Ayurveda views digestion through rasa (taste), virya (potent energy, either heating or cooling), and vipaka (post-digestive effect). There are 6 stages of digestion, each taking about an hour. Each stage is associated with a taste, each taste can be represented through the elements, there is either a heating or cooling quality, the sub- doshas are present and ultimately the food moves from mouth to colon nourishing the body and all of the dhatus (tissues). The process is described below.
Stage 1/ First Hour: Food enters the mouth and immediately the tongue begins to taste. See the callout below for the 6 classifications of taste. Digestion is said to begin in the mouth. Earth and water are present and provoke kapha secretions. Bodhaka kapha is at work here as saliva is increased allowing the food to be chewed and swallowed. Prana vayu and sadhaka pitta are also present at this stage of digestion. Prana assists with the downward travel of the food until it reaches the stomach. Samana vayu initiates the churning process. Bodhaka and kledaka kapha are present in the stomach as they work to liquify the food.
This first stage of digestion is known as the sweet stage because the sweet taste is predominant. The sweet taste in sanskrit is mandhura. Kapha is increased during the first and second stage of digestion.
Sweet/ Mandhura = Earth + Water (Cooling) -> Sweet
Sour/ Alma = Earth + Fire (Heating) -> Sour
Salty/ Lavana = Water + Fire (Heating) -> Sweet
Pungent/ Katu = Air + Fire (Heating) -> Pungent
Bitter/ Tikta = Air + Ether (Cooling) -> Pungent
Astringent/ Kasaya = Air + Earth (Cooling) ->Pungent
Stage 2/ Second Hour: Food travels into the lower part of the stomach. The food continues to get broken down into smaller pieces. Earth and fire are present. Here the stomach becomes lighter because of the fire element. The heaviness of the food is still present which is why the earth element is represented. Kledaka kapha protects the stomach from acid as hydrochloric acid is released. Protein and fat begins to digest.
The second stage of digestion is known as the sour stage because the sour taste is predominant. The sour taste in sanskrit is alma. Kapha is increased and all bodily kapha is nourished during these first stages of digestion.
Stage 3/ Third Hour: Food begins to travel out of the stomach into the duodenum, the first part of the small intestine. Samana vayu, pachaka pitta and ranjaka pitta from the liver are responsible for this stage of digestion. Bile from the gallbladder (ranjaka pitta) and pancreatic enzymes mix with the food thus creating the salty taste. Protein, fat and carbohydrates are digested.
The third stage of digestion is known as the salty stage because the salty taste is predominant. The salty taste in sanskrit is lavana. Pitta is increased during the third and fourth stage of digestion.
Stage 4/ Fourth Hour: This stage begins when the food travels into the jejunum, the second part of the small intestine. Air and fire are predominant in this stage. Fire creates increased heat. Air makes the bones porous which allows for absorption into the asthi dhatu (bone tissue). Digestion of protein, fat and carbs continue.
The fourth stage of digestion is known as the pungent stage because the pungent taste is predominant. The pungent taste in sanskrit is katu. Pitta is increased and all bodily pitta is nourished during these middle stages of digestion.
Stage 5/ Fifth Hour: The food continues to travel into the ileum, the last and longest part of the small intestine. Ether and air are present during this stage of digestion. The air element stimulates samana vayu, which maintains peristalsis, ie the continued movement of food through the digestive tract. Absorption is rapid and the stomach can begin to feel lighter.
The fifth stage of digestion is known as the bitter stage because the bitter taste is predominant. The bitter taste in sanskrit is tikta. Vata is increased during the fifth and sixth stage of digestion.
Stage 6/ Sixth Hour: Apana vayu and samana vayu push the food through the cecum, a pouch that forms the first portion of the large intestine. This begins the final stage of digestion. Air and earth are present. Air allows for the final absorption of any remaining nutrients through minerals and liquids. Earth allows for waste to be created through the formation of feces.
The sixth stage of digestion is known as the astringent stage as the astringent taste is predominant. The astringent taste in sanskrit is kasaya. Vata is increased during this stage and all bodily vata is nourished during these final two stages of digestion.
"The timing of the various tastes is not fixed. It varies person to person, from constitution to constitution. To simplify, the first hour of digestion is sweet, the second is sour, then salty, pungent, bitter, astringent. So, within 6 hours all six tastes enter ahara rasa. In this way, the six stages nourish the asthayi dhatus within 6 to 12 hours after eating. However, the nutrition inside the cells in the sthayi dhatus takes much longer - 5 days per dhatu. Thus sthayi rasa dhatu is nourished 5 days after eating a food and 35 days pass before sthayi shukra/artava receives full nourishment." - Dr. Vasant Lad.
To put it in layman's terms. On average digestion takes about 6 hours to complete. There is variation from person to person and the individuals unique constitution. (To understand more about Ayurvedic terms check out the following post here) The 6 tastes are present when food enters the mouth (assuming all 6 tastes are in the meal) and all 6 tastes are present during the digestive process (even if the 6 tastes are not in the meal). Within 6 to 12 hours after eating the tissues of the body have selected the nutrients from the food but have not yet assimilated this into the fully formed tissues. There are 7 recognized tissue layers in Ayurveda: plasma, red blood cells, muscle tissue, adipose tissue, bone tissue, bone marrow, and reproductive tissue. Providing nutrition to the stable and fully formed tissues takes 5 days per tissue. Thus you "carry" the food you ate today with you for 35 days!
This is why if there is a sensitivity or food allergy it takes the body 35 days for that item to be removed. This is also why there may appear to be a delayed reaction to something an individual consumes.
The process of digestion as described by Ayurveda and Western science has many more complexities. This is just scratching the surface but hopefully allows for an introductory explanation into the digestive process as outlined by Ayurveda. For more posts about Ayurvedic nutrition please refer to the Ayurveda section on my blog. Enjoy!