Insoluble vs. soluble fiber
There are several types of fiber. Each works differently in your body and gives you distinct health perks. You may be familiar with the terms "soluble fiber" and "insoluble fiber," but within each of those labels are many different kinds of the nutrient.
All types of soluble fibers slow digestion, so it takes longer for your body to absorb sugar (glucose) from the foods you eat. This helps prevent quick spikes in your blood sugar levels – an important part of managing diabetes. Soluble fibers also bind with fatty acids, flushing them out of the body and helping to lower LDL (bad) cholesterol.
Insoluble fibers help hydrate and move waste through your intestines. That helps prevent constipation and helps keep you regular.
Most of us get both types of fiber from foods and supplements. You can get the nutrient from fruits, vegetables, nuts, beans, and grains. “Functional” fiber is extracted from its natural sources, and then added to supplements or fortified foods and drinks to boost their fiber content.
Most nutritionists say to get fiber from whole foods because they're healthy in other ways, too. But if you don’t get enough from your diet, fiber supplements can help fill in the gap. And evidence shows that most of us aren’t getting enough. The average person only gets about half of the fiber needed daily. Research shows that low income is linked to low fiber intake. Women 50 and younger should try to get 25 grams a day, and men should shoot for 38 grams.
Aim to eat a wide variety of different types of fiber. This chart shows the most common types of dietary and functional types and explains where they come from and how they can keep you healthy.
|Types of Fiber||Soluble or Insoluble||Sources||Health Benefits|
|Cellulose, some hemicellulose||Insoluble||Naturally found in nuts, whole wheat, whole grains, bran, seeds, edible brown rice, skins of produce.||"Nature's laxative": Reduces constipation, lowers risk of diverticulitis, can help with weight loss.|
|Inulin oligofructose||Soluble||Extracted from onions and byproducts of sugar production from beets or chicory root. Added to processed foods to boost fiber.||May increase "good" bacteria in the gut and enhance immune function.|
|Lignin||Insoluble||Found naturally in flax, rye, some vegetables.||Good for heart health and possibly immune function. Use caution if you have celiac disease or are gluten intolerant.|
|Mucilage, beta-glucans||Soluble||Naturally found in oats, oat bran, beans, peas, barley, flaxseed, berries, soybeans, bananas, oranges, apples, carrots.||Helps lower bad LDL cholesterol, reduces risk of coronary heart disease and type 2 diabetes. Use caution if you have celiac disease or are gluten intolerant.|
|Pectin and gums||Soluble (some pectins can be insoluble)||Naturally found in fruits, berries, and seeds. Also extracted from citrus peel and other plants boost fiber in processed foods.||Slows the passage of food through the intestinal GI tract, helps lower blood cholesterol.|
|Polydextrose polyols||Soluble||Added to processed foods as a bulking agent and sugar substitute. Made from dextrose, sorbitol, and citric acid.||Adds bulk to stools, helps prevent constipation. May cause bloating or gas.|
|Psyllium||Soluble||Extracted from rushed seeds or husks of plantago ovata plant. Used in supplements, fiber drinks, and added to foods.||Helps lower cholesterol and prevent constipation.|
|Resistant starch||Soluble||Starch in plant cell walls naturally found in unripened bananas, oatmeal, and legumes. Also extracted and added to processed foods to boost fiber.||May help manage weight by increasing fullness; helps control blood sugars. It increases insulin sensitivity and may reduce the risk of diabetes.|
|Wheat dextrin||Soluble||Extracted from wheat starch, and widely used to add fiber in processed foods.||Helps lower cholesterol (LDL and total cholesterol),and may lower blood sugar and reduce risk for heart disease; more research is needed. Avoid if you have celiac disease or are gluten intolerant.|
Soluble fiber foods and benefits
Foods rich in this type of fiber include oatmeal, nuts, beans, apples, and blueberries.
The health benefits include:
Heart protection: Inside your digestive system, soluble fiber attaches to cholesterol particles and takes them out of the body, helping to reduce overall cholesterol levels and the risk of heart disease. Oatmeal may offer the most heart protection.
Diabetes protection: Because soluble fiber isn’t well-absorbed, it doesn't contribute to the blood sugar spikes that can put you at risk for type 2 diabetes and heart disease. If you already have diabetes (either type 1 or type 2) soluble fiber can even help keep your condition under control.
Weight loss: Soluble fiber can also help you get to – or stay at – a healthy weight by keeping you feeling full without adding many calories to your diet.
Healthy bowel movements: Soluble fiber soaks up water as it passes through your system, which helps bulk up your stool and guard against constipation and diarrhea. In fact, most fiber supplements contain mostly soluble fiber.
Insoluble fiber foods and benefits
This is found in the seeds and skins of fruit (so always eat your peels) as well as whole-wheat bread and brown rice.
The health benefits include:
Weight loss: Like soluble fiber, insoluble fiber can play a key role in controlling weight by staving off hunger pangs.
Digestive health: Eating lots of insoluble fiber also helps keep you regular. And if you do get constipated, adding more of it to your diet can get things moving. Insoluble fiber can also improve bowel-related health problems, like constipation, hemorrhoids, and fecal incontinence (problems controlling your bowel movements.)