The journey from the first bite to the colon: what happens to food at each stage, how long it takes, and when digestive symptoms are worth showing to a doctor.
Digestion happens every day, but we usually only think about it when we feel heaviness, bloating, or irregular bowel movements. Understanding how this process works makes it much easier to understand your body's signals as well.
This article is based on information from the U.S. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), the Mayo Clinic, the British National Health Service (NHS), and studies where the path of food was measured using ingestible capsules. You will find the sources at the end of the article, and they are marked in the text with numbers, for example [1]. We write more about the gut in the article "The Gut: How it works and how to support it with nutrition".
What is digestion?
Digestion is a process during which food is broken down into small substances that the body can absorb: carbohydrates into simple sugars, proteins into amino acids, and fats into fatty acids and glycerol [1]. What the body does not digest, mostly fiber, travels on to the colon.
Digestion is both mechanical and chemical. The mechanical part is performed by chewing and muscle movements: food moves through the digestive tract via peristalsis, where muscles behind the bolus contract and push it forward, while those in front relax [1]. The chemical part is performed by enzymes, stomach acid, and bile.
The small and large intestines together are about 5 meters long, and about two-thirds of this length consists of the small intestine [8].
How does digestion happen? Step by step
1. Mouth
Digestion begins with chewing. Saliva softens the food, and the enzyme amylase contained within it begins to break down starch [1, 2]. This is why eating slowly and chewing well facilitates further work.
2. Esophagus
Once swallowed, peristalsis pushes the food down the esophagus into the stomach. The esophagus does not produce digestive juices [1].
3. Stomach
The glands of the stomach lining produce acid and enzymes, and stomach muscles mix them with food [1]. The main stomach enzyme, pepsin, breaks down proteins and works best when the pH is 2–3 [2]. Only particles smaller than 2 mm enter the duodenum [2], so the stomach mixes and grinds the food until it becomes semi-liquid.
4. Small intestine
This is where the majority of digestion occurs. Pancreatic juices, bile produced by the liver, and the intestinal juices themselves together finish breaking down proteins, carbohydrates, and fats, and the intestinal wall absorbs water and nutrients [1]. Between meals, bile is stored in the gallbladder and released when we eat [1].
5. Large intestine
What is not digested enters the large intestine. Here, water is absorbed and stool is formed, while bacteria help break down remaining nutrients and produce vitamin K [1]. This is the longest stage of digestion.
| Organ | What happens | How long it takes |
|---|---|---|
| Mouth | Chewing, salivary amylase begins to break down starch [1, 2] | As long as we chew |
| Esophagus | Peristalsis pushes the bolus into the stomach [1] | Briefly |
| Stomach | Acid and pepsin begin to break down proteins, food is mixed [1, 2] | Together, on average, about 6 hours [3] |
| Small intestine | Digestion is completed, nutrients and water are absorbed [1] | |
| Large intestine | Water is absorbed, stool is formed, bacteria are active [1] | On average, up to 36–48 hours [3] |
How long does digestion take?
The Mayo Clinic states that food travels through the stomach and small intestine for an average of about 6 hours, and can take 36–48 hours in the large intestine [3]. Thus, the entire journey usually takes about a couple of days.
More precise data is provided by studies in which people swallow a small measuring capsule. As it travels, it measures acidity, temperature, or pressure, making it possible to determine exactly when it reaches each part of the digestive tract. A 2023 systematic review collected data from 22 studies with 1,885 healthy volunteers [4].
| Stage | Average duration in different studies |
|---|---|
| Gastric emptying | 0.4–15.3 hours |
| Small intestine | 3.3–7 hours |
| Large intestine | 15.9–28.9 hours |
| Entire digestive tract | 23.0–37.4 hours |
Gastric emptying time varies the most in studies because it depends on what and when was eaten before swallowing the capsule. This is confirmed by a study of 215 healthy volunteers: when the capsule was swallowed immediately after a meal, gastric emptying was shorter [5]. In the same study, the total transit time for the digestive tract was longer in women than in men, with a median difference of 263 minutes, which is about 4.4 hours [5].
Therefore, digestion time is highly individual. It depends on the composition of the meal, fluids, movement, age, gender, and other factors.
What do these numbers mean for you?
If you don't have a bowel movement every day, it doesn't automatically mean something is wrong. More important is your usual rhythm and any changes to it. The NHS advises showing your doctor any changes in bowel habits that are unusual for you [10]. Equally important is how you feel: whether there is any pain, bloating, or heaviness.
What breaks down proteins, fats, and carbohydrates?
Each group of nutrients requires its own enzymes. Some of them work in the mouth and stomach, but the bulk of the work is done by pancreatic enzymes and enzymes in the wall of the small intestine [1, 2].
| Nutrient | Where and what breaks it down | End product |
|---|---|---|
| Carbohydrates | Salivary and pancreatic amylase break down starch; intestinal wall enzymes maltase, sucrase, and lactase break down disaccharides | Simple sugars, such as glucose |
| Proteins | Pepsin in the stomach; pancreatic trypsin, chymotrypsin, and other enzymes in the small intestine | Amino acids |
| Fats | Bile emulsifies them and pancreatic lipase breaks them down; some fat is also broken down by lingual and gastric lipases | Fatty acids and glycerol |
| Fiber | Human enzymes do not break it down, so it reaches the large intestine, where bacteria break down part of it | Some fiber is excreted with stool |
Pancreatic enzymes that break down proteins are released in an inactive form and only become activated in the duodenum [2].
What affects digestion daily?
- Fiber. EFSA considers 25 g of fiber per day to be a sufficient amount for normal bowel function in adults [6]. We write about where to find it in our guide "Fiber: what is it and where is it abundant?".
- Water. Fiber draws water into the gut, so when eating more fiber, you need to drink more fluids [7].
- Movement. Physical activity also helps bowel function.
- Eating pace. Rushing leads to swallowing more air, which can cause bloating.
- Stress and sleep. The digestive system is closely linked to the nervous system.
- Medications. Some medications can affect digestion. If you notice changes, consult your doctor or pharmacist.
Daily habits for digestion
- Eat slower and chew well. Digestion begins in the mouth [1].
- Dedicate half your plate to vegetables. Choose whole grain products and legumes as well.
- Drink water throughout the day. Especially if you are eating a lot of fiber [7].
- Go for a walk after eating. Even a short walk is a great habit.
- Don't overeat before bed. Leave a few hours between dinner and sleep.
- Increase fiber intake gradually. Suddenly increasing the amount can cause bloating and gas [7]. We write about this in more detail in the article "Bloating: common causes and daily habits".
Important: this research data is about human digestion and nutrition in general. It is not a description of the effect of a fruttberry product and does not replace a doctor's consultation.
When is it worth seeing a doctor?
Most digestive discomfort passes on its own. However, the NHS points out signs that should always be evaluated by a doctor [9, 10]:
| Sign | What to do |
|---|---|
| Persistently recurring indigestion or severe pain | Consult a family doctor |
| Difficulty swallowing | Consult a family doctor |
| Weight loss without a known cause | Consult a family doctor |
| Frequent vomiting or a lump in the abdomen | Consult a family doctor |
| Unusual changes in bowel habits, frequent urge to defecate | Consult a family doctor |
| Blood in vomit or stool | Consult a family doctor |
| Black or dark red stool, diarrhea with blood | Seek urgent help |
| Persistent bleeding from the anus | Call emergency services |
In such cases, it is important to find the cause, rather than trying to mask it.
Fiber for your daily life: fruttberry fiber mix
We created fruttberry out of a personal need, because we wanted a fiber mix ourselves that would be pleasant to drink daily. If you are not getting enough fiber from food, the mix can help supplement your daily amount.
Ingredients
- Psyllium husk (psyllium) is the foundation of the mix.
- Inulin from agave is a soluble fiber fermented in the gut.
- Freeze-dried strawberries (12%) and blackcurrants (8%) provide flavor and color from real berries, not from flavorings.
- Glucomannan from konjac (amorphophallus) tubers is another soluble fiber.
How much fiber is in one teaspoon?
100 g of the mix contains 77 g of fiber. In an independent study by the KTU Food Institute, our mix sample was found to contain as much as 84.4 g of fiber per 100 g. One teaspoon (5 g) provides about 3.86 g of fiber and only 11 kcal. The mix contains no added sugar, gluten, lactose, or preservatives, and is suitable for vegans.
Mix one teaspoon in 200–250 ml of water and drink it immediately, and increase the amount every 3–4 days. Psyllium and glucomannan swell, so always drink the mix with a sufficient amount of water: drinking too little fluid carries a risk of choking. If you have difficulty swallowing, do not use such fiber.
For home, the most convenient is the 250 g package, and for work and travel, the 30 portions of 5 g each.
All fruttberry dietary fibers in one place.
Common questions about digestion
Where does digestion begin?
In the mouth: chewing breaks food down, and salivary amylase begins to break down starch [1, 2].
How long does food stay in the stomach?
It varies greatly. The Mayo Clinic states that food travels through the stomach and small intestine together for about 6 hours [3], and in capsule studies, gastric emptying time depends heavily on the meal [4, 5].
How long does the entire digestion take?
Usually about a couple of days, because food can take 36–48 hours in the large intestine [3]. In capsule studies, the average total tract time ranged from 23 to 37.4 hours [4].
Why might women's digestion take longer?
In a study of 215 healthy volunteers, women's gastric emptying, colonic, and total tract transit times were longer than men's [5]. This shows that slower digestion does not necessarily mean a disorder.
Is fiber digested?
Human enzymes do not break down most fiber, so it reaches the large intestine. There, bacteria break down part of it [1]. This is exactly why fiber intake should be increased gradually and why you should drink enough water [7].
Why is there a feeling of heaviness after eating?
Usually because of portions that are too large, fatty food, or eating too quickly. If the heaviness recurs constantly, consult a doctor [9].
Sources
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Your Digestive System & How It Works. 2017.
- Patricia JJ, Dhamoon AS. Physiology, Digestion. In: StatPearls. Treasure Island (FL): StatPearls Publishing; updated 2022.
- Mayo Clinic. Digestion: How long does it take? 2025.
- Nandhra GK, Chaichanavichkij P, Birch M, Scott SM. Gastrointestinal Transit Times in Health as Determined Using Ingestible Capsule Systems: A Systematic Review. Journal of Clinical Medicine. 2023;12(16):5272.
- Wang YT, Mohammed SD, Farmer AD et al. Regional gastrointestinal transit and pH studied in 215 healthy volunteers using the wireless motility capsule: influence of age, gender, study country and testing protocol. Alimentary Pharmacology & Therapeutics. 2015;42(6):761–772.
- EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on Dietary Reference Values for carbohydrates and dietary fibre. EFSA Journal. 2010;8(3):1462.
- British Dietetic Association. Fibre: Food Fact Sheet. 2021.
- Helander HF, Fändriks L. Surface area of the digestive tract – revisited. Scandinavian Journal of Gastroenterology. 2014;49(6):681–689.
- NHS. Indigestion. Reviewed 2026.
- NHS. Symptoms of bowel cancer. Reviewed 2026.
The information provided is of a general nature and does not replace a consultation with a doctor or dietitian. Scientific data is presented about fiber and nutrition in general and is not a description of the properties of a specific product. If you have chronic illnesses, take medication, are pregnant, or are breastfeeding, consult a healthcare professional before starting to use dietary supplements. A dietary supplement does not replace a varied and balanced diet.
