Digestion is a process where the body breaks down food into smaller particles to absorb them into the bloodstream.

Complete digestion of food takes anywhere between 24 to 72 hours and depends on several factors, including the type of food eaten and the presence of digestive issues.

This article looks at the digestive process and potential digestive problems and recommends ways to improve digestion.

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On average, food takes 6 to 8 hours to pass from the stomach and small intestine to the large intestine. From there, it may take over a day to digest further.

In many cases, the food moves through the stomach and small intestine within 6 to 8 hours. It then passes to the large intestine (colon).

However, the exact time varies and depends on factors such as:

  • Amount and type of food eaten: Protein-rich foods and fatty foods, such as meat and fish, can take longer to digest than high-fiber foods, such as fruits and vegetables. Sweets, such as candy, crackers, and pastries, are among the fastest foods digested.
  • Gender: A 1980s study found that the transit time through the large intestine alone was 47 hours for women and just 33 hours for men.
  • The presence of digestive issues: Crohn's disease, diverticulitis, and irritable bowel syndrome are some of the conditions that may slow down digestion.

Once food reaches the large intestine, it may remain there for up to a day or more as it undergoes further breakdown.

It's a commonly held belief that digestion only takes place in the stomach. In fact, there are three separate stages of digestion:

Oral stage of digestion

Chewing food breaks it down into smaller particles and mixes them with saliva. An enzyme present in saliva, called amylase, acts on carbohydrates in the food to break them down. The food particles can then form a soft mass that's easy to swallow, known as a bolus.

Gastric stage of digestion

In the stomach, an enzyme called pepsin helps to break down proteins into smaller particles. Stomach acid also plays an important role in preventing food-borne illness as it kills any bacteria or viruses that may have been present in the food.

Intestinal stage of digestion

Nutrients and water that have been removed from the digested food pass through the walls of the small intestine. They enter the bloodstream and travel to various areas of the body where they are used to repair and build.

The unabsorbed and undigested food that remains then moves to the large intestine. Here, some more nutrients and water are absorbed. The remainder is stored in the rectum until it leaves the body through a bowel movement.

To enjoy a healthy digestive system and to prevent constipation and diarrhea, try the following:

Eat a balanced diet

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Plant foods that are sources of fibre, including apples, legumes, and whole grains, may aid healthy digestion.

Fiber-rich foods, including fruits, vegetables, legumes, and whole grains, help move food through the digestive system more rapidly. They also help prevent constipation, feed gut bacteria, and help with weight loss.

Meat, particularly red meat, is hard to digest so should be eaten sparingly.

Processed and fast foods are often high in fat, making them difficult to digest. They are also rich in sugar, which may upset the balance of bacteria in the gut.

These types of food also contain additives that can cause stomach upset in some people and contribute to poor health.

Stay hydrated

Drinking enough water and other liquids, such as teas and juices, can prevent constipation and keep food moving through the digestive system.

Take probiotics

Probiotics are beneficial bacteria that help restore the balance of bacteria in the body by reducing the growth of harmful bacteria in the gut. The following foods are rich in probiotics:

  • natural yogurt
  • kefir
  • sauerkraut
  • kimchi
  • miso
  • fermented vegetables

Probiotics are also available in supplement form.

Make sure to include fiber-rich and prebiotic-rich foods to feed the probiotics you ingest as well as the healthy bacteria already in your colon.

Regular physical activity

Engaging in daily exercise benefits the digestive tract, as well as the rest of the body. Some people find that a gentle walk after meals reduces bloating, gas, and constipation.

Stress management

Being stressed can slow down digestion and contribute to symptoms such as heartburn, cramping and bloating. To reduce stress levels, engage in meditation, deep breathing exercises, and yoga. Even a few simple deep breaths before you eat can help. It is also important to get enough sleep every night to reduce stress and aid digestion.

Dental hygiene

As digestion begins with chewing in the mouth, problems with the teeth can interfere with this important step. Older adults, in particular, can be affected by improper chewing techniques due to dental issues. Brush and floss the teeth daily, and visit a dentist regularly.

Digestive enzymes

People with low stomach acid, chronic stress, digestive diseases and other conditions may benefit from taking supplements containing digestive enzymes. While these are freely available from health stores, it can be helpful to discuss enzyme supplementation with a doctor first.

Manage digestive conditions

Several medical conditions can cause problems with digestion. People with these conditions should always work with their doctor to manage their symptoms and reduce digestive distress.

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Suffering from gastro‐esophageal reflux disease, or GERD, may affect digestion. If digestive problems are persistent, a doctor should be consulted.

Possible digestive problems include:

  • gastro‐esophageal reflux disease (GERD)
  • celiac disease
  • irritable bowel syndrome (IBS)
  • inflammatory bowel disease (IBD)
  • diverticulosis
  • lactose intolerance
  • eosinophilic esophagitis (EoE)

These conditions can cause issues with digestion, and contribute to symptoms such as heartburn, bloating, constipation, and diarrhea.

Those who regularly experience symptoms of poor digestion, such as gas, bloating, constipation, heartburn, or diarrhea, should see a doctor who can rule out any serious conditions.

If anyone experiences any of the following symptoms, they should see a doctor immediately:

  • rectal bleeding
  • significant weight loss
  • fever
  • persistent vomiting
  • feelings of food blockages in the food pipe

Digestive symptoms that get progressively worse or change abruptly also require medical attention.

The time it takes to digest food varies between 24 and 72 hours and depends on several factors. To enjoy optimal digestion, eat a balanced, high-fiber diet, engage in regular exercise, reduce stress, and manage any digestive conditions that may be present.

If symptoms of digestive distress are severe, persistent, or change over time, it is important to see a doctor.