Why There Are Calories in Soluble Fiber

Oatmeal with blueberries
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Soluble fiber is a little different from insoluble fiber. Soluble fiber can dissolve in or be absorbed by water, whereas insoluble fiber cannot. What that means for your low carb diet is simple. When considering dietary fiber, which is derived from plants such as fruits and vegetables, of the two types of fiber, insoluble fiber doesn't have calories because it "goes right through." However, soluble fiber does count calorie-wise.

When you count carbs, you can subtract both soluble and insoluble fiber from the total carbohydrate count on food labels.

Soluble Fiber

Soluble fiber includes gums, pectins, mucilages, and some hemicelluloses. According to the FDA, soluble fiber is listed on food labels as having calories because it does, in a roundabout way, contribute calories to the body. This is because most soluble fiber is used by the bacteria in the colon to produce short-chain fatty acids which, in turn, are used by the body as energy. These calories do not raise blood sugar, so when counting carbs, those in soluble fiber (like insoluble fiber) don't count towards the total. This is also true of oligosaccharides, which may or may not also be listed as fiber.

Insoluble Fiber

Insoluble fiber includes cellulose, some hemicellulose, and lignins. It can be found in the seeds and skins of fruits and vegetables as well as whole grains like whole wheat and brown rice. It cannot be used by the body for energy. Insoluble fiber is referred to as roughage and has a number of health benefits, including staving off hunger, keeping your bowel movements regular and the like.

Health Benefits

Higher dietary fiber is associated with lower weights and less cardiovascular disease. And while insoluble fiber is known to improve immune function and reduce the risk of diverticulitis, soluble fiber has many more benefits. Soluble fiber is known to increase good bacteria in the gut, which improves digestive health. Another positive of soluble fiber is its ability to slow down digestion, which helps you maintain that full feeling after a meal longer. The slowdown in digestion is good for you if you're on a low-carb diet as it will help you control your appetite.

Oligosaccharides and Soluble Fiber

While oligosaccharides act like fiber in that over 90% of them are not digestible and pass through the small intestine. Yet they are not listed separately as soluble and insoluble fiber is in the US. Oligosaccharides, including inulin and oligofructose act as prebiotics in the colon which develops short-chain fatty acids (SCFAs) and certain B-vitamins. Oligosaccharides are also known to improve mineral absorption of calcium and magnesium.

Foods High in Soluble Fiber

Americans typically only get about half of the recommended amount of 25 grams of dietary fiber a day. The most popular sources of fiber in the American diet are processed flours, grains, and potatoes. The least popular are fruits, legumes, and nuts. Here are fiber-filled foods to add to your low-carb diet:

  • Oatmeal
  • Legumes such as peas, beans, and lentils
  • Barley
  • Fruits and vegetables, especially oranges, apples, and carrots
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