There is no doubt that fiber is a healthy nutrient. Our gut microorganisms can extract energy and nutrients from dietary fiber and produce the short-chain fatty acids that have been linked to many health benefits.
For example (1,2)…
Reduced risk of coronary heart disease, stroke and hypertension (high blood pressure)
Reduced risk of diabetes
Reduced risk of obesity
Reduced risk of gastrointestinal disorders such as Inflammatory Bowel Disease (IBD)
Reduction of constipation
Improved immune function
It’s simple! Let’s all eat more fiber!
Alas, this is not that easy to do. Though some people can suddenly increase the fiber in their diet and not be bothered by ill effects, others experience gas, bloating/swelling of the abdomen and painful cramping. These symptoms are caused by the excess gas that is produced when gut bacteria digest fibrous food that they are not accustomed to. Symptoms can be so unpleasant that, even though they are temporary, attempts to increase dietary fiber are abandoned, leaving no opportunity to enjoy all the health benefits that dietary fiber can bestow.
The gut microbiome of a healthy person is a fairly stable population of bacteria and other tiny organisms that is able to break down and glean the valuable nutrients from the foods commonly consumed by that person. Someone who eats lots of plant-based foods will have an intestinal microbiome that is able to deal with those types of foods. On the other hand, a person who eats high amounts of animal-based foods will have the different gut microbes needed to digest animal-based foods (1).
This factor is of the utmost importance because human beings simply do not have very many digestive enzymes of their own. Enzymes are substances that allow the breakdown of structural components present in whole grains, vegetables, fruits, legumes, nuts and seeds so that their nutrients can be absorbed by our bodies. Surprisingly, humans possess only seventeen genes dedicated to the digestion of fiber. On the other hand, our microbiome encompasses between 60,000 and 100,000 genes for processing fiber and effectively takes over this activity for us (3). The more diverse the species of microbes in our gut, the higher the variety of digestive enzymes available to process healthy foods such as fiber.
It might be tempting to think that if we cannot digest fiber on our own, we must not need it. This idea cannot be farther from the truth. Human beings and their microbiomes have evolved together in mutual benefit over millions of years of evolution while eating diets very high in fiber. Some of the most healthful foods for modern-day humans are those that are rich in fiber and processed by a healthy gut microbiome. Simply eating a fiber-rich diet can increase our own gut microbe diversity quite quickly (1).
Why Does Dietary Fiber Sometimes Create an Uncomfortable Bowel?
People who eat lots of fiber do not suffer from excess gas, bloating or abdominal pain. On the other hand, people who eat only a small quantity of fiber-containing foods present a problem for their gut when they increase fiber intake because they simply do not have enough of the gut microorganisms necessary to process fiber. If we have only limited numbers of gut bacteria that are good at digesting a certain fibrous material, the process will not be fast or efficient and excess gas with its accompanying bloating and cramping will be the result.
How To Improve Your Body’s Fiber Digestion
The paradox here is that the people who need to increase their fiber the most are the people who will struggle the most to increase that fiber. They simply don’t have the gut bacteria needed to process it. But don’t despair! It is possible to increase your fiber intake even if you have tried before and were not successful. The secret is patience.
The following is a step by step method for increasing your dietary fiber content without painful side effects. This process should be adjusted to suit your own situation.
If you are healthy and are already eating a fair amount of fiber you can expect a relatively easy transition. You should be able to increase your added fiber fairly quickly and it may take only a few weeks to adjust to the increased fiber intake.
If you are not currently eating much fiber at all, have a gastrointestinal condition, or have already tried to increase your fiber but been unsuccessful, then you need to go about this process very slowly. It may take several months for your body to adjust to higher fiber consumption (4).
1 The very first step is to be sure you are not constipated when you start increasing your fiber intake. A constipated bowel will cause congestion along the route your fiber must take to reach your colon and sometimes may cause a complete stoppage.
To relieve constipation start by increasing the amount of water you drink and taking 10 minute walks after each meal. If this doesn’t help, try magnesium. It is a gentle and effective laxative and easily available at your local pharmacy. Milk of Magnesia or magnesium citrate oral solution are both good choices.
2 Drink lots of water every daty Fiber absorbs a significant amount of water as it passes through the digestive tract. Drinking extra water will help to replace this water and also help fiber pass more easily through the intestines.
3 Exercise regularly. It promotes movement of food through the intestines.
4 Make the task of your gut microorganisms an easier one by spreading fiber consumption throughout the day. Eat fiber-rich foods at each meal (4,7).
5 Whatever type of diet you have been eating, you are probably ingesting at least a few vegetables. So the first step is to simply increase your intake of these vegetables.
6 Avoid all types of raw vegetables at the start of this process.
7 When you feel you are ready for a new fiber source, add in well-cooked vegetables that are easily-digestible. Examples are starchy roots (potatoes, sweet potatoes, carrots) and squash (5).
8 After adding the new fiber sources, wait until your bowel is giving you no trouble. Then you can try some different cooked vegetables. These might include green beans, asparagus, spinach and kale. Later, introduce vegetables such as sweet peppers, broccoli, cauliflower and brussels sprouts. If you’re having trouble adjusting, add the new vegetables in small amounts and one vegetable at a time. (5)
9 Add in whole grains.
10 Add in nuts and raw foods.
11 Lastly add in legumes (lentils, beans, pulses). Start with lentils, the easiest legume to digest. Other easily-digested legumes are mung beans and split peas. If you notice that legumes are causing gas symptoms, cut them back to only one spoonful a day and increase the amount slowly week by week. When you’ve conquered lentils you can begin to add beans and other legumes. Within the bean family, smaller beans (black beans, adzuki beans, navy beans) are easier to digest than larger beans (lima beans, kidney beans). Other legumes include peas such as chickpeas and black-eyed peas.
Extra Tips For Decreasing the Formation of Gas From Beans
Beans are an example of a food very high in healthy fiber. However they are infamous producers of “fragrant” and sometimes painful intestinal gas. This is because beans contain nutrients called oligosaccharides for which humans possess no enzymes to help break them down. Consequently they are fermented in the colon (the last section of the gastrointestinal tract) through enzymes derived from the microorganisms living in the gut (6).
In their book, “Becoming Vegan: Comprehensive Edition”, dieticians Brenda Davis and Vesanto Melina explain how to reduce the amount of oligosaccharides in beans to reduce gut gas production (6).
1 Use fresh instead of dried beans because oligosaccharide content increases during storage. If you use dried beans, use them up within a few months.
2 Rinse canned beans well before eating.
3 Soak dried beans for at least 12 hours then discard the soaking water and rinse the beans well. It is even better to perform this soaking process twice, using fresh water each time. If you do not have enough time for soaking, boil the dried beans briefly then let them sit in the boiling water for 1 to 2 hours. Discard the water once again, rinse, add fresh water and cook.
4 Remove any white foam that forms on the surface of boiling beans as it contains oligosaccharides.
5 Make sure your beans are cooked thoroughly for easier digestion. Beans are done when they can be crushed easily between the tongue and the roof of the mouth.
6 Fermented bean products (tempeh, miso), tofu and sprouted beans are easier- to-digest forms of beans.
In the End…
Most people in the Western world are deficient in fiber. Canada’s dietary guidelines state that women should eat 25 grams of fiber daily and men 38 grams. Most Canadians eat only about half that much (8). Furthermore, the suggested daily fiber amount in dietary guidelines are only a minimum. Our human ancestors consistently consumed somewhere between 70 grams and 150 grams of fiber daily (9).
It is never too late to increase the fiber content of your diet. You can accomplish this by jumping right in with lots of new fiber sources or through gradual fiber increases. But, however you do it, once your body becomes accustomed to the extra fiber in your food, you will be able to eat all you want without experiencing any unwanted symptoms. Rest assured that your body will thank you for it.
1 Holscher, H.D. Dietary fiber and prebiotics and the gastrointestinal microbiota. Gut Microbes. 2017; 8(2): 172–184.
2 Anderson, J., et al. Health benefits of dietary fiber. Nutrition Review. 2009; 67(4):188-205.
3 Youtube – Understanding The Microbiome, Erica Sonnenburg, PhD. Jan 10, 2018.
6 Davis, Brenda, Melina, Vesanto. Becoming Vegan: Comprehensive Edition. 2014. ISBN: 1570672970.
9 Eaton, S.B., Eaton III, S.B., Konner, M.J. Paleolithic nutrition revisited; A twelve year retrospective on its nature and implications. Eur J Clin Nutr 1997; 51: 207-216.