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How Long does it Take to Digest Food?

Updated on February 17, 2014

How long does it take to digest food? Food is one of the basic needs of humans to survive. It is the body's main source of nutrition. When we take in food, it has to be converted to something that the body can actually use. Food has to be digested first before it can be beneficial to the body. Digestion starts in the mouth when we chew the food. The food materials will then have to traverse the whole digestive tract to undergo the physical and chemical changes required for its conversion to substances that can be used by the body for energy and tissue growth and repair.

How much time is actually needed to turn the food that enters the mouth to smaller molecules that the body can make use of? The answer varies depending on each individual and the kind of food material ingested. The length of time needed for digestion also differs between males, females and children. The condition of the individual can likewise have an influence on how long the food travels through the digestive tract. Illnesses, psychological stresses, and even reproductive status can affect the time it takes to complete digestion.

What is Digestion?

Digestion is the process by which food is converted to materials that can be used by the body. It involves both mechanical as well as chemical digestions. Digestion happens in the digestive tract and involves various organs of the digestive system. The food spends time in each of these organs depending on the kind of digestion that the food is subjected to.

How long does it take to digest food?

The time needed for complete digestion has been the subject of many investigations and research. And though there is no exact duration for digestion, studies have come up with average figures. On the average, food digestion takes between 24 and 72 hours to complete from mastication to defecation. Meanwhile, the mean time for food digestion in children is 33 hours. The length of time that the food stays in each part of the digestive system also varies.

The Digestive Process

Food is digested by the body’s digestive system which involves the following:

  • Mouth

Digestion starts in the mouth when we chew our food. The food undergoes mechanical digestion as the teeth grind and tear it into smaller pieces. The enzyme, amylase, found in the saliva, begins to break down the simple sugars and starches contained in the food. When the food particles are small enough, they are pushed by the tongue towards the back of the mouth to be swallowed.

  • Esophagus

The bolus, or ball of masticated food from the mouth, travels through the esophagus to the stomach with the aid of peristalsis. Peristalsis is the muscle action that helps push the food through the digestive tract. Liquids take a second to pass through the esophagus, while solids may take 5 seconds.

  • Stomach

When the food reaches the stomach, the gastric juices act on the food to further digest the starches. Furthermore, the breakdown of proteins also begins in the stomach. Thru the churning action, the food becomes partially digested and turned into chyme. This is slowly transferred into the small intestine for further digestion. How long does it take to digest food in the stomach? Generally, the food stays in the stomach for about 2.5 hours. This highly varies depending on the quantity of food taken in, the stomach size as well as the materials already present in the intestines.

  • Small Intestine

The bulk of digestion actually takes place in the small intestine which is about 21 feet long. The partially digested food enters the duodenum. When this happens, the gall bladder and pancreas release substances that facilitate in the chemical digestion of the food in the intestine. When food is transformed into smaller molecules or chemical elements that are useful to the body, these are absorbed by the villi which line the wall of the small intestine and released to the blood stream. It takes between three to six hours to completely digest the food in the small intestine.

  • Large Intestine

The colon or large intestine is the next stop for what remains of the digested food from the small intestine. Minerals and water are removed resulting in a more solid waste consisting mainly of bacteria and food waste. The bacteria present are generally of the good kind as they help in the processing of waste products, in the synthesis of minerals and vitamins, as well as in fighting bad bacteria. It needs around 36 hours to prepare the waste for elimination. When it is ready, it is transferred to the rectum for evacuation.

  • Rectum and Anus

The colon is connected to the anus by the rectum. The food waste is received by the rectum from the colon where it awaits elimination. A message is sent to the brain which then sends signals to relax the sphincter muscles and contract the rectum to evacuate the waste to the anus. The anus is made up of two anal sphincters and pelvic floor muscles. These muscles help us have better control on the release of fecal matter.

Digestion of Different Food Materials

How long does it take to digest food materials? As mentioned above, the time needed by food to pass through the digestive tract is variable depending on the type of food ingested. Carbohydrates are digested much more easily than fats and meats. So if the meal is high in fat and processed foods, digestion would be slower because these materials are harder to break down and need more time for absorption. The fiber content also affects the rate at which food is processed in the digestive system. Fiber improves the passage of digested food and effective evacuation of waste. In addition, toxins in food attach to certain fibers which can then be eliminated from the body thereby reducing absorption of harmful substances.

So, how long does it take to digest food? Between 24 to 72 hours is the average. Since digestion is influenced by a number of factors, it can be improved by eating the right kinds of foods, taking the appropriate supplements, chewing the food properly before swallowing, taking adequate amounts of fluids, and managing stress effectively.

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      Robert Morgan 22 months ago from Hutchinson Island, FL - Myrtle Beach, SC - Scottsdale AZ

      Thank you for this short and informative article. With the breakdown of proteins in the stomach the food becomes partially digested and turned into chyme. Thanks again.

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