The Power of Plants: How Fiber Supports Gut Health

‍ ‍The Power of Plants: How Fiber Supports Gut Health

Joy Stepinski, MSN, RN-BC

July 18, 2026

We discussed in a previous article how constipation is often the “elephant in the room”, a topic people may feel uncomfortable discussing. Healthy bowel habits are important throughout the entire lifespan, from infancy to older adulthood. Constipation not only disrupts daily routines and quality of life, but if not addressed, can contribute to more serious health conditions. Healthy bowel habits start with healthy lifestyle choices, and nutrition is a key contributor.

When we think about regular bowel movements, one of the most important factors discussed again and again in health literature is sufficient dietary fiber intake. Fiber comes from plant foods, such as fruits, vegetables, legumes, whole grains, nuts, and seeds [1]. It is a complex carbohydrate, categorized as soluble or insoluble. Insoluble fiber adds bulk to stool and helps promote regular bowel movements. Soluble fiber, on the other hand, has different roles. By absorbing water to form a gel, it lowers LDL cholesterol, binds bile acids that aid in fat digestion, and slows down the release of glucose into the bloodstream, preventing blood sugar spikes.

Soluble fiber is also important for supporting the gut microbiome. The gut microbiome is a complex community of microorganisms that live in the digestive tract [2]. Described as a “universe of bacteria” (p. 29) by Martin J. Blaser, these microorganisms help break down fibers and digest starch. During this process, microbes produce short-chain fatty acids (SCFA), compounds that are beneficial to digestive health. Some crucial roles of SCFA include providing energy for intestinal cells, regulating gut motility, and protecting the intestinal barrier [3], all contributing to healthy bowel function.

While fiber is known for supporting bowel regularity, research suggests that its benefits may extend throughout the body. One Japanese study [4] investigated the association of fiber intake and dementia among 3,739 participants over approximately 20 years. During the follow-up period, 670 individuals were diagnosed with dementia. Researchers determined that a higher intake of soluble fiber was associated with a lower risk of dementia. The study also found that lower blood pressure levels were associated with reduced dementia risk, suggesting that dietary patterns are linked to brain health.

Another study researched the association between dietary fiber intake and benign prostatic hyperplasia (BPH) [5]. BPH is a condition in men where the prostate becomes enlarged, causing inadequate bladder emptying, urinary frequency, and dribbling. The authors noted that BPH is a common problem among American men and those who follow a Western diet. The study compared 8 overweight men who engaged in a two-week diet and exercise program with 7 men who had followed a low-fat, high-fiber diet and exercised regularly. The results concluded that a high-fiber, low-fat diet with exercise reduced prostate cell growth markers.

In a cross-sectional study [6], researchers investigated the connection between fiber and advanced colorectal cancer. A total of 688 eligible participants completed a food questionnaire and provided stool samples. The subjects were equally divided (n = 344) between individuals diagnosed with cancer and healthy controls. Lower dietary fiber and SCFA production were seen in the cancer group, concluding that a high-fiber dietary pattern is associated with a healthy gut and may play a role in colorectal cancer risk.

Despite the benefits of a high-fiber diet, most Americans do not meet recommended levels. The U.S. Department of Health and Human Services reports that more than 90% of women and 97% of men do not consume enough fiber to meet current recommendations [7]. This shortfall is due to low intake of fiber-rich foods, such as fruit, vegetables, legumes, and whole grains. Consistently consuming a low-fiber diet puts people at risk for chronic health conditions.

Research examining the relationship between constipation and ultra-processed foods (UPF) suggests that diet may influence bowel regularity [8]. Higher consumption of UPFs was linked with constipation in this study population, while minimally processed foods were associated with more regular bowel movements. This cross-sectional study analyzed data from 12,716 participants in the National Health and Nutrition Examination Survey (NHANES) from 2005–2010.  

A study published in the New England Journal of Medicine [9] examined whether removing cow’s milk from the diet improved symptoms of chronic constipation in young children. A total of 118 participants under age six participated. All patients were diagnosed with chronic constipation, having bowel movements every 3 to 15 days. After 15 days of observation, the subjects were randomly assigned to receive dairy milk or soy milk. Results showed that children who consumed soy milk experienced significant improvement in bowel movements, compared with those who continued to consume dairy.

Finally, separate research examined the relationship between lifestyle factors and bowel movement frequency [10]. The cross-sectional study had 20,630 participants, aged 22 – 97 years. The total number of bowel movements was calculated. Researchers found that vegetarians, vegans, and people who consumed high amounts of dietary fiber reported more frequent bowel movements compared to individuals who consumed meat.

Maintaining healthy bowel movements begins with small daily dietary choices. As we have seen, research shows the important role that dietary fiber, found in plant foods, plays in gastrointestinal health. While constipation may be an uncomfortable topic, including fiber-rich foods in your diet supports a healthy gut microbiome, promotes regular bowel habits, and contributes to overall health. The summer is the perfect time to try ripe fruits and vegetables at local farmers’ markets or farmstands!

‍References:

‍ 1.      Daley, S. F. (2025). The role of dietary fiber in health promotion and disease prevention: A practical guide for clinicians. StatPearls. https://www.statpearls.com/point-of-care/22867

‍ 2.      Blaser, M. J. (2014). Missing microbes: How the overuse of antibiotics is fueling our modern plagues. Henry Holt and Company.

‍ 3.      Parada Venegas, D., De la Fuente, M. K., Landskron, G., González, M. J., Quera, R., Dijkstra, G., ... & Hermoso, M. A. (2019). Corrigendum: Short chain fatty acids (SCFAs)-mediated gut epithelial and immune regulation and its relevance for inflammatory bowel diseases. Frontiers in Immunology, 10, 1486. https://doi.org/10.3389/fimmu.2019.01486

‍ ‍4.      Yamagishi, K., Maruyama, K., Ikeda, A., Nagao, M., Noda, H., Umesawa, M., ... & Iso, H. (2023). Dietary fiber intake and risk of incident disabling dementia: The Circulatory Risk in Communities Study. Nutritional Neuroscience, 26(2), 148-155. https://doi.org/10.1080/1028415X.2022.2‍ ‍

5.      Barnard, R. J., Kobayashi, N., & Aronson, W. J. (2008). Effect of diet and exercise intervention on the growth of prostate epithelial cells. Prostate Cancer and Prostatic Diseases, 11(4), 362-366. https://doi.org/10.1038/pcan.2008.6

6.      Chen, H. M., Yu, Y. N., Wang, J. L., Lin, Y. W., Kong, X., Yang, C. Q., ... & Fang, J. Y. (2013). Decreased dietary fiber intake and structural alteration of gut microbiota in patients with advanced colorectal adenoma. The American Journal of Clinical Nutrition, 97(5), 1044-1052. https://doi.org/10.3945/ajcn.112.046607

7.      USDA. (2020). Dietary guidelines for Americans 2020 – 2025. https://www.dietaryguidelines.gov/sites/default/files/2020-12/Dietary_Guidelines_for_Americans_2020-2025.pdf

8.      Lo, C. H., Zhao, L., Steele, E. M., Pan, C. W., Lee, J. K., Zhang, X., ... & Samadder, N. J. (2024). Association of Ultra-processed Food and Unprocessed or Minimally Processed Food Consumption With Bowel Habits Among US Adults. Clinical Gastroenterology and Hepatology, 22(11), 2309-2318. https://doi.org/10.1016/j.cgh.2024.04.036

9.      Iacono, G., Cavataio, F., Montalto, G., Florena, A., Tumminello, M., Soresi, M., ... & Carroccio, A. (1998). Intolerance of cow's milk and chronic constipation in children. New England Journal of Medicine, 339(16), 1100-1104. https://www.nejm.org/doi/pdf/10.1056/NEJM199810153391602

10.   Sanjoaquin, M. A., Appleby, P. N., Spencer, E. A., & Key, T. J. (2004). Nutrition and lifestyle in relation to bowel movement frequency: A cross-sectional study of 20,630 men and women in EPIC-Oxford. Public Health Nutrition, 7(1), 77–83. https://doi.org/10.1079/phn2003522