Types and Benefits of Soluble Fiber

Brussels Sprouts
Brussels sprouts are a low-carb way to get some valuable soluble fiber.

Verywell / Alexandra Shytsman

Soluble fiber just means dietary fiber that disperses in water when the food is broken down. A lot of soluble fiber is viscous, which allows it to form a gel. This tends to regulate the speed of digestion, stabilize blood glucose, and permit better absorption of nutrients. Soluble fiber has also been shown to reduce blood cholesterol. Also, soluble fiber is mostly fermentable, which contributes to colon health and the health of the body as well.

Common Sources: Sources of soluble fiber include psyllium seed, flax seeds, chia seeds, beans, peas, oatmeal, berries, apples, and some non-starchy vegetables such as Brussels sprouts, okra, and asparagus.

Types of Soluble Fiber

There are four types of soluble fiber you might hear about.

  1. Pectins, such as in some fruits, some vegetables, and legumes
  2. Beta-glucan, in some grains such as oats and in the konjac plant, the tuber from which shirataki noodles are made
  3. Naturally-occurring gums found in some seaweed (carrageenan) and some seeds (guar, acacia, locust bean)
  4. Inulin, such as in chicory, Jerusalem artichokes, and onions. Inulin is also becoming popular as a food additive, for example, in some protein bars.

Health Benefits of Soluble Fiber

1. Digestive benefits: Soluble fiber, particularly the viscous type that forms a gel, helps to slow and regulate the passage of food through the digestive system. This is thought to be one reason for the blunting of the glycemic response to carbohydrates when soluble fiber is present. It also ensures that nutrients have the opportunity to be fully absorbed in the intestines.

2. Benefits to blood sugar: In addition to the above, there is evidence that soluble fiber (as well as resistant starch) stimulates a glucose-regulating hormone called GLP-1. It's possible that this effect is actually achieved by fermentation of soluble fiber in the colon, which brings us to:

3. Benefits to colon health: By now you have heard that there is a whole world of activity going on in your colon thanks to the friendly bacteria that live there, especially if we keep them happy with a high-fiber diet. In particular, most types of soluble fiber are good food for these bacteria, which produce vitamins, valuable short-chain fatty acids which are difficult to get in the diet, and other helpful substances which are good for our colons and the rest of our bodies as well. We are just scratching the surface in learning about the benefits of a healthy microbiome.

4. Reduced cholesterol and other cardiovascular benefits: Soluble fiber intake has been consistently shown to be related to the reduction of blood cholesterol, as well as (less consistently) blood pressure and the overall risk of cardiovascular disease.

Low-Carb Sources of Soluble Fiber

When people think about foods with soluble fiber, they usually think first of oatmeal and beans, but there are other options for people who are watching their carbs.

1. Flax seeds and chia seeds: Both of these seeds have high levels of fiber, including soluble fiber, with very little starch or sugar. They also have provide healthy fats.

2. Psyllium: Husks of the psyllium seed are often sold as a fiber supplement because they are rich in soluble fiber. The product Metamucil and similar supplements are made from psyllium husks.

3. Some non-starchy vegetables: A half-cup of cooked Brussels sprouts has 2 grams of soluble fiber, and a serving of asparagus has almost as much. Other vegetables with a fair amount of soluble fiber include okra, turnips, carrots, and ​artichokes.​

Also, a lot of vegetables have at least some soluble fiber, which can add up. For example, cooked spinach has between half a gram and a whole gram of soluble fiber per half-cup serving.

4. Legumes: Legumes are perhaps the food most loaded with soluble fiber. A lot of the starch in beans (especially if you cook them yourself instead of buying canned beans) is resistant starch. This type of starch doesn't raise blood sugar and is great for the colon. Soy beans have very little starch, but do have some soluble fiber. Black soy beans taste like black beans but have the protein and lack of carbs of regular yellow soy beans.

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  1. Food sources of soluble fibre. Dietitians of Canada. Updated March 16, 2012.

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