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“Drink more water to clear up your skin” is popular common sense advice, but is there any science to back it up? Surprisingly, there wasn’t evidence that drinking more water could improve your skin until very recently! Let’s have a look at what the science says…
There’s nothing to back up drinking 2 litres of water a day
First off, some mythbusting. You’ve probably heard the recommendation that you need to drink 2 litres (or 8 glasses) of water a day – it turns out that it’s not actually backed up by any science! On average, you lose about 2.5 L of water a day, but you also consume about 1 L of water in food and produce 300 mL of water through metabolism, so you actually only need to drink about 1.2 L of water to replace what you’ve got. Most health authorities recommend drinking when you’re thirsty (“when you’re thirsty it’s already too late” is another myth!), unless you’re in a very hot climate or you’re exercising very hard.
Studies on drinking more water and skin
I could only find 4 peer-reviewed studies on the effect of drinking more water on the skin, and unfortunately none of them have a control group (a group of people who didn’t drink extra water during that time). This is really annoying, because you can’t tell if any skin changes are due to something else entirely, like if it rained a lot during the study period and the humid weather caused skin hydration. For these reasons, none of these study results should be taken as definitive.
- 80 people (about half-half male and female, aged 50-74 years) drank an extra 1 litre of Evian water a day for 6 weeks, on top of their normal diet.
- They found that forearm skin hydration increased by 14%, which is a similar effect to using a moisturiser. Transepidermal water loss (TEWL: evaporation of water from the skin) also increased.
- There were improvements in facial skin roughness, dryness and elasticity, though it wasn’t very noticeable for the participants.
- 86 people (about 2.5 times more women than men, average age 31.8 years) drank 2.25 L of either mineral water or tap water a day for 4 weeks on top of their normal diet.
- The effects depended on the type of water used: mineral water led to decreased skin density and slightly increased skin thickness, while tap water gave the opposite result. pH decreased for the tap water group but stayed the same for mineral water.
- Skin roughness and wrinkliness didn’t decrease overall, but the skin of some individuals in both groups became smoother
- 34 women (average age 24.5) drank an extra 2 L of bottled water on top of their normal diet for 30 days
- Superficial and deep hydration in the skin improved in the people who normally drank less water (average 792 mL a day), but TEWL did not
- There were very few significant changes in people who normally drank more water (average 1260 mL a day)
- 49 women (average age 24.5) drank an extra 2 L of water on top of their normal diet for 30 days
- Women who normally drank more water (more than around 1 L) experienced less skin changes than those who normally drank less
- Superficial and deep hydration in the skin improved, while epidermal barrier function and TEWL did not
- Measurements of the skin’s “envelope function” (its elasticity, “bounciness” etc.) had mixed results
What can we tell from these studies?
There isn’t any solid evidence of what extra water can do, but we can pick out some general trends from these studies:
- Drinking an extra 2 L of water a day can have noticeable effects on the amount of water in your skin, especially if you don’t drink much water normally
- If you’re lucky, it’ll make your skin noticeably smoother, but it doesn’t seem like a common result
If you don’t drink much water normally, upping your water intake could be worth trying for smoother skin. It’s cheap, and adequate hydration has other benefits too like improving energy levels, brain function and helping with weight loss. However, at the moment, the evidence that drinking more water works for improving everyone’s skin (or even the majority of people’s skin!) is far from clear-cut.
R Wolf, D Wolf, D Rudikoff and LC Parish, Nutrition and water: drinking eight glasses of water a day ensures proper skin hydration-myth or reality? Clin Dermatol 2010, 28, 380-383
S Mac-Mary, P Creidi, D Marsaut, C Courderot-Masuyer, V Cochet, T Gharbi, D Guidicelli-Arranz, F Tondu and P Humbert, Assessment of effects of an additional dietary natural mineral water uptake on skin hydration in healthy subjects by dynamic barrier function measurements and clinic scoring, Skin Res Technol 2006, 12, 199-205
S Williams, N Krueger, M Davids, D Kraus and M Kerscher, Effect of fluid intake on skin physiology: distinct differences between drinking mineral water and tap water, Int J Cosmet Sci 2007, 29, 131-138
ML Palma, L Tavares, JW Fluhr, MJ Bujan and LM Rodrigues, Positive impact of dietary water on in vivo epidermal water physiology, Skin Res Technol 2015, 21, 413-418
L Palma, L Tavares Marques, J Bujan and LM Rodrigues, Dietary water affects human skin hydration and biomechanics (open access), Clin Cosmet Investig Dermatol 2015, 8, 413-421