Bruce Lee was the most influential martial artist of the 20th century. In the 1970’s, his fame as a movie star and martial arts instructor sparked North American interest in Asian martial arts. He brought martial arts to North America by founding Jeet Kune Do, which is the basis for modern mixed martial arts. On July 20, 1973, at age 32, he died suddenly with massive swelling of his brain. The cause of his brain swelling was not proven by an autopsy, but was originally reported as possibly caused by sensitivity to aspirin. Now, almost 50 years after his death, a well-researched paper with solid journal references explains that he probably died from hyponatremia, drinking too much water (Clin Kidney J, Dec 2022;15(12):2169–2176).

• Hyponatremia occurs when drinking too much water dilutes the salt level in your bloodstream.
• However, the level of salt in your brain usually remains normal or high.
• Fluid moves from tissues that have low-salt levels to dilute those that have high-salt levels.
• Blood fluids move from the bloodstream into the brain, so the brain expands with extra fluid.
• The brain is in a tight box called the skull that cannot expand, so the enlarged brain is crushed inside the non-expanding skull.
• The person stops breathing and dies.

Early Years and Movie Career
Lee was born in Chinatown, San Francisco, the son of Lee Hoi-chuen, a leading Chinese opera and film actor and Grace Ho, daughter of extremely wealthy Hong Kong entrepreneurs and philanthropists. Lee’s family returned to Hong Kong when he was three months old and he was raised there. His father arranged for him to get minor parts in movies, and he had roles in 20 films by the time he was eighteen.

Lee became the leader of a street gang, and after he came home from school one day with wounds from a fight, his father began to teach him martial arts. All this did was encourage him to get into more street fights with rival gangs. When he was 18, he beat up the son of a prominent gang leader and word got out of a contract to kill him. Fearing for his life, his father sent him to the safety of the United States to live with his older sister, Agnes Lee, in San Francisco.

In March 1961, Lee enrolled at the University of Washington to major in drama. There he met Linda Emery, and they were married in August 1964. They had two children, Brandon and Shannon, both of whom became actors. Lee dropped out of college in the spring of 1964 and moved to Oakland to open a martial arts studio with James Yimm Lee. He then moved to Los Angeles where he taught martial arts and starred in a television series, “The Green Hornet,” in 1966 and 1967. However, he was not able to get movie jobs in Hollywood, so he left Los Angeles for Hong Kong in the summer of 1971. There he quickly became a major star in “Fists of Fury,” followed by an even more popular film, “The Chinese Connection.” In 1972, he founded a company to make his own film, “Return of the Dragon.”

Fitness and Health Food Obsession
Bruce ran virtually every day, usually in the late afternoon, and did a lot of stretching. Whenever he watched television he would exercise and stretch. He had almost no fat in his body and was always in top shape. He also became good enough at table tennis to compete successfully with some of the best players in his area.

Several times a day he would drink special protein mixes or vegetable cocktails. His drinks contained commercial protein powders, powdered milk, eggs with their shells, vegetable oils, peanut flour and bananas. He juiced carrots, celery and apples regularly. He also took a lot of vitamin and mineral pills and drank water frequently throughout the day. No good research supports any of these “health food” habits, but they may have been responsible for the tremendous amount of excess fluids that he took in that caused his death.

Events That Led to His Death
On May 10, 1973, two months before his death, Lee had an attack of brain swelling. He suffered headaches followed by a seizure, and fell on the floor while working on the movie “Enter the Dragon”. He was rushed to Hong Kong Baptist Hospital where doctors diagnosed that he had massive swelling of his brain. A very competent physician saved his life by immediately giving him intravenous mannitol. This drug increases the concentration of sugar in the bloodstream to shrink the brain by drawing fluid from the brain into the bloodstream. The mannitol also acts on the kidneys to draw the extra fluid out of the body and into the urine.

On July 20, 1973, while reviewing a movie script at the home of Taiwanese actress Betty Ting Pei, Lee complained of a headache and took a painkiller called Equagesic, which contained aspirin and meprobamate, a muscle relaxant. He went to sleep and then could not be awakened. A doctor and ambulance were called, but he was dead before he reached the hospital.

An autopsy showed that his brain was massively swollen. The only drugs found in his body were aspirin, meprobamate and small amounts of marijuana. A reaction to aspirin can cause brain swelling, confusion and seizures, but now researchers believe that hyponatremia was a more likely cause (Clin Kidney J, Dec 2022;15(12):2169–2176).

Since low blood salt levels can cause massive brain swelling, and the brain is enclosed in the skull and has nowhere to go, it is squashed to cause headache, nausea, and blurred vision. As blood salt levels drop even lower, the person becomes confused, develops seizures and falls unconscious.

Risk Factors for Hyponatremia
Lee had multiple risk factors for hyponatremia:
• High chronic fluid intake. he preached a high intake of fluids as the healthiest way to live and drank water throughout the day.
• Marijuana (found at autopsy) increases thirst so you drink more.
• Acute kidney damage causes the body to retain fluids. His physician said that blood urea nitrogen (a measure of kidney damage) at Baptist Hospital was very high at 92 mg/dL, but was normal on May 25 when Lee was examined previously.
• Alcohol (Lee drank frequently), which can cause low blood salt levels.
• Low dietary salt and high fluid intake. His wife says that in her husband’s final months, he had stopped eating solid food and was existing primarily on fluids, mostly carrot juice and apple juice
• Recent weight loss. He looked emaciated and had lost 15 percent of his total body weight in the previous two months, and he had minimal body fat to start.
• Active exercise and inadequate food and fluid intake. He continued to exercise every day on his meager diet. Exercise can cause salt loss through sweating (Wilderness Environ Med 2020; 33: 50–62)
• Some evidence that he was taking diuretics, which can deplete the body of salt.
• Possible prescription and over-the-counter drugs. Various reports say that he took aspirin, diuretics, phenytoin and painkillers.
• Possible anabolic steroids, which can cause adrenal insufficiency that causes salt loss

Lessons From Bruce Lee’s Death
You need extra fluid when you exercise, particularly in hot weather, but how much fluid should you drink? You will not become thirsty during exercise until you have lost between two and four pints of fluid, so you can’t wait for thirst to encourage you to drink. Blood has a much higher concentration of salt than sweat, so when you sweat, you lose far more water than salt, so you will not become thirsty until you are significantly dehydrated. Dehydration makes you tired and it is unlikely that you could maintain your race pace after you become thirsty, because you will have to slow down while you drink enough fluid to replace what you have lost.

The American College of Sports Medicine recommends up to five cups of fluid per hour, but for a person who is not exercising near their maximum, this could be too much. People slowed down by fatigue, or those out of shape, should limit fluid intake, probably to less than two water bottles per hour. If you are exercising for more than an hour, you should also replace salt, either with salted sports drinks or salted foods. More on hyponatremia

Bruce Lee
Nov 27, 1940 – July 20, 1973