Soluble fiber is a type of fiber that dissolves in water and forms a thick, gel-like mixture in the stomach. This gel helps support healthy digestion and provides several benefits, including relieving constipation, improving heart health, aiding weight management, and helping prevent or manage diabetes.
Foods rich in soluble fiber include apples, oats, avocado, wheat germ, green beans, and fava beans and can be included in everyday meals and snacks.
Most foods naturally contain both soluble and insoluble fiber, but the proportion of each type varies from one food to another. Eating a varied, balanced diet helps ensure you get a good mix of both kinds of fiber.
Main benefits
The main benefits of soluble fiber include:
1. Supporting weight loss
Soluble fiber forms a thick gel when mixed with water, which helps it stay in the stomach longer. This can increase fullness, reduce hunger, and support weight loss.
2. Improving bowel function and preventing disease
Soluble fiber acts as a prebiotic, feeding beneficial gut bacteria and supporting a healthier balance of the microbiota. It can also help regulate bowel movements, easing both constipation and diarrhea.
In addition, a high-fiber diet, including soluble fiber, may help lower the risk of diverticulitis, which is inflammation of small pouches (diverticula) in the colon wall.
3. Supporting heart health
Soluble fiber can help lower LDL (“bad”) cholesterol by binding to bile acids in the intestine and helping remove them from the body. This may reduce the risk of heart problems such as heart attack, high blood pressure, atherosclerosis, and stroke.
4. Preventing and helping manage diabetes
Because its gel-like texture can slow digestion and the absorption of carbohydrates, soluble fiber may help stabilize blood glucose levels. This can be helpful for people with type 2 diabetes or for those trying to prevent blood sugar spikes.
5. Strengthening the immune system
Because of its prebiotic effect, soluble fiber may help strengthen the immune system. It serves as a substrate for certain microorganisms in the gut and supports the growth of bacteria that are beneficial to health.
6. May help prevent colorectal cancer
Soluble fiber serves as food for certain gut bacteria and helps support a balanced intestinal flora.
When these bacteria break down soluble fiber, they produce butyrate, a short-chain fatty acid that is a main energy source for the cells that line the intestine. Butyrate may also trigger cancer cell death or slow the multiplication of colon cancer cells.
7. Reducing the risk of metabolic syndrome
Soluble fiber may help reduce the risk of metabolic syndrome, which is a group of conditions that increases the risk of developing heart disease, type 2 diabetes, heart attack, and other health problems.
Some scientific studies have shown that soluble fiber helps reduce waist circumference, regulate blood sugar levels, lower blood pressure, and reduce total cholesterol and triglycerides.
Food sources
Soluble fiber is found mainly in fruits and vegetables, but it can also be found in some grains.
The table below shows the amount of fiber found in 100 g of various grains:
The following table shows the amount of fiber in 100 g of various vegetables:
The table below shows the amount of fiber contained in 100 g of different fruits:
The fiber content and thickness (viscosity) of a plant can vary with its stage of maturity. As the plant matures, levels of some fiber types (such as cellulose and lignin) increase, while the amount of another type, pectin, tends to decrease.
Dietary supplements
Dietary fiber supplements are useful when it is not possible to meet daily fiber needs through food alone. They offer similar benefits and are available in capsule or powder form. The powder can be mixed into water, tea, milk, or natural fruit juice, for example.
Soluble vs insoluble fiber
Soluble fiber can dissolve in water and form a gel. This helps it stay longer in the stomach and intestines, which can increase fullness and help regulate blood sugar and cholesterol levels. In addition, this type of fiber is fermented by bacteria in the gut microbiota, which may help reduce inflammation and, as a result, help prevent gastrointestinal diseases.
Insoluble fiber does not dissolve in water and is not fully metabolized by the gut microbiota. However, when it reaches the intestine, it increases stool bulk and stimulates intestinal transit, which helps relieve constipation.
Therefore, to support overall health, it is essential to include foods rich in both soluble and insoluble fiber in everyday meals. Read more about how to include high-fiber foods in your diet.