“Why is sodium important for athletes?” is a great question. Athletes are frequently told to drink as much water as possible even if they aren’t thirsty. But, is that really what makes the body perform better? Or, more importantly, is it safe?
As great as water is for hydration for light exercises, endurance athletes deal with a very different physiology due to significant electrolyte and water losses that are not typical. Loss of electrolytes and consumption of hypotonic drinks such as water (without electrolytes) is the leading cause of low blood sodium levels in endurance athletes.
Sodium is an electrolyte that plays an important role in hydration for people of all activity levels, but especially for endurance athletes. Without sodium, an athlete is sure to experience hyponatremia (a low blood sodium level) and its deleterious effects.
It is fair to say that staying well hydrated will lead to better performance. But it still begs several questions: how much water should I drink? Is water the best? What about electrolyte or sports drinks for rehydration? And, most importantly, how much water is too much?
Hyponatremia in athletes is common because endurance athletes lose electrolytes through sweat at a high rate. It is estimated that about 20% of endurance athletes develop mild-moderate hyponatremia in the field.
Normal blood sodium level is maintained closely in between the range of 132-140 meQ/L. Ingestion of water and salt is closely regulated by several hormones that control excretion of sodium and water and contribute towards maintaining this sodium level within that defined range.
In simplistic terms, the human body is a bag of salt and water. About 70% of our body is water and this water circulates between the blood vessels (or intravascular space) and outside the cells or the extravascular space. Water, minerals and nutrients are in a constant state of flux, or movement, to ensure nutrients reach individual cells within the body.
This might make you wonder, “does magnesium affect sodium levels?” and the answer is yes. Magnesium is an electrolyte that is just as important as sodium, though often overlooked. And magnesium can also affect levels of potassium.
Water excretion from the kidney is determined by a hormone called anti-diuretic hormone (ADH) or vasopressin. In a dehydrated state, ADH is secreted from the brain and helps in retention of water through the kidney. This allows us to conserve every drop of water by reducing the amount lost in the urine.
In endurance races, athletes are dehydrated due to ongoing water and sodium losses. If the athlete only consumes water, the combined effect of high ADH level as well as sodium loss in sweat can lead to a drop in the blood sodium level leading to hyponatremia.
Symptoms of hyponatremia are similar, at times, to what can happen if your potassium level is too low: headaches, nausea, muscle weakness and fatigue.
If the hyponatremia is due to excessive consumption of water (imagine drinking 2 gallons of plain water during a marathon), then kidneys excrete the excessive water and bring the sodium levels up to normal. Additionally, as the individual eats, sodium is delivered through food at the same time the water is being excreted. These mechanisms ensure that as long as the kidney function remains normal, excessive water intake or a low amount of sodium intake do not alter the blood level of sodium for too long.
If the hyponatremia is moderate, the symptoms can be concerning. These include worsening headaches, confusion, muscle weakness, cramping and even seizures. These symptoms require immediate action.
Frequently, medics infuse hypertonic saline (3% of sodium chloride) in the field to quickly bring up the sodium levels in the blood in an athlete who has suspicion for severe hyponatremia.
The recovery time from low sodium levels depends on the severity of hyponatremia. Mild hyponatremia, particularly in athletes, corrects itself over a period of time due to adaptive mechanisms.
At times, more intense monitoring in the hospital may be required. If hyponatremia is severe and persistent, it can cause brain edema and could be lethal. The famous martial athlete Bruce Lee supposedly died of hyponatremia.
The risk for moderate hyponatremia is real in endurance athletes or ultramarathoners. Studies that have looked at symptoms of cramping or muscle weakness have not completely correlated with blood sodium levels in this group. Despite this, it is commonly believed that mild cases of hyponatremia are much more common than previously thought, largely because mild cases by definition are not symptomatic enough to be investigated. Unusually challenging and long endurance activity combined with improper hydration can turn a mild case into a severe one.
Here are some simple ways to ensure adequate hydration without putting yourself at a risk for hyponatremia:
MAGNAK Electrolyte Mix is formulated with electrolytes that are necessary for preventing hyponatremia, including sodium, magnesium, and potassium. Drink MAGNAK for increased endurance, a faster recovery time after exercising, and a well-hydrated body.
Learn more about MAGNAK here.
Dr. Kharait is an MD and a practicing Nephrologist in Northern California. He completed his Residency in Internal Medicine and Fellowship in Nephrology from the University of California, San Francisco. He has a PhD in Molecular Physiology from the University of Pittsburgh and specializes in treating patients with electrolyte disorders and kidney diseases.
