In this blog post, we’ll take a closer look at why drinking too much water can be harmful to your health, focusing on risks such as hyponatremia.
What happened to A?
After learning that the secret to the glowing skin of people with firm, supple complexions was “drinking enough water,” A decided to start drinking plenty of water that very day. A consistently drank 1 liter of water every day, but she didn’t notice any significant changes in her skin. Eager to achieve firm, elastic skin as soon as possible, she gradually increased her water intake. However, unexpected changes gradually began to occur in her body. Unlike before, she felt tired easily and occasionally experienced muscle cramps. At times, she even complained of nausea and severe headaches. Eventually, she collapsed, fell unconscious, and was rushed to the emergency room. There, she was diagnosed with hyponatremia.
Hyponatremia! Caused by excessive water intake
The basic structural and functional unit of the human body is the “cell.” Water exists in both the internal and external spaces of the cell, and the cell membrane serves to separate these two spaces. Water accounts for about 60% of human body weight; one-third of the water in the body exists as “extracellular fluid,” and two-thirds as “intracellular fluid.” The cell membrane is composed of a phospholipid bilayer that restricts the movement of polar molecules. In contrast, although water molecules are polar, their small size allows them to pass freely through the cell membrane. If a difference in osmotic concentration arises between the intracellular and extracellular spaces, water molecules move in the direction that eliminates this difference, thereby maintaining the same osmotic concentration in both spaces.
Consider the situation of placing cabbage in brine. In this case, the osmotic concentration of the extracellular fluid increases. This is because the external environment affects the extracellular fluid first, rather than the intracellular fluid. Osmolarity refers to the concentration of solutes—such as molecules and ions—that determine the magnitude of osmotic pressure. Sodium ions (Na⁺) and chloride ions (Cl⁻) have the greatest influence on intracellular osmolarity. To explain osmolarity simply, it can be thought of as indicating how salty a saltwater solution is. A solution with a high osmolarity is salty water, while a solution with a low osmolarity is unsalty water. The chemical formula for salt is NaCl, and when NaCl dissolves in water, it acts as the ions that determine osmotic pressure.
Let’s understand osmolarity through the following example. Suppose a container is divided into two compartments by a semipermeable membrane. This semipermeable membrane allows water to pass through but blocks the solute, salt. This is similar to the function of a cell membrane. Let’s assume that 100 g of salt is added to 1 L of water in the left compartment, and 1 g of salt is added to 1 L of water in the right compartment. We also assume that the volumes of both compartments are equal. Which compartment’s saltwater solution is saltier? Obviously, it is the left compartment. Therefore, we can say that the osmotic concentration in the left compartment is higher.
The process continues until a “state of equilibrium” is reached, where the difference in osmotic concentration disappears. If there were no semipermeable membrane, the excess salt in the left compartment would move to the right compartment, and the excess water in the right compartment would move to the left compartment, eventually reaching a state of equilibrium. However, when a semipermeable membrane is present, salt particles cannot move to the other compartment. This is because the semipermeable membrane selectively allows certain substances to pass through. Salt particles cannot pass through the membrane, but water molecules are small enough to pass freely through the semipermeable membrane. Therefore, to equalize the osmotic concentrations in both compartments, more water moves from the right compartment to the left compartment. As a result, the left compartment ends up containing more water than the right compartment.
Why did the left compartment end up with more water? This is to equalize the saltwater concentrations in both compartments. If there is 100 g of salt in the left compartment and 1 g of salt in the right compartment, you would use 2 L of water to equalize the concentrations of the two compartments. In this case, you must add more water to the left compartment to make the saltwater concentrations in both compartments equal. This is the principle by which, in the presence of a semipermeable membrane, a greater amount of water exists in the left compartment at equilibrium.
Now, let’s return to A’s story. While we’ve discussed salt so far, it is actually sodium ions that play a crucial role in regulating osmotic concentration within the body. A’s excessive water intake resulted in an excessively low osmotic concentration of the extracellular fluid. As the osmotic concentration outside the cells decreased, water flowed into the cells, causing them to swell.
Hyponatremia is the condition in which cells cannot function normally because a large amount of water flows into them due to the difference in osmotic concentration. Brain cells, in particular, are susceptible to damage when an excessive amount of water enters them. Since the brain is located inside the rigid skull, brain cells are subjected to pressure from the skull when they swell. This is similar to a pair of loose pants becoming tight after gaining weight. When brain cells are compressed, they can suffer severe damage; this is precisely why A felt dizzy and had a headache, eventually falling into a coma.
Treating Hyponatremia by Utilizing the Cause of the Disease in Reverse
Hyponatremia occurs when the osmotic concentration of extracellular fluid drops sharply, causing an excessive amount of water to flow into the cells, leading to cell swelling and loss of function. Cells must maintain a constant size and osmotic pressure to function normally; if they swell abnormally due to water imbalance, various functional problems arise. The brain is the tissue most sensitive to this condition. Unlike other cells, brain cells are confined within the skull, which lacks sufficient space for expansion; therefore, when pressure builds due to excessive water influx, brain damage accelerates. For this reason, patients with hyponatremia may experience dizziness, headaches, and even fall into a coma.
Since this condition arises from a difference in osmotic concentration, it can be treated by reversing this process. To normalize the osmotic imbalance, an isotonic solution must be used to restore the osmotic concentration of the extracellular fluid. An isotonic solution is one in which the osmotic pressure inside and outside the cells is the same, meaning it is adjusted to match the body’s natural osmotic pressure. When an isotonic solution is injected into the bloodstream, the osmolarity of the extracellular fluid gradually returns to normal, causing the excess water that had flowed into the cells to flow back out. During this process, the volume of the cells returns to normal, and the swollen cells regain their proper function.
This treatment is of great importance; in cases such as hyponatremia, rapid treatment is essential.
This is because prolonged pressure on brain cells can lead to irreversible damage. The administration of isotonic solution is a key treatment to reduce this risk. The effects of isotonic solution administration go beyond simply regulating cell size. When the osmolarity of the extracellular fluid normalizes, the body’s overall fluid balance is restored, allowing other organs and tissues to function properly. The permeability of cell membranes also normalizes, restoring normal function to the nervous and muscular systems.
In addition to isotonic solutions, hypertonic solutions may be used in certain cases to restore the osmolarity of the extracellular fluid more rapidly. Hypertonic solutions have a higher concentration than the body’s internal osmolarity, and their administration accelerates the movement of water out of the cells. However, if hypertonic solutions are used excessively, they can cause excessive loss of intracellular water and lead to dehydration; therefore, they are used only under the careful judgment of a specialist.
Another important factor in the treatment of hyponatremia is the restriction of fluid intake. If a patient, like A, has consumed an excessive amount of water, the situation worsens if they consume more water before the body has naturally excreted the excess fluid. Therefore, patients with hyponatremia are restricted from drinking water for a certain period. This is a measure to normalize the body’s fluid concentration and restore the balance between extracellular and intracellular fluids.
Ultimately, while hyponatremia is caused by excessive water intake, the method to correct it also involves regulating the movement of water. Treatment using isotonic or hypertonic solutions is based on this principle and focuses on restoring normal osmotic concentration within cells. This helps restore the water balance inside and outside cells and can quickly alleviate the patient’s symptoms.
Excessive water intake can actually be harmful
While water plays an essential role in the body’s energy metabolism, consuming excessive amounts of water can be dangerous. Water performs various functions in the body, including not only metabolic processes but also temperature regulation, waste elimination, and nutrient transport. However, no matter how important water is, excessive intake can actually be harmful to health. In particular, drinking too much water when fluid metabolism is not functioning properly can cause the osmotic concentration of extracellular fluid to drop sharply, potentially leading to conditions such as hyponatremia.
Our bodies have the ability to regulate water intake to maintain fluid balance. The kidneys play a crucial role in this process, excreting excess water through urine. However, drinking too much water in a short period of time can overwhelm the kidneys’ capacity to process it, leading to fluid imbalance. The kidneys can process approximately 800 mL to 1 L of fluid per hour; if water intake exceeds this amount, the body’s balance begins to break down. At this point, as excess water accumulates in the body, the osmotic pressure inside and outside the cells changes, causing water to flow excessively into the cells and causing them to swell.
A particular concern in this process is the dilution of sodium concentration. Sodium is essential for maintaining electrolyte balance in body fluids and regulating nerve and muscle function. However, consuming too much water can lead to a relative deficiency of sodium, resulting in hyponatremia. Hyponatremia refers to a condition where the sodium concentration in body fluids is excessively low, which can cause abnormalities in various bodily functions. In mild cases, symptoms such as headaches or nausea may occur, but in severe cases, it can lead to coma or death.
Furthermore, excessive water intake can cause cerebral edema. Unlike other parts of the body, the brain is enclosed within the rigid skull, leaving little room for expansion.
When excessive fluid enters the brain cells, the brain swells, increasing pressure inside the skull, which causes headaches, dizziness, vomiting, and vision problems. In severe cases, this can lead to neurological symptoms such as impaired consciousness, and if this condition persists for a long time, the risk of brain damage increases.
Another concern is the strain placed on the heart. Excessive fluid intake increases blood volume, which means the heart must pump more blood. The heart works harder to circulate this additional blood throughout the body, and over time, this can place a burden on the heart and increase the risk of cardiovascular disease.
Therefore, it is most important to drink water in moderation. Generally, the recommended daily water intake for adults is about 2 to 2.5 liters, though this may vary depending on an individual’s activity level, weight, and climate. However, consuming significantly more than this amount should be avoided. In particular, drinking large amounts of water in a short period can place a heavy burden on the kidneys and the body’s fluid regulation system, potentially causing adverse health effects.
In addition, one must consider their physical condition to maintain a balanced water intake. If your body is unable to excrete fluids properly or if you suffer from certain medical conditions, you must regulate your water intake more carefully. For example, patients with heart failure, liver disease, or kidney failure cannot efficiently excrete fluids from their bodies, so excessive water intake can be dangerous. Therefore, it is essential for people with these conditions to adjust their fluid intake according to their doctor’s advice.
In conclusion, while water is essential for maintaining health, it is important to remember that drinking too much can actually be harmful. As with everything, moderation is key when it comes to water intake. Rather than drinking excessive amounts simply because water is important, it is crucial to consume an amount appropriate for your body and to listen to your body’s signals to regulate your water intake.
