With the summer stretching out in front of us, it may be useful to note that there is such a thing as drinking too much water. When the online media dubbed hyponatremia as water intoxication, they actually considered just one of the three causes of this syndrome. It is nevertheless useful to pay attention to how much liquids you consume. You might be also be careful in what conditions you consume them.
When the sodium concentration in the blood is below 135 mEq/L, we might be looking at a classical hyponatremia case. Levels under 125 mEq/L define the severe form.
Acute hyponatremia equals the onset of characteristic symptoms in under 48 hours. When the condition develops in over 48 hours it is a situation of chronic syndrome.
There are specific affections that trigger this phenomenon, such as heart, liver or kidney failure or pneumonia. The induced state may result from ingesting a certain quantity of water during exercise or endurance events. This is called EAH – exercise associated hyponatremia.
The main causes for hyponatremia
Depending on what mechanisms provoke the critical lowering of sodium concentration in the blood, there are three known causes, and one miscellaneous causes’ subdivision:
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Hypervolemic hyponatremia
Hypervolemia translates into fluid overload. This is a state where the blood contains too much fluid, therefore it increases its volume. Due to this blood volume expansion, the molecular sodium levels drop, thus resulting hyponatremia. In other words, the sodium electrolytes become diluted. They cannot perform their usual role and the body’s water levels remain on the rise.
Some of the causes for hypervolemic hyponatremia are liver, heart or kidney malfunctions/failures. Edema of any cause is also listed as a factor.
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Hypovolemic hyponatremia
Hypovolemia is the opposite of the above-described trigger. This time the body suffers a rapid fluid loss, more specifically an abnormal decrease in the volume of blood plasma.
This may occur due to a hemorrhage or to dehydration (due to vomiting, use of diuretics or endocrine conditions).
When 10-20% of the total-blood volume disappears it also takes with it an important quantity of water and sodium. This triggers a critical imbalance. The extracellular fluid/intracellular fluid equilibrium is disturbed. Sodium regulates the extracellular liquid, whose volume (ECF) is decreased. Total body water (TBW) decreases and total body sodium decreases as well (Na+), because of the initial loss of fluid.
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Euvolemic hyponatremia
This phenomenon functions in a similar way to hypovolemic hyponatremia. In this case the body suffers a volume expansion, which results in an imbalance between the total body sodium and the total body water.
The pathophysiology of this situation is most commonly linked to the syndrome of inappropriate anti-diuretic hormone secretion (SIADH). Severe pain or nausea may also provoke similar effects, as well as hypothyroidism and glucocorticoids.
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Miscellaneous hyponatremia
Only in this category does the water ingesting as a cause of hypernatremia appear. This source lists the quantity of over 12 liters of water/day. Ingesting so much water might result from primary polydipsia (abnormal thirst sensation caused by hyperglycemia, psychiatric illnesses or other dysfunctions), or other circumstances.
Either way, when the necessary urine excretion required to get rid of such an extra fluid quantity surpasses the body’s abilities. An imbalance occurs, and the body ends up with too much liquids. Thus the molecular sodium levels become lower than usual, the patient testing positive for hyponatremia.
Why did it all became “water intoxication” and how?
We have shown above that ingesting a vast amount of water is just one of hyponatremia’s causes. The fluid has to be ingested in a short time span. Making it impossible for the kidneys to apply their efficient excretion function is one circumstance. Plus it all has to involve exercising, or a state of considerable effort for the body.
Apparently hyponatremia migrated towards “water intoxication” via a study published in 2005. The paper titles “Hyponatremia in Marathon Runners”. It tried to estimate the incidence of hyponatremia among marathon users, hyponatremia caused by excessive fluid intake (one of the miscellaneous causes mentioned above).
The study, published in the New England Journal of Medicine, became heavily quoted. Especially wellness, diet and healthcare advice publications made use of it. Its findings that “13 percent of Boston Marathon runners developed hyponatremia from drinking too much water” created sensation.
In fact, what the study itself concludes is that hyponatremia may be “a greater problem than previously recognized”. It also mentions that a link might exist between this condition and excessive fluid consumption. The composition of the consumed fluids seemed not to be relevant. Another element is that hyponatremia “associated with the running of marathons — and more broadly, with high-endurance exercise” might be a preventable condition.
The same study also mentions “the context of certain limitations”. These should accompany any interpretation of the results. Some of these limitations would be linked to the study’s subjects, others to the lack of sodium baseline measurements before the marathon.
In conclusion,
keep in mind that we should always strive for balance even in hydrating ourselves during hot summer days. Drinking a healthy amount of water during a normal amount of time remains good for our bodies and minds.
Fatal water intoxication exists, but it requires quite a few factors to be met. This condition is disputed in the medical world. It was certainly not defined nor certified as critical by the previously mentioned study. The water intoxication panic that propagated via online media is just a word-of-the-mouth phenomenon. While we need not exaggerate when we drink water or liquids, we should pay attention on how much fluids we normally require. However, we are not all athletes running the marathon. Hyponatremia is a clearly defined phenomenonn that has more than one cause. Drinking plenty of water does not result in hyponatremia.
