Uploaded May 2025 | Updated September 2026, 2 weeks ago
It lowers blood cholesterol, reduces inflammation, improves immune function, curbs the appetite, reduces the risk of colon cancer and fights depression! No, it is not a new pill developed by a pharmaceutical company. It is dietary fiber. But as is usually the case, the story isn’t as straight forward as implied by cereals, gummies and even candy bars that scream added “fiber” on their packaging. Simply stated, fiber is the component of food that we cannot digest, meaning that as it passes through the stomach and small intestine it isn’t broken down into nutrients that can be absorbed into the bloodstream. As a result, it passes through to the colon.
Now things get more complicated because fiber is not a single entity. Cellulose, lignin, pectin, inulin, psyllium, guar gum, polydextrose, beta glucan and resistant starch can all be labeled as “fiber” but have different chemical compositions and different physiological effects. Some of these serve as tasty meals for the hundreds of species of bacteria that inhabit the colon while bacteria have no interest in the likes of cellulose or psyllium. These, after absorbing water, exit the colon and thereby serve as laxatives. On their way out, they can also absorb bile acids that normally would be reabsorbed into the bloodstream. This means the liver has to synthesize a new supply which it does from cholesterol, the result being a lowering of blood cholesterol.
Fiber that can be digested by bacteria is referred to as “fermentable fiber” and fermentation produces acetic, propionic and butyric acids, known as short chain fatty acids that have diverse effects. They can inhibit the growth of harmful bacteria, stimulate the release of appetite-suppressing hormones, alleviate depression and by helping to maintain the mucus layer that coats the intestine they can prevent bacteria from entering the bloodstream where they can cause inflammation.
Because of the benefits that have been attributed to an increase in dietary fiber, many products now feature “added fiber.” This generally tends to be just one type of fiber, usually inulin isolated from chicory, cellulose from wood pulp, bran from grains or synthetic polydextrose whereas the health benefits seen in studies have been from a melange of various types of fiber that are ingested when vegetables, fruits, nuts and whole grains are consumed. Inulin, for example, can foster short chain fatty acid release but has no laxative effect. Methylcellulose acts as a laxative but isn’t fermentable. So, the best bet to meet the recommended 25 grams of fiber a day is to eat a diversity of plant products and not rely on fiber added to packaged foods.
It lowers blood cholesterol, reduces inflammation, improves immune function, curbs the appetite, reduces the risk of colon cancer and fights depression! No, it is not a new pill developed by a pharmaceutical company. It is dietary fiber. But as is usually the case, the story isn’t as straight forward as implied by cereals, gummies and even candy bars that scream added “fiber” on their packaging. Simply stated, fiber is the component of food that we cannot digest, meaning that as it passes through the stomach and small intestine it isn’t broken down into nutrients that can be absorbed into the bloodstream. As a result, it passes through to the colon.
Now things get more complicated because fiber is not a single entity. Cellulose, lignin, pectin, inulin, psyllium, guar gum, polydextrose, beta glucan and resistant starch can all be labeled as “fiber” but have different chemical compositions and different physiological effects. Some of these serve as tasty meals for the hundreds of species of bacteria that inhabit the colon while bacteria have no interest in the likes of cellulose or psyllium. These, after absorbing water, exit the colon and thereby serve as laxatives. On their way out, they can also absorb bile acids that normally would be reabsorbed into the bloodstream. This means the liver has to synthesize a new supply which it does from cholesterol, the result being a lowering of blood cholesterol.
Fiber that can be digested by bacteria is referred to as “fermentable fiber” and fermentation produces acetic, propionic and butyric acids, known as short chain fatty acids that have diverse effects. They can inhibit the growth of harmful bacteria, stimulate the release of appetite-suppressing hormones, alleviate depression and by helping to maintain the mucus layer that coats the intestine they can prevent bacteria from entering the bloodstream where they can cause inflammation.
Because of the benefits that have been attributed to an increase in dietary fiber, many products now feature “added fiber.” This generally tends to be just one type of fiber, usually inulin isolated from chicory, cellulose from wood pulp, bran from grains or synthetic polydextrose whereas the health benefits seen in studies have been from a melange of various types of fiber that are ingested when vegetables, fruits, nuts and whole grains are consumed. Inulin, for example, can foster short chain fatty acid release but has no laxative effect. Methylcellulose acts as a laxative but isn’t fermentable. So, the best bet to meet the recommended 25 grams of fiber a day is to eat a diversity of plant products and not rely on fiber added to packaged foods.
