Does Grain Cause Constipation? The Role of Whole vs. Refined Grains

December 22, 2025 •

4 min read

Approximately 16% of U.S. adults experience constipation, according to the National Institutes of Health (NIH). The type of grain consumed is key, as the answer isn't straightforward.

Quick Summary

The impact of grain on constipation depends on whether it's whole or refined. Fiber-rich whole grains help prevent constipation, whereas refined grains, stripped of fiber, can contribute to it.

Key Points

Refined vs. Whole Grains: Refined grains (white bread, white rice) are stripped of fiber and can cause constipation, while whole grains (oats, brown rice) are fiber-rich and promote regularity.
Fiber is Key: The dietary fiber in whole grains adds bulk and softness to stool, helping it pass more easily through the digestive tract.
Hydration is Essential: Increasing fiber intake without enough water can worsen constipation, as fiber needs water to function effectively.
Gluten Sensitivity: For individuals with celiac disease or gluten sensitivity, gluten-containing grains can cause constipation and should be avoided.
Lifestyle Matters: Regular exercise, stress management, and not ignoring the urge to go to the bathroom are all crucial for preventing constipation.
Beneficial Gut Bacteria: The fiber in whole grains acts as a prebiotic, nourishing the healthy bacteria in your gut microbiome that are vital for proper digestion.

Understanding the Connection: Whole vs. Refined Grains

When people ask, "Does grain cause constipation?" they often don't realize there's a significant difference between whole and refined grains. The answer depends on which type is being consumed and other factors like hydration and individual sensitivities. A diet high in refined, low-fiber products can lead to constipation, while a diet rich in whole grains is known to promote healthy bowel movements.

The Impact of Refined Grains

Refined grains are products that have undergone a milling process, which removes the bran and germ from the grain kernel. Unfortunately, the bran and germ are where the fiber, iron, and B vitamins are primarily located. The result is a starchy, low-fiber food that can contribute to constipation, particularly if consumed frequently and with little fiber from other sources. Common refined grain products include:

White bread and pasta
White rice
Pastries, cakes, and cookies
Pretzels and many crackers

When your diet lacks sufficient fiber, stools can become hard, small, and difficult to pass. This occurs because fiber adds bulk to stool and helps it retain water, keeping it soft and moving smoothly through the digestive tract. A diet heavy in refined grains often lacks this crucial element.

The Benefits of Whole Grains

In stark contrast, whole grains contain the entire grain kernel—the bran, germ, and endosperm—meaning they are packed with dietary fiber. This fiber is your ally in the fight against constipation. Whole grains provide both soluble and insoluble fiber:

Insoluble fiber acts as a natural laxative, adding bulk to stool and speeding up the passage of food through the digestive system. Good sources include brown rice and whole wheat bread.
Soluble fiber dissolves in water to form a gel-like substance that softens stool, making it easier to pass. Oats and barley are excellent sources.

Studies confirm the positive effect of whole grains on bowel function. For instance, a study in young women with functional constipation found that brown rice and wheat-based diets both significantly improved bowel function and reduced colonic transit time compared to a white rice diet. Whole grains also act as prebiotics, feeding the beneficial bacteria in your gut microbiome, which is essential for overall digestive health.

Comparison: Whole Grains vs. Refined Grains


Feature	Whole Grains	Refined Grains
Processing	Minimally processed; contains the entire kernel.	Heavily processed; bran and germ removed.
Fiber Content	High in both soluble and insoluble fiber.	Low in fiber.
Nutrient Density	Rich in fiber, vitamins, minerals, and protein.	Stripped of most nutrients; often enriched.
Digestive Impact	Promotes regular bowel movements and gut health.	Can contribute to constipation and slow digestion.
Gut Microbiome	Provides prebiotics to nourish beneficial gut bacteria.	Does not provide the same prebiotic benefits.
Constipation Risk	Lowers the risk when combined with adequate hydration.	Increases the risk, especially in a low-fiber diet.

What About Gluten?

For some individuals, especially those with celiac disease or non-celiac gluten sensitivity, gluten—a protein found in wheat, barley, and rye—is a specific cause of constipation. Celiac disease is an autoimmune disorder where consuming gluten triggers an immune response that damages the small intestine. Chronic constipation is a common symptom. For these individuals, a completely gluten-free diet is necessary to manage symptoms. However, for most people without a gluten intolerance, gluten-containing whole grains are beneficial for digestive health due to their high fiber content.

The Crucial Role of Hydration and Lifestyle

Eating fiber-rich grains is only half the solution. Fiber works best when it can absorb water to add bulk and softness to your stool. In fact, if you increase your fiber intake without also increasing your fluid intake, you can make constipation worse. Drinking plenty of water throughout the day is essential for a healthy digestive system.

Other lifestyle factors also play a critical role:

Exercise: Regular physical activity helps stimulate muscle contractions in your intestines, promoting bowel movements.
Stress Management: Stress and anxiety can disrupt the gut-brain axis and slow down digestion.
Timing: Not ignoring the urge to have a bowel movement helps maintain regularity.

Conclusion: Making Informed Choices for Digestive Health

So, does grain cause constipation? The answer is a clear "it depends." Refined grains like white bread and white rice, which are low in fiber, can certainly contribute to the problem. However, whole grains such as oats, brown rice, quinoa, and whole wheat are powerful allies for digestive health, providing the essential fiber that promotes regularity and feeds beneficial gut bacteria. The key is to distinguish between these two types and to supplement your grain intake with plenty of water and a healthy lifestyle. For those with specific sensitivities like celiac disease, a gluten-free diet is the necessary course of action. By making informed choices, you can use grains to improve your digestive wellness, not hinder it.

Visit Mayo Clinic for more information on the causes of constipation.

Frequently Asked Questions

Refined grains, such as white bread, white rice, and pastries, are more likely to cause constipation because they have had the fiber-rich bran and germ removed during processing. This makes them low in the dietary fiber necessary for healthy bowel movements.

Yes, whole grains are excellent for relieving constipation. They contain high amounts of dietary fiber, which adds bulk to stool and helps soften it, promoting regular and healthy bowel movements. Examples include oatmeal, quinoa, brown rice, and whole wheat bread.

Fiber, especially from whole grains, helps prevent constipation by adding bulk to your stool and absorbing water, which makes the stool softer and easier to pass. It also helps speed up the transit time of food through your intestines.

For most people, gluten is not the cause of constipation. However, for those with celiac disease or a gluten sensitivity, consuming gluten (found in wheat, barley, and rye) can trigger digestive issues, including constipation. A gluten-free diet is necessary for these individuals.

Yes. When increasing your fiber intake from sources like whole grains, it is crucial to also increase your fluid intake. Fiber works like a sponge and needs water to add softness and bulk to your stool. Without enough water, higher fiber can worsen constipation.

Yes, some whole grains are especially beneficial. Oats and barley, for instance, are rich in soluble fiber (beta-glucan), which is highly effective at softening stool. Brown rice and quinoa also offer a great mix of soluble and insoluble fiber to promote regularity.

Some individuals with Irritable Bowel Syndrome (IBS) may find that certain high-fiber grains can cause bloating. It may be helpful to consult with a healthcare professional or registered dietitian. Some people with IBS find that a low-FODMAP diet, which may limit certain grains, helps manage their symptoms.