Since the 1990s, medical researchers have discovered more and more benefits when dietary fiber is significantly increased in our diet. Fiber is a substance in plants. Dietary fiber, also called bulk or roughage, is the kind we eat. It is the edible portions of plant cell walls; hence, it is found only in plant foods like fruits and vegetables, whole grains, nuts and seeds, as well as beans and legumes.
Fiber is a carbohydrate and is usually listed under “Total Carbohydrates” on the “Nutrition Facts” label. Humans lack the digestive enzymes to breakdown fiber. Therefore, it is undigested and not absorbed into the bloodstream and it arrives at the colon pretty much intact. Fiber has zero calories. Instead of being used for energy, it is excreted from the body.
The current recommended daily intake for adults who are 50 years or younger is 25 grams/day for women and 38 grams/day for men. For adults over 50 years of age, the recommendation is 21 grams/day for women and 30 grams/day for men. Unfortunately, for many who eat a typical American diet, it can be a huge challenge to consume that much fiber everyday. Most people top out at an average of 15 grams/day, regardless of how many calories they eat.
Maybe if we understand more about the different types of fiber and how they can immensely contribute to better health and lower disease risks, there will be more incentives to increase the daily fiber intake. Fiber is an important part of a healthy, balanced diet. Apart from helping us stay regular, fiber has a long list of other health benefits. The following will distinguish the different types of fiber, their specific health advantages, and which foods contain these fiber.
Classifications Of Fiber
There are several ways to classify the different types of fiber. However, as their characteristics do overlap, experts have yet to agree on the best categorization. For decades, the most commonly used classification is soluble and insoluble fiber. These days, as researchers discover the benefits of fermented fiber, another classification – fermentable and non-fermentable fiber – is also used. However, do know that both soluble and insoluble fiber have some that are fermentable and some that are non-fermentable, though soluble fiber is more easily fermented.
Soluble and Insoluble Fiber
The major difference between soluble and insoluble fiber is that they have different properties when mixed with water, hence the designation between the two.
- Soluble fiber is soluble in water. When mixed with water, it forms a gel and swells.
- Insoluble fiber does not absorb or dissolve in water. It passes through the digestive system in close to its original form.
Both types of fiber serve their own purposes and have different health benefits. Most plant foods contain both soluble and insoluble fiber, just in different proportions. For instance, wheat is about 90% insoluble fiber. Oats are 50/50. Psyllium plant is mostly soluble fiber.
Fermentable and Non-Fermentable Fiber
Some fibers are readily fermented by bacteria that colonize the colon, others are not. Fermentable fiber is used by the colon’s friendly bacteria as a food source. Fermentation results in the formation of short-chain fatty acids (acetate, butyrate, and propionate) and gases. Epithelial cells that line the colon use butyrate as the main source of energy.
Researchers found that butyrate exerts a wide range of health benefits. It:
- Decreases inflammation and oxidative stress,
- Prevents colon cancer, irritable bowel syndrome (IBS), and Crohn’s disease,
- Strengthens the bowel wall,
- Improves the body’s ability to absorb essential nutrients such as calcium,
- Makes hormones that control appetite and anxiety.
Foods High in Soluble Fiber
Fruits: blueberries, apple, oranges
Grains: barley, oats
Legumes: beans, lentils, peas
Vegetables: Brussels sprouts, carrots
- Digestion and weight control. When soluble fiber dissolves in water and becomes gel-like, it helps prolong stomach emptying and slows down digestion, making you feel full longer and have less room for other not-so-healthy food cravings.
- Blood sugar regulation. Soluble fiber slows down the digestion rate of many nutrients, including carbohydrates, so it helps stabilize glucose levels and prevent after-meal blood sugar spikes.
- Cholesterol and heart health. Soluble fiber binds to cholesterol and bile acids (made by the liver and stored in the gall bladder for the digestion of fats) in the small intestine and promotes their excretion. Studies found that consuming more soluble fiber leads to a decrease in LDL (bad) cholesterol levels, hence, reducing the overall risk of cardiovascular disease.
- Healthy bowel movements. Soluble fiber soaks up water as it passes through your system, which helps bulk up the stool and guard against constipation.
- Colon health. Prebiotic fiber is a type of fermentable and soluble fiber that is used by the colon’s friendly bacteria (probiotics) as a food source. Prebiotics and probiotics work together to maintain the balance and diversity of intestinal bacteria, especially increasing the good bacteria like lactobacilli and bifidobacteria.
Foods High in Soluble Prebiotic Fiber
(In parenthesis is the name of the fiber)
Asparagus (inulin and oligofructose)
Banana (inulin and oligofructose)
Burdock root (inulin and oligofructose)
Chicory root (inulin and oligofructose)
Cocoa (flavanol compounds)
Dandelion greens (inulin and oligofructose)
Garlic (inulin and oligofructose)
Jerusalem artichoke or sunchoke (inulin and oligofructose)
Jicama root (inulin)
Konjac root or glucomannan fiber (see Note)
Leeks (inulin and oligofructose)
Onion (inulin and FOS)
Psyllium (mucilage) – used as a fiber supplement, always buy organic due to pesticides
Wheat bran (arabinoxylan oligosaccharides or AXOS)
Yacon root (FOS and inulin)