Eight glasses of water a day? It’s more complex than that

7 Dec 2022

A recent study published in the Clinical Kidney Journal proposed that actor Bruce Lee, who died in 1973 at the age of 32, suffered from fatal hyponatraemia.

The popular belief that eight glasses of water is the right amount to adequately hydrate the average person is a myth, according to Professor Razeen Davids, head of the division of nephrology at Stellenbosch University and Tygerberg Hospital.

“There is no evidence that supports this for healthy people. You should be guided by thirst,” says Davids.

Even though, according to experts, six to eight glasses a day seems to be the recommended amount of fluid the body needs to function, this does not necessarily include only drinking water from a tap. The body extracts water from everything it consumes; “from the water in your sandwich to your coffee, it all adds up,” writes Maverick Life journalist Sarah Hoek in the article “This week we’re listening: You’ve been lied to about how much water you really need”.

However, there are conditions where high water intake may be beneficial, says Davids. Patients who are prone to developing kidney stones are encouraged to increase water intake to achieve a urine output of at least two litres a day, he adds.

Hyponatraemia: what is it?

Under specific circumstances, drinking too much water may be fatal, as suggested by a study titled Who killed Bruce Lee? The hyponatraemia hypothesis, published in the Clinical Kidney Journal in March 2022.

Martial artist Lee died on 20 July 1973 at the age of 32 in Hong Kong. The authors of the study suggest: “Bruce Lee brought attention to martial arts in the Western world and popularised the quote ‘Be water, my friend’ […] The cause of death is unknown, although numerous hypotheses have been proposed, from assassination by gangsters to the more recent suggestion in 2018 that he died from heatstroke. The necropsy showed cerebral oedema. A prior episode was diagnosed as cerebral oedema two months earlier. We now propose, based on an analysis of publicly available information, that the cause of death was cerebral oedema due to hyponatraemia. In other words, we propose that the kidney’s inability to excrete excess water killed Bruce Lee.” In summary, they argue that he suffered from an acute case of hyponatraemia, or water intoxication, which led to a fatal case of brain swelling.

Davids explains that acute hyponatraemia develops within 48 hours and is a result of drinking too much water in the presence of something that inhibits the kidneys’ function of excretion.

“Normally, the kidney would just excrete all the water and there would be no problem,” says Davids. “However, various factors, including pain, nausea, and many medications, can stimulate the release of antidiuretic hormone (ADH) which causes the kidney to inappropriately hold onto water instead of excreting the water load.”

On the day of Lee’s death, the study finds that he was predisposed to water intoxication due to a number of risk factors. Not only did he ingest a high chronic fluid intake, report the study’s authors, but traces of marijuana were found during his autopsy which allegedly increases thirst and water consumption.

Furthermore, the presence of prescription drugs (diuretics, non-steroidal anti-inflammatory drugs, opioids, and antiepileptic drugs) in his system possibly increased the secretion of ADH or impaired his bodily response to the hormone. Subsequently, the increased levels of ADH or lack of response would have inhibited his kidneys to excrete excess fluids. The presence of alcohol, low intake of solid foods and exercise on the day Lee died also increased his vulnerability to develop acute hyponatraemia.

From water intoxication to brain swelling

According to Davids, hyponatraemia is further characterised by low sodium concentration in blood plasma or blood serum. The “diluted-down” sodium levels cause water to start “moving into cells”, he adds.

“When the [sodium] level falls, water moves into cells by osmosis and cells are therefore swollen. This is of greatest concern in the brain as the brain is housed within the rigid skull and therefore brain swelling (cerebral oedema) may cause high intracranial pressure, which can be fatal,” Davids explains.

What does this look like? A severe case of acute cerebral oedema resulted in Lee’s brain at his death weighing 1,575g, compared with the normal 1,400g.

“One would usually expect serious complications only with severe hyponatraemia,” Davids says. “If hyponatraemia develops slowly over days, brain cells are able to adapt and will not be swollen, even with really low levels of blood sodium.”

The gradual development of less-lethal hyponatraemia is known as chronic hyponatraemia, he adds, explaining that acute hyponatraemia is more common among long-distance runners who drink excessively during a race.

Symptoms of severe water intoxication

Symptoms typically include brain dysfunction, such as sluggishness and confusion, and muscle twitching and seizures in severe cases of water intoxication. In extreme cases, unresponsiveness and, eventually, a coma occur prior to possible death.

Lee’s symptoms soon before his death are described as feeling “faint, having a headache, vomiting, and impaired moveability”. After lying down to rest, he was found unconscious about two hours later and pronounced dead.

Even though the body comprises 60% water, drinking large amounts at a faster rate than the kidneys can excrete the excess may have lethal consequences.

“Severe hyponatraemia is an emergency. To treat it, doctors slowly increase the level of sodium in the blood with intravenous fluids and sometimes with a diuretic,” according to Dr James L Lewis III in the online MSD Manual Consumer Version. “Increasing the sodium level too rapidly can result in severe and often permanent brain damage.”

Not too much, not too little

If excess water intake could pose serious threats to health, a deficiency of water in the body – or dehydration – could be lethal in severe cases.

Dehydration can be caused by vomiting, diarrhoea, excessive sweating, burns, kidney dysfunction and the use of diuretics, according to Lewis. While there is no evidence to suggest a specific amount of fluid intake for all persons, it becomes generally important to increase water intake during warmer temperatures. Especially while spending long hours in the sun or working and exercising on hotter days, he adds.

Benefits and tips to staying hydrated

Water plays a significant role in maintaining the balance between body fluids; balanced bodily fluids are necessary for optimal digestion, absorption, blood circulation and body temperature. It can also help to reduce toxins, alleviate pain from menstrual cramps to headaches, and can improve metabolic rates.

Dr Opeyemi Adeyemi recommends drinking hot water upon waking up in the morning to improve digestion and reduce constipation. Eating more water-concentrated foods, such as fruits and vegetables, can help boost hydration – especially tomatoes and cucumbers. It is also recommended to carry a water bottle around and to choose water above sugary beverages. And as Davids noted, “be guided by thirst”, and listen to your body carefully. DM/ML

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Hyponatraemia: what is it?

From water intoxication to brain swelling

Symptoms of severe water intoxication

Not too much, not too little

Benefits and tips to staying hydrated