This blog post scientifically examines how our body maintains pH homeostasis through blood buffering and respiration, based on common perceptions about acidic and alkaline foods.
We consume various types of food to obtain the energy needed for daily life and to maintain our health. To achieve these goals, people seek information about food and choose what they deem suitable for their needs. In this process, most have encountered information about food pH at some point. For instance, we often hear that cola is an acidic food harmful to dental health, while alkaline foods like potatoes, sweet potatoes, and carrots are beneficial. This naturally raises a question: Could consuming more acidic foods make our bodies acidic, and eating alkaline foods make them alkaline?
However, living organisms possess the characteristic of maintaining their internal environment relatively constant regardless of changing external conditions, a property known as homeostasis. In reality, consuming food with a specific pH does not directly change the body’s internal pH to that value. If the body’s pH were to change drastically in response to an environment, it would struggle to perform its normal functions properly, and in severe cases, life could be threatened. This explanatory text will examine the buffering action of blood—one of the crucial mechanisms our bodies employ to maintain stable internal pH and prevent damage to organ function—and the diseases that arise when this buffering action is impaired.
Before understanding buffering action, it is necessary to grasp the concepts of pH, acids, and bases. The criterion distinguishing acids and bases is the concentration of hydrogen ions present in a solution. The scale indicating this degree of hydrogen ion concentration is pH. pH is defined as the negative logarithm of the hydrogen ion concentration in a solution formed when a substance dissolves in a solvent. According to the modern definition, it is expressed as the negative common logarithm of the hydrogen ion concentration.
That is, a higher pH value indicates a lower concentration of hydrogen ions in the solution, while a lower pH value indicates a higher concentration of hydrogen ions. With neutral water defined as pH 7, a pH below 7 is acidic, and a pH above 7 is basic. Acidity and basicity can also be classified by degree. Based on the order of hydrogen ion production when dissolved in a solvent, substances are categorized as strong acids, weak acids, neutral, weak bases, or strong bases. For example, substances like hydrochloric acid or sulfuric acid produce a very large amount of hydrogen ions when dissolved in a solvent, resulting in a very low pH. Consequently, they are classified as strongly acidic substances. Conversely, substances like sodium hydroxide produce a very low concentration of hydrogen ions when dissolved in a solvent, resulting in a high pH and thus are understood to be strongly basic substances.
Buffering action refers to the effect of minimizing changes in hydrogen ion concentration when acid or base is added to a solution. The reason this buffering action is possible in blood is because the weak acid carbonic acid present in blood and the base bicarbonate ion, formed when this weak acid releases hydrogen ions, exist in equilibrium with each other. If acid is added to the blood, the increased hydrogen ions combine with the bicarbonate ions, which act as a base, to reform carbonic acid. This prevents the blood from becoming excessively acidic. Conversely, when an alkali is added, the reaction proceeds in the opposite direction. Carbonic acid ionizes, producing bicarbonate ions and hydrogen ions. This prevents the blood from becoming excessively alkaline. Through this process, the blood buffers the effects of acids or alkalis introduced from outside. As a result, even when we consume acidic or alkaline foods, the blood’s pH remains relatively constant.
However, problems with blood pH regulation can occur if the blood’s buffering action is impaired or due to the entry or exit of other substances. Carbonic acid and bicarbonate ions, which play a crucial role in blood buffering, are formed when carbon dioxide produced within the body dissolves into body fluids. Carbon dioxide is a gas generated during tissue metabolism or inhaled from the outside or exhaled through respiration. If respiration weakens or gas exchange becomes inefficient, the concentration of carbon dioxide in the body increases. Higher carbon dioxide levels lead to increased carbonic acid formation in the blood. As carbonic acid ionizes, the amount of hydrogen ions increases, lowering the body’s pH. This condition is called acidosis.
Conversely, if breathing becomes excessively rapid or the concentration of carbon dioxide becomes excessively low, the production of carbonic acid decreases. Consequently, the production of hydrogen ions also decreases, causing the body’s pH to rise. In such situations, alkalosis can occur.
Synthesizing these principles, we see that the blood’s buffering action is one of the key mechanisms supporting homeostasis by maintaining the equilibrium between acids and bases. Particularly, by regulating pH to stably maintain the functions of cells and organs, and thereby helping the human body sustain normal physiological processes, the blood’s buffering action holds significant importance in safeguarding our health.
