Constipation Isn’t Just About Fiber: A Functional Look at Root Causes
Chronic constipation—specifically functional constipation with no clear underlying medical condition—is an incredibly common experience in modernized societies. The reasons are multifactorial. Dr. Denis Burkitt is often cited for his work in African communities, where he measured transit time and noted that populations consuming traditional, unprocessed diets rich in fiber had large, soft stools and rapid transit times (Cummings & Engineer, 2018). This mirrors the nutritional anthropological work of Dr. Weston A. Price, who studied indigenous, ancestral-based populations globally during the 1930s. These groups subsisted on ancestrally appropriate diets, free from what Price coined “the diets of modern commerce”—notably high in refined sugars and grains, and low in fiber, prebiotics, and probiotic-rich lacto-fermented foods, which are routinely found in ancestral diets worldwide (Price, 1939).
And yet, according to Krause and Mahan’s Food & the Nutrition Care Process (2020), constipation rates in modern-day Americans may be as high as 29% in children and 79% in adults. Why is everyone so backed up?
Allopathic medicine is often criticized for its reflexive reliance on pharmaceutical agents. While medication is necessary in some cases, we must also consider the underlying etiology of this process. This condition appears inextricably intertwined with our modern lifestyle—specifically our food choices and movement patterns, or lack thereof. Much modern anthropological study has noted the movement patterns of indigenous groups, including their tendency not only to move frequently but also to spend significant time in squatting positions. While this may seem like a small or unimportant detail, squatting aligns the anorectal angle, reducing straining and promoting complete evacuation. Could even our modern chairs and toilets be contributing factors in our difficulty with proper elimination?
Let’s now consider how chronic constipation affects the body from a pathophysiological perspective and explore nutrition and lifestyle strategies that support improved function. While often viewed as a mechanical issue of slow transit, functional constipation in otherwise healthy adults may reflect deeper disruptions—particularly within the gut microbiome, motility signaling, and modern lifestyle behaviors.
Functional constipation has many negative physiological implications. The slowed colonic transit creates an environment in which water reabsorption is increased. This leads to drier stools that are harder to pass (Raymond & Morrow, 2020). From there, straining or bearing down becomes a real challenge and may lead to further problems such as hemorrhoids, anal fissures, and anal prolapse. This decreased evacuation leads to physical discomfort, including gas and bloating.
Additional considerations are the changes in commensal bacterial colonies populating the large and small intestine. When stool is not effectively passed, more pathogenic bacterial and yeast colonies may proliferate. Of note, certain Firmicutes and Methanobrevibacter smithii strains (higher methane producers) may thrive, suppressing beneficial colonies such as Bifidobacteria and Lactobacillus spp., which are generally considered motility-supportive. A bacterial strain gaining interest that may additionally be disrupted with chronic constipation is Akkermansia muciniphila. Akkermansia, a gram negative bacteria present within first year of life but with a tendency to decrease in the elderly, is thought to help maintain the mucosal lining and thus gut barrier through its role in consuming old mucin and stimulating the production of new, healthy mucin (Zhang et al., 2019).
These pathophysiological changes creating constipation may lead to upstream nervous system dysfunction. When transit time is chronically slowed, this may decrease enteric nervous system tone. Our autonomic nervous system has a third arm not often discussed—the enteric nervous system, which is entirely devoted to the brain–gut axis. It becomes a bit of a “use it or lose it” scenario, where lack of defecation reduces the urge and nervous system signaling.
When seeking to address constipation, it is imperative the practitioner consider hidden obstacles such as hormonal changes, including hypothyroidism. Additionally, when working with female clients, it’s worth noting the role that the changing hormonal landscape plays in constipation etiology. For instance, during the fertile years, higher levels of progesterone during the luteal (post-ovulation) phase are notorious for creating sluggish motility. Additional hormonal fluctuations through perimenopause and menopause can also contribute. It is also important to consider the use of certain supplements, such as calcium and iron, which may contribute to slowed peristalsis.
Once hormonal and supplemental considerations have been made, a smart strategy would be to consider how this client may be living out of alignment from an ancestral perspective. Where is their daily fiber—both soluble and insoluble—at? While recommended ranges for women and men typically fall between 25–50 grams daily, some may benefit from even higher intake. This, by the way, aligns with modern-day hunter-gatherer societies such as the Hadza people, who have been extensively studied for their fiber intake and gut microbial biodiversity (Schnorr et al., 2014). The Hadza people consume a comparatively high-carbohydrate diet relative to many modern hunter-gatherer societies. According to Loren Cordain’s nutritional anthropological analysis (2000) of 229 contemporary hunter-gatherer groups, estimated carbohydrate intake typically ranges between 22% and 40% of total energy intake. However, a key distinction in the Hadza’s robust metabolic health lies in the quality and composition of those carbohydrates. Their diet, rich in fibrous tubers, fruits, and wild honey, delivers over 100 grams of fiber daily—a stark contrast to the low-fiber, refined carbohydrate intake common in industrialized societies. This substantial fiber load likely plays a protective role in gut health, protection against chronic constipation as well as glycemic regulation. Hadza’s fiber rich carbohydrates primarily come from tubers, baobab fruit, berries, and honeycomb. This amounts to four to five times more fiber than the average American (15–20 g/day). While these levels may not be appropriate for many individuals, it highlights the vast difference in modernized American society, which is reliant on hyperpalatable, ultra-processed foods devoid of nutrient including fiber.
Next would be to address likely gut bacterial dysbiosis. In a functional medicine setting, a GI-MAP (Gastrointestinal Microbial Assay Plus) is usually ordered. This is an in-depth DNA fragment test (PCR) that looks not only at classic pathologies such as H. pylori, Salmonella, and C. difficile, but also provides a broad view of commensal, pathogenic, and opportunistic bacterial and yeast strains.
Whether or not this test is available—since it may be cost-prohibitive and many traditional medical practices don’t use it—the next step would be to add fermented foods. These are the original probiotics that have nourished our ancestors throughout history and were only recently removed from the food supply due to industrial expedience, often at the cost of our well-being.
Additional medical-grade probiotics may be considered if the constipation is severe, or if fermented foods alone are not producing meaningful change. However, these should always be used under the care of a qualified practitioner, as critically ill patients—as well as those with underlying autoimmunity—may not always respond well to formulated probiotic supplements.
Increased water intake is often a necessary consideration, as much of the population is mildly dehydrated. There is no established RDA for water intake due to the multifactorial nature of hydration needs. Increased metabolic demands, higher fiber intake, exercise, hormonal fluctuations, and even altitude all significantly influence both water and electrolyte requirements. The IOM recommend fluid levels (including food) at 2.7-3.7 liters for women and men respectively but again many factors play a role (IOM, 2005).
In general, urine should be light or pale yellow as an indicator of adequate hydration. While standard AHA and USDA dietary recommendations tend to promote a “less is always better” mentality regarding sodium, the reality is that the same aforementioned factors impact sodium requirements as well.
Sodium, a primary electrolyte, is required in adequate amounts not only to help drive water into cells but also to maintain plasma levels sufficient to prevent the release of aldosterone from the adrenal glands. Ironically, when sodium drops too low, aldosterone secretion increases which can lead to potassium dumping, promoting water retention and potential downstream dehydration and electrolyte imbalance. According to a meta-analysis by Graudal et al. (2023), this aldosterone to plasma sodium inverse relationship may be more present in normotensive populations than in those with underlying hypertension.
For this reason, in functional nutrition practice—and with the important caveat that sodium-sensitive hypertension is considered—many practitioners recommend modest use of high-quality sea salt. These salts often provide a better balance of sodium chloride, potassium chloride, and trace minerals to support hydration and electrolyte homeostasis.
Lastly, additional lifestyle factors should be considered. Parasympathetic drive is involved in enteric digestive processes—the adage “rest and digest” has merit. For this reason, stress reduction must be addressed. Our modern sitting contraptions also mechanically restrict the digestive organs. The patient may be encouraged to take work-break walks, try gentle exercises like yoga, and possibly invest in a standing or walking desk setup.
A final note—specific to IBS-C: if IBS is suspected to be part of the picture, and possibly SIBO, considerations of a low FODMAP diet and even the Specific Carbohydrate Diet (SCD) may be appropriate. The GAPS Diet—a variation used in the functional medicine world—builds on SCD principles with additional focus on gelatinous foods to support the gut lining and fermented foods to rebalance gut microbiota.
Chronic constipation is both a small and large picture problem. It creates inconvenience, discomfort, and emotional distress. If left unaddressed, it may create cascading roadblocks to wellness through its role in gut dysbiosis and the many downstream systems that science is increasingly recognizing as connected to gut health—including metabolic health, immune function, and cognitive performance.
References:
Cordain, L., Brand Miller, J., Eaton, S. B., Mann, N., Holt, S. H., & Speth, J. D. (2000). Plant-animal subsistence ratios and macronutrient energy estimations in worldwide hunter-gatherer diets. The American Journal of Clinical Nutrition, 71(3), 682–692. https://doi.org/10.1093/ajcn/71.3.682
Cummings, J. H., & Engineer, A. (2018). Denis Burkitt and the origins of the dietary fibre hypothesis. Nutrition research reviews, 31(1), 1–15. https://doi.org/10.1017/S0954422417000117
Graudal, N., Hubeck-Graudal, T., & Jurgens, G. (2023). A low dietary sodium dose is associated with a more pronounced aldosterone response in normotensive than in hypertensive individuals. Scientific Reports, 13, Article 19027. https://doi.org/10.1038/s41598-023-46285-8
Institute of Medicine. (2005). Dietary reference intakes for water, potassium, sodium, chloride, and sulfate. National Academies Press. https://doi.org/10.17226/10925
Price, W. A. (1939). Nutrition and Physical Degeneration: A Comparison of Primitive and Modern Diets and Their Effects. Paul B. Hoeber, Inc.
Raymond, Janice, L. and Kelly Morrow. Krause and Mahan’s Food and the Nutrition Care Process Elsevier eBook on VitalSource. Available from: Purdue University Global Bookshelf, (15th Edition). Elsevier - Evolve, 2020.
Schnorr, S. L., Candela, M., Rampelli, S., Centanni, M., Consolandi, C., Basaglia, G., ... & Crittenden, A. N. (2014). Gut microbiome of the Hadza hunter-gatherers. Nature Communications, 5, 3654. https://doi.org/10.1038/ncomms4654
Zhang, T., Li, Q., Cheng, L., Buch, H., & Zhang, F. (2019). Akkermansia muciniphila is a promising probiotic. Microbial Biotechnology, 12(6), 1109–1125. https://doi.org/10.1111/1751-7915.13410