It feeds friendly gut bacteria and some types of fiber help to prevent constipation, prevent colon cancer, promote weight loss, as well as lower blood sugar level in your body.

Types of dietary fibers

Dietary fibers can be classified based on several factors like solubility (soluble and insoluble fiber), viscosity (viscous and non-viscous fiber), and fermentability (fermentable and non-fermentable fiber).

Soluble and insoluble dietary fibers

However, the most common classification of dietary fiber is based on their solubility: soluble and insoluble fiber. You do not want to worry about these two types of fiber since high fiber diets have both soluble and insoluble fiber, but richer in one type than the other.

  • Soluble fiber dissolves in water to form a gel-like material. It can provide some calories to the body with the help of bacteria in the large intestine. Foods rich in soluble fiber include oats, nuts, beans, barley, blueberries, apple, and carrot.
  • Insoluble fiber does not dissolve in water. It can increase stool bulk and promote movements of material through the intestine. Vegetables such as potatoes, cauliflower, green beans and wheat bran, nuts, beans, and whole wheat flour are foods rich in insoluble fiber.

Viscous fibers

Viscous fibers are a type of soluble fibers that creates a thick gel when combined with water. These bulky masses slow down digestion and absorption, giving you a prolonged feeling of fullness. Beans and legumes are rich in viscous fibers.

Fermentable fibers

Fermentable fibers are the type of fibers that are used as fuel by the friendly bacteria in our large intestine. The existence of these bacteria in our gut is crucial as they play a major role in different functions such as weight management, good immune health, brain function, and blood sugar control. Fermentable fibers are found in abundance in asparagus, Brussels sprouts, oats, legumes, and flax seeds.

All the above classifications are about the functional and health effect of dietary fibers. You may also come across the term functional fibers as a type of fiber found in the food we consume. These are the fibers that are extracted from whole foods and then added to processed foods.

Health benefits of dietary fiber

  1. Healthy bowel movements – Insoluble fiber bulk up stool and softens the bowel function. A bulky stool is easier to pass and guard against chronic constipation, hemorrhoids, and irritable bowel syndrome.
  2. Diabetes protection – Insoluble fiber-rich foods can help regulate blood sugar levels by slowing the absorption of sugar. It reduces the risk of developing type 2 diabetes.
  3. Heart protection – Soluble fiber-rich foods may help to lower LDL cholesterol in the blood. Researchers have shown that high fiber foods may have benefits for the heart such as reducing blood pressure and inflammation.
  4. Weight loss – Foods rich in both soluble and insoluble fiber add bulk to your diet. So, you can eat less and stay satisfied longer. A high fiber diet has fewer calories so you may gain less weight by eating the same volume of food if you incorporate more fiber into your diet. Fiber can also move fat faster through the digestive system while reducing the fat absorption to the body.
  5. Balance intestinal pH – Some soluble fiber undergoes bacterial fermentation helping to balance intestinal pH.
  6. Reduce cancer risk – Studies have shown that high fiber intakes such as cereal fiber associated with reducing the risk of cardiovascular disease and colon cancers.
  7. Skin health– Seed fiber can flush toxin out of the body and improve the health and appearance of your skin.

How much dietary fiber should you intake?

Daily fiber intake depends on the age and sex of the people. Dietary fiber adequate intake (AI) for adult men is 33.6 grams per day and for women is 28 grams, as per the Dietary Guidelines for Americans.

According to surveys, People in European countries do not consume an adequate amount of dietary fiber. Since both soluble and insoluble fiber having health benefits, you need to include both fibers in your diet. Nutrition experts have recommended a minimum daily intake of fiber depending on the age and gender as follows.

Minimum recommended daily fiber intake (in grams)
Age Male Female
9-13 31 26
14-18 38 26
19-30 38 25
31-50 38 25
51-70 30 21
Over 70 30 21
Source: Food and Nutrition Information Center, USDA

Sources of dietary fiber

Most dietary fiber foods are plant-based. So, vegetarians and vegans can easily get the required fiber intake. Following examples of Legumes, vegetables, fruits, nuts, and seeds contain high fiber content according to the Dietary Guidelines of Americans 2015-2020.

Dietary fiber examples include a lot of varieties of foods. If you can plan your diet, you can easily get the required daily value of fiber intake.

Legume fiber
Source Serving size Dietary fiber in grams
Navy beans 100g 10.5g
Pinto beans 100g 9g
Black beans 100g 8.7g
Split peas 100g 8.3g
Lentils 100g 7.9g
Mung beans 100g 7.6g
Kidney beans 100g 6.4g
Soybeans 100g 6g
Green peas 100g 4.1-5.5g
Fruit fiber
Raw pear 1 medium fruit 5.5g
Avocado ½ a cup 5g
Raspberries ½ a cup 4g
Blackberries ½ a cup 3.8g
Orange 1 medium fruit 3.4g
Prunes 5 prunes 3.4g
Banana 1 medium fruit 3.1g
Guava 1 medium fruit 3g
Vegetable fiber
Potato 1 large potato 6.3g
Sweet potato 1 large sweet potato 5.9g
Parsnips 1 boiled parsnip 5.8g
Winter squash 1 cup 5.7g
Broccoli 1 cup 5.1g
Nuts & Seeds fiber
Almond 1 ounce 3.5g
Popcorn 3 cups 3.5g
Pecans, oil roasted 1 ounce 2.7g
Pistachios, dry roasted 1 ounce 2.8g
Quinoa, cooked ½ a cup 2.6g

Does fast food contain dietary fibers?

Unfortunately, in the present, most people are consuming fast food since they are cheap and more convenient in a busy lifestyle. Obtaining the required amount of dietary fiber is a challenge for those who consume fast foods more often. Many fast-food meals contain little or no fiber.

Here are some tips to get more fiber from fast foods.

  • Choose fast foods made with whole wheat or whole grain
  • Choose either nine-grain wheat bread or honey-oat bread
  • Add avocado to a sandwich
  • Select salad or nuts instead of potato chips
  • Choose fast food made with vegetables
  • Choose foods which are containing oats

How much fiber is too much fiber?

While researches have shown that most people do not intake an adequate daily amount of dietary fiber, there can also be instances where people consume too much dietary fiber. Eating more than 70g per day  is not advised.

Following are the consequences of consuming too much fiber.

  • Decrease in appetite
  • Nutrient deficiencies such as calcium, magnesium, and zinc due to fiber may limit the absorption of these nutrients.
  • Bloating, gas, and cramping
  • Risk of blocking intestine with inadequate water. This is rare and may occur when you consume too much fiber.

If you are feeling the above consequences you can reduce the discomfit by,

  • Skip foods increasing bloating
  • Remove added fiber-rich foods in your diet
  • Avoid raw vegetables and choose processed/cooked vegetables.
  • Choose legumes and cereals which are low in fiber

Things to remember

  • Adequate intake of fiber for adult men is 33.6g and 28 for adult women
  • Replace/include fruit in your dessert
  • Try to eat fruits & vegetable with its peel
  • Don’t forget to include legumes in your diet
  • Process food are usually less in fiber

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