I suffered from acid reflux (commonly known as “acidity”) for a long time in my childhood. My father (being a doctor) advised me to consume “curd” or “cold milk” but not “water”, and this cure worked. But, I had two questions in my mind (which many teachers and doctors failed to answer), which I will try to answer in this blog post:
Q1: We know that curd and milk are acidic in nature, since both have pH value approximately 5 and 6 respectively. But still Doctors advise us to consume curd or milk in acidity. How can this help our stomach buffer to tackle acidity?
Since milk is a weak acid, it can act like a buffer solution (not exactly a buffer). Hydrogen ions (H+) make a solution acidic; the more H+, the more acidic a solution is. As a result, when we mix milk and stomach acid, the resulting solution will be less acidic than stomach acid. And also due to the presence of calcium salts in milk, it acts much like antacids. Calcium carbonate, a popular antacid, acts as a buffer as well, absorbing H+ ions to resist changes in pH. Also cold milk is suggested as it is feebly dissociated as an acid.
In case of curd, we have probiotics, useful bacteria that help digestion. Due to conversion of lactose to lactic acid, while formation of curd from milk, the pH level decreases. But the bacteria count also increases, thus mitigating the effect of fall in pH and helping in maintaining stomach pH.
Q2: Our stomach contains HCl of pH 2 (approximately). Then why doesn’t we feel the burning sensation if we drink water to “kill” hunger when we are very hungry?(since addition of water in acid is highly exothermic).
The credit for this goes to the special structure of our stomach. The average adult stomach holds about three liters of fluid. Our stomach is made up of a variety of layers, like: the serosa (the outer layer that acts as a covering for the other layers); two muscle layers (the middle layers that propel food from the stomach into the small intestine); the mucosa (the inner layer made up of specialized cells, including parietal cells, g-cells and epithelial cells).
Parietal cells produce HCl (hydrochloric acid), a strong acid that helps to break down food. The g-cells produce gastrin, a hormone that facilitates the production of HCl by the parietal cells. The stomach is protected by the epithelial cells, which produce and secrete a bicarbonate-rich solution that coats the mucosa. Bicarbonate is alkaline, a base, and neutralizes the acid secreted by the parietal cells, producing water in the process. [This continuous supply of bicarbonate is the main way that our stomach protects itself from autodigestion (the stomach digesting itself) and the overall acidic environment.] In general, this mechanism is stable enough to protect stomach from highly exothermic reaction involved in addition of water to acid.
Hence, we should not drink water in case of acidity, since our stomach’s acid-defense mechanism is already in poor state.