Foods That Cause or Worsen Constipation, Plus Easy Swaps

The foods that cause constipation most reliably are low-fiber, highly processed ones: fast food, chips, frozen meals, processed meats, refined grains and sugary drinks. In U.S. survey data, adults who ate the most ultra-processed food had about twice the odds of constipation of those who ate the least^[1].

A few single foods can also firm stools, such as green bananas and persimmons^[2], and dairy matters for some people but not most^[3]. Below is what the research shows for each culprit, which popular claims are myths, and a simple swap for each one.

What foods cause constipation the most?

No single food has been proven to be the main cause. The pattern matters more: a diet built on processed, low-fiber foods. NIDDK advises people who are constipated to avoid foods with little to no fiber, naming chips, fast food, meat, frozen meals, snack foods and processed foods such as hot dogs^[4].

Long-term data back this up. In three U.S. cohorts of about 96,000 adults, a Western dietary pattern was linked to 22% higher risk of developing chronic constipation, while a plant-based pattern was linked to 20% lower risk^[5]. These links held even after accounting for total fiber and ultra-processed food intake^[5].

Ultra-processed and fast food

In 12,716 U.S. adults, the highest quarter of ultra-processed food intake carried 2.20 times the odds of constipation compared with the lowest^[1]. People who ate the most unprocessed or minimally processed food had less than half the odds^[1].

Replacing 10% of ultra-processed intake with minimally processed food was linked to 10% lower odds^[1]. This is survey data, so it shows an association, not proof of cause.

White bread, white rice and other refined grains

Refined grains swap fiber-rich whole grains out of the diet. In a 4-week randomized trial in 39 Korean women with functional constipation, brown rice and wheat-based diets both shortened total colon transit time by about 17 hours. A white rice diet lengthened it by about 7 hours^[6]. The trial was small and open-label, but the direction is consistent with fiber guidance^[4].

Meat-heavy meals with no plants

Red meat, poultry and processed meats such as hot dogs contain no fiber, which is why NIDDK puts meat on the avoid list during constipation^[4]. The issue is what meat crowds out. In the cohort data, vegetable and nut intake was linked to lower constipation risk^[5], and in another U.S. survey people with constipation ate 1.21 cups of vegetables a day versus 1.59 cups in those without it^[7].

Sugary drinks and sweets

Among 7,979 U.S. adults, those with the highest sugar-sweetened beverage intake had 1.57 times the odds of constipation of the lowest group^[8]. A Luxembourg survey of 1,431 adults also tied sugary products and higher total energy intake to higher constipation scores^[9]. Candy, caramel, pastries and soda all fall in this group.

Chips and salty snacks

Chips and snack foods are on NIDDK's low-fiber list^[4]. In the Luxembourg survey, higher sodium intake was linked to higher constipation scores^[9]. Unsalted nuts are a better crunchy swap, since nut intake tracked with lower risk^[5].

Green, unripe bananas

Unripe bananas contain 100 to 250 mg of tannins per 100 g plus amylase-resistant starch, and a pediatric review says they can cause or worsen constipation^[2]. Ripening lowers both. See the banana section below for the full picture.

Persimmons

Persimmons get their astringency from soluble tannins. The same review notes that tannic acid reduces small-intestinal secretions and inhibits peristalsis, and that even ripe persimmons can cause painful stools in healthy people^[2]. This is a review-level claim without trial data in adults.

Milk and dairy, for some people

Dairy is a problem mainly in two groups. In lactose intolerance, about 30% of people present with constipation rather than diarrhea^[10]. In children, cow's milk protein allergy is a separate cause: in 25 constipated children, 28% recovered on a milk protein-free diet and relapsed within 48 to 72 hours of drinking milk again^[11]. For most adults, dairy is not a clear culprit (see the cheese section).

Alcohol

Alcohol's effect depends on strength and pattern. Drinks above about 15% alcohol appear to slow down stomach emptying, and a single bout of drinking can slow small-bowel transit^[12]. Wine and beer, by contrast, can speed stomach emptying, and long-term heavy drinking can speed transit^[12]. So alcohol may constipate some people and loosen stools in others.

Iron supplements and some medicines

These are not foods, but they are often mistaken for a diet problem. A meta-analysis of 43 trials in 6,831 adults found ferrous sulfate more than doubled the odds of gut side effects versus placebo^[13]. NIDDK also lists calcium and aluminum antacids, narcotic pain medicines, calcium channel blockers, diuretics and some antidepressants^[14]. Do not stop a prescribed medicine on your own; ask your prescriber about alternatives.

Do bananas cause constipation?

Ripe bananas usually do not, but green ones can. As bananas ripen, their tannins and resistant starch fall and their sugars rise; a ripe banana has about 3 g of fiber per 120 g, mostly soluble^[2].

The binding effect of green bananas is real enough that it is used on purpose. A meta-analysis of 9 trials in 3,996 young children found that green banana foods nearly doubled the rate of recovery from diarrhea^[15]. That firming effect is the opposite of what you want when constipated.

Resistant starch is still a useful prebiotic fiber, covered in our resistant starch prebiotic guide. If you are constipated, choose fully ripe bananas, and save green ones for when your stools are loose.

Does cheese cause constipation?

For most adults, the evidence does not show that cheese causes constipation. In an Australian study of 1,241 adults, cheese intake was not associated with constipation in women or men^[3]. Women who ate 1 to 2 servings of total dairy a day actually had about half the odds of constipation of those eating less than one^[3].

Cheese can still contribute in two ways. A cheese-heavy meal often replaces fiber-rich foods, which is the main dietary driver of constipation^[4]. And if you have lactose intolerance, gut microbes may turn undigested lactose into methane, which may slow intestinal transit^[10].

Foods often blamed that probably are not the problem

Some foods get a bad reputation the research does not support.

• Dark chocolate. In a Japanese study in women, dark chocolate high in cacao protein increased bowel movement frequency and stool amount compared with white chocolate^[16]. It is a single study, so treat it as early evidence.
• Fats in general. In the Luxembourg survey, lipid-rich foods and total fat were linked to lower constipation scores, not higher^[9]. Greasy fast food is a different matter because of what else it lacks.
• Coffee. It is often blamed, but we found no study in this review that links it to constipation; the evidence on coffee and the bowel is in why coffee makes you poop.
• Not drinking enough water. Fluid only seems to help when you are actually dehydrated, according to a review of constipation myths^[17]. Still, U.S. adults with the highest water intake from food and drinks had about half the odds of constipation^[18].

Can too much fiber cause constipation?

It can for some people, especially those with severe or slow-transit constipation. A review in the American Journal of Gastroenterology states that many people with more severe constipation get worse when they add fiber^[17].

One uncontrolled study of 63 adults with idiopathic constipation is striking. Those who stopped fiber went from one bowel movement every 3.75 days to one a day, while those who stayed on a high-fiber diet stayed at one every 6.83 days^[19]. Bloating and straining also fell in the low-fiber groups^[19]. Groups were self-selected, so this needs confirming.

For most people, fiber still helps. A meta-analysis of 16 trials found 66% of adults responded to fiber supplements versus 41% on control, with the best results from psyllium at doses above 10 g a day for at least 4 weeks^[20]. Fiber also raised gas^[20], so add it slowly, as NIDDK advises^[4]. Our high-fiber foods for constipation list shows where to start.

What should you eat with slow transit constipation?

If your gut moves slowly, piling on fiber may add bloating without helping^[17]. Everyone in the low-fiber study had a colonoscopy first to rule out other causes, which is a good reason to get assessed before cutting fiber^[19]. Slow transit needs a clinician's plan; our chronic constipation page covers the options.

Easy swaps and examples of high-fiber foods

The best swap is a food with trial evidence behind it. The 2025 British Dietetic Association guideline, built on 75 randomized trials, made recommendations for kiwifruit, prunes, rye bread and high mineral-containing water^[21]. It made no recommendation for whole-diet approaches because the trial evidence was lacking^[21].

Adults need 22 to 34 g of fiber a day, depending on age and sex^[4]. NIDDK's examples of high-fiber foods are whole grains such as oatmeal and bran flakes, legumes such as lentils and chickpeas, fruits such as berries, pears and apples with the skin on, vegetables such as broccoli and green peas, and nuts such as almonds^[4]. Our gut healthy foods guide has a wider list.

Which dried fruit is good for constipation?

Prunes have the best support: they are one of only three foods the British Dietetic Association guideline made recommendations for^[21]. For the amounts trials used, see prune juice for constipation.

What is the best dinner to eat for constipation?

Build the plate around vegetables, legumes and a whole grain, such as a lentil or bean dish with brown rice and greens. That combines the fiber sources NIDDK recommends^[4] with a grain that sped colon transit in a trial^[6], and it mirrors the plant-forward pattern linked to lower risk^[5].

How these foods affect your gut bacteria

Your colon bacteria ferment fiber into short-chain fatty acids such as butyrate, and the foods above give them little to work with. Diets that emphasize plants and healthy fats were linked to lower constipation risk in the large U.S. cohorts^[5].

The chocolate study offers a glimpse of the microbial side: after dark chocolate, women had more butyrate producers such as Faecalibacterium and Roseburia, and stool amount tracked with Roseburia^[16]. Methane-producing microbes, such as Methanobrevibacter smithii, appear more common in people with chronic constipation, and methane may slow transit^[10]. Whether changing these microbes treats constipation is not yet proven.

Why am I suddenly constipated?

Sudden constipation often comes from a change in routine rather than one food. NIDDK lists travel, pregnancy, ignoring the urge to go, changing your medicines and changing how much and what you eat^[14]. Low fluid intake and inactivity are also on the list^[14].

New supplements are easy to miss. Iron is a common one^[13], as are calcium antacids^[14]. If constipation keeps coming back, our page on chronic constipation covers causes, testing and probiotics for constipation.

When to see a doctor

See a doctor if constipation does not improve with self-care, or if you have a family history of colon or rectal cancer^[14]. Get care right away if constipation comes with any of these^[14]:

• bleeding from the rectum or blood in your stool
• constant belly pain, vomiting or fever
• being unable to pass gas
• lower back pain or losing weight without trying

This article is for general educational purposes and is not medical advice. Diet changes affect people differently, and food is only one of many causes of constipation. Talk to a qualified healthcare professional before changing your diet or supplements, particularly if you are pregnant, immunocompromised, taking prescription medication, or managing a diagnosed condition.