Why High-Protein Diets Can Cause Constipation, And How Prebiotic Fiber Supports Bowel Regularity

High-protein diets are popular for a reason. They help build muscle, support satiety, and promote weight management. Whether it is a low-carb regimen, a fitness-focused meal plan, or simply an effort to eat “cleaner,” many people today are loading up on protein-rich foods like chicken, eggs, fish, and protein shakes.

But as many soon discover, a common side effect often creeps in constipation.

While protein itself is not the direct culprit, the dietary imbalances that come with high-protein eating can disrupt digestion and slow down bowel movements. Fortunately, the solution does not mean giving up your protein. It means adding back the prebiotic fiber your gut needs to stay regular.

Why High-Protein Diets Often Lead to Constipation

A well-balanced diet depends on a variety of nutrients, and fiber is one that is often overlooked when protein takes center stage. Here are the main reasons why high-protein diets tend to backfire on your digestion.

1. Low Fiber Intake

Many high-protein diets such as keto, carnivore, or paleo limit or exclude carbohydrates, which are also the main sources of dietary fiber. Without enough fiber, stool lacks bulk and moisture, slowing transit time in the intestines [1].

Over time, this can lead to hard, dry stools, infrequent bowel movements, and bloating. Since protein-rich foods such as meat, eggs, and dairy contain no fiber, people on these diets often miss the recommended amount of fiber per day [2].

2. Reduced Prebiotic Fiber

Not all fibers are the same. Prebiotic fibers, found in foods like garlic, onions, leeks, asparagus, and bananas, specifically feed beneficial gut bacteria. These microbes ferment prebiotics to produce short-chain fatty acids (SCFAs) such as butyrate, which help stimulate intestinal contractions and maintain healthy digestion [3].

When you cut out prebiotic-rich foods while eating more protein, your gut microbiome loses these important fuel sources. This can lead to fewer beneficial bacteria, slower motility, and greater risk of constipation [4].

3. Dehydration

High-protein diets increase the body’s production of urea, a waste product of protein metabolism. To excrete urea, the kidneys pull more water from the body, which can lead to mild dehydration if you are not drinking enough fluids [5]. Less water in the body means less water in your stool, and harder stools are more difficult to pass.

4. Altered Gut Microbiome

Studies show that diets very high in animal protein and low in fiber can change the composition of gut bacteria. This shift tends to favor species that produce harmful metabolites while reducing the diversity of beneficial microbes that promote regularity [6]. This microbial imbalance, or dysbiosis, does not just slow digestion. It may also increase intestinal inflammation and discomfort.

Why Fiber, Especially Prebiotic Fiber, Is Key

Fiber is not only about adding bulk. Different types of fiber serve specific functions that directly affect bowel health.

• Insoluble fiber (found in whole grains and vegetable skins) adds mass to stool and speeds up movement through the intestines.
• Soluble fiber (found in oats, apples, and legumes) absorbs water to soften stool.
• Prebiotic fiber (found in garlic, onions, leeks, and chicory root) nourishes good bacteria that produce compounds to support gut motility and overall digestive balance [7].

Prebiotic fibers like inulin and fructooligosaccharides (FOS) are particularly effective because they work on both fronts: softening stool and stimulating gut motility through microbial fermentation [8].

How Prebiotic Fiber Supports Bowel Regularity

When prebiotics reach the colon, beneficial bacteria ferment them into short-chain fatty acids (SCFAs) including acetate, propionate, and butyrate. These SCFAs play several key roles:

• Stimulating muscle contractions in the colon, helping stool move more efficiently
• Increasing stool water content, making bowel movements softer and easier
• Feeding colon cells, improving gut barrier function and reducing inflammation [9]

In fact, clinical studies show that supplementing with prebiotic fibers like inulin or galactooligosaccharides can significantly improve bowel frequency and stool consistency in people struggling with constipation [10].

Why Food Alone May Not Be Enough

While it is ideal to get prebiotic fibers from natural foods, most people fall short. Research suggests that the average diet provides less than 5 grams of prebiotics daily, whereas optimal gut health benefits are observed at around 10–15 grams per day [11].

For those following a high-protein or low-carb diet, this gap can be even greater since many prebiotic-rich foods are restricted. This is where prebiotic fiber supplements come in.

The Role of Prebiotic Fiber Supplements

Prebiotic fiber supplements, such as ADVAGEN Prebio, offer an easy and effective way to support digestive balance, especially for those who prioritize protein but do not get enough fiber from food.

Derived from plant-based sources like corn, ADVAGEN Prebio is a fully soluble, non-gelling, and tasteless prebiotic fiber that can be easily mixed into your daily meals, smoothies, or drinks.

Regular intake can help:

• Promote bowel regularity by softening stool and stimulating movement
• Feed beneficial gut bacteria, improving microbial diversity
• Reduce bloating by promoting smoother digestion over time
• Enhance nutrient absorption and overall gut comfort

Unlike laxatives, which provide temporary relief, prebiotic fibers work at the root of the problem by improving the ecosystem of your gut.

Tips to Prevent Constipation on a High-Protein Diet

If you are committed to your protein goals, here is how to keep digestion on track:

1. Take prebiotic fiber daily and foods like garlic, onions, bananas, or with a prebiotic supplement like ADVAGEN Prebio.
2. Stay hydrated by aiming for at least 2 liters of fluids per day.
3. Include plant-based sides and pair protein with fiber-rich vegetables or legumes where possible.
4. Get moving because regular activity helps stimulate the intestines.
5. Listen to your body and respond promptly to natural urges to prevent stool buildup.

The Bottom Line

A high-protein diet can help you achieve your fitness or wellness goals, but without enough fiber, it can also leave you feeling sluggish and constipated.

By balancing your plate with prebiotic fiber, you can nourish your gut bacteria, improve bowel regularity, and keep your digestive system running smoothly without compromising your protein intake.

Think of it as the perfect partnership: protein for your muscles, and prebiotics for your gut. Together, they support a body that is not only strong but also comfortable, balanced, and healthy from the inside out.

References

1. Slavin, J. (2013l) ‘Fiber and Prebiotics: Mechanisms and health benefits,’ Nutrients, 5(4), pp. 1417–1435. https://doi.org/10.3390/nu5041417.
2. Anderson, J.W. et al. (2009b) ‘Health benefits of dietary fiber,’ Nutrition Reviews, 67(4), pp. 188–205. https://doi.org/10.1111/j.1753-4887.2009.00189.x.
3. Gibson, G.R. et al. (2017g) ‘Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics,’ Nature Reviews Gastroenterology & Hepatology, 14(8), pp. 491–502. https://doi.org/10.1038/nrgastro.2017.75.
4. Makki, K. et al. (2018g) ‘The impact of dietary fiber on gut microbiota in host health and disease,’ Cell Host & Microbe, 23(6), pp. 705–715. https://doi.org/10.1016/j.chom.2018.05.012.
5. Martin, W.F., Armstrong, L.E. and Rodriguez, N.R. (2005) ‘Dietary protein intake and renal function,’ Nutrition & Metabolism, 2(1). https://doi.org/10.1186/1743-7075-2-25.
6. David, L.A. et al. (2013d) ‘Diet rapidly and reproducibly alters the human gut microbiome,’ Nature, 505(7484), pp. 559–563. https://doi.org/10.1038/nature12820.
7. Holscher, H.D. (2017c) ‘Dietary fiber and prebiotics and the gastrointestinal microbiota,’ Gut Microbes, 8(2), pp. 172–184. https://doi.org/10.1080/19490976.2017.1290756.
8. Davani-Davari, D. et al. (2019d) ‘Prebiotics: definition, types, sources, mechanisms, and clinical applications,’ Foods, 8(3), p. 92. https://doi.org/10.3390/foods8030092.
9. Koh, A. et al. (2016g) ‘From dietary fiber to host physiology: Short-Chain fatty acids as key bacterial metabolites,’ Cell, 165(6), pp. 1332–1345. https://doi.org/10.1016/j.cell.2016.05.041.
10. Micka, A. et al. (2016b) ‘Effect of consumption of chicory inulin on bowel function in healthy subjects with constipation: a randomized, double-blind, placebo-controlled trial,’ International Journal of Food Sciences and Nutrition, 68(1), pp. 82–89. https://doi.org/10.1080/09637486.2016.1212819.
11. Healey, G. et al. (2018b) ‘Habitual dietary fibre intake influences gut microbiota response to an inulin-type fructan prebiotic: a randomised, double-blind, placebo-controlled, cross-over, human intervention study,’ British Journal of Nutrition, 119(2), pp. 176–189. https://doi.org/10.1017/s0007114517003440.