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Soluble and Insoluble Fiber for Blood Sugar Balance

As I noted before, one of the things that makes a complex carbohydrate “complex” is its fiber content. When fiber is digested, the body handles it differently than it does other carbohydrates. Part of the fiber goes through the digestive system without breaking down at all. This is important for a couple of reasons.

One, fiber doesn’t cause a spike in blood sugar levels or trigger an insulin release like other carbs do, so they’re essentially “free” carbs when it comes to glucose balance. For this reason, if you want to determine how many actual, glucose-affecting carbs (a.k.a. “net” carbs) are in a food, subtract the number of fibers from the number of total carbs. For example, a slice of bread that has 12 carbohydrates and five fibers really only has seven net carbs per slice (12 total carbs – 5 fibers = 7 net carbs).

What’s more, both types of fiber (soluble and insoluble) are needed to keep bowels regular. Soluble fiber dissolves in water, forming a gel, so it helps water stay in the stool, making it softer and easier to pass. Insoluble fiber does not dissolve in water, so it adds bulk to the stool, making the colon feel full so that it begins the elimination process. Too much bulk-forming insoluble fiber, though, and not enough soluble fiber can actually make constipation worse instead of alleviating it.

Many high fiber foods contain both soluble and insoluble fiber, but they are usually higher in one than the other. Some of the top sources of bulk-forming insoluble fiber are high-carbohydrate foods like wheat and other whole grains, lentils, and beans. They are not keto-friendly, obviously, so keep that in mind if you decide to switch fuels.

Some low carb, keto-friendly options that are high in insoluble fiber include:

  • flaxseed

  • chia seeds

  • leafy greens

  • broccoli

  • cauliflower

  • celery

Keto-Friendly foods with water-absorbing soluble fiber include:

  • nuts

  • psyllium (or psyllium husk)

  • carrots (in moderation)

  • onions

  • chicory root

Some non-keto foods with water-absorbing soluble fiber include:

  • apples

  • pears

  • brussels sprouts

  • oats

  • rye

  • barley

Typically, adult women should try to get at least 25 grams of fiber daily, and men should try for 35 grams. This could be higher for those with high cholesterol or who are at risk for heart disease, as studies have shown that soluble fiber can lower both total cholesterol and LDL cholesterol. (1) Other studies show greater fiber intake can substantially reduce the risk of coronary heart disease, and particularly coronary death. (2)

Getting this much fiber every day may seem like a difficult task for some (especially if you go keto), but it’s not impossible. It just requires planning and diligence. Here are a couple of ways to incorporate more fiber into your diet:

  • Eat a big garden salad at least once every single day.

  • Add chia seeds, hemp seeds, and flaxseed to your smoothies.

  • Add psyllium husk to your homemade baked goods.

  • Have raw veggies (broccoli, celery, cauliflower) with a homemade dip as your snack.

Please note: if you aren’t used to eating this much fiber, ease into it. Do not start with the recommended 25-35 grams/day as it can make you gassy if your system isn’t used to it.


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