Tim Noakes on the Serious Problem of Overhydration in Endurance Sports

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Man and water. Photo: Shutterstock

South African exercise scientist Dr. Tim Noakes wants to change the way endurance athletes think about hydration. He believes that, over the course of the last 30 years, people have been scared into drinking too much fluid while exercising. As a result, he says performance has suffered and people have died. He’s counted a dozen deaths in endurance events caused by exercise-associated hyponatremia, a condition that results when athletes drink too much fluid.

Noakes earned Doctor of Medicine and Doctor of Science degrees from the University of Cape Town in South Africa and has raced in more than 70 marathon and ultramarathon events. He has written more than 50 studies on the subject, but his pièce de résistance is Waterlogged: The Serious Problem of Overhydration in Endurance Sports, a 429-page book released last month. He said all of the overhydration started with the dawn of sports drinks and guidelines that called for people to drink ahead of thirst. Since Noakes began his fight, the American College of Sports Medicine has changed some of its guidelines, but he wants more. We called Noakes to talk about his ideas for the new rules of hydration during endurance exercise, which he points out are actually old rules.

Why write this book?
I had a responsibility. I was one of the few people around in the 1960s running and I’m still around now. I’ve seen the change in advice that people have been given. I was around when people were advised not to take fluids during exercise. Then we went to the phase where we were told to drink a lot of water during exercise. Now we are getting back to more appropriate guidelines. I was also the first person to discover a lady who developed hyponatremia; she drank too much and almost died as a consequence. We were the first to show that, and it came at a time that was very inappropriate because the industry was just starting to encourage runners to drink more than they need. So I had a responsibility to say, Listen, if you advise runners to overdrink you are going to have problems. That did happen. This book explains exactly why it happened and how it could have been avoided.

How did your view of hydration change over time?
I ran my first marathon in 1972 and I remember there was one aid station at 20 miles. The only reason was because they wanted you to take your time while you were running the race. The rules were that you shouldn’t drink during exercise, or if you did drink, you were only allowed to drink after 10 miles in the marathon, and then only every three or four miles. You were actively told not to drink. So having run my first marathon, and having read the literature, and having read a paper by two South Africans, Wyndham and Strydom, who suggested that if you don’t drink you’re going to die, I decided that it was my responsibility to try and make people drink more during exercise. I started a bit of a campaign and wrote articles—some were published in Runner’s World in the United States—saying that it was ludicrous to prevent runners from drinking during exercise. I said you should drink up to 900 mL per hour [30 ounces].

In May 1981, I wrote an article saying you should drink as much as you can. Wherever you can find fluid on a race course, you must drink it. The next month, I received a call and a letter from Eleanor Sadler, a South African runner who had lost consciousness in the Comrades Marathon. She had almost died, and had been unconscious for four days. She said, What happened? I had absolutely no idea at the time. All we knew was that her blood sodium concentration was very low. The question was, had she drunk too much, or had she lost too much salt, or was it a combination of both? And over the next four years, I decided that she had drunk too much. Then I realized that if we were going to tell people to drink more than about 800 mL per hour [27 ounces] you’re going to get into trouble, particularly with women runners who are smaller and run slowly. I saw there were going to be deaths and I predicted it would be among young women running marathons. And sadly that’s what happened.

Waterlogged: The Serious Problem of Overhydration in Endurance Sports

What happens when someone has exercise-associated hyponatremia?
You become confused and very typically lose consciousness, or else as you lose consciousness you have an epileptic seizure. That’s the usual presentation in the advanced cases. The other presentation that I frequently see is that people who finish the race become very withdrawn. They lie down in the fetal position. They don’t want to speak to anyone. They don’t want to look at the lights. When you speak to them, they are extremely dull and slow. You think, Gosh, these are very stupid people. But it is because their brains have swollen and are not functioning normally. As soon as you treat them properly, they lose fluid and that starts reducing the swelling of the brain. They become lucid and you can’t believe the change—that this person who was stupid and confused is now absolutely alert and sharp.

What happens in the body of the people that have hyponatremia?
What I’ve found is that all of these people were probably drinking 1.2 liters per hour [40 ounces]. They continue to drink like that for four or five hours. Now, normally, if you’re drinking at that rate, you simply pass it out as urine. A person who is overdrinking will start passing urine so frequently that they’ll realize, This is stupid. I’m going to stop drinking.

But what happens in hyponatremia is that, for some reason, the brain interprets that the person is dehydrated and secretes the antidiuretic hormone. As a consequence, that prevents all urine production. Although they are sweating, they may be sweating at a rate of 20 ounces per hour, but they are drinking at a rate of 40 ounces per hour. Every hour they are accumulating 20 ounces. You can do that for a couple of hours, but once you’ve accumulated about 60 to 80 ounces of water in your body, all of your tissues become bloated, and the organ that becomes most affected is the brain.

The brain swells, and because it is in a rigid skull, it cannot swell very much. The more it swells, the more pressure, and that eventually squeezes the arteries supplying blood to the brain. Ultimately, there is less oxygen getting to the brain, and certain parts become damaged. Once it affects your breathing centers, then you’re in real trouble, because it stops breathing, and that is essentially irreversible.

In the book you mention humans suffer from hyponatremia because they haven’t evolved to drink these large amounts of water. Can you explain this?
If you look at the history of evolution, it looks like we started in Africa on the savannah. We had to be hunters in midday heat. In Africa, the lions hunt at night, and they have brilliant vision. The Bushmen, who were the traditional hunters in Africa, won’t get out of their camps before 10 o’clock in the morning. They know that by then the lions will start to slow down, so it’s safe to be outside. So humans evolved to hunt in midday heat, and we developed this incredible capacity to sweat and to run, even though we’d become dehydrated. The great hunts that had been followed in Southern Africa could last for four to six hours. That’s how long it takes for a hunter to run an antelope down. It takes four to six hours before the antelope’s body temperature is so high that it becomes exhausted and has to stop running. That occurs at temperatures of 40 to 43 degrees centigrade, well over 100 degrees Fahrenheit.

We know now that humans evolved this incredible ability to hunt in the heat, and we must presume that they didn’t have access to water because they couldn’t carry much water with them. All they had was ostrich eggs which [they used as canteens and] only could contain a couple of liters [67 ounces]. So we know they had to have run without fluid ingestion. When they killed the animals, they would actually take the water content from the intestines. They would replace their fluid losses by drinking both the blood and the intestinal water content from the animals that they killed. So they had to wait until after they killed the animal until they could drink.

When did we start drinking more water?
Well, the sports drink industry was involved. In 1969 a great American physiologist, David Costill, started new studies. Gatorade was just getting into the market, and he went to them and said, Listen, you produce this product, do you know if it works? Is it of any value? He said, I’ll do the studies and let’s see if it works. His focus was to try and raise money to fund his laboratory. He did the first study where he had people like Amby Burfoot—who writes the forward for the book and won the 1968 Boston Marathon—not drinking anything. Costill had them run when they drank up to 1.2 liters per hour on the treadmill, and [then run] when they didn’t drink. When they did drink, he showed their body temperatures were much lower and he presumed that was better. But if you ask Amby Burfoot, he said he felt much better when he ran without drinking. Costill assumed then that drinking was good for you, although the study hadn’t really shown that because it wasn’t a performance trial, and all the runners found when they didn’t drink was that there were no problems associated with not drinking. The American College of Sports Medicine asked David Costill to write the first drinking guidelines, which he did in 1975. He said that runners should drink regularly during exercise, which is pretty good advice.

Then, what I discovered, which was really eye-opening, was that a single individual working for the U.S. military decided that water was a tactical weapon. That if the military could be encouraged to drink more during maneuvers, they’d have less heat stroke and less illness and they’d be more productive and could be better soldiers. It was purely his idea. It had no scientific basis at all. Two years later he published a paper supposedly saying that if the US soldiers drank 1.9 liters per hour [64 ounces] when they were exercising in the heat they would perform much better. There was utterly no concrete evidence that that was true. The problem was, his advice was embraced by the U.S. Military. They changed their drinking guidelines to say that you should now drink 1.9 liters per hour. The same people who drew up those guidelines were then invited by the American College of Sports Medicine to get involved with drawing up guidelines for runners.

In 1996, that culminated with the new American guidelines, which said that you must drink as much as tolerable during exercise, up to 40 ounces per hour. That became the mantra—that you had to drink before you became thirsty, and as much as possible during exercise. It was after that the problems of hyponatremia really become problematic around the world.

In 2007, the ACSM changed it's guidelines. Are there still reforms you would suggest?
Drink to thirst regardless of how much weight you lose. The ACSM guideline that one should not lose more than 2 percent body weight is contrary to the published evidence and the findings in elite athletes that drinking “ahead of thirst” impairs exercise performance.

Can you talk a little bit about the history of dehydration and sports marketing?
One of the principles of selling a product, and if it’s a medical product and you make medical claims, is that you must maximize your market. In my view, those 1996 guidelines, what they do is they maximize the markets for sports drinks. What they are essentially saying is that it’s dangerous to lose any weight during exercise. In other words, it doesn’t matter what exercise you’re doing, you must drink at the same rate that you are sweating. And you mustn’t wait to become thirsty. What that means is that if you go to a gym and start exercising for 10 minutes, you must start drinking before you start, and within 10 minutes you must have drunk a certain amount. That increases the market size for your product, from just marathon runners to everyone who exercises. So when you go onto the street and you see runners jogging along for a couple of miles, they are carrying water with them. They become a target user for your product. They managed to change drinking behavior out of competitive sport for runners and cyclists and triathletes to gym exercisers as well. The consequence of that is that the sale of their product just rocketed thereafter. They had to demonize hydration and make it a disease.

Now, dehydration is not a disease, and it only has one symptom, and that is thirst. If you start to exercise, and you don’t drink, after a period of time, you will become thirsty—that’s your body’s way of telling you to drink. The idea that you should drink ahead of thirst is absolutely nonsensical. As I’ve said, we’ve evolved from other creatures. We don’t need to be told when to drink. They regulated their fluid purely by thirst. So why should humans be different from every other creature on earth to be told when and how to drink? The reality is you don’t need to be told when and how much to drink. We have a 300 million year developed system that tells you with exquisite accuracy how much you need to drink and when you need to drink. It’s called thirst. If you rely on thirst you won’t ever become dehydrated, and you won’t also ever become overhydrated.

Dr. Tim Noakes in Stockholm in 2011.

So what hydration advice would you give to people running their first recreational marathon?
That’s a great question, because it wouldn’t be any different from the advice that I’d give to anyone else. It’s listen to your body, and your body will tell you. It’s very important to make this point. There’s now evidence to suggest that if you drink ahead of thirst, that if you drink ahead of the signs, your performance will be impaired, just as it will be impaired if you drink less than you should at thirst. Thirst is your body trying to tell you, Listen, I need fluid. If you don’t replace that fluid, I’m going to slow you down until you drink. Only when you drink am I going to allow you to perform optimally again. The brain, unfortunately, can’t tell you that when you overdrink, you’re going to go slower. So you don’t pick up the messaging. You just go slower without realizing it. It’s very important.

And people don’t have to worry about overheating? Or people shouldn’t relate dehydration to overheating?
You shouldn’t relate overheating to dehydration. You overheat when you run too fast. That’s the key. You don’t overheat because you become dehydrated. The brain’s too clever. If you’re not going to drink, the brain will slow you down, and that will lower your body temperature, not raise it. So, we’ve got some great studies where we look at people running half marathons, marathons, short ultramarathons, and long ultramarathons. The longer the race, the lower the temperature, because they are running slower. Their levels of dehydration are pretty much the same whatever distance they run. There’s some sort of regulation, that whatever distance you run, if you drink appropriately, you always get the same level of dehydration, however far you run. But the key is that the faster you run, the hotter you are. But it’s still absolutely safe to expect your body temperature to rise. And the fact is that heat stroke occurs very, very infrequently. It’s the exception, not the rule. And when it does happen, there are exceptional circumstances. Most of those people have some other genetic circumstances that are a problem, or they are taking drugs, or they have an infection. It’s not normal to develop heatstroke during a race. If you do develop heatstroke during a race, something else is going on, and that’s affected your body’s ability to control it’s temperature, but it’s not the normal procedure. Normally it’s perfectly safe to run in the heat, and your body will make sure that your to the finish before your temperature rises too high.

Are sports drink companies responsible for the perpetuation of a myth?
What I learned in writing this book is that we just have to be very careful about the information that we accept. We have to interrogate it very, very carefully to see if it’s true, or if it’s biased information that we’re being forced to believe because it has a commercial drive behind it. People must read this book and draw their own conclusion. In the future, there must be more suspicions when the industry supports medical claims. Be very suspicious of scientists who are speaking on behalf of industry. How independent are they? That’s a very important question that we have to ask.

What do you think the response will be in the running community to this book? What do you hope the response will be?
I think there will be a lot of anger, and the anger will be directed at me because I’m kind of challenging a dogma. People often don’t like changing their ideas. There will be many people who will find, My gosh, it actually works. I don’t have to drink as much as I thought I did. In fact, many people are already adapting that way.

I think it’s going to be a slow process, but ultimately, the truth prevails. Runners will find they don’t need to drink as much as they thought they did. Performances are actually improved when they drink to thirst and they don’t become waterlogged because they overdrank. I don’t know what industry is going to do. I don’t know if they’re going to completely ignore it, and continue on their merry way, promoting overdrinking. Or they might just attack me, but I don’t think that’s a really good way to go about it, because that will just draw more attention to it and more people will read the facts and more people will realize where the truth lies.

My hope is that people will keep their minds open and say, Tim Noakes is just the messenger. I’m just giving you the truth. If it’s wrong, that’s fine. Get someone to write the book that contradicts it.

For more, check out Waterlogged: The Serious Problem of Overhydration in Endurance Sports, by Dr. Tim Noakes.

—Joe Spring

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