Despite clear evidence, most populations consume less than the recommended levels of dietary fiber, contributing to the rising burden of non-communicable diseases globally. Dietary fiber is an important component of our diet. In recent years, research has shown that dietary fiber may reduce the burden of chronic diseases such as diabetes mellitus, hypertension, and cardiovascular diseases. Dietary fiber may also be beneficial in the management of obesity and certain gastrointestinal disorders.
There is a gap between knowledge about the benefits of dietary fiber and its actual use. This decreases the global intake of the recommended levels of dietary fiber, particularly in developing countries. Research has shown that this decreasing intake of dietary fiber is due to use of highly processed foods.
The aim of this article is to explain the different types of dietary fiber, their mechanisms, and the evidence-based benefits of dietary fiber in helping the body fight against chronic illness.
ASPEN (American Society for Parenteral and Enteral Nutrition) states that dietary fiber is a type of carbohydrate comprising polysaccharides, oligosaccharides, lignin, and associated plant substances that are edible and resistant to digestion and absorption in the human body, unlike other nutrients such as proteins. Gut microbiota can ferment dietary fibers and produce short-chain fatty acids (SCFAs), which have beneficial effects on the body.
The Global Burden of Disease (GBD) 2023 study indicates a massive shift toward non-communicable diseases (NCDs) such as cardiovascular diseases, cancer, and diabetes. Dietary fiber plays an important role in preventing and reducing the risk of these diseases.
It is necessary to understand dietary fiber, its different types, and the food sources that are rich in fibers. Dietary fiber is classified into insoluble fiber, soluble fiber, and resistant starch. Insoluble fiber, as the name suggests, does not dissolve in water but absorbs it and helps bind waste to be excreted with fecal bulk. These fibers are beneficial in patients with diarrhea, constipation, hemorrhoids, and bowel cancer.
Soluble fiber, on the other hand, dissolves in water and forms a gel; in this way, it slows gastric emptying and delays glucose absorption, helping maintain blood glucose levels. It also acts as a prebiotic.
Resistant starch, another form of fiber present in pulses and plant foods, performs the same role as insoluble fibers.
Here is a list of a few foods very rich in fiber and should be included in the diet, e.g., broccoli, asparagus, eggplant, cauliflower, cabbage, spinach, coconut meat, apples, bananas, kiwis, pears, raisins, and all three kinds of berries. Raspberry is, in fact, a high-fiber fruit; one cup of raspberries contains about 7 g of fiber. Other rich sources are avocados, pistachios, almonds, and corn.
Refined and processed foods are poor sources of fiber. The grain-refining process removes the outer coat, called bran, and lowers the amount of fibers and other nutrients in the grain. Examples of refined grains include white bread, pasta, and cereals. Instead of refined foods, choose foods like whole-wheat bread, brown rice, and bran cereals.
The World Health Organization (WHO) recommends a daily fiber intake of at least 25 g for adults, and for children (6–9 years), 15–21 g daily is recommended.
The National Academy of Medicine gives the following daily fiber recommendations for adults: 21 grams for women older than age 50, 25 grams for women age 50 or younger, 30 grams for men older than age 50, and 38 grams for men age 50 or younger.
Dietary fiber plays a key role in multiple aspects of health. It supports cardiovascular health by reducing low-density lipoprotein cholesterol, improves glycemic control in individuals with diabetes, promotes gut health through microbiome modulation, and supports weight management by increasing satiety.
Beyond classification, dietary fiber exerts multiple physiological effects through metabolic, microbial, and anti-inflammatory pathways.
Anti-inflammatory effects: Dietary fiber exerts significant anti-inflammatory actions by modulating the gut microbiome, producing beneficial metabolites, and directly influencing immune cell activity. A high-fiber diet, often rich in whole grains, fruits, vegetables, and legumes, is associated with lower levels of systemic inflammatory markers such as C-reactive protein (CRP), interleukins (IL-6), and tumor necrosis factor-alpha (TNF).
Metabolic effects: Dietary fiber, particularly soluble types, slows gastric emptying and glucose absorption in the body, helping maintain blood glucose levels.
Microbiome effects: A high-fiber diet promotes the growth of beneficial gut bacteria. These bacteria produce short-chain fatty acids such as butyrate that protect the inner lining of the intestine from inflammation.
Evidence suggests that very high fiber intake, such as 50 g per day in controlled settings, may improve glycemic control in individuals with diabetes, although such intake levels should be interpreted in the context of specific clinical studies rather than general recommendations.
A large meta-analysis study shows that soluble fiber may help reduce low-density lipoprotein and cardiovascular disease risk.
A low-fiber diet may increase the risk of inflammatory bowel disease if high-fiber intake is avoided.
High-fiber diets are also associated with improved satiety and weight management.
Research has shown that a diet high in fiber may reduce the risk of developing diverticulitis a condition in which small pouches in the intestines become inflamed and painful. These patients may need to undergo surgical procedures if antibiotics fail. These pouches normally grow in adults and remain silent otherwise.
The incidence of breast cancer may decrease with an increased intake of high-fiber diets. Research suggests an 8% to 12% decrease in the risk of breast cancer if females consume a high-fiber diet, as it decreases the production of the estrogen hormone in the body.
High fiber intake has been associated with a lower risk of certain infections, including respiratory illnesses such as COVID-19, although more research is needed.
Dietary fiber may also influence the gut-brain axis, with emerging evidence suggesting a role in reducing neuroinflammation and supporting mental health, although further research is required.
In many Indian dietary patterns, fiber intake remains suboptimal due to increased consumption of polished rice and refined wheat products. Traditional diets that include whole grains such as millets, legumes such as lentils, and a variety of vegetables and fruits are important sources of dietary fiber and can help bridge this gap.
While dietary fiber has multiple benefits, excessive or rapid increases in fiber intake can lead to bloating, abdominal discomfort, and altered bowel habits. In certain conditions such as acute flares of irritable bowel syndrome or inflammatory bowel disease, a low-fiber diet may be temporarily recommended. Additionally, high fiber intake may interfere with the absorption of certain medications and nutrients, and clinical guidance is advised when making significant dietary changes.
There are significant misconceptions about fiber.
Not all types of fiber relieve constipation; insoluble fiber has this benefit over soluble fiber. Wrong fiber choices can even cause bloating. Similarly, not all fiber can decrease cholesterol levels.
Fiber supplements are available in pills and gummies, but they cannot replace natural sources of fiber. These supplements have their own side effects, e.g., abdominal cramps, bloating, diarrhea, constipation, nausea, and vomiting.
Serious side effects include intestinal blockage and reduced absorption of nutrients.
Not having a fiber-rich diet is a global issue. People face many barriers to adding fiber to their diet. Some think fiber-rich foods are expensive, while others do not have time for them or dislike their taste. Some people may experience unwanted side effects, and some have dietary restrictions preventing high-fiber intake, e.g., during flare-ups of IBS and IBD.
Do consult a nutritionist before suddenly increasing or decreasing fiber intake in your diet. Also, increase your water intake if you increase fiber in your diet.
A daily intake of a high-fiber diet seems difficult, but here are some tips you can easily practice
Replace highly processed foods, i.e., white rice, bread, and pasta, with less processed foods and whole grains like barley, millet, and brown rice.
Eat fresh fruits instead of drinking fruit juices.
Take raw vegetables or a handful of almonds instead of crackers and chips.
Fiber supplements like Ispaghol husk can also be used to replenish the need for fiber.
Keep in mind that fiber should be added gradually to the diet to avoid bloating.
MedBound Times connected with Sidra Zafar, DHND, (Doctor of Human Nutrition and Dietetics), she recommends fiber in two forms: either in salads, mostly at lunch time—a bowl full of salad helps reduce appetite and lose weight—or one tablespoon of psyllium husk dissolved in water, which improves gastric emptying and helps reduce bad cholesterol in the body.
Can I eat too much fiber?
Yes, consuming too much too quickly can cause bloating, gas, and cramping.
What are high-fiber foods on a label?
A food is considered high-fiber if it contains 5 or more grams per serving, while a "good source" has at least 3 grams per serving
American Society for Parenteral and Enteral Nutrition. ASPEN Adult Nutrition Support Core Curriculum. 2025.
Mayo Clinic. “Dietary Fiber: Essential for a Healthy Diet.” Accessed 2026. https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/fiber/art-20043983
Kabisch, S., et al. “Impact of Dietary Fiber on Inflammation in Humans.” International Journal of Molecular Sciences 26, no. 5 (2025): 2000.
Giuntini, E. B., et al. “The Effects of Soluble Dietary Fibers on Glycemic Response.” Foods 11, no. 23 (2022): 3934.
Ghavami, A., et al. “Soluble Fiber Supplementation and Serum Lipid Profile.” Advances in Nutrition 14, no. 3 (2023): 465–474.
Hawkins, A. T., et al. “Diverticulitis: An Update.” Current Problems in Surgery 57, no. 10 (2020): 100862.
Farvid, M. S., et al. “Fiber Consumption and Breast Cancer Incidence.” Cancer 126, no. 13 (2020): 3061–3075.