Drinking too much water can cause dangerously low blood sodium levels, also known as hyponatremia or water intoxication. Sustained, excessive intake of water, sports drinks, or other fluids – exceeding the body's ability to eliminate fluids in the form of sweat and urine – is the major risk factor for exercise-associated hyponatremia (EAH).
Symptoms typically include headache, vomiting, confusion and seizures, resulting from swelling of the brain (cerebral edema). Without immediate treatment, severe hyponatremia can be fatal.
Myth 3: Stay hydrated to prevent heat stroke
TRUTH: Heat stroke is a life-threatening condition where your body temperature rises above 40°C. Dehydration simply makes you more prone to it. "People who are dehydrated are hotter," says Casa. In fact, in a study published in the Journal of Athletic Training, Casa determined that for every one percent of body mass lost through sweat, your body temperature increases by half a degree, "which makes hydration hugely important for preventing heat stroke," he says. However, there are several other factors that play a role; body size, exercise intensity, fitness level, and age as well as humidity and air temperature can affect who does or doesn't develop heat stroke. Staying hydrated is a good call and can reduce your risk, but paying attention to the whole picture is a better predictor.
Myth 4: Sports drinks are healthy
TRUTH: NO. Unless you do sports, you do not need a sports drink. A sports drink contains the same amount of sugar as a soft drink. Studies have also shown a link between consumption of sports drinks and irreversible damage to the teeth – the high acidity levels in the drinks erode tooth enamel, the glossy outer layer of the tooth. So, drink with purpose and in moderation.