Soluble and Insoluble Fiber in Managing Diabetes

How Both Can Help Control Blood Sugar, Aid Weight Loss, and More

A close-up view of wheat.
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If you have diabetes, including plenty of fiber in your diet is a smart move. This important nutrient can help you lose weight (if you need to), play a role in controlling your blood sugar levels, and more. Not all dietary fiber is the same, though: There are two types—soluble fiber and insoluble fiber—and each functions differently in the body.

To make the most of a higher-fiber diet, then, it can help to understand the differences between them in terms of how they can be most beneficial in helping you manage your diabetes, what the best sources of each are, how much daily fiber is ideal, and the smartest ways to meet that goal.

soluble v. insoluble fiber
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Benefits of Fiber for Managing Diabetes

Dietary fiber is the part of whole plant foods the body can't break down and digest. This factor separates fiber from other forms of carbohydrates (starches and sugars) —fiber is not absorbed by the body so it does cause a spike in blood glucose the way other carbs can.

Research has consistently shown that, for people with type 2 diabetes, eating more fiber can help improve blood glucose control. The amount of daily dietary fiber intake considered to be helpful in managing blood sugar levels is at least 25 and 38 grams per day in women and men, respectively. Eating more fiber can also help control weight and improve cardiovascular health - both of which can help with managing type 2 diabetes overall.

Both soluble and insoluble fiber contributes to these benefits, but they work differently in the body.

Soluble Fiber

This type of fiber attracts water: It turns to a gel when eaten and slows the rate of digestion. Soluble fiber makes it harder for the body to convert carbohydrates into glucose that can be absorbed into the bloodstream. This can help prevent dramatic increases in blood sugar levels, which in turn helps insulin work better.

Soluble fiber also allows the body to more easily take in and use nutrients, and has been shown to lower blood cholesterol and block the absorption of fat—benefits known to reduce the risk of stroke, diabetes, gastrointestinal disorders, heart disease, and some cancers. And because soluble fiber is fermentable, it contributes to colon health.

Insoluble Fiber

Often referred to as "roughage," insoluble fiber comprises the cell walls of plants and is made of cellulose. As such, it's bulky and doesn't dissolve in water. It speeds the movement of food through the digestive system, functioning much like a scouring pad by "polishing" the intestines along the way. Insoluble fiber also adds bulk to stools and increases the regularity of bowel movements, helping to prevent constipation.

Adding Fiber to Your Diet

Just 5% of all people in the United States get adequate fiber in their diets. The U.S. Department of Agriculture reports that the mean dietary fiber intake of all people 2 older is 16 grams per day—far lower than current recommendations.

Although the 2015-2020 Dietary Guidelines from the U.S. Department of Health recommend between 19 grams to 38 grams per day, depending on gender and age, men and women looking to get the full benefits of dietary fiber should aim for 25 and 35 grams, respectively.

Tips

Increasing the amount of fiber in your diet can lead to uncomfortable digestive symptoms such as bloating, gas, constipation, diarrhea, or cramps . Take it slow: Increase the fiber in your diet gradually, adding a bit more every few days. Spread your fiber intake throughout the day rather than cramming a lot of fiber into single meals or snacks, and drink plenty of water. Some simple ways to start: 

  • Aim to eat 3 to 5 servings of non-starchy vegetables each day (a serving is 1/2 cup cooked or 1 cup raw)
  • Consume two servings of high-fiber fruits such as berries, apples, or pears daily
  • Include plenty of whole grains, such as whole-grain bread, oatmeal, and ancient (quinoa, bulgar, barley, farro, millet, freekeh)
  • Snack on unsalted nuts—one serving is 1/4 cup or one handful
  • Sprinkle ground flax, hemp, or chia seeds into your yogurt 
  • Toss legumes, such as chickpeas, into your salad for a protein and fiber boost

When reading labels, note that any food containing 5 grams of fiber is considered an "excellent" source, according to the American Diabetes Association, and foods with 2.5 grams to 4.9 grams are "good" sources. In time, you'll become familiar with the amount of fiber in your favorite foods and getting more of these will become second nature.

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