Water - Your Cheap, Effective & Safe Nootropic - Up to 31% Increased Cognitive Performance With 25ml of Plain Water

The complex neuronal clockwork in your brain needs water to run smoothly. But how much water does it need?
If you have been reading SuppVersity articles for more than a week, you will know that a lack of water can easily turn an Einstein into a Neanderthal (learn more).

Fully convincing experimental evidence for the efficacy and, more importantly, optimal amount(s) of water as a 'nootropic supplement' in non-dehydrated individuals, as it has just been provided by a recent study from the University of East London and the University of Westminster (Edmonds. 2016), however, has not been available...

Not available, yet?! That is, obviously, before Edmonds and colleagues set out to investigate the dose-response characteristics of the effects of acute water supplementation on cognitive performance and mood.
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And the scientists did not stop with a classic 'proof of concept study' in which they tested the generality of the phenomenon by assessing both adults (Study 1) and children (Study 2), but they also explored this phenomenon systematically in adults and children, using visual attention (letter cancellation) and memory (digit span) tasks that have been employed in previous studies.
Figure 1: Overview of the study design (Edmonds. 2017).
"All participants completed the thirst and mood scale, followed by baseline cognitive tests. They were then offered either 25 ml, 300 ml, or no water and were encouraged to drink the full amount, which all of them did. After water consumption there was an interval of approximately 20 min, which is the interval commonly reported in the literature reviewed above, during which the participants spent time quietly. Following the interval, participants completed the second set of scales and cognitive tests." (Edmonds. 2016).
In all experiments, the subjects (3x32 adults, mean age of participants was 21.0 years in
114 each group (300 ml, SD = 2.5 years; 25 ml, SD = 3.6 years; no water, SD = 2.8 years in Study 1 | 60 children aged 7 to 10 years in Study 2) were offered either no water, 25 ml or 300 ml water to drink. In both studies, performance was assessed at baseline and 20 min after drinking (or no drink); on thirst and mood scales, letter cancellation and a digit span test.
Figure 2: Relative changes in cognitive performance (vs. baseline test) in all three conditions (Edmonds. 2016)
As you would expect, for both children and adults, a large drink (300 ml) was necessary to reduce thirst. What may surprise, you that even a small drink (25 ml) was sufficient to improve the subjects' visual attention (at least in the letter cancellation test).
Figure 3: Rel. change in thirst and mood in adults and kids according to treatment condition (Edmonds. 2016).
The scientists own analyses of their results highlight the following main study outcomes:
  • in adults, a large drink improved digit span, but there was no such effect in children, 
  • in children, but not adults, a small drink resulted in increased thirst ratings
  • both children and adults show dose-response effects of drinking on visual attention
The most important finding of the study at hand is thus probably that the subject's visual attention is enhanced by small amounts of fluid and appears not to be contingent on thirst reduction.
Don't waste your money on hydrogen-rich (H+) water. Its only scientifically verifiable effect is that it makes those people who sell it rich and those who fall for the scam poor | learn more.
What's the mechanism here? Well, even though the study at hand provides interesting insights into the practical applicability of water consumption on memory performance, but it does not really reveal the underlying mechanism.

In contrast to what the researchers expected, the effect was not consistently related to thirst reductions and most importantly, it appeared to differ for children and adults according to tasks. As the authors point out these "contrasting dose-response characteristics could imply cognitive enhancement by different mechanisms for these two domains" - further research with well-hydrated (and thus smart) scientists is, therefore, necessary.

Changes in the hemodynamic response in the brain would be a worthwhile starting point for such studies, for example. Links to mouth rinsing could be explored and plain water could and should be compared to flavored low-/no-energy drinks and energy-containing drinks like those of which previous studies have shown that they can increase cognitive performance even if they are not ingested, but (mouth-)rinsed (Sanders. 2012; Turner. 2014) | Comment!.
  • Edmonds, Caroline J., et al. "Dose-response effects of water supplementation on cognitive performance and mood in children and adults." Appetite 108 (2017): 464-470.
  • Sanders, Matthew A., et al. "The gargle effect rinsing the mouth with glucose enhances self-control." Psychological Science 23.12 (2012): 1470-1472.
  • Turner, Clare E., et al. "Carbohydrate in the mouth enhances activation of brain circuitry involved in motor performance and sensory perception." Appetite 80 (2014): 212-219.
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