When we eat food, it passes through various parts of our digestive tract (e.g. food pipe (esophagus), stomach, small intestine, large intestine etc. At each stage the food undergoes number of changes which are essential to digest it completely.
Food pipe connects mouth with the stomach and acts as a passage for food. Stomach churns the food and mixes it thoroughly with acid converting food in easily absorbable form. Secretions form liver and pancreas help digest food further. Almost 3 hours are needed for primary breakdown of food. Then the food passes to small intestine.
The wall of small intestine absorbs nutrients from digested food which are ultimately utilized for day to day energy balance and metabolism. Absorption in small intestine may take up to 6 hours after which leftover part of the food is passed on to large intestine. The walls of large intestine absorb water and process of stool formation begins. This entire phenomenon from ingestion to absorption of food is known as- ‘digestion’.
Time required for complete digestion of food varies according to age, gender, type of activity and most importantly- the type of food eaten. Youngsters, those with active lifestyle i.e. those who exercise regularly, digest food at faster rate while elderly, sedentary people need more time.
A heavy meal (a meal rich in fats, animal proteins) or high fiber meal take longer to get completely digested compared to a light meal. On an average, food digestion takes about 12 to 40 hours. Clear liquids take only 20-30 minutes to get digested. Fresh fruits and veggies take 30 to 60 minnutes, carbohydrates take 3-4 hours while meats and high fat foods may take up to 24-30 hours for the entire process.
Thus, understanding the process of digestion, rates of digestion for different foods and choosing the right food with adequate activity are the keys to good health!