Many Americans have access to enough fiber-rich foods, but most are still not eating enough.
Women should generally eat 25 grams of fiber per day and men should eat 38 grams daily. In other words, you should get about 14 grams of fiber for every 1,000 calories you eat, per the Academy of Nutrition and Dietetics. Doing so can help you feel full, lower cholesterol, improve your digestion, and is even linked to preventing disease and helping you live longer overall.
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In fact, eating 25 to 29 grams of fiber a day is linked to a 15 to 30 percent lower risk of all-cause and heart-related mortality, per a February 2019 meta-analysis in The Lancet. The researchers note, however, that most people get less than 20 grams of fiber per day.
Dietary fiber can't be digested or absorbed, and so it passes through your stomach, small intestine and colon mostly intact.
There are two types of fiber: Soluble fiber and insoluble fiber. Soluble fiber dissolves in water and forms a gel-like material, and can help lower glucose levels and blood cholesterol, per the Mayo Clinic.
You can find soluble fiber in foods such as:
- Citrus fruits
- Psyllium fiber (a powdered supplement)
Meanwhile, insoluble fiber can benefit those who have constipation or irregular stools because it helps material move through the digestive system and increases stool bulk.
Insoluble fiber is found in foods such as:
- Whole-wheat flour
- Wheat bran
- Vegetables (such as cauliflower, green beans and potatoes)
Eating both types of fiber will benefit your health and longevity in a number of ways, and many fiber-rich foods contain both soluble and insoluble fiber.
The Health Benefits of Fiber
Fiber largely has a reputation for easing constipation, but its benefits go far beyond that. It's important to eat plenty of fiber regularly to protect your heart, gut and much more.
1. Fiber Is Good for Your Gut and Digestion
"Fiber supports digestive health and improves mood and immunity through its positive impact on the makeup of bacteria in your gut," Cynthia Sass, RD, CSSD, a Los Angeles- and New York City-based performance nutritionist, tells LIVESTRONG.com.
Some soluble fibers have the added benefit of being gut-friendly prebiotics.
Prebiotics can help the beneficial bacteria in your gut grow and may improve gastrointestinal health and potentially enhance how much calcium your body absorbs.
You can include more prebiotics in your diet by eating plenty of fruits, vegetables and whole grains — think bananas, onions, leeks, garlic, asparagus, artichokes, beans and barley.
Of course, fiber also benefits your digestive system. Insoluble fiber adds bulk to stool and helps food move through your stomach and intestines, per the U.S. National Library of Medicine. This, in turn, can promote regularity and prevent constipation.
Because soluble fiber turns into a gel in your body, it slows digestion, which can help keep you full for longer.
Soluble fiber, like that found in beans or oats, may help lower total blood cholesterol levels by lowering "bad" LDL cholesterol, per the Mayo Clinic. High-fiber foods may benefit the heart in other ways, such as by reducing blood pressure and inflammation.
Observational studies show that dietary fiber intake is associated with a lower risk of heart disease, the leading cause of death in the United States.
For instance, every 10 grams of fiber per day was linked to a 15-percent lower risk of death from coronary heart disease in a May 2012 study of more than 306,000 participants published in the European Journal of Clinical Nutrition.
What's more, insoluble fiber is linked with slower progression of heart disease in high-risk people, per the University of Wisconsin Health.
Choosing foods that are high in fiber is a key part of the DASH (Dietary Approaches to Stop Hypertension) Diet, an eating plan promoted by the National Heart, Lung and Blood Institute.
The diet involves eating plenty of fiber-rich foods, including:
- six to eight daily servings of whole grains
- four to five daily servings of fruits
- four to five daily servings of vegetables
- four to five weekly servings of nuts, seeds and legumes
3. Fiber Can Help You Maintain a Healthy Weight
High-fiber foods tend to make you feel fuller than low-fiber foods, so you're likely to stay satisfied for longer and eat less, per the Mayo Clinic.
It also typically takes you longer to digest high-fiber foods, which are often less energy-dense than other foods — meaning you take in fewer calories for the same volume of food.
In fact, increasing fiber intake by just 4 grams per day (the amount in a half-cup of raspberries) is associated with an additional 3 pounds of weight loss over six months in people on various diets in an October 2019 study in The Journal of Nutrition.
The researchers concluded that dietary fiber intake, independent of calorie or macronutrient (carbohydrates, proteins and fats) intake, promotes weight loss in people who are overweight or obese.
Keep in mind that some specialty diets may limit the number of fiber-rich foods you consume, so consult with your doctor before starting one. For instance, you may find it more difficult to get enough fiber when you're on a wheat-free or gluten-free diet.
4. It's Tied to Preventing and Managing Diabetes
Getting enough fiber is associated with a reduced risk of type 2 diabetes, according to a February 2014 meta-analysis of prospective studies in the European Journal of Epidemiology.
One of the risk factors of type 2 diabetes is being overweight, per the Centers for Disease Control and Prevention. A high-fiber diet can help prevent weight gain that can lead to type 2 diabetes. Fiber can also be helpful if you already have diabetes, as treatment typically involves monitoring your blood sugar and eating a healthy diet.
"Increasing your fiber intake can help play a role in regulating blood sugar and insulin levels, leading to steady, balanced energy," Sass says.
Your body digests high-fiber foods like vegetables, fruits and whole grains more slowly than refined carbohydrates (like crackers, pasta, white bread, candy and soft drinks), which means your blood sugar doesn't drastically rise after eating them, per Harvard Health Publishing.
Soluble fiber, in particular, appears to improve insulin sensitivity by lowering blood sugar levels, which means you may need less diabetes medication if you eat a high-fiber diet, Harvard Health Publishing states. But, of course, always check with your doctor before making any changes to your diet or the medicine you take.
5. It's Associated With a Reduced Cancer Risk
Fiber may play a role in preventing a number of cancers.
For instance, eating more fiber is linked with an 8-percent lower risk of breast cancer in an April 2020 meta-analysis in the journal Cancer. Soluble fiber intake, in particular, had a statistically significant effect on risk.
Although most of the studies looked at postmenopausal breast cancer, the protective effect of fiber on premenopausal fiber was even greater — women who ate the most fiber were observed to have an 18-percent lower risk.
Eating plenty of fiber is also associated with a lower risk of esophageal cancer, per a September 2017 study in Critical Reviews in Food Science and Nutrition. Plus, it appears to be linked to a lower risk of colorectal adenoma, the precursor of colorectal cancer, per a March 2014 meta-analysis in the journal Gastroenterology.
Although more research is needed to fully determine the effect fiber has on cancer risk, eating a healthy diet filled with fiber-rich foods is generally considered a cancer prevention strategy.
You should aim for a nutritious diet filled with a variety of vegetables, fruits and whole grains, per the American Cancer Society.
- Academy of Nutrition and Dietetics: "Easy Ways to Boost Fiber in Your Daily Diet"
- The Lancet: "Carbohydrate quality and human health: a series of systematic reviews and meta-analyses"
- Mayo Clinic: "Dietary fiber: Essential for a healthy diet"
- European Journal of Clinical Nutrition: "Dietary fibre intake and ischaemic heart disease mortality: the European Prospective Investigation into Cancer and Nutrition-Heart study"
- UW Health: "Fight Heart Disease with Fiber"
- National Heart, Lung, and Blood Institute: "DASH Eating Plan"
- My Food Data: "Raspberries"
- The Journal of Nutrition: "Fiber Intake Predicts Weight Loss and Dietary Adherence in Adults Consuming Calorie-Restricted Diets: The POUNDS Lost (Preventing Overweight Using Novel Dietary Strategies) Study"
- Cell Host & Microbe: "Fiber-Mediated Nourishment of Gut Microbiota Protects against Diet-Induced Obesity by Restoring IL-22-Mediated Colonic Health"
- European Journal of Epidemiology: "Dietary Fiber Intake and Risk of Type 2 Diabetes: A Dose-Response Analysis of Prospective Studies"
- U.S. Centers for Disease Control: "Diabetes Risk Factors"
- Harvard Medical School: "Healthy eating for blood sugar control"
- U.S. National Library of Medicine: "Soluble vs. insoluble fiber"
- Cancer: "Fiber consumption and breast cancer incidence: A systematic review and meta‐analysis of prospective studies"
- Critical Reviews in Food Science and Nutrition: "Dietary Fiber Intake Reduces Risk for Barrett's Esophagus and Esophageal Cancer"
- Gastroenterology: "Dietary Fiber Intake Reduces Risk for Colorectal Adenoma: A Meta-analysis"
- CA: A Cancer Journal for Physicians: "American Cancer Society guideline for diet and physical activity for cancer prevention"