A Bible on Overhydration

South African sports scientist Tim Noakes says the scientific guidelines behind hydration are a sham

Jan 7, 2013
Outside Magazine

Overhydration.    Photo: Shutterstock

On May 1, 2012, Dr. Tim Noakes released a 429-page doorstop of a book summarizing three decades of study on overhydration in sports. He had already published more than 50 papers on the subject, but wanted to document everything he’d learned in one place for a very simple reason. “The science of hydration is utterly bogus,” he said in a 2012 TEDx Talk. “There is no science to it. It was dreamed up by marketers to sell product.”

Noakes began looking into the issue of overhydration in 1981. A man had just pulled his wife out of South Africa’s Comrades marathon because she didn’t recognize him. She eventually went into a coma. The woman had fluid in her lungs, a low sodium concentration in her blood, and swelling in her brain. Noakes didn’t know it at the time, but she had the first case he had seen of exercise-associated hyponatremic encephalopathy. That’s a clunky way to say she drank way too much water while exercising.

Over the next three decades, Noakes would pile up more evidence on the condition. Since 1981, he’s documented roughly 1,600 cases, 12 of them deaths, from hyponatremia in the medical literature. In the '70s, '80s, and '90s, the conventional wisdom was to drink more during exercise. Noakes had promoted such an agenda himself at one time. But by the late '80s, Noakes had evidence that said otherwise. Even in the mid-'90s, the American College of Sports Medicine said to drink as much as 40 ounces per hour. Noakes raised a red flag. In the past decade, they have changed their guidelines. The American College of Sports Medicine’s 2007 guidelines do not recommend drinking as much, but Noakes still isn’t entirely in agreement with the new rules. “Drink to thirst regardless of how much weight you lose,” he told Outside in a June 2012 interview. “The ACSM guideline that one should not lose more than two percent body weight is contrary to the published evidence and the findings in elite athletes that drinking ‘ahead of thirst’ impairs exercise performance.”

Noakes does not make this list for his book alone. On September 13, South Africa’s National Research Foundation awarded him their Lifetime Achievement Award. He has committed himself to questioning conventional wisdom about nutrition and fitness by conducting longterm studies that rely on huge amounts of evidence. He tackles big questions. Do muscles regulate exercise performance or is it something else? Is it possible to swim in Arctic or Antarctic waters for a long period of time without dying? Are low fat diet diets really healthy for you? He says he’ll be studying that last question for probably the next two decades. “What I’ve learned in life is that 50 percent of what we learn is wrong,” he said in the 2012 TEDx Talk. “The problem is we don’t know which 50 percent it is, and our job as educated people is to find out which 50 percent is which.”