The Importance of Fiber
The importance of macronutrients (proteins, carbohydrates, and fats) for health, performance, and body composition are well known. Fiber is technically not considered a macronutrient, but due to its importance in optimizing health & recovery and promoting healthy digestion, detoxification & blood sugar balance it is practically the “fourth macronutrient”.
What is Fiber?
Fiber is a material found only in plant food; it is essentially the cell walls of plants. Our digestive systems cannot digest or break down fiber. For this reason, fiber is sometimes referred to as “bulk” or “roughage.” There are two main classifications of fiber, soluble and insoluble, and each play important roles in maintaining gut health and assisting your body in elimination of waste.
“Soluble” refers to the fact that it can be dissolved in liquid and digestive fluids and turns into a gel-like consistency.
Prebiotics are specialized plant fibers. Although not all dietary fibers are prebiotics, all prebiotics are dietary fibers. They act like fertilizers that stimulate the growth of healthy bacteria in the gut. Bacteria in gut microbiome are responsible for breaking down what you consume so that your body can effectively absorb them, in modifying the host immune response, in protecting against infection, in the metabolism of drugs, and in participation in and regulation of host metabolism. The recommended intakes of dietary fiber provides prebiotics to the diet and is vital to promoting a healthy gut flora balance.
Types of soluble fibers:
This type of fiber is found mostly in legumes (beans), oatmeal, barley, broccoli, and citrus fruits. An especially rich source of soluble fiber is oat bran.
- Fructans: It is a polymer of fructose molecules. Wheat and onions are the biggest sources of fructans.
- Inulin: Inulin is a starchy substance found in a wide variety of fruits, vegetables, and herbs, including wheat, onions, bananas, leeks, artichokes, and asparagus.
- FOS (fructooligosaccharides): They are a type of carbohydrate called oligosaccharides, sources are blue agave, yacon root, garlic, onion, leeks, chicory root, asparagus, bananas.
- Oligofructose: It is a subgroup of Inulin, a prebiotic dietary fiber that promotes gut health and supports digestive function. It is derived from chicory root, asparagus, leeks, Jerusalem artichoke, wheat bran and other foods.
- Galactan: These are Polysaccharides that are composed of galactose derivatives. Galactans are found in lentils, chickpeas, broccoli, beans, Brussels sprouts and soy-based products.
- Pectin: Pectin is a type of starch, called a heteropolysaccharide, that occurs naturally in the cell walls of fruits and vegetables and gives them structure. When combined with sugar and acid, it is what makes jams and jellies develop a semisolid texture when they cool. Some fruits, like apples and quince, and the rinds, seeds, and membranes of citrus are naturally very high in pectin.
- Beta-glucan: Beta glucan is one form of soluble dietary fiber that’s strongly linked to improving cholesterol levels and boosting heart health. Sources are whole grains, oats, bran, wheat, and barley.
The term “insoluble” refers to the fact that this type of fiber cannot be dissolved in water.
This type of fiber is found mostly in the skins of fruits and vegetables and in whole grain products and wheat bran.
Insoluble fiber speeds the passage of material through the gastrointestinal system, thus helping the body get rid of waste. It is responsible for adding volume to bowel movements and aiding in motility. It binds with bile in the intestinal tract to help transport toxins out of the body through excretion.
A lack of insoluble fiber decrease body’s ability to export toxins through the intestines, leading to re-absorption of the very materials your body is trying to get rid of leading to irregularity or even digestive distress.
Some of the insoluble fiber sources are:
- Vegetables – corn, eggplant, green beans, broccoli, spinach, kale, legumes (e.g. chickpeas, lentils etc.)
- Fruit -grapes, kiwi, strawberries, rhubarb, raspberries, pineapple, blueberries, raisins
- Bread – gluten free multigrain, wholemeal
- Grains – brown rice, burghal, oat bran, rice bran, buckwheat, quinoa
- Nuts – peanuts, almonds, walnuts
- Seeds – pumpkin, chia, sesame
The general recommendation for fiber consumption is that “Total dietary fiber intake should be 25 to 30 grams a day from food, not supplements.”
Although there is no dietary reference intake for insoluble or soluble fiber, many experts recommend a total dietary fiber intake of 25 to 30 grams per day with about one-fourth — 6 to 8 grams per day — coming from soluble fiber.
However, these guidelines do not account for the drastic potential variation in an individual’s food consumption and microbiome needs. A safe starting place is about 15g per 100g of carbohydrates. This should be quite easy if one is consuming 1-2 servings of vegetables with each of whole-food meals, which is something highly recommend.
Soluble fiber is good for both diarrhea and constipation. Foods high in insoluble fiber are best for constipation only. However, both are great for health.
Some easy ways to increase fiber are including servings of grains and cereals, legumes and beans, and fruits and vegetables in diet.
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- What is Fiber? https://www.cdc.gov/diabetes/prevention/pdf/posthandout_session6.pdf
- Fiber and Prebiotics: Mechanisms and Health Benefits : https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3705355/
- Increasing Fiber Intake: https://www.ucsfhealth.org/education/increasing-fiber-intake
Abhinav Malhotra is an award-winning personal trainer, coach and sports nutritionist in Dubai, UAE. He also offers online services to clients around the world. A personal trainer par excellence, Abhi has worked with the world’s leading fitness chains, supplement brands and founded his own fitness academy in India. He has achieved successes for many clients from all backgrounds and has trained the Indian Army Rugby Team. He is the first International Kettlebell Sport athlete from India.