In 2012 Professor Tim Noakes (a high profile doctor and sports scientist) published a somewhat controversial book titled ‘Waterlogged - The Serious Problem of Over-hydration in Endurance Sports’ where he advocates ‘drinking plain water to thirst’ as the best way to avoid hydration-related issues such as hyponatremia and to maximise athletic performance. Rather than of drinking to a hydration plan and/or consuming any additional electrolytes through sports drinks.

The book was widely talked about in the media and his stance has become very popular. But is it right for everyone, all of the time? Here's where Precision Hydration stands on this debate...

Contents:

The background to "Waterlogged"

Prof Noakes was motivated to write his book after many years spent studying a worrying trend; athletes becoming very sick (or even dying) from the over consumption of water and weak sports drinks during competition.

These unfortunate people were falling victim to a condition called hyponatremia that occurs if you dilute your blood sodium levels down below a critical level. Given the measured prevalence of hyponatremia in some modern sporting events, his concerns were valid and remain very real. 

In the book, Noakes is adamant that it’s the sports drink industry (Gatorade in particular) who's to blame for the problem. He suggests that they mis-interpreted research findings (wilfully or otherwise) and have relentlessly encouraged athletes to do things like drink to replace 100% of their sweat losses, to drink ahead of thirst or ‘as much as is tolerable’ during exercise, primarily because this suits their agenda of selling more drinks.

He makes a very good case for this and its hard to disagree that the industry has played a very significant role in the rise of hyponatremia in sport...

The problem with sensationalism

With that said, Noakes clearly has a very personal axe to grind with Gatorade (though the exact reason is unclear) and I think this clouds his judgement and makes some of his views come across as bitter and somewhat extreme to the more impartial reader.

It’s also not unknown for Tim to take a contrarian view on big topics in sport and exercise (he’s done it numerous times in his career) and he's built a reputation around being deliberately disruptive and by attacking ‘conventional wisdom’, so to a degree it feels like he's also deploying a formula that has worked for him in the past with Waterlogged.

Throughout a large portion of the book, Noakes builds a narrative around the idea that simply ‘drinking plain water to thirst’ (instead of drinking to a pre-determined strategy and/or consuming any supplementary sodium through sports drinks) is not only the best way to avoid hyponatremia, but also to maximise athletic performance.

He cites anecdotal examples from the early 1900s and into the 1970s, during which time athletes were actively discouraged from drinking during marathons and other endurance events (yet performed very well), as well as interpreting some of the research in new ways that back up his claims. In all he does paint a pretty convincing sounding picture that just ‘listening to your body’ and drinking plain water as and when you feel like it is all you need to do.

Because of Noakes’ long standing reputation in the sports science community (until relatively recently he was held in very high regard, though his reputation has has taken a beating of late due to his borderline fanatical stance on the low carb/high fat diet debate!), his recommendation to ‘just drink water to thirst’ has received a lot of airtime and has definitely been taken very seriously by many in the sports science and athletic community.

But, we’ve heard lots of (unofficial but credible) reports of athletes following this idea in big races and ending up in hospital with dehydration-related issues as a direct result.

In even more extreme cases, Noakes’ ideas have even been stretched thin enough that I’ve genuinely heard some athletes proclaiming that more dehydration is actually a good thing because the bodyweight loss it promotes could improve performance due to an increase in power to weight ratios (a pretty dubious claim at best, but I don’t want to digress too much here!). 

To be clear, I can definitely see that the idea of drinking plain water to thirst has some merits. It's also an appealing concept, after all it keeps things very simple and makes an excellent media-friendly soundbite. But, taken to the extreme (as it often is), it also reminds me of the famous Henry L. Mencken quote "For every complex problem there is an answer that is clear, simple, and wrong".   

That's not because drinking water to thirst is inherently ‘wrong’. It is in fact probably the correct thing to do a lot of the time, and many of our own personalised hydration recommendations advocate using this approach when appropriate.

The quote comes to mind because, despite Noakes' book and the common media portrayal of his outlook, drinking just plain water to thirst just doesn't apply to all sporting situations, all of the time.

What is most misleading in all of this is the assertion that drinking only water to thirst is some kind of simple fixed and universal truth, that it's all you need to know about hydration.

That's where I take issue with the way drinking water to thirst has been presented in the sporting world since Waterlogged was published. It's seen as a simple tug of war between ‘old thinking’ (drinking to a plan or strategy that seeks to maximise fluid/electrolyte intake) and ‘new thinking’ (just drink water to thirst and you’ll be fine).

This kind of polarised debate consumes attention with lots of hyperbolic statements and conflict. But, crucially, it misses out a lot of the nuances around fluid and electrolyte intake for athletes, so ends up leaving most people confused or mislead on the topic.

Issues with the "drink water to thirst" approach

So to delve a bit deeper into the issue, I’ll start by considering some pros and cons of the key pillars of the ‘drink water to thirst’ argument...

Theory #1: Drinking to thirst will prevent hyponatremia

Noakes’ initial aim with Waterlogged seemed to be to raise awareness of the increasing prevalence of hyponatremia in endurance athletes and to help eradicate the needless deaths and disabilities that the condition can cause. 

In this regard his ‘drink water to thirst mantra’ does make sense. It's highly unlikely that anyone just drinking water to thirst would become dangerously hyponatremic under normal circumstances. That's because of how your body sweats and how your thirst mechanism works to help correct for fluid lost in your sweat.

Essentially sweat, even the sweat of people who lose a lot of of sodium, is ‘hypotonic’ to blood plasma (i.e. it is more dilute) so whenever you sweat you lose proportionally more water than sodium. As a result, your blood becomes saltier rather than more dilute as you start to dehydrate.

Rising blood sodium concentrations are a key part of what drives you to become thirsty so, if you then drink water only in response to thirst, you should only ever dilute the blood back down to an acceptable level, before the cycle repeats itself.

As a result you should never end up badly diluted (hyponatremic) unless you drink ahead of thirst (or go for hours and hours without replacing any salt), assuming your body and brain are functioning properly.

Viewed exclusively through this lens, the idea of drinking solely to the dictates of thirst basically gets the thumbs up as the first line of defence against hyponatremia for most people, most of the time.

(But maybe not if you're a very salty/heavy sweater...)

As a brief but relevant counterpoint to this idea though, there may be some more extreme circumstances in which this theory does not stand up as watertight (pun intended). Such as at times when certain athletes (those with very high sodium losses) are doing long duration exercise in the heat.

These athletes are likely to be at an increased risk of hyponatremia even if they drink ‘moderately’. That's because their very high rates of sodium loss make a relative dilution of their sodium levels occur much more easily than when sodium losses are more modest.

We recently published a pair of case studies in the BMJ to highlight this idea. And, when you think about it, this should not be controversial. But, it's worth pointing out that these cases are likely to be relatively rare, so for many athletes, the advice to drink to thirst would likely protect them against developing hyponatremia, in most normal circumstances.

Theory #2: Drinking to thirst is ‘natural’

Like the proponents of barefoot running or paleo diets have argued that running un-shod or eating only certain types of unprocessed foods is far superior to the modern alternatives, ‘drinking water to thirst’ has been touted as better than taking any sort of strategic approach to hydration on the basis that ‘natural’ is simply ‘best’ and that sports drinks are the work of the Devil because they're man-made.

(But a lot's changed since our days as hunter/gatherers...)

Whilst there's a lot of merit in looking at our bodies through an evolutionary lens to better understand how they work, I think it's wilfully ignorant to gloss over the fact that what we often ask our bodies to do as athletes in the modern world is very, very different to what they were asked to do back in the distant past, when all our major physiological traits were hardwired in by natural selection.

It's also naive to presume that just because something is ‘natural’ it's inherently superior to anything modern and ‘man-made’ (be that an idea, concept or physical product). 

For example, our ancestors may have engaged in ‘persistence hunting’ (the running down of prey animals on the hot African savannah for several hours in the heat of the day) - as Noakes describes in Waterlogged - drinking water alone but is that really directly comparable with doing an Ironman triathlon at 70% of your maximum heart rate, in a hot and humid environment for 8+ hours until you collapse at the finish line?

There is, I believe, a huge difference between what was required to simply ‘survive’ a persistence hunt without going down with hyponatremia and with performing optimally in modern sporting scenarios.

The environment that we now live in the majority of the time - specifically in terms of our free and ready access to water (and also importantly, salt) - is very different from that of our ancestors. Expecting modern people to be as finely ‘tuned in’ to physiological cues like thirst (and a craving for salt) as our ancestors would likely have been in a time when resources were much more scarce and conditions a lot harsher, is probably a bit unreasonable.

Whilst most of us of course do realise when we’re really thirsty (or not), developing a keenly honed instinct for this whilst taking part in a demanding and often complex sporting event can’t be taken for granted, especially when taking into account situations where tactics and logistics prevent you from drinking as and when you’d like anyway.

I don’t think we'd expect novice athletes to have excellent internal pace judgement when it comes to metering out effort in a long distance race, so why should those same athletes suddenly have the finely-tuned innate skills to allow them to determine how much to drink in real time, and how much electrolyte they might need in that drink, exclusively from biofeedback?

Yes they'll no doubt drink if they get really thirsty, but is that compatible with optimal performance over a long period of time? It doesn’t seem likely.

I think we should all definitely try to learn to be more aware of thirst signals and what they're telling us (as a general rule, the elite athletes we work with are very in touch with their bodies). But, simply expecting them to guide us 100% of the time in modern sporting endeavours is a little bit idealistic and possibly even naive.

Although sports drinks are arguably overused by a lot of people, they have been proven time and time again to provide performance-enhancing benefits to athletes in the right scenarios.

I basically believe that, whilst it doesn’t hold all of the answers, modern sports science can do a bit better than just chucking out a catchy one-liner to cover all that needs to be known about how to drink to maximise performance. 

Theory #3: Drinking to thirst removes the need to supplement with sodium, and is all that is required to optimise your performance

Where I think the ‘drink plain water to thirst’ argument has been stretched thinnest is in the assertion that it's completely optimal when it comes to maximising human performance in absolutely any scenario - something that is expressly promoted in Waterlogged and by drink water to thirst zealots.

Whilst drinking water to thirst is very likely sufficient for short and light activities where sweat losses are low to moderate, when you get into longer and hotter events (where sweat losses can be considerable over many hours), it's a lot less clear whether just sipping some water to thirst is actually enough to keep you performing at your very best.

(There's lots of evidence/anecdote to the contrary!)

There are many early examples of athletes using homemade sports drinks to replace the fluids and sodium lost during hot, long races with great success. Like Comrades Marathon winner Arthur Newton using a homemade concoction made of lemonade, sugar, salt and bi-carbonate of soda and aptly called ‘The Corpse Reviver’. Newton was clearly not being paid to promote this ‘product’ yet continued to use it for many years and it was copied by many of his competitors presumably for no other reason than it worked.

In the world of industry it was discovered through exhaustive trial and error that adding salt to workers' drinking water when they were doing incredibly sweaty manual labour for long hours and in hot conditions (such as in foundries, mines and the like) was extremely beneficial to physical performance and health. “Fluid replacement is necessary and should include sufficient sodium chloride, otherwise the individual will suffer from fatigue, cramp, or collapse”, was the finding of one such study.

The incredibly successful use of Oral Rehydration Salts (a drink containing a lot of salt and a small amount of sugar) to rehydrate those suffering sickness and diarrhoea in the developing world in the 1970s that adding electrolytes and some sugar to drinks given to people losing large amounts of body fluid is considerably more effective at rehydrating them than plain water. That's due to the way the salt and sugar assist in the transportation of fluid across the gut wall and retention of that fluid in the bloodstream once it arrives there. Leading medical journal The Lancet described this as the most important medical advance of the 20th century.

More recent research into the performance of triathletes who were given either salt tablets or a placebo during a middle distance race showed that the group taking salts were ~26 min faster on average, and that they rehydrated more effectively than the control group.

Interestingly, in this study all of the athletes were allowed to drink as much (or little) as they wanted to (i.e, not to a pre-determined schedule) and those taking the salts were presumed to have drank more intuitively because the intake of salt offset some of what they lost in sweat and consequently helped to stimulate their thirst mechanism.

That study certainly tallies with many of my own experiences using sodium supplements with success during long, hot races. It also seems to validate what we see in "the real world" with the large numbers of endurance athletes who seem to find considerable benefit in taking in supplementary sodium during events.

Should you just drink plain water to thirst if you're training or racing shorter hours/distances in cooler conditions?

There are lots of scenarios where just drinking water to thirst is sensible, like for basic day to day hydration (if you're a healthy individual).

For many people engaging in training or events involving shorter distances/periods of time in cool to moderate conditions, drinking water to thirst is also likely to be sufficient much (but not all) of the time. This is what we recommend in our Personalised Hydration Plans if that's what you tell us about how you train and compete.

There may be some benefit to having a basic hydration plan to follow, or in taking steps to ensure you start properly hydrated. But, basically listening to your body (and making sure you have fluids readily available if needed) ought to be enough to guide your fluid intake. 

If you don’t get it quite right the consequences are likely to be quite limited and fluid and electrolyte homeostasis (or balance) is likely to be achieved in the hours after you finish sweating.

Should you just drink plain water to thirst if you're training or racing longer hours/distances in tougher conditions?

When you're sweating over many hours (either in a single day, or collectively on many days back to back) and accumulating large sweat and sodium losses in a condensed period of time, I remain wholly unconvinced that simply relying on drinking plain water to thirst is enough to optimise your hydration and performance.

There's just too much solid evidence (either from the studies cited above or the more anecdotal kind from fellow athletes) out there showing athletes at all levels using electrolyte supplements in sporting events to very positive effect (and the opposite when they don't).

We have a lot of data on the huge variation in sweat and sodium losses from athlete to athlete, and plenty of examples of individuals with very high losses in particular who have found they need to take a much more pro-active and pre-meditated approach to fluid and electrolyte replacement than the average person.

If you're training/racing longer distances, especially (but not exclusively) in hotter/more humid conditions, it's definitely worth ensuring you have a considered hydration strategy. Your plan should be individualised and flexible enough to be tweaked on the go as you use biofeedback (including a big reliance on your sense of thirst) to determine how much fluid and sodium you take in.

At Precision Hydration we call this process an "n=1 experiment", where you take all the available information about how much fluid and sodium you might need for a given activity and you then go out and test this in training and competition.

That’s why we developed our free online Sweat Test to help you get started on this process. If you take a systematic and intelligent approach you'll end up iterating your way to a successful hydration plan that you can then go out and apply in events and during heavy training sessions.

For those that want to take things to the next level, we also have our Advanced Sweat Test available at various test centers around the world. The test tells you exactly how much sodium you lose in your sweat (which is largely genetically determined and varies from ~200mg/l to 2,000+mg/l) and so helps you dial in how much sodium you might need to be adding to your drinks.

In reality most people’s hydration plan should involve some strategic and premeditated consumption of fluids and sodium, balanced with a healthy degree of relying on ‘drinking to thirst’ to ensure that you don’t end up vastly over (or under) doing your intake on a given day.

So, the next time you read/hear "just drink water to thirst", you can say "ah, well, it depends..."

Further Reading