We have all heard plenty of times that fiber is good for us because it keeps our bowels regular. But is this all we need fiber for? Are there other benefits of fiber? As it turns out, yes. There are many!
But before we start going into the benefits of fiber, it’s important to note that there are different types of fiber and that they have slightly different roles and therefore benefits. The main groups of fiber are:
- Soluble fiber, which includes fibers like gums, mucilage, pectin, Beta glucans, Resistant starch and resistant oligosaccharides. When found in foods, these are usually soft, slimy and mucilaginous and are found in foods like fruits (e.g. figs, apricots, prunes) , vegetables (e.g. okra, green peas, green beans), whole grains (e.g. barley, oats), and legumes (e.g. beans).
- Insoluble fiber, which includes cellulose, lignin and hemicellulose. When found in foods these are generally harder and rougher than soluble fiber, and are found in foods like nuts, seeds, whole grains (e.g. wheat) and the bran of grains, (e.g. wheat bran)
Insoluble fiber is beneficial but it only has one main benefit: It bulks up the stool. And this is beneficial because it helps train your gut muscles, keeping them strong so that you can have smooth and regular bowel movements, enabling you to eliminate wastes that could otherwise be harmful if allowed to build up (as discussed in Why do I poop?). Soluble fiber however has a few other interesting benefits:
Benefits of Fiber
1.) Fiber delays gastric emptying (i.e. it slows down food release from the stomach)
Studies have shown that some soluble fibers (like pectins and guar gum) slow down release of food from the stomach. In medical jargon we say they delay gastric emptying.1-4
Why is this a benefit? For several reasons:
(a.) Delayed gastric emptying helps with sugar balancing
If sugar is released slowly from the stomach rather than all at once, it means that there isn’t a huge spike of sugar levels after a meal, but instead a more sustained trickle of sugar giving a prolonged source of energy. This is particularly useful for people who suffer from blood sugar imbalances like diabetics, insulin-sensitive people and people who experience frequent hypoglycaemia.
Fiber’s role in sugar balancing is also beneficial in reducing the risk of certain diseases linked with sugar imbalances. High sugar levels in the blood increase the risk of inflammation, oxidation, tissue damage by glycosylation and cardiovascular disease, to name but a few.
(b.) Delayed gastric emptying helps keep you fuller for longer
People trying to lose weight can benefit from the effect of delayed gastric emptying because if your stomach is full for longer, it increases satiety. As a result, you don’t feel as hungry and you are less likely to snack on unhealthy things between meals, or have another meal a short time after finishing the last. Nestle’s breakfast cereal, “Shreddies”, banked on this benefit of fiber by using the slogan “Keeps hunger locked up till lunch!” as seen in the attached video.
Note: Although I recognize Shreddies as a source of fiber I am not promoting them as a recommended source of fiber because they are made of whole grain wheat, a common ingredient that people are intolerant to.
The sugar-balancing and insulin-modulating effect that delays gastric emptying can really help with weight management.
2.) Fiber Lowers cholesterol
Numerous studies have found that some soluble fibers can lower cholesterol (most notably fiber in oats, psyllium and flaxseeds).5-9
How does fiber decrease cholesterol? It seems that the mechanism is not fully understood but hypotheses include:
- Fiber may help bind cholesterol and cholesterol-derivatives (like bile) in the intestines. Binding prevents its reabsorption into the body and helps to package it off for elimination in the faeces. Because our body needs the presence of bile in the intestines to aid digestion, the removal of bile via fiber-binding encourages more bile to be made in the liver from cholesterol, so that you use up more of your body’s stores of cholesterol. This cycle repeats as long as you have a good fiber intake with bile being excreted and more being made to replace it. The result is a reduction in cholesterol levels in the body.
- Although we can’t break down soluble fiber, our gut bacteria can. They digest them into new byproducts like short-chain-fatty-acids, which are absorbed into the body and may reduce cholesterol levels by possibly inhibiting cholesterol production in the liver.
- Fiber may decrease the gut’s absorption of raw materials like fat from which cholesterol can be made.
- Fiber decreases “transit time” of the stool in the intestine. The less time the stool is in the gut, the less time there is to reabsorb the cholesterol byproducts (bile).
Via lowering cholesterol, soluble fiber is also good for cardiovascular and heart health.
3.) Fiber soothes an irritated gut
The smooth, soft, mucilaginous and moist soluble fiber should be soothing to an irritated or inflamed gut wall. Sufferers of inflammatory gut disorders like ulcerative colitis may therefore benefit from soluble fiber.
Note: This is one benefit of soluble fiber which is a polar opposite to insoluble fiber. Insoluble fiber is harsh and irritating to the gut wall and should be avoided in people with sensitive guts.
4.) Fiber promotes elimination of waste
Like insoluble fiber, soluble fiber also helps the passage of the stool. Whilst insoluble fiber creates the bulk of the stool, soluble fiber enhances the water-capacity of the stool, helping to keep it at a softer, smoother texture that is easier to pass.
Eliminating waste properly is really important for a number of reasons as discussed in the article Why do I poop?.
5.) Fiber feeds the gut bacteria
Inside our guts is a whole ecosystem of helpful bacteria. One of the gut flora’s main foods is soluble fiber, so by eating it, you are feeding them, keeping them alive and well.
Why are gut bacteria beneficial to us? They help us in several ways :
- They break down certain foods that we can’t break down ourselves, releasing their nutritional content for us to utilize.
- They provide us with more energy through the byproducts of their own digestion. One such useful byproduct is the short-chain fatty acids they produce.
- They act as an immunological barrier in the intestines, strengthening our immunity in the gut by fighting off any nasty “bugs” that are around.
- They can help with gut healing and health maintenance by playing a role in normalizing the gut pH, producing food for the intestinal cells, and helping to maintain mucosal integrity. For this reason they can be helpful in inflammatory gut problems.
- They even make some vitamins for us, like vitamin K and some B vitamins.
- They boost absorption of some nutrients like calcium, magnesium and iron.10,11
6.) Fiber helps prevent all sorts of diseases and problems
Good soluble fiber intake has been correlated with decreased risk of the following conditions: appendicitis, constipation, colon cancer, coronary heart disease, diabetes, diverticular disease, gallstones, haemorrhoids, hiatus hernia, hyperglycaemia, hypoglycaemia, varicose veins, obesity and being overweight.
How much fiber per day should you have?
It’s clear that fiber is a beneficial addition to the diet, but how much fiber do you need to reap its benefits?
The American Dietetic Association advises a daily intake of 20-35 grams of fibrous foods for all adults, and 30g or more for those with constipation. An average high-fiber food contains 3-4g fiber per 100g, whilst some like nuts and seeds can contain around 6g fiber per 100g. So if you’re incorporating high fiber foods at every meal and snack, you should be reaching your 20-35g a day. Most people do not meet this requirement without conscious awareness of the need for fiber. According to the NDNS survey, most people only consume an average of 12.6 – 15.2g fiber a day.
High fiber foods to increase include:
- vegetables, especially okra, green peas and green beans.
- fruit, especially figs, apricots and prunes
- cereal grains like wheat germ, oats, barley, rye, buckwheat,
- legumes like beans,
- nuts, seeds and their products, like nut butters, seed butters and tahini. Flax seeds are a particularly good addition to the diet. You can grind them and put them in your breakfast cereal
- algae and seaweeds.
Low fiber foods to decrease include highly refined foods (like white rice, white bread and similar white products), junk food and protein-only diets such as Atkins.
Remember to wash down fiber with a lot of water otherwise some sources of fiber can lead to constipation instead of helping to alleviate it.
Word of warning about increasing fiber intake
As just mentioned, it’s important to drink plenty of water when consuming a high fiber diet. 6-8 glasses of water a day is ideal.
Another thing to watch out for is that increasing fiber in someone who is not accustomed to eating large amounts of indigestible matter can cause bloating, gas and digestive discomfort. These side effects can be avoided if the fiber is introduced in gradually increasing amounts.
Too much fiber can also interfere with absorption of nutrients if the transit time is too fast to allow efficient absorption.
Generally the body adapts to your increased fiber intake over a period of weeks.
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Every effort has been made to ensure that the information contained in this article is accurate. However the information contained in this article is for educational purposes only. Suggestions contained in this article are not intended as a substitute for consultation with a health professional. All matters regarding health and supplementation require medical supervision and careful examination of contraindications and possible interactions. The author does not accept responsibility for the use of this information, nor shall the author be liable for any loss, injury or damage allegedly arising from any information or suggestions in this article.
1. Landin et al 1992. Guar gum improves insulin sensitivity, blood lipids, blood pressure and fibrinolysis in healthy men. Am J Clin Nutr. 56. 1061-1056
2. Holt et al. 1979. Effect of gel fibre on gastric emptying and absorption of glucose and paracetamol. The Lancet, Volume 313, Issue 8117, Pages 636 – 639, 24
3. Schwartz et al. 1982. Sustained pectin ingestion delays gastric emptying . Gastroenterology. Oct;83(4):812-7
4. Torsdottir et al 1991. A Small Dose of Soluble Alginate-Fiber Affects Postprandial Glycemia and Gastric Emptying in Humans with Diabetes. J. Nutr. 121: 795-799
5. Brown et al. 1999. Cholesterol-lowering effects of dietary fiber: a meta-analysis. American Journal of Clinical Nutrition. 69(1):30-42.
6. Kelley et al. 1994. Oat bran lowers total and low-density lipoprotein cholesterol but not lipoprotein (a) in exercising adults with borderline hypercholesterolemia. Journal of the American Dietetic Association. 94(12):1419- 1421
7. Anderson et al. 1999. Effects of psyllium on glucose and serum lipid responses in men with type 2 diabetes and hypercholesterolemia. American Journal of Clinical Nutrition. 70(4):466-473
8. Bierenbaum et al. 1993. Reducing atherogenic risk in hyperlipemic humans with flax seed supplementation: a preliminary report. J Am Coll Nutr. 12(5):501-504.
9. Prasad et al. 2000. Flaxseed: a source of hypocholesterolemic and antiatherogenic agents. Drug News Perspect. 13(2):99-104.
10. Coudray et al. 1997. Effect of soluble or partly soluble dietary fibres supplementation on absorption and balance of calcium, magnesium, iron and zinc in healthy young men. Eur J Clin Nutr. 51:375-380
11. Guarner & Malagelada 2003. Gut flora in health and disease. Lancet 361 (9356): 512–9
I have read this post and found it thoroughly interesting.
The article is worth reading. Fibre power!!