Gastrointestinal Transit: How Long Does It Take To Digest Food?

An average person eats food multiple times a day. Sometime later, this food exits the body in the form of waste after it has been broken down into nutrients in digestion.

How Long Does It Take for Food to Digest?

The entire process of digestion is divided into three different stages. The oral stage involves chewing food to break it into smaller pieces and mixing it with the saliva. In the gastric stage, the stomach enzyme helps further break down the proteins contained in the smaller food particles. Meanwhile, the intestinal step removes water and nutrients from the digested food to allow them to enter the bloodstream and travel to the different parts of the body.

The entire digestive process can take several hours. It is generally accepted that food takes 24 to 72 hours to move through the digestive tract. When food enters the stomach, it takes 2 to 4 hours before it turns into a liquefied substance called chyme. The chyme then passes through the small intestine, where it spends 3 to 5 hours for nutrient absorption. Afterwards, the remaining food moves through the large intestine with transit time from 4 to 72 hours.

In a systematic study led by Gursharan Kaur Nandhra, a team of researchers assessed gut transit time using ingestible capsules that can be tracked throughout the journey. The result of their study suggests a more precise calculation that slightly differs from the transit time previously accepted.

The research reveals that food can take from 0.4 to 15.3 hours to leave the stomach and from 3.3 to 7 hours to pass through the entire small intestine. Meanwhile, the indigestible part of food spends 15.9 to 28.9 hours inside the large intestine.

Factors Affecting Food Digestion

According to gastroenterologist Christine Lee, several factors can affect the time it takes to digest food. Different types of food are broken down and absorbed by the body at different rates. This means that some parts of the meal may enter the large intestine while the others are still in the stomach.

Foods rich in complex carbohydrates, fats, protein, and dietary fiber tend to be digested longer than foods low in these nutrients. Meanwhile, heavily processed foods tend to be digested more quickly since they lack these nutrients.

Lifestyle factors can also affect gut transit time. Chewing thoroughly and staying hydrated can speed up the digestive process by increasing the food's surface area, which will be exposed to digestive enzymes. Exercise helps increase gut motility and promotes peristalsis, or the rhythmic contraction of digestive muscles.

Digestion can also be affected by a person's age and stress level. Adults tend to produce less stomach acid and digestive enzymes as they age while their guts become less motile. Meanwhile, stress and anxiety can increase gut transit time by altering gut motility and reducing gastrointestinal blood flow.

Finally, certain medical conditions and medications can either slow down or speed up digestion. For instance, diabetes is the common cause of gastroparesis, where food lingers in the stomach for a long time. On the other hand, opiates and anticholinergic drugs suppress nerve signals responsible for involuntary muscle movements, slowing down gut transit that can lead to constipation.