If you were to ask a room of people how much water you should drink in a day, you'd be hard pressed to find someone who doesn't know the adage 'eight glasses (or two litres) of water a day'. The benefits of drinking copious amounts of water pop up everywhere, from the world of fitness and performance to interviews with celebrities about their beauty secrets and TikToks discussing what it takes to be 'That Girl'. So common is this received wisdom that we have already explored whether it's possible to drink too much water, given the current trend for gallon water bottles.
Underneath all this is the assumption that because we need water to survive, the more of it the better. Crucially, it's assumed that the baseline of two litres a day is an absolute minimum. But this is based not on fact but on a combination of shoddy science and paid-for research, propelled by our old friend capitalism. And at a time when people are more fixated than ever on their health and the concept of wellness, it's vital to interrogate where these truths come from, who they serve and the impact they have on us.
On a Decoder Ring episode exploring hydration, science writer Christie Aschwanden, who is the author of Good To Go: What The Athlete In All Of Us Can Learn From The Strange Science Of Recovery, says "it’s only a slight overstatement" to say that hydration was "invented".
Obviously as a species we need to drink water. Without water we would die and it would be disingenuous to say that humans haven’t always known this. But there’s a difference between knowing your body craves something and deliberately examining what effect hydration, specifically dehydration, can have on us. This first came to the fore via sports science. While there was no major public health ruling around water consumption for a large part of the 20th century in Western countries, athletes were actually encouraged not to drink as it was thought that water just sloshed around in your body and weighed you down. This changed in 1965 with the invention of Gatorade in the US and its emphasis on dehydration as a problem to avoid.
Gatorade combined water, sugar, salt (which the makers of the drink referred to by its scientific name: electrolytes) and lemon juice and was marketed to athletes. According to Decoder Ring, around the same time they started bringing the drink to market, its makers also started funding studies into the impacts of dehydration. This marks the beginning of science around hydration being funded by companies and used as a marketing tool – a trend that continues to this day across the nutrition industry.
The supposed benefits of being amply hydrated are as well known as how much you’re meant to drink, with improved performance in sport, better focus or mental clarity and better skin the most commonly cited. But robust evidence to back up these claims is scant. A 2013 study into the impact of hydration on cyclists’ performance in which the participants had no idea how hydrated they were (fluid was given intravenously) found there was no performance difference between those who were fully hydrated and those who received no fluids. Studies on focus, particularly in children, have found some positive impact but also some negative impact. In 2013, research found that participants performed better in cognitive tests after drinking but fared worse in a test of rule-learning. In this case, all participants were fully conscious of how much they were drinking. As for skin, there is even less research, with only one nominal study showing any improvement in skin hydration when you drink more water – and the improvement is barely noticeable to the naked eye.
Research that does lay claim to the unequivocal benefits of water is out there. However it is funded by vested interests. This happens on a big scale, like the 2011 Hydration for Health initiative which was sponsored and created by Danone, the company behind bottled waters Volvic, Evian and Badoit. But it comes through in smaller instances, too, such as water filter makers Brita sponsoring content about how water "works wonders for your wellbeing".
At the heart of these statements are two interlinking ideas: if some water is good, more water is better; and the goal of two litres a day is undisputed fact. But neither is true.
The eight glasses or two litres of water a day concept first appeared in the 1940s in the US as a brief footnote, when the Food and Nutrition Board of the National Academy of Sciences published its dietary guidelines. It based its recommendation on the average male diet of 2,500 kilocalories and this recommendation was repeated in the 1948 revision with no reference or authority cited in the calculation, and has been repeated ever since. But as Margaret McCartney wrote for the British Medical Journal (BMJ) back in 2011: "The 'we don’t drink enough water' idea has endless advocates ... This is not only nonsense, but is thoroughly debunked nonsense." What you likely do in fact need is around one and a half to two litres of fluid a day (which includes all drinks bar alcohol and the liquid in food) but even that varies from person to person depending on level of activity and climate.
The idea took hold thanks in large part to people’s increasing interest in their health, first in the form of fitness and now wellness, which directly linked hydration and performance. This was compounded by advances in materials (specifically the first PET plastic bottle in the 1970s) which made water both accessible everywhere and – crucially – saleable, giving brands the opportunity to take something we genuinely need and have free access to and sell it back to us while espousing the health benefits. With these benefits, of course, being proven by studies funded by those same companies.
On top of that, water consumption became a status symbol. From Gwyneth Paltrow clutching a bottle of Evian in the '90s to Kendall Jenner touting her gallon bottle in 2021, drinking water is both accessible and aspirational. Stripped to its basics, carrying water signals a respect for the self and a prioritising of ‘wellness’ without a self-congratulatory gym selfie or the self-consciousness of ‘clean’ eating. There’s a reason why it’s so embedded in the idea of being ‘That Girl’.
The problem with all this is that we are encouraged to dismiss our body’s natural regulatory rhythms and instead adhere to guidelines (ideally spending while we do so). How we drink and what we expect it to do for us is now disconnected from the reality of thirst. The physical threat of drinking too much water for your body is rare but not impossible – over-dilution of the electrolytes in your body and bloodstream can result in water intoxication. Far more common is the psychological impact of disengaging from our gut instincts.
Dee Johnson, a senior accredited counsellor and former nutritional therapist on the Counselling Directory, says that consciousness of water intake can easily veer into obsession and become its own form of health anxiety, and it's growing increasingly common. "People are fearful that if they don't hydrate [they will lose] all the positive benefits of it and it flicks from health anxiety into very obsessional behaviour. People are not drinking naturally, they're forgetting that you get water from food as well and this real obsession that they've got to carry their water bottles and measure out how much they drink each day." This is only exacerbated by living through a pandemic. We have been encouraged to be hyperaware of our bodies and our health at all times for the sake of public safety. That vigilance spills out and manifests in many different ways, including a focus on water intake that can swiftly get out of hand, says Johnson. "We're not allowing our gut instinct and the natural way of things – our body will tell us when we're thirsty. Instead we're focusing on what you've 'got to do'. It's coming from a real fear-driven place and when someone starts to really obsess about something, they no longer have a natural relationship with it."
Of all the problems we face today, drinking a bit too much water is not the end of the world. But neither is drinking ‘not enough’. As with so many ideas linked to fitness and wellness, we buy into the notion that this is something we do to benefit us but the reality is that it benefits big companies which privatise the natural resources essential to human life or make us anxious about yet another way we’re supposedly failing ourselves.
If you are someone for whom water is a fixation, Johnson advises looking into what is at the root of this anxiety with the help of a professional therapist. "Why are you so anxious and fearful that you're doing this as a coping strategy that comes from a good place? It's a manifestation of deep-rooted anxiety and fear. Is it fear of bad health? Is it fear of death? Is it fear of not being in control? Fear of not doing the right thing? That's the driver that comes from somewhere else."
On a smaller scale, she suggests finding small ways to disrupt the habitual behaviour. Change where you store your water bottle, or try making short trips without it to interrupt the compulsion. Remember that water is water and it doesn't need to be specially filtered or ionised to be 'better' for you. Crucially, start looking at your physical body signs and begin engaging with natural thirst cues instead of working towards a specific quantity of water.
If this isn’t something you fixate on and you just drink when you’re thirsty, rest assured that you’re probably drinking enough as it is. Food contains so much fluid – pizza contains 40-49% water, while a baked potato is 75% water. All fluids (bar alcohol) count too, including caffeinated beverages. The goal is not a set amount but straw-coloured urine and a health response to your body's natural cues.
You don’t need a big water bottle to feel like you’re taking care of yourself or try to drink beyond your natural thirst limits. Water may be essential to life but it is not a magic cure for health problems big and small.
The only ‘cure’ in that vein is balance, listening to our bodies and always checking who is funding the research.