There’s an old stereotype: washing down food actually “extinguishes the fire of digestion”. Dmitry Pikul dives deeper into the topic with the help of science.
I find it somewhat tiresome when I see people adopting clumsy stereotypes put in their heads by the mass media, wonder-nutritionists, fanatics, charlatans and other kinds of “brainwashers.”
Here I’m talking about the well-known and seemingly unshakable dogma of Sheldon-Ayurveda that washing down your food right in the middle of a meal or shortly after it “extinguishes the fire of digestion”, as it supposedly dissolves gastric acid and enzymes and prevents normal digestive function.
Based on our current scientific knowledge of human physiology this dogma seems rather inconsistent. Some chemical reactions do occur using digestive enzymes, but these enzymes actually require water to work! Water is contained in saliva and gastric juices. These mixtures break down food during digestion using enzymes, as well as step-by-step processes to make them effective for digestion and absorption into the walls of the bowel.
To put it shortly: drink water anytime you find suitable — during, with, shortly after or before taking food. However, be fairly moderate and don’t drink more than one liter of water, as it’ll have no time to leave your stomach. However, it won’t significantly affect acidity or digestion.
PHYSIOLOGY AND DIGESTION: THE STOMACH
(1) the bottom of the stomach, (2) the great curvature, (3) the body, (4) the lower pole of the stomach, (5) the pyloric part, (6) the pyloric opening, (7) the angular notch, (8) the small curvature, (9) the mucosal folds.
Anatomically, the stomach includes several sections: the cardiac part, the bottom of the stomach, the body of the stomach with the pacemaker zone, the antrum, pylorus, and the point where the duodenum begins.
Functionally, the stomach is divided into the proximal part (for tonic contraction, with the function of food storage) and the distal section (with the function of mixing and processing).
A tone is kept in the proximal part of the stomach, depending on the filling of the stomach. The main purpose of the proximal part of the stomach is to store food that has entered it.
After consumption of food in the stomach, liquids and gastric juice flow over the edges of relatively hard components with layers and into the distal section. Food is gradually transferred to the pylorus. The liquid is quickly evacuated into the duodenum with an exponential decrease of its quantity in the stomach.
Hard components of the food don’t travel through the pylorus until they have been crushed into particles of no more than 2-3 mm in diameter. 90 percent of the particles leaving the stomach have a diameter of no more than 0.25 mm. The pylorus contracts when peristaltic waves reach the distal part of the antrum.
The pylorus is the narrowest part of the stomach at the point where it is connected to the duodenum. It is closed even before the antrum fences itself from the body of the stomach. Under pressure, food slides back up into the stomach, and hard particles grind against one another, causing them to be crushed up even further.
Emptying of the stomach is controlled by the vegetative nervous system, intramural nerve branches, and hormones. In the case of a lack of impulses from the vagus nerve (if it was severed for instance), the peristalsis of the stomach is significantly weakened and the process of emptying the stomach slows down.
The peristalsis of the stomach grows larger under the influence of hormones such as cholecystokinin and gastrin in particular, and it is inhibited by secretin, glucagon, vasoactive intestinal peptide, and somatostatin.
Thanks to the free passing of the liquid through the pylorus, the speed of its evacuation mostly depends on the different levels of pressure in the stomach and the duodenum. In addition, pressure in the proximal section of the stomach is the main regulator. Evacuation of hard particles from the stomach mostly depends on the resistance of pylorus and, thus, on the size of the particles. Receptors in the small intestine play a role in regulating gastric emptying, together with factors such as its filling, the size of the particles and the viscosity of its content.
The acidic filling is evacuated from the stomach slower than the neutral, hyperosmolar content, which is evacuated slower than the hypoosmolar, and lipids (especially those containing fatty acids with chains of more than 14 carbon atoms), but slower than the cleavage products of proteins (except tryptophan). Both hormonal and nervous mechanisms are involved in regulating evacuation, and secretin plays a particularly important role in its inhibition.
SHOULD YOU DRINK WATER DURING YOUR MEAL OR RIGHT BEFORE/AFTER IT?
There is one important feature of the entire mucous membrane of the gastrointestinal tract: its ability to partially absorb water and transport it to your blood.
The following text is taken from the textbook “HUMAN PHYSIOLOGY” Volume 3, edited by R. Schmidt and G. Tevs:
Water consumed on an empty stomach is not stored in the proximal part of the stomach, but immediately travels into the distal part of the stomach, from where it is quickly evacuated into the duodenum.
Water consumed with food acts in the same way, but the food stays in the proximal part of the stomach.
It’s interesting that even water-based nutritious solutions (those containing glucose) behave a little differently when taken with food: they also remain in the proximal part of the stomach.
There are a number of scientific tests that study the speed of movement of various types of liquids from the stomach through the gastrointestinal tract. According to these, water leaves the stomach somewhere between 5 and 15 minutes after ingestion.
Using MRI, scientists found that there are so-called “pockets” for storing water in the stomach and small intestine. There can be up to 20 of them in the small intestine (in a state of hunger their number is 8 and this is increased with the amount of taken water, each of which can store from 1 to 160 mg of water). The stomach itself has a wall with folds which line the wall of the intestine from the stomach entry point to the pylorus of the duodenum.
In other words, water that you drink during a meal doesn’t fall down like a waterfall into the stomach, flushing everything down into the duodenum along its way — including gastric juice, mucous, and enzymes — as people often believe, but it actually goes into the duodenum and gradually further in portions. Thus, 240 mg of water taken on an empty stomach can travel to the largest gastric fold (the distal stomach) in just two minutes.
DOES WATER REALLY “EXTINGUISH THE FIRE OF DIGESTION”?
Let’s look at the pH level of the stomach and the allegedly catastrophic effect of consuming water with food.
No water that is taken with food (neither just before nor right after a meal) has a considerable effect on the acidity level of the stomach (pH) or the work of enzymes in the gastric juice. The stomach is a pretty complicated mechanism that can regulate the amount of gastric juice on its own in a healthy human being. Taking a considerable amount of water is likely to have a positive effect on its action.
The pH level in the gastrointestinal tract is a work of many variables: conditions of food intake and time, volume and content of food, volume of excretions, and pH value changes across the entire gastrointestinal tract as well.
Hungry people have a pH level of 1.0, while the average is about 2. After eating, the stomach’s pH level increases to 6-7.0, which gradually decreases hunger over approximately four hours, based on factors such as contents of food, volume, and individual pH level. The pH level of a full stomach varies from 2.7 to 6.4.
DRINKING WATER ON AN EMPTY STOMACH
Drinking water on empty stomach can slightly influence its pH level. In one study, scientists modeled the state of a hungry stomach. 20 minutes after introduction of 250 mg of water, the pH level decreased from 2.4 to 1.7 in 60 minutes.
Nevertheless, we do know that water isn’t stored for very long in the stomach of a healthy person and such a volume of liquid will be excreted into the duodenum in no more than 30 minutes, accounting for various other factors.
There are many scientific studies in which researchers measured the pH level in patients who ingested water on an empty stomach, or shortly before, or shortly after. The data from all this research shows that the pH level of the stomach isn’t significantly affected by water consumption.
For example, one study determined that an intake of 300 mg of water by patients with obesity on an empty stomach, or together with food, two hours before measurement does not affect the volume of liquid in the stomach or its pH level.
WATER TAKEN WITH FOOD
Due to the effects of several processes in the body, food intake itself influences the pH level: it increases and decreases over time at the anticipation of food intake, visualization, smell, and worked-out reflexes.
Therefore, after ingesting general food with 1000 calories, the pH level increased to approximately 5.0. After one hour, the pH level had dropped to 3.0. After a further 2 hours, it was lower than 2.0.
Water has a clear impact on digestion. Drink water when you need to — before, during and after food intake — as you wish. The only important thing is to keep it to a reasonable amount of water. Don’t drink more than one liter of water as it won’t have time to be excreted from your stomach.
However, it doesn’t affect the acidity of the stomach or harm the process of digestion. If you feel thirsty, drink. Thirst is the best indicator that your body needs more water. If it feels good to wash down your food with water, please keep doing so.
Water — just like every other beverage consisting mainly of water — has several functions during a meal:
- it improves the transportation of food parts through the esophagus into the stomach;
- it helps to flush down large pieces of food;
- it helps stomach acid and enzymes to access specific pieces of food.