Plant-based diets, including vegetarian and vegan diets, are gaining popularity due to their potential health and environmental benefits. These diets, rich in fruits, vegetables, legumes, whole grains, nuts, and seeds, are often associated with improved bowel health. This article explores the effects of plant-based diets on stool, bowel movement frequency, and overall digestive well-being, drawing on available research and data.
The Role of Fiber in Bowel Health
Dietary fiber is crucial for preventing large-bowel diseases. Fiber intake in many high-income countries falls below recommended daily amounts. Plant-based diets are rich in fiber-dense foods, including fruits, legumes, and green leafy vegetables. These diets influence gut motility and the composition of the human gut microbiota.
Plant-Based Diets and Bowel Movement Frequency
Vegetarian diets have been associated with a higher frequency of bowel movements and softer stools. This suggests that vegetarians may experience constipation and other bowel disorders less frequently. Some studies indicate an inverse relationship between meat consumption and defecation frequency. However, it's important to consider that vegetarian populations vary significantly in their dietary patterns, which can affect bowel habits.
Research Findings
One study using data from the National Health and Nutrition Examination Survey (NHANES) (2007-2010) examined the bowel health of 9531 non-vegetarians and 212 vegetarians. The study assessed bowel health using the Bristol Stool Scale (BSS), bowel movement (BM) frequency, and the Fecal Incontinence Severity Index (FISI). While vegetarians consumed significantly more fiber than omnivores (21.33 vs. 16.43 g/day, p < 0.001), they had a lower moisture intake (2811.15 vs. 3042.78 g/day, p = 0.045). The study found no significant associations between vegetarian status and the examined bowel health items (BM frequency, BSS, and FISI).
Another study examined bowel health and defecation patterns in 65 physically active German university students randomly assigned to either a vegan or a meat-rich diet for eight weeks. Weekly BM frequency slightly increased in vegans, while it remained unaltered in participants assigned to a meat-rich diet. Fiber intake increased significantly in vegans (34.89 (18.46) g/d) whereas it decreased in those assigned to the meat-rich group (22.79 (12.5) g/d). No significant intergroup differences in BSFS and CCFIS patterns were observed.
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Contradictory Evidence
These findings contrast with other research suggesting that plant-based diets lead to more frequent bowel movements. A University of Oxford study of 20,000 people found that vegans poop more than vegetarians, who poop more than meat-eaters.
Factors Affecting Stool Consistency and Bowel Health
Fiber and Water Intake
Getting enough fiber is crucial for regular bowel movements, but it only works if you’re also getting enough water. Staying hydrated softens stools and makes them easier to pass. A high-fiber diet combined with adequate water intake and regular exercise promotes healthy bowel movements. Skimping on water intake with a high-fiber diet may lead to constipation.
The Cleveland Clinic recommends about eight 8-ounce glasses of water per day. The National Academy of Sciences recommends women consume 2.7 liters (nearly 11.5 cups) of total water per day and men drink 3.7 liters per day (about 15.5 cups). This includes water from food, beverages, and drinking water. Hydration requirements differ based on individual needs, exercise, illness, and environment.
Gut Microbiome
Sixty percent of stool weight comes from gut bacteria of the microbiome. When you feed gut bacteria the fiber-rich plant foods they prefer, they thrive and multiply, resulting in larger bowel movements. A healthy gut microbiome leads to better nutrient absorption, which can indirectly affect gut function. Beneficial bacteria improve gut function, motility, and transit, leading to better-formed and regular bowel movements.
Other Factors
Hormonal changes, regular exercise, and stress-reduction techniques such as yoga and meditation can also play a role in bowel health. Pelvic floor dysfunction, where muscles that are supposed to relax during pooping actually tighten up, can also cause constipation.
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Using the Bristol Stool Scale
The Bristol Stool Form Scale (BSFS) is a tool used to assess stool consistency. It ranges from type 1 (separate hard lumps) to type 7 (watery, no solid pieces). Stool type 1 and 2 may indicate constipation. Type 4, described as a long, bulky, soft sausage or snake, smooth without lumps, is considered ideal.
Potential Issues with Plant-Based Diets
Constipation
It is possible to be plant-based and still experience constipation. Other factors, such as hormonal changes, can play a role. Pasricha diagnoses about 50 percent of constipated patients with pelvic floor dysfunction, where muscles that are supposed to relax during pooping actually tighten up. The fix? Pelvic floor physical therapy.
Irritable Bowel Syndrome (IBS)
For individuals with Irritable Bowel Syndrome (IBS), a plant-based diet may present challenges. IBS symptoms include diarrhea, constipation, bloating, and abdominal pain. A low-FODMAP diet, which restricts certain foods, has been found to reduce IBS symptoms in up to 70% of those with IBS. Combining a plant-based diet with a low-FODMAP diet can be restrictive and may lead to nutritional deficiencies.
Nutrient Deficiencies
A vegan diet, if not well-planned, can lead to Vitamin B12, iodine, calcium, and omega-3 deficiencies.
Preventing Constipation
A study published in Gastroenterology tracked the dietary patterns of nearly 96,000 middle-aged and older adults for several years. It found that people who consistently followed a Mediterranean or plant-based diet were less likely to develop chronic constipation than individuals who adhered to a Western or inflammatory diet.
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Dietary Modifications
Adherence to a Mediterranean diet or plant-based diet was associated with a 16% and 20% decreased risk for constipation, respectively. It may not be just isolated nutrients like fibers. People have to do some of the hard work in terms of dietary modification rather than just adding a certain specific food or a specific supplement to try to prevent constipation.
Treat Poop Like a Vital Sign
When your poop is off, it’s a red flag that your gut bacteria aren’t being treated with TLC. Heed the warning. Since gut health is integral to all health, dysbiosis may manifest into other disease states. Constipation can precede diagnosis of Parkinson’s disease by as many as 20 years and is common in up to two-thirds of patients. It’s also linked to an increased risk for breast cancer and mood disorders. Tend to your gut microbes with a diverse menu of 30 different kinds of plants per week, and if you see pencil-thin poops or blood, or don’t feel like you’re completely emptying your bowels, call your doctor for a workup.