First, a quick reminder on digestion, which is the transformation of food into nutrients. To achieve this, the food bolus must pass through several stages, from the mouth to the colon.
Starting with chewing: the teeth grind the food, and the amylase in the saliva begins chemical digestion. Then the passage through the esophagus takes a few seconds.
It’s then the arrival in the stomach, where the presence of hydrochloric acid and enzymes begins the breakdown of proteins and fats.
We continue with the passage into the first part of the small intestine: the duodenum. The presence of pancreatic and intestinal juices breaks down the nutrients, and bile promotes the absorption of fats. We then move along the entire length of the small intestine, where the rest of the nutrients are absorbed by the intestinal wall.
Intestinal contractions facilitate the movement of the food bolus into the colon (large intestine), which contains only non-assimilable nutrients, fibers, and residues, brought to the anus for evacuation.
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On average, how long does it take to digest?
Office spaces are often quiet in the hours following a meal. And the digestive process is often blamed, as if it lasted 3 hours.
Does that sound familiar? Yet, this cycle takes much longer! It is estimated that it takes about 24 hours on average to fully digest a meal.
This time can also be extended for heavier meals, reaching 72 hours in some cases.
While the passage through the esophagus lasts only a few seconds, the rest of the journey is slower:
- about 4 hours in the stomach
- 6 hours on average in the small intestine
- 7-8 hours for the colon
- about 6 hours in the rectum
Between a 24-hour digestion and a 72-hour one, there’s a big difference. This discrepancy is explained by several factors that can influence the progress of the food bolus.
What factors influence digestion time?
The nature of the foods
No, your green salad and steak are not going to be assimilated and digested at the same time. It’s because not all foods have the same digestion speed that it is advised against eating certain rich meals in the evening.
It’s in the stomach that foods differ the most on their digestion time.
Fruit and vegetable juices, and liquid foods in general, are very easy to digest, which also explains why they don’t provide a lasting feeling of fullness.
Why? They don’t undergo the entire digestion process: no chewing, the nutrients are already broken down, which makes the job easier. Therefore, it takes no more than 20 minutes for digestion in the stomach!
For whole fruits and vegetables, the time is a bit longer, averaging 1 hour. Unless they are fried and covered in sauce, they contain a lot of water, but few proteins and fats.
For whole grains and legumes, their nutrient richness coupled with the presence of fibers allows for gastric digestion of about 1 hour and 30 minutes.
White cereals, on the other hand, are more quickly digested, taking around 1 hour.
Nuts like almonds, walnuts, hazelnuts, etc., have a gastric digestion of a few hours – 3 hours on average – due to their richness in fatty acids.
As for fish and meats, it all depends on their composition! Lean meats and white fish are digested in less than 2 hours.
While fattier meats and fish are the last to reach the finish line from the stomach to the duodenum, the pylorus. Their gastric digestion time can exceed 4 hours.
Another enemy of fast digestion? Alcohol. Its presence requires a significant effort from the digestive system, especially since alcohol is strong.
In summary, fibers promote muscle contractions, known as peristalsis, and a rapid digestion, while cooked fats slow down the process. The key is to find the right balance between the two!
The richness of the meal
If you eat sparingly and in small amounts, your intestinal system has little work to do.
Conversely, if you’ve just finished a big family meal or a well-stocked TV dinner, chances are that your digestion will be long: the grinding requires more effort, and the digestive enzymes have many nutrients to break down.
Physical activity
A good intestinal motility is an essential factor for good digestion and helps accelerate it.
Physical activity helps to stimulate blood circulation and intestinal muscle contractions. The result? The food bolus moves more quickly, preventing stool hardening.
People who exercise regularly generally have fewer digestive issues than sedentary people.
Hydration
Proper hydration facilitates intestinal transit and prevents constipation problems. So don’t forget to drink at least 1.5 liters of water per day to ensure good digestion!
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