Soluble and Insoluble Fiber Breakdown
Fiber is a type of carbohydrate that the body can’t digest. Though most carbohydrate foods are broken down into sugar molecules, fiber passes through the body undigested. Despite its inability to be digested, fiber serves vital roles in the body and is an important part of a healthy diet.
There are two main categories of fiber; soluble and insoluble. Both are beneficial in their own ways and provide distinct health advantages. Understanding the differences between soluble and insoluble fiber can help you better understand food labels and make informed dietary choices.
What is Soluble Fiber?
Soluble fiber has a remarkable ability to dissolve in water and form a gel-like substance in the gut. This gives it some unique properties and health benefits compared to insoluble fiber.
As soluble fiber travels through the digestive system, it helps bind to compounds like cholesterol and glucose, limiting how much of those substances get absorbed into the bloodstream.
Eating soluble fiber helps:
- Lower LDL “bad” cholesterol levels.
- Control blood sugar levels.
- Provide a feeling of fullness and slow digestion.
Good sources of soluble fiber include oats, barley, berries, citrus fruits, carrots, apples, and legumes like beans, peas and lentils. Many foods contain both soluble and insoluble fiber in varying amounts.
The gel-like texture that soluble fiber develops helps keep the intestines lubricated and regulates bowel movements to promote regularity. There’s also evidence that soluble fiber helps feed the beneficial gut bacteria, improving the health of the gut microbiome.
What is Insoluble Fiber?
While soluble fiber breaks down and forms a gel, insoluble fiber does not dissolve in water and mostly passes through the digestive system unchanged and intact. Insoluble fiber helps add bulk to stool and pushes waste rapidly through the intestines.
Consuming insoluble fiber is especially helpful for:
- Preventing constipation.
- Maintaining regular bowel movements.
- Reducing risk of diverticular disease and other intestinal issues.
Good sources of insoluble fiber are found primarily in whole grains like wheat, brown rice, nuts, seeds, the skins of fruits and vegetables, and plant foods like cauliflower, green beans and potatoes.
The roughage and bulking ability of insoluble fiber helps move waste through the body more efficiently. It adds bulk to stool and increases stool frequency. Insoluble fiber is not broken down in the digestive system like other foods, so it provides few calories itself.
The Fiber Gap and Recommended Intake
While soluble and insoluble fiber offer different benefits, most people don’t get enough of either type and should increase their total fiber intake. Only about 5% of people meet the recommended daily fiber targets.
The adequate intake (AI) for fiber is:
- Men: 38 grams per day
- Women: 25 grams per day
In reality, most Americans get less than half of their recommended intake. The average fiber consumption is only around 16 grams per day, according to the National Institutes of Health.
Insufficient fiber intake is linked to several chronic diseases and health issues like heart disease, diabetes, diverticular disease, hemorrhoids and constipation. Getting enough fiber can help with weight management, gut health, cholesterol levels and more.
To increase fiber intake, focus on eating more plant-based foods like fruits, vegetables, whole grains, beans, nuts and seeds. Choose whole, unprocessed foods over refined, fiber-stripped versions.
Read food labels to determine the amount and type of fiber in packaged foods.
Be sure to increase fiber intake slowly over time and drink plenty of water. Rapidly boosting fiber without extra fluids may lead to bloating, gas or constipation. Start with an extra 3-5 grams per day and work up to the recommended levels.
Both Soluble and Insoluble Fiber Are Vital
While soluble and insoluble fiber have some distinct properties and health impacts, both play essential roles and are vital parts of a balanced, fiber-rich diet. Eating enough of both types daily is important for overall health.
Soluble fiber promotes gut health, blood sugar regulation and helps lower harmful cholesterol levels. It provides important support for cardiovascular and metabolic health. Sources include oatmeal, beans, berries and citrus fruits.
Insoluble fiber offers benefits aimed at the bowels and digestive system by preventing constipation and promoting regularity. It adds bulk to stool and helps food move through the intestines efficiently. Good sources are found in whole grains, nuts, seeds and vegetables.
Most high-fiber foods contain a mix of both soluble and insoluble fiber types. Eating a variety of fruits, vegetables, grains, legumes and nuts is the best approach to get sufficient amounts of each.
Other tips for boosting fiber intake include:
- Choosing whole, unprocessed plant foods over refined versions.
- Start each day with a high-fiber food like oatmeal or bran cereal.
- Add beans, lentils and peas into meals and snacks.
- Swap out refined breads and pastas for 100% whole grain options.
- Keep fresh fruits and vegetables prepared and readily available.
- Use chia, flax and other seeds to add fiber to meals and snacks.
Gradually increasing fiber intake over time while drinking more water will help prevent any minor gastrointestinal discomfort.
Aim for at least the recommended daily target to take advantage of fiber’s various benefits from improving gut health to lowering cholesterol levels and boosting weight management.
In Summary
Soluble and insoluble fiber are the two primary categories of dietary fiber. Soluble fiber dissolves in water and has benefits like lowering cholesterol, controlling blood sugar levels and regulating bowel movements.
Insoluble fiber does not dissolve and helps push food through the intestines, adds bulk to stool and promotes regularity. To reap the full health advantages of fiber, aim for the recommended intake by eating plenty of high-fiber plant foods like fruits, vegetables, whole grains and beans.
