Digestion
Digestion is a complicated process where your body breaks down the food you eat into smaller, water-soluble molecules that can be passed into the bloodstream and transported to each cell in your body.
Depending on the function of the cells, these molecules are used for energy, growth and repair of tissues, or maintaining the immune system. The parts of the body involved in the digestive process are called the digestive system.
Sometimes digestive pain or discomfort can be linked to other conditions, such as gastroenteritis or constipation. Find out more at the links below.
Learn more about gastroenteritis
Learn more about constipation
Learn more about gastroenteritis
Learn more about constipation
The digestive system
The digestive system is made up of the gastrointestinal tract (GI tract or digestive tract), and the liver, pancreas and gallbladder.
The GI tract is around 8 metres long1and is made up of ‘hollow’ organs including:
mouth
oesophagus
stomach
small intestine
large intestine
anus
As it is digested, food travels through these ‘hollow’ organs while the ‘solid’ organs of the liver, pancreas and gallbladder aid the digestive process.
The digestive system
The digestive system is made up of the gastrointestinal tract (GI tract or digestive tract), and the liver, pancreas and gallbladder.
The GI tract is around 8 metres long1and is made up of ‘hollow’ organs including:
mouth
oesophagus
stomach
small intestine
large intestine
anus
As it is digested, food travels through these ‘hollow’ organs while the ‘solid’ organs of the liver, pancreas and gallbladder aid the digestive process.
1. Mouth
2. Oesophagus
3. Stomach
4. Small intestine
5. Large intestine
6. Rectum and anus
1. Mouth
Digestion begins in the mouth when you chew your food. Your teeth grind up the food which is mixed with saliva, making it easy to swallow. Saliva also contains enzymes which begin the process of digesting carbohydrates. After chewing, food becomes a round blob known as a bolus, which enters the oesophagus after we swallow.
2. Oesophagus
When you swallow, food enters the oesophagus which is the muscular tube that carries food from the mouth to the stomach. At the end of the oesophagus is a ring of muscle which relaxes to let food in and contracts to keep stomach contents from escaping back up into the oesophagus. Food leaves the oesophagus and enters the stomach.
3. Stomach
The stomach contains gastric juices, made up mostly of hydrochloric acid and pepsin.3These gastric juices help break down the bolus even more, including breaking down protein further, so it’s ready to enter the small intestine. On average, it usually takes between two to four hours for food to move from the stomach to the small intestine.
Simple carbohydrates such as rice, pasta or simple sugars may only take between 30 to 60 minutes, while food containing protein and/or fat can take up to four hours.4
By the time food leaves the stomach, it resembles a thick, soupy liquid called chyme, and moves onto the next stage of digestion in the small intestine.
4. Small intestine
Also known as the small bowel, the small intestine is around 5 metres long and 3.5cm in diameter. In the small intestine, the digestive process continues with the help of digestive enzymes which are released from the pancreas, and bile which gets produced in the liver then stored in the gallbladder.
The walls of the small intestine are lined with millions of finger-like structures called villi. These villi absorb water and the digested nutrients into the bloodstream. Most of the digestion of proteins, fats and carbohydrates finishes in the small intestine.6Any undigested food and water then moves onto the large intestine.
5. Large intestine
The large intestine is also known as the colon or large bowel and is about 1.5 metres long and around 7.5cm wide. The lining of the large intestine absorbs water, vitamins and mineral salts, while undigested fibre is mixed with mucus and bacteria to nourish the walls of the large intestine and keep it healthy.8
Anything left over that the body can’t use is deemed waste products. As the large intestine absorbs water, this waste turns from liquid into faeces (stools or poo), which move through the large intestine into the rectum.
6. Rectum and anus
Faeces are stored in the rectum and passed through the anus. When it’s full, receptors in the rectum stimulate the desire to have a bowel movement (poo), and these waste products are passed out of the body.
How long does it take to digest food?
Digestion time varies for each person. On average, after eating it takes around six to eight hours for food to pass through your stomach and small intestine. It then takes about 36 hours for food to move through the large intestine. However, because the digestion process varies between individuals and depends upon the type of food eaten, the time between swallowing your food and waste products leaving your body as faeces can be anywhere between two to five days.
Gas
Gas— Gas is a normal part of the digestion process, as is passing gas either through a burp or through your anus (farting). When you eat and drink, it’s common to swallow air, which can lead to gas. However, the break down of certain foods during digestion can also cause more gas, as can taking some medications such as:
aspirin
antacids
anti-diarrhoea medications
opioids
fibre supplements
iron supplements
Bloating
Bloating — Sometimes gas can build up in your stomach and intestines and cause swelling in your abdomen and a feeling of being ‘too full’. This is called bloating. Bloating is usually only uncomfortable, but sometimes it can be painful.
Heartburn
Heartburn — This condition is characterised by pain or a burning sensation in your chest, just behind your breastbone, which usually occurs after eating and gets worse when bending over or lying down. It is caused by stomach acid flowing back up into the oesophagus. Heartburn is sometimes referred to as reflux or gastro-oesophageal reflux disease (GORD).
Diverticulitis
Diverticulitis — This occurs when small, bulging pouches form in the intestines and become inflamed or infected. Diverticulitis can cause severe abdominal pain, fever, nausea and a change in your bowel habits.
Irritable bowel syndrome (IBS)
Irritable bowel syndrome (IBS) — The main symptom of IBS is abdominal pain either before or after a bowel movement. It’s also common to experience diarrhoea, constipation or both. A number of factors are thought to contribute to IBS including changes in gut microbes, stress and diet.
Stomach ulcers
Stomach ulcers — Also known as a gastric ulcer, stomach ulcers occur when there is a break or tear in the lining of the stomach, which can become inflamed and painful. Ulcers are usually caused by the Helicobacter pylori bacterium or anti-inflammatory medications.
Gastroenteritis
Gastroenteritis — Commonly shortened to ‘gastro’, this is a short-term infection or inflammation of the stomach and intestines. Symptoms usually include stomach cramps, vomiting and/or diarrhoea.
Diarrhoea
Diarrhoea — Diarrhoea is characterised by loose, watery stools and the need to have frequent bowel movements. It can be caused by numerous things including food intolerances and allergies, infections or adverse reaction to medication.
Constipation
Constipation — Constipation is the passing of hard or dry stools during a bowel movement, or having difficulty passing a bowel movement. It too can be caused by a number of factors, including diet, lack of exercise, medication, dehydration, or illness.
Other medical conditions may also cause or contribute to digestive problems. These include:
Coeliac disease — an autoimmune disease which causes the immune system to react abnormally to gluten
Lactose intolerance — inability to fully digest sugar (lactose) in milk
Inflammatory bowel disease such as ulcerative colitis, and Chrohn’s disease
When should you see a doctor?
Having an upset stomach, heartburn, diarrhoea or other digestive problem every now and then is quite normal and nothing to be worried about.
However, there are some symptoms that shouldn’t be ignored as they may indicate a more serious issue. You should visit your doctor if you:
have persistent heartburn, heartburn that gets worse, makes you throw up frequently, or you need medication for several weeks to get relief
throw up blood
have unusual or persistent abdominal pain
feel that food is caught in your chest
experience unexplained weight loss
have pain or difficulty when swallowing
have persistent hoarseness or sore throat
notice black or bloody stools
experience persistent diarrhoea
have two or fewer bowel movements per week
you notice changes in your bowel habits
Digestive issues can be caused by numerous factors, including medication. At MediADVICE we can help you manage your health with a Medication Review, where one of our pharmacists will review your medication and discuss which ones may be contributing to your digestive problems, and how we can best help you manage them.
At your local MediADVICE, our friendly Pharmacists can also provide advice on products that may assist with your digestive symptoms, or may refer you to your Doctor for further treatment.
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Disclaimer
General advice only – this information should not replace the information provided to you by your health care professional. If symptoms are severe or persist, please speak to your health care professional. Information current as of date of publishing.
Sources