Hyperhydration or hyponatremia
Hyperhydration is also known as water intoxication or water poisoning, and is where the normal balance of electrolytes (such as Sodium) in the body is unbalanced because of a rapid intake of water. This can seriously affect the brain's ability to function and so can lead to death if medical supervision is not available.
The first symptoms of hyperhydration might include light-headedness, nausea, vomiting and headache. However, if the balance of electrolytes continues to be upset, this can lead to seizures, coma and death.
Hyperhydration mainly affects levels of sodium in the body and so a sports person who is losing sodium through sweat but who is only consuming water in large quantities may experience Hyperhydration. This is especially true for sports people such as marathon runners. To avoid Hyperhydration, sports performers should drink little and often, and consider adding specific electrolytes to their drinks to replace lost electrolytes.