Ignore Tom Brady 37 Glasses of Water a Day Is Too Many

September 8, 2018

The next time you go to the supermarket, stop in front of the dairy section. Pick up a 1-gallon (3.8-liter) container of milk in each hand and take a good look at it. This is about the same water that New England Patriots quarterback Tom Brady drinks every day while exercising.

According to his recently published book, The TB12 Method (Simon and Schuster, 2017), Brady drinks 150 ounces (4.4 liters) of water “on a given day,” according to the New York Daily News, “nearly twice as much” – the equivalent of about 2.3 gallons (8.7 liters), or 37 cups – when he works out.

It’s all part of Brady’s daily nutrition regimen to achieve what he calls “sustained peak performance.” And for readers who want to hydrate like he does, he recommends the following.” Drink at least half of your body weight in water every day… Ideally, you’ll drink more water, and add electrolytes.”

It goes without saying that the human body – 60% of its average weight is water – needs water to exist. And the services that water provides to the body range from regulating internal temperature and transporting nutrients to lubricating joints and even serving as a shock absorber for vital organs.

So Brady’s advice may be correct in principle: Because highly active people lose more water through sweat throughout the day than sedentary people, athletes need to drink more water than couch potatoes to replenish their fluids. But is 37 cups really necessary? And is there any merit to Brady’s one-half weight-ounce rule? Let’s snap the ball to science for answers.

The truth about 1/2BW.
As it turns out, Brady wasn’t the first to come up with this benchmark – according to a 2015 study in the Journal of Water Resources and Conservation, it’s actually a popular hydration myth that’s as common as the “8×8” rule (which recommends that people drink eight 8-ounce glasses of water a day).

But there doesn’t seem to be any scientific basis for either rule.

“Just as the 8×8 rule has an unknown precise origin, the 1/2BW rule has an unknown origin,” the study authors write.” Not to mention being scientifically validated (we were unable to find any documentation).”

When the authors compared the actual fluid intake of a group of hospital patients to the amount they needed to drink under the 1/2BW rule, the researchers found that the targets set for heavier patients were particularly unreasonable.” In our sample, one patient weighed 345 lbs. 156 kg],” the authors write.” According to the 1/2BW rule, he needed 21.6 glasses of water per day – intuitively, this seems excessive.”

An inherent flaw in rules like these is that they ignore the amount of water people consume through food each day. The National Academy of Sciences estimates that the average North American consumes about 20 percent of their daily water through their meals – a factor that should be factored in when considering hydration needs. Brady’s rule also ignores non-water beverages, such as coffee, tea, juice and milk, which the Mayo Clinic considers to be effective sources of daily water. Contrary to a popular myth, research shows that coffee is not dehydrating (although consuming too much caffeine can otherwise dehydrate your body).

But simply forcing yourself to drink a lot of water to reach an arbitrary goal is not just excessive – it can also be dangerous.

Too much of the wet stuff.
People who take in more fluid than they sweat out are prone to a condition called hyponatremia, a condition in which the body’s water imbalance occurs when too much fluid flushes too much sodium out of a person’s bloodstream. The over-saturated cells can cause swelling throughout the body, leading to headaches, vomiting, seizures and, in the worst cases, stroke or death.

According to a 2015 study in the Clinical Journal of Sports Medicine, authored by 17 international experts in sports medicine, “one of the most important risk factors [for hyponatremia] is sustained, excessive fluid intake greater than the loss of water excretion through sweat, respiration, and kidneys.”

The authors write that when hyponatremia occurs, usually within 24 hours of exercise, it can affect anyone, although it’s common in distance runners.Between 2008 and 2014, three American high school football players died suddenly from hyponatremia after training. According to the Journal of Clinical Sports Medicine, these boys had been encouraged to drink large amounts of water and sports drinks to treat their muscle spasms. (The journal continues to discourage excessive water drinking as a “panacea” for sports injuries).

That’s just one reason why it’s unwise to drink water in order to achieve arbitrary drinking goals. So what’s the healthiest water plan you can subscribe to?

“The safest individualized hydration strategy before, during, and immediately after exercise is to consume palatable fluids when thirsty,” the study authors wrote.

As Live Science previously reported, there is no universal formula for daily water intake. Each person has different hydration needs based on their age, weight, physical activity level, overall health, and even the climate in which they live. Drinking water when you’re thirsty – and drinking a little more when you exercise – is the only reliable rule for healthy hydration.