When Helen Trengove, a 61-year-old resident of Gold Coast in Australia, started off on a 14-day detox and cleanse health programme in October 2014, she did not expect to land in a coma. The programme included a regimen of drinking a litre of water every two hours. On her very first day, Trengove ingested five litres after which she felt light-headed and woozy.

Speaking to journalists later, Trengove and her husband described how she began to feel cold and nauseous and went to bed. She fell unconscious, started having spasms and was rushed to a hospital. She then fell into a coma that kept her in the intensive care unit for three days.

Trengove was diagnosed with hyponatremia, a condition in which sodium levels in the body are abnormally low. Sodium is an electrolyte that regulates the balance of water in the body. If a person drinks too much water, like Trengove did, it dilutes sodium in the body, causes cells to take up excess water and can lead to mild or life-threatening health conditions.

This water intoxication can actually cause the brain to swell, restricting a person’s ability to breath, possibly leading to unconsciousness and death. Water intoxication, even makes it to Discovery Life's show, Curious and Unusual Deaths.

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In fact, even the much-touted “rule” for good health of drinking at least eight glasses of water a day can lead to hyponatremia. New research from the University of Melbourne and Monash University published in the Proceedings of the National Academy of Sciences confirms that the body has its own mechanism to regulate the intake of water and ensure that there is no excess. The study demonstrated the presence of “swallowing inhibition”, a hard-wired process in the human ody that kicks in after excess fluid has been drunk.

The researchers used functional Magnetic Resonance Imaging to measure brain responses to swallowing efforts by participants when they were thirsty and again when they had had excess water. The results showed that there was a three-fold increase in the effort to swallow water in the second case, confirming the presence of swallowing inhibition.

Endurance athletes have often borne the worst of the “rules” of drinking water rather than listening to their bodies and their swallowing inhibitions. In 2014, a high school football player in the United States drank large amounts of water and Gatorade to alleviate cramps he experiences during practice. Media reports suggest that he drank about 15 litres of water by the end of the practice session. The boy collapsed after he reached home and dies a few days later in hospital.

Earlier research has shown that many long distance runners and cyclists while aware of the dangers of dehydration do not take care to avoid water intoxication. One study has even shows that 13% of Boston marathon runners experienced exercise-induced hyponatremia.