Soluble Fiber
The figure above highlights different kinds of soluble fibers. Viscous, or soluble, fiber is made up of polysaccharide compounds found in the walls of plant cells. These compounds include beta-glucans, mucilage, pectins, gums and psyllium. Soluble fiber blend with water forming a gel-like substance that helps to slow down digestion, in particular, the absorption of sugars. Processed foods have all the fiber removed causing rapid absorption of sugar and a spike in blood glucose. The prevention of prevent quick spikes in your blood sugar levels is important part in managing diabetes. Soluble fibers also bind with fatty acids preventing their absorption into the body.
Pectin, a compound found in various fruits and vegetables, is an example of a soluble fiber that is an important part of our diets. Because of its ability to dissolve in water and form a gel, pectin is also used as a thickener when making jams and preserves.
Soluble fiber is found exclusively in plant-based foods. The best sources are usually derived from non-woody parts of plants, such as fruits, vegetables, grains, and nuts. Beans (like chickpeas, kidney beans, and lentils), oats, barley, and bran are very rich in soluble fiber.
Black beans, for example, contain about 15 grams of soluble fiber per cup, which is about half the recommended daily intake value for dietary fiber.
 Avocados are also a good source of soluble fiber, containing over 4g of soluble fiber in each fruit.
There is a subset of soluble fiber that can be obtained from supplements rather than the diet. They are extracted from natural sources then added to supplements or fortified foods and drinks to boost their fiber content. Psyllium husk is a soluble fiber supplement that is made from the seeds of the Plantago ovata plant. It is sold as the supplement ‘Metamucil.’ Although supplements are one way of adding soluble fiber to the diet these supplements lack the other nutrients and benefits offered by natural whole food sources.
Starches are the main types of carbohydrates present in the diet. They are long chains of glucose molecules, found in potatoes, grains and many other foods. Usually starch is digested into the constituent glucose molecules in the gut. However, some starch pass through the digestive tract unchanged. Scientists say they are resistant to digestion and have labelled them as Resistant Starch (RS). We bring them up here because they function like soluble, fermentable fiber in the gut. Resistant starch has numerous health benefits including:
- improving digestive health
- enhancing insulin sensitivity
- lowering blood sugar levels
- significantly reducing appetiteÂ
Good food sources of resistant starch include green bananas, various legumes, cashews and raw oats. The figure to the right illustrates many more good sources.
Additionally, certain starchy foods like white potatoes and white rice tend to form large amounts of resistant starch if they are cooled down after cooking.
Raw potato starch is also very high in resistant starch so some people eat it as a supplement.
