These are not random metaphors. Stomach aches, bowel disruptions, nausea, and even vomiting are often expressions of a mental state, and the stomach sometimes tells us things that the brain has not yet managed to process.
Our stomach is not just a physical area, but the "beating heart" of the digestive system – there take place the main processes that drive our body. Although the digestive system extends from the mouth to the end of the track in the intestines, the area we call "the stomach" is the center of gravity where the most complex processing procedures drain, and where the richest neural dialogue with our brain exists.
To understand how all this happens, we will go on a journey step by step: let us take one sandwich – whole grain bread, a hard-boiled egg, tahini, and cucumber – and see what happens to it, from the moment you smell it until the body settles the account with it. On the way, we will stop at several stations that can improve your daily digestion.
The role of the digestive system is to break down the food we eat and allow its absorption into the body so that it serves as a source of energy and components for building. In order for the body to be able to use the food, it must break it down into smaller particles that are suitable for absorption. The process includes several stages that take place simultaneously: receiving the food, breaking it down, absorbing essential components, and finally evacuating what is not required.
How does the body know we are about to eat?
It is enough to see the sandwich, smell it, or even think about it, for the digestive system to spring into action. The salivary glands begin to secrete saliva, and the stomach produces acids. This happens even without real food in front of us: watching a movie where a lemon is squeezed to season a salad can cause the salivary glands to operate. The body responds to stimuli, to smell, and to appearance, even before the food enters the mouth.
The moment you take a bite of the sandwich, the initial breakdown process begins. This is a stage where both mechanical breakdown and chemical breakdown occur. The teeth grind the food into smaller pieces, and the tongue mixes it with the saliva. Thus a soft paste is created that is more convenient for further digestion. The mechanical breakdown is particularly important, because it increases the surface area of the food, and thus allows enzymes to act on it with greater efficiency.
At the same time, the saliva secreted into the oral cavity contains enzymes that begin to break down certain components in the food already at this stage. This is an initial chemical breakdown, which eases the continuation of the process along the digestive system. Already at this moment begins an initial breakdown of the carbohydrates from the bread, while the protein from the egg and the fat from the tahini will continue to break down mainly in the next stages of the journey.
Tip: As the chewing is more thorough and slower, so the breakdown is more efficient, and the food components are more available for the next stages. From the mouth, the food passes to the esophagus – a tube whose length is about 25 cm. The muscles of the esophagus create a wave-like movement that propels the food toward the stomach, and it occurs in one direction only, regardless of our position. When the food reaches the end of the esophagus, a valve opens and allows it to enter the stomach.
Usually the movement remains in this direction. If the direction is reversed, acids from the stomach rise upward, and one feels a familiar burning sensation – heartburn. This is a relatively common phenomenon, and sometimes it is related to eating habits, types of food, medications, excess weight, pregnancy, or other medical conditions.
Tip: To reduce the chance of heartburn, it is recommended to minimize high-fat foods; reduce spicy and hot food; cut down on caffeine, carbonated drinks, and alcohol; eat smaller amounts, and avoid lying down or bending over after a meal.
What happens when we feel full?
The sandwich has now arrived at the stomach. The stomach is a particularly muscular and flexible organ, which can expand from a volume of about 50 ml in its empty state up to a liter and more after a full meal, which allows it to contain the amount of food we consume.
It has an opening from the esophagus and an opening to the small intestine, and its muscles mix the food inside the stomach juices, which contain acids and enzymes that continue its breakdown until it becomes a thick paste. The particularly acidic environment assists in efficient breakdown of proteins, and also acts as a protective barrier against bacteria that arrive with the food. At this stage the food is not yet broken down into components small enough to be absorbed into the bloodstream, but it is an essential preparation stage where it becomes more suitable and available for the continuation of the breakdown in the small intestine. In the stomach occurs a significant breakdown of the proteins, while the fat components are digested more slowly and remain in it for a longer duration.
Here arises a question that I am often asked: Does drinking water during the meal or after it interfere with digestion? Usually, drinking water during the meal does not harm digestion. The liquids even assist in softening the stool and preventing constipation. When the stomach fills up, neural messages are sent to the brain updating it with a feeling of fullness.
And at the same time, one can sometimes hear noises from the stomach. These rumblings do not appear only when we are hungry. They can also be heard during digestion or following stimuli like the smell of food, and it is a normal movement of the digestive system. The hunger and appetite are controlled by a complex system of neural signals and substances produced in the digestive system and operating similarly to hormones. These substances, such as ghrelin, which increases the feeling of hunger, and leptin, which is related to the feeling of fullness, transfer messages between different organs and regulate the appetite. When one does not eat for some time, they are released and activate an area in the brain that arouses the need to eat.
Tip: Meals rich in fat, such as fried food, high-fat pastries, or meals based on fatty cheeses or fatty meat, may create a feeling of heaviness and stay longer in the stomach. Combining them with vegetables, fresh or cooked, can ease the feeling. The sandwich has passed a significant stage in the journey, but the main part of the breakdown and absorption is still ahead of us. Next week we will move with it to the small intestine, and it will begin to become clear what will happen to each of the components: the carbohydrates from the bread, the protein from the egg, and the fat from the tahini – who will be absorbed in the body and who will move onward.