It may not be glamorous. But fiber’s effects in the body—from blood sugar stabilization and weight control to disease prevention—are nothing short of show-stopping.
Dietary fiber has been consistently linked to protecting against the development of Type 2 diabetes. Clinical studies show that higher fiber intake, especially from whole foods, lowers blood sugar markers and fasting blood glucose.
And while fiber doesn't directly "speed up metabolism," it does modulate metabolic systems by
- reshaping gut bacteria
- improving insulin sensitivity
- and affecting how your body process and stores energy.
There's more. Research has demonstrated fiber’s cardioprotective and anti-inflammatory abilities. Studies shows it reduces the risk of many types of cancer, including breast cancer (postmenopausal), colorectal, pancreatic, endometrial, ovarian, esophageal, and gastric. Recent research indicates fiber may even reduce your risk of dementia. One 16-year study followed almost 4,000 adults ages 40 to 64 and found that those who consumed the most daily fiber, an average of 20 grams, experienced the lowest dementia rates.
How Much Fiber Do You Need?
The recommended daily fiber intake is 21 to 25 grams for women and 30 to 38 grams for men. Ninety-five percent of Americans fail to reach the recommended daily amounts.
Soluble and Insoluble Fiber
Found exclusively in plant foods, fiber is either soluble or insoluble.
Soluble fiber aids nutrient absorption by creating a gel in your gut that feeds beneficial gut bacteria as it slows digestion and carbohydrate absorption. This helps provide a steadier insulin response and prevents blood sugar crashes.
Insoluble fiber adds bulk to the stool, helping waste—and toxins—pass more quickly from the intestines. It helps with satiety and calorie control and is associated with lower body weight and reduced fat over time.
While both types of fiber are important, soluble fiber in particular has been shown to benefit healthy cholesterol. One study found that 6 grams daily of concentrated oat beta glucan reduced total and LDL cholesterol in men and women with elevated levels after 6 weeks.
Other research shows that a low saturated-fat diet supplemented with another source of soluble fiber, psyllium (Plantago ovata husk), also raised HDL (healthy) cholesterol levels compared to supplementation with insoluble fiber.
In addition to psyllium, good sources of soluble fiber include oats, beans, lentils, and apples. Good sources of insoluble fiber include whole wheat, brown rice, and many vegetables.
Total fiber (both soluble and insoluble) from food sources appears to have an inverse relationship with certain cancers. One large-scale study indicates that the highest intake of dietary fiber (more than 30 grams per day, especially from whole-grain cereals and fruit) was linked to a reduced risk of breast cancer in premenopausal women.
Varieties of Fiber
You may be surprised to learn that the classification of fiber does not end with soluble and insoluble. There are several different types.
Brans, gums, and mucilages
These help regulate blood glucose and lower cholesterol levels while supporting toxin removal. Find these types in oatmeal, oat and rice bran, sesame and fennel seeds, and dried beans. Guar gum also belongs in this group—but anyone who has trouble swallowing or has experienced GI surgery is wise to avoid this fiber source.
Psyllium Husk
A strong internal cleanser, psyllium husk is one of the most popular supplemental fibers for regularity. This viscous fiber source thickens in the gut, binding bile acids. It helps in lowering LDL cholesterol and improving markers of metabolic syndrome. Metabolic syndrome is a cluster of five conditions—abdominal obesity, high blood pressure, high blood sugar, high triglycerides, and low HDL cholesterol—that significantly increase a person's risk of heart disease, stroke, and Type 2 diabetes.
If you're new to supplementing with fiber, start by mixing a half teaspoon of psyllium into a glass of water or a protein shake. As your gastrointestinal tract adjusts to the increased fiber (too much too fasts causes GI issues), you can build up to taking 5 grams twice daily
Cellulose
Cellulose is the indigestible fiber found in the skins of plant foods. Useful sources include apples, beets, broccoli, carrots, celery, pears, and whole grains. Helpful for regularity and hemorrhoids, cellulose removes cancer-causing substances from the colon.
Hemicellulose
Hemicellulose is another complex carbohydrate the body cannot digest. As it moves through the digestive system, it absorbs water—helping to promote weight control and alleviate constipation, and supporting intestinal and colon health.
Apples, bananas, beans, corn, green leafy vegetables, pears, and whole-grain cereals contain hemicellulose.
Lignan Fiber
Lignan fiber is most abundant in flaxseeds but is also found in apricots, broccoli, cabbage, kale, sesame seeds, tofu, and whole grains, among other plant-based foods. This form may support healthy cholesterol. A phytoestrogen, lignan is not recommended in supplement form for women who are pregnant or breastfeeding.
Pectin
Pectin helps control blood sugar by slowing the absorption of food after meals. Find this soluble fiber in apples, grapefruits, oranges, and other fruits, veggies, and legumes.
A nutritional supplement called modified citrus pectin, or MCP, is a form of pectin that has been molecularly altered to improve its bioavailability. Its potential benefits include removal of heavy metals from the body and cancer prevention.
Experts recommend alternating among several different supplemental fiber sources along with a fiber-rich diet. If you choose to take single or combination fiber formulas, do so at a separate time from any other supplements or medications to avoid decreasing the latter’s effectiveness.
