We all need to drink at least about two litres of water every day. Not juice, not sodas, not coffee, not tea: plain water. None of these other liquids have the properties of water, nor do they have the desirable effects of water on the body. Most of us don’t however, and so we are chronically dehydrated. Whether it is 75% or as high as 90%, it is evident that a very large portion of the population is chronically dehydrated.

The digestive system can be viewed as the most fundamental because everything used to sustain life in the body goes through it. In a very real sense, we are a digestive system, supplemented by a central nervous system and refined sense organs to allow us to devise ways to get food (and avoid being eaten), coupled to a refined locomotor system to allow us to gather the food (and run away when it is needed). Since every component of every cell in the body is made from the nutrients in our food, it is obvious that everything in the body depends on the digestive system. And for the digestive system, the single-most important element is the presence of ample amounts of water.

As soon as we even think about eating, the digestive system starts to get ready. The pancreas secretes a little jolt of insulin just in case carbohydrates come in, and the stomach starts to produce the highly acidic digestive gastric juice (pH of 1-2). This gastric juice is composed of only a little bit (0.5%) of hydrochloric acid (HCl) and a lot of salt, both sodium chloride (NaCl) and potassium chloride (KCl). The stomach has sensor cells to know exactly how much protein, fat and carbohydrates are present at any given time, and thus can adjust the production and composition of the gastric juice.

Although present in very small amounts, the hydrochloric acid is the essential compound for activating the enzymes responsible for breaking down protein, which is its main purpose because both fats and carbohydrates are mostly broken down in the intestine. But to make it to the stomach without causing any damage along the way, the two constituents of this highly corrosive acid, the hydrogen (H) and the chlorine ions (Cl), are produced separately and transported to the inside of the stomach where they combine to form the acid.

The delicate lining of the stomach with all its different kinds of highly specialised cells, is protected from the acidic gastric juice by an alkaline layer of mucus. This mucus is between 90 and 98% water, with some binding molecules and a few other components. It can be regarded as a blanket of water whose primary role in the stomach is to protect its lining from the gastric acid. The very thin mucosa that produces and maintains the mucus layer, also secretes sodium bicarbonate that sits in it, and neutralises the acid upon contact when it penetrates the layer, leaving only sodium chloride (salt), water and carbon dioxide. The neutralisation reaction is simple: HCl + NaHCO3 -> NaCl + H2O + CO2.

As we get progressively more dehydrated, not only are the stomach cells incapable of releasing adequate amounts of water into the stomach in order to allow for the proper mixing of the food and acid into chyme with the optimal consistency, but the thickness of the protective mucus layer decreases, thus allowing the acidic contents to damage the fragile lining. This is what eventually leads to stomach ulcers, according to a well known specialist in the matter, Dr Batmanghelidj, author of Your Body’s Many Cries for Water.

The contents of the stomach are churned and blended between one and three hours depending on the amount and composition, until the chyme is liquified and smooth, at which point it is poured into the duodenum, the first part of the small intestine. It is in the small intestine that the real work of the break down and absorption of nutrients into the bloodstream takes place over a period of about 24 hours. The sensor cells in the duodenum will immediately determine the pH and composition of the chyme in order to send the messenger hormones to the pancreas to secrete the right amount of the alkaline, watery sodium bicarbonate solution necessary to neutralize the acid, and to the liver to secrete the right amount of bile needed for the breakdown of fats.

And even though the pancreas is known primarily for its role in producing and secreting insulin needed to clear the bloodstream of sugar, it is arguably its role in secreting this alkaline solution that is the most important. Indeed, as the duodenum does not have a protective layer of mucus as the stomach, it is this sodium bicarbonate solution that protects it and the rest of the small intestine from the devastating effects that the highly acidic chyme can have on it.

However, just as even partial dehydration causes the protective mucus layer in the stomach to dry out and shrink, making it permeable to the gastric acid that eats away at the delicate soft tissues, dehydration also causes the pancreas to be unable to secrete as much of the watery sodium bicarbonate solution as is required to fully neutralise the acidic chyme that, therefore, also damages the intestine. In fact, that there are several times more cases of duodenal as there are stomach ulcers attests to the reality that the lining of the intestine is all that much more fragile as it is unprotected and thus directly exposed to the excessively acidic chyme.

Therefore, water is of the utmost importance in protecting the lining of the stomach and intestine from the acid required for the break down of proteins into amino acids. Water is of the utmost importance for proper digestion and absorption of the nutrients in the food. And hence, water is of the utmost importance in maintaining a healthy digestive system meal after meal, day after day, and year after year throughout our life.

We must make sure that the body and digestive system are properly hydrated before eating. And for this, all we need to do is drink half a litre of plain water 30 minutes before meals, and not drink during nor after the meal for two to four hours.

Drinking during or soon after a meal will only dilute the chyme, making it excessively watery. This will not lower the pH, because water does not neutralise acid. It is best to ensure proper hydration prior to the start of the digestive process, providing the water necessary for the mucosa and pancreas to function optimally, and allow the stomach to adjust the water content of the chyme on its own. I personally usually wait two hours after a snack or small meal, and at least three to four hours after a large meal.

The time needed for the chyme to leave the stomach through the pyloric sphincter and enter the duodenum depends on its amount and composition. For example, fruit or any other food consisting mostly of simple sugars eaten on an empty stomach will make it into the intestine, and the sugar into the blood, in a matter of minutes: Since there is no protein, no acid is required for its breakdown in the stomach; and since there is no fat, no bile is required to break it down in the intestine.

Naturally, the time needed for the stomach to process a small meal will be less than that needed to process a large meal of more or less equal composition. In fact, given that our stomach is a very small pouch with an empty volume of about 50 ml, and a full volume of about 1 litre (up to a max of 2-3 litres when it is really extended),  the time needed for large meals increases substantially and disproportionately compared to smaller meals.