Do Potatoes Make You Constipated?

Potatoes, on their own, do not cause constipation in most people. A medium potato with its skin provides a few grams of fiber and a meaningful dose of potassium, both of which support regular bowel movements rather than hinder them. The reputation potatoes have as a constipation culprit probably has more to do with how they are prepared and what they replace in the diet than with the potato itself. Once you look past the french fry and the loaded baked potato drowning in cheese and sour cream, the plain potato turns out to be a surprisingly gut-friendly food.

What Happens When You Eat a Potato

A boiled or baked potato is mostly water and starch, with a modest amount of dietary fiber concentrated in and just beneath the skin. That fiber adds bulk to stool and helps it move through the colon. But the starch story is more interesting than it sounds, because not all of it gets digested in the small intestine. When cooked potatoes cool down, some of their starch rearranges into a form called resistant starch, which passes through to the large intestine largely intact. There, gut bacteria ferment it, producing short-chain fatty acids that nourish the cells lining the colon and promote healthy motility. Reheating a cooled potato (think leftover potato salad or yesterday’s roasted potatoes warmed up for lunch) preserves much of that resistant starch.

Clinical trials looking at resistant potato starch have found that certain forms of it actually increase stool frequency and soften stool consistency. One randomized trial in young adults tested different types of resistant potato starch and found that one variety significantly increased both how often participants had bowel movements and how soft those movements were, with only a mild uptick in flatulence as a side effect.¹ That is the opposite of constipation. The catch is that not all resistant starches behave the same way, and the effects depend on the specific type and the person eating it.

How Cooking Method Changes Everything

The way you cook a potato matters far more than whether you eat a potato at all. A plain boiled potato and a basket of deep-fried french fries are nutritionally different foods despite starting as the same vegetable. Frying a meal dramatically slows gastric emptying, which is how quickly food leaves the stomach and enters the small intestine. One study found that total gastric emptying time jumped from about 227 minutes after a non-fried meal to about 317 minutes after the same meal was fried, a roughly 40 percent delay.² When food sits in the stomach longer, everything downstream slows too. Slower transit through the colon means more water gets absorbed from the stool, making it harder and more difficult to pass.

On top of the frying effect, consider what typically accompanies fried potatoes: cheese, bacon, sour cream, butter, gravy. These high-fat additions compound the transit-slowing problem. A person who eats french fries or loaded potato skins daily and then blames potatoes for their constipation is really blaming the preparation. Swap those for a baked potato eaten with the skin, or a simple boiled potato dressed with olive oil and herbs, and the digestive picture shifts considerably.

Mashed potatoes sit somewhere in between. When made from scratch with the skins removed, they lose most of their fiber. Add butter and cream, and you are adding fat without adding anything that helps motility. Instant mashed potatoes can be even worse, since the processing strips away resistant starch and fiber while sometimes adding thickeners. If constipation is a concern, the simplest fix is to keep the skin on and go easy on the fat.

The Resistant Starch and Microbiome Connection

Resistant starch from potatoes does not just add bulk. It feeds specific bacterial populations in the gut that appear to be linked to bowel regularity. A clinical trial examining resistant potato starch at two different doses found that changes in constipation scores tracked with shifts in particular gut bacteria. At the higher dose, decreases in constipation correlated with decreases in a bacterium called Granulicatella. At the lower dose, consumption led to significantly fewer instances of constipation compared to a placebo, and those improvements correlated with changes in Turicibacter and certain Gammaproteobacteria.³

The effects were subtle. Overall bowel symptom scores, including constipation, did not change dramatically across the board. But the bacterial shifts were real and measurable, and they tracked in a direction consistent with improved regularity. The evidence is still early-stage, but the emerging picture suggests that the starch in potatoes, particularly resistant starch from cooled or reheated potatoes, acts as a prebiotic that nudges the gut microbiome toward better digestive function rather than worse.

That said, not every type of resistant potato starch produces the same result. The trial in young adults mentioned earlier found that one variety of resistant potato starch increased stool frequency while another did not, even though both were derived from potatoes.¹ The laxation-promoting variety also shifted the ratio of major bacterial groups in the gut, while the other did not. So “resistant starch from potatoes” is not one thing with one predictable effect. The chemistry of the starch and how it was processed both matter.

The Potassium Factor

Potatoes are one of the richest common food sources of potassium. A medium baked potato with skin delivers roughly 900 milligrams, which is about a fifth of what most adults need in a day. Potassium plays a direct role in the muscle contractions that push food through the intestines. When blood potassium drops too low, a condition called hypokalemia, the result is sluggish intestinal motility that shows up as constipation, bloating, and abdominal cramping.⁴

Most people with a varied diet are not clinically potassium-deficient, but surveys consistently show that average potassium intake in Western countries falls well short of recommended levels. People who are chronically low on potassium, whether from diet, medications like certain diuretics, or heavy sweating, might find that adding potassium-rich foods like potatoes actually helps their constipation rather than causing it. The irony is that someone cutting out potatoes to “fix” constipation may be removing one of the best potassium sources in their diet.

Why Some People Feel Worse After Eating Potatoes

Even though potatoes are generally pro-motility, some individuals do report feeling more bloated or backed up after eating them. Several things could explain this.

First, a sudden jump in resistant starch intake can cause temporary gas, bloating, and a feeling of fullness while the gut microbiome adjusts. Someone who rarely eats starchy vegetables and then has a large serving of cold potato salad might feel uncomfortable for a day or two. This usually passes as gut bacteria adapt to the new substrate.

Second, context matters. If potatoes are replacing higher-fiber foods in the diet, like beans, lentils, or whole grains, overall fiber intake can drop even though the potato itself contains fiber. A diet built heavily around peeled, mashed, or fried potatoes with little variety could genuinely contribute to constipation, not because of what the potato does but because of what it displaces.

Third, individual genetics influence how you process starch. People vary in how many copies they carry of the gene for salivary amylase, the enzyme that begins breaking down starch in the mouth. Those with more copies tend to break down starch more thoroughly in the upper digestive tract, meaning less resistant starch reaches the colon. People with fewer copies may deliver more undigested starch to their gut bacteria, which could mean more fermentation, more gas, and different effects on motility. Research has shown that amylase gene copy number is associated with distinct patterns of gut bacteria, including differences in populations linked to resistant starch degradation.⁵ In plain terms, two people can eat the same potato and have genuinely different digestive experiences because of inherited differences in their starch-digesting machinery.

Potatoes and Inflammatory Bowel Disease

For people with inflammatory bowel disease like Crohn’s disease or ulcerative colitis, the potato question gets more complicated. Potatoes contain naturally occurring compounds called glycoalkaloids, mainly solanine and chaconine, which are concentrated in the skin and any green-tinged flesh. In healthy people eating normal amounts, these compounds pass through without apparent harm. But laboratory and animal research has found that glycoalkaloids can disrupt the intestinal lining in a dose-dependent way, and that this effect is significantly more pronounced in animals genetically predisposed to IBD.⁶

A follow-up study using two different mouse models of IBD confirmed that feeding fried potato skins with moderate glycoalkaloid content ramped up pro-inflammatory signals in the colon and increased intestinal permeability. The inflammatory response intensified when potatoes with higher glycoalkaloid levels were used.⁷ Increased intestinal permeability and inflammation can disrupt normal motility in both directions: some people with IBD flares experience diarrhea, while others develop constipation as the intestinal muscles struggle to coordinate.

This does not mean anyone with IBD needs to avoid potatoes entirely. The concentrations used in these studies were at the upper end of what a person might encounter from normal eating, and the effect was specific to animals already predisposed to gut inflammation. Peeling potatoes removes most glycoalkaloids, and avoiding green or sprouted potatoes eliminates the highest-concentration specimens. But if you have IBD and notice that potatoes consistently worsen your symptoms, the glycoalkaloid connection is a plausible explanation worth discussing with a gastroenterologist.

Peeled Versus Unpeeled

Peeling a potato changes its nutritional profile in ways that matter for digestion. The skin contains the majority of the potato’s fiber, along with higher concentrations of vitamins and minerals. A medium potato eaten with skin provides roughly twice the fiber of the same potato peeled. For someone concerned about constipation, that difference is meaningful. Two to three grams of fiber might not sound like much in isolation, but most people fall short of the recommended daily fiber intake, and small additions throughout the day add up.

On the other hand, peeling removes most glycoalkaloids, which can matter for the IBD-sensitive population described above. It also removes the slightly bitter, earthy flavor that some people dislike, which is more of a preference issue than a health one. For the general population, eating potatoes with their skins is the better choice for regularity.

Common Foods Unfairly Blamed for Constipation

Potatoes are not the only whole food that gets wrongly accused of causing constipation. Bananas, rice, and cheese are frequently named as constipation culprits in folk wisdom and internet lists, with varying levels of evidence behind those claims. The common thread is that these foods are often consumed in processed or high-fat forms, or eaten in place of higher-fiber options. White rice, for instance, has had its bran and germ removed, stripping it of most fiber. But a baked potato with skin has meaningfully more fiber than white rice per serving, along with more potassium, making it the stronger choice for someone trying to stay regular.

The BRAT diet (bananas, rice, applesauce, toast), which is sometimes recommended for diarrhea or upset stomachs, has contributed to the idea that starchy foods are inherently binding. That diet works for diarrhea precisely because those foods are low in fiber and gentle on the gut. It does not follow that those foods cause constipation when eaten as part of a normal, varied diet. The problem arises when people eat a BRAT-style pattern habitually, which is low in fiber, fat, and variety, and wonder why they are constipated.

Practical Advice for Potato Lovers

If you eat potatoes regularly and have no issues with constipation, there is no reason to change anything. Potatoes are not a constipation risk for most people. If you do struggle with regularity, a few adjustments can ensure potatoes work with your digestion rather than against it:

Keep the skin on: This preserves fiber and nutrients that support motility.
Cook and cool: Letting potatoes cool after cooking increases resistant starch content, which feeds beneficial gut bacteria. Potato salad, cold roasted potatoes in a grain bowl, or reheated leftovers all count.
Limit frying: Fried preparations slow gastric emptying and add fat without adding fiber.
Watch the toppings: Heavy butter, cream, cheese, and sour cream turn a gut-friendly food into a high-fat meal that can slow transit.
Stay hydrated: Fiber works best when you drink enough water. Adding fiber without fluid can paradoxically make constipation worse.

Potatoes also pair well with other high-fiber foods. A baked potato alongside a salad, a bowl of lentil soup, or roasted vegetables creates a meal with substantially more fiber and variety than the potato alone. Constipation is almost always a pattern-level problem rather than a single-food problem, so looking at your overall diet usually matters more than obsessing over any one ingredient.

Green Potatoes and Sprouted Eyes

You may have heard that green potatoes are toxic, and that warning has a kernel of truth relevant to gut health. When potatoes are exposed to light, they produce chlorophyll (the green color) and, more importantly, elevated levels of glycoalkaloids. The same compounds that can aggravate IBD in sensitive individuals are present at higher concentrations in green-skinned or sprouted potatoes. At very high doses, glycoalkaloids can cause nausea, vomiting, abdominal cramps, and diarrhea in anyone, not just those with pre-existing bowel conditions.

In practice, the risk is small if you follow the standard advice: cut away any green patches and remove sprouts before cooking. The flesh of a potato that is only slightly green on the surface generally contains glycoalkaloid levels well below the threshold for symptoms. But if you have a potato that is green through much of its flesh, discard it. Cooking does not significantly reduce glycoalkaloid content, so you cannot fry or boil the problem away. For the vast majority of potatoes you encounter at the grocery store, this is a non-issue, but it is worth knowing if you grow your own or buy from farms where storage conditions vary.