Everybody has heard that we need to eat more fiber. When you ask them why we need more fiber, the almost universal answer is so we can poop regularly. While this is true, this is only the tip of the iceberg. Fiber is a huge subject and should be classed as a food group all on its own, just like protein, fat, and carbs. But chemically fibers are made from huge networks of tiny carbohydrate molecules, which are very much like proteins that are made from thousands of tiny amino acids.
There are many, many types of fiber. Old school chemists would group them simply into soluble and insoluble fibers based on whether they would dissolve in water, while nutritionists would break them down to digestible and indigestible fibers based on whether we had the enzymes in our gut to break the fibers down. As our understanding of the functions each fiber expresses in our gut grows, our classifications are expanding. For instance, a few types of fibers have been found that specifically keep certain bad bacteria from attaching and growing in our gut. These are now called contrabiotics (the opposite of probiotics) and include fibers found in plantains, bananas, and broccoli. This is particularly relevant because chronic inflammation caused by these bad bugs causes colitis and is the chief cause for colon cancer.
The indigestible and insoluble fibers are the ones that we associate with providing the bulk that keeps our bowels moving. However even this category is expanding because even though we can’t digest them, many of the good guy bacteria in our guts can break them down. They eat the fiber bits they break off and produce a chemical called butyrate, which decreases inflammation and provides the primary nutrition for the cells that form our colon: the colonocytes. Examples of the indigestible fibers are the woody stems in leafy greens, and the tough chewy parts of fibrous vegetables. An additional benefit to insoluble fibers is that they help regulate blood sugar by increasing insulin sensitivity, possibly by their impact on the gut microbiota. This helps lower blood sugar levels, resulting insulin levels, and therefore diabetes.
The water soluble fibers dissolve to form gooey gelatinous gunk that our good bacteria love to eat. It gets turned into butyrate and other life supporting substances just like some of the insoluble fiber does, but by different good bacteria. The goo slows down the rate of nutrient absorption in the gut, so we don’t get big spikes of food molecules and minerals in the blood that can overwhelm our system. Being water soluble means that they will absorb a lot of water and swell up. So be sure you are drinking plenty of water when eating these types of fibers. Otherwise they might get stuck as a lump in the gut when we take them in a commercially prepared dry form. In nature they will already be loaded with water in the plant.
The government says we should be consuming 25 grams of fiber daily, even though our ancestors generally ate a lot more than that. On the other hand studies of the modern teenager studied in their natural habitat find they generally only consume less than 5 grams of fiber a day. Instead they primarily consume simple sugars and carbs, which feed the nasty health destroying bacteria. It is a good thing that the young have a good supply of healthy tissue that will last them several years before they wear out the good tissues and begin to develop the common health complaints that come with age.
This is the key point of this article. Carbohydrates, sugars, excess protein and omega 6 fats, as well as all the food chemicals, preservatives, coloring agents, and what not are all slowly destroy the integrity of your gut lining. When you are young and healthy your gut lining (which is only one cell thick) is protected by a thick coating of mucous filled with good guy bacteria and immunoglobulins that keep the bad stuff out of your blood stream. With each passing year of dietary abuse, this protective coating gets thinner. Eventually it gets wiped out all together and your gut lining cells start breaking down. Leaky gut results and now bad boogie stuff is able to get into our blood stream and poison us. Yes, poison us – slowly and definitely. A leaky gut is the starting point of most all the degenerative diseases of our modern times.
Fiber helps to slow this process down, even reverse it. Fiber in its various forms contributes to the health of our gut in many ways. So what fiber foods are the “best”? This question is tricky because each food source will have several different fibers, and each fiber has different beneficial effects. It is not simply about what food source has the most fiber. The highest fiber common food is cooked beans, with 8 grams of fiber per half cup. However that same half cup also has 16 grams of simple carbs that turn into sugar after you eat it. There is also the issue with the high levels of lectins in beans if they have not been pressure cooked long enough. Whole grains have 2 – 3 grams of fiber per half cup of cooked mush, but again have the same issue with even higher carb levels, plus the lectin concern and gluten which is not destroyed by cooking which damages everybody’s gut lining to some degree.
So as you can see, the “best” fiber has to consider the larger context of the plant involved. When I researched what fibers have the most beneficial impact on the gut and the microbiome, I actually found studies addressing this. In order of benefit, the most beneficial has been found to be pectins, followed by guar gum, glucomannan (konjac root), inulin, and psyllium fiber. Of those, probably the only one you are likely to encounter in normal food is the pectins as they are found in fruit like apples and possibly inulin if you eat jicama. The others would more likely be found in an advanced fiber supplement.
Other excellent sources of fiber are all your leafy green vegetables as well as avocado, broccoli, and Brussels sprouts. I recommend at least 3 to 4 cups of green veggies every day. The very best high fiber fruit is raspberries, blackberries, oranges, blueberries, apples, and slightly green bananas. With the fruit limit yourself to one serving per day due to the high sugar levels in fruit. Vegetables are your best bet for high quality fiber without the sugar.
Personally, in addition to the green vegetables I eat every day, I also use a homemade blend of the five best fibers plus berries and green banana in my morning nutrient smoothie. I thought that with writing this article I could make up some of my fiber blend for folks that come into the office – maybe even boost it with some super 4X blueberry concentrate for adding to smoothies. It makes getting our 25 grams of fiber a day much easier when we can drink some of our fiber.