We all know that water is good. After all, the rule of threes tells us that we last a mere 3 days without access to water.1 We’re told to drink 8 glasses of water every day, and we at DermLetter have also promoted proper hydration both for health and for making your skin look good. Today we look at two Skincare sages – and what they have to say.
Does drinking more water make your skin more hydrated?
Short answer: Extremely marginally in otherwise healthy people. Experiments have shown that drinking water, at best, plays a very small factor in hydration at the surface of the skin (called the stratum corneum).2
Source: According to Stephen Alain Ko, a cosmetic chemist, and blogger who did some digging of his own:
- While popularly cited as an incontrovertible fact, there are very few high-quality studies on this subject. (He found 6 studies of which 5 are experimental).
- The effect of drinking 1 to 2 liters more on the hydration of stratum corneum is marginal but still statistically significant. The change is more significant for people who previously drank less water.
- No difference in TEWL (transepidermal water loss – basically, how much moisture is lost from the skin through normal evaporation).
- Little to no difference in skin smoothness, skin elasticity. Some possible effects with mineral water.
- Hydration of the stratum corneum is affected by other factors like natural moisturizing factor (NMF), intercellular lipids, the structure of corneocytes.3
Conclusion: The benefit of overloading on the water is probably overstated, especially for people who are already relatively health-conscious and well hydrated. One factor that is still untested, however, is with people who are legitimately dehydrated, possibly on a semi-regular basis. It’s quite hard to tell if this would be a very small proportion of the population or a relatively common scenario, and whether they might benefit simply from hydrating adequately (not excessively). Proper clinical studies are extremely difficult to even construct with such constraints, given that even moderate dehydration would likely be deemed unsafe.4
So, does drinking more water improve your skin?
Short answer: If you’re dehydrated, yeah. If you’re healthy, not so much.
Source: We bring in an expert we’ve been to before – labmuffin aka Michelle.
- The 8 glasses a day (2 liters) advice is all over the Internet. This is more of a common-sense claim posing to be a scientific fact. “By the time you’re thirsty, you’re already dehydrated,” is a myth – most health authorities actually recommend drinking when thirsty. There are some important exceptions, such as when in a hot climate or exercising vigorously, or old age.5
- Very few studies – none with a control group – so the quality of the study is questionable. This is important as there are many variables like the humidity in the air on that day.
- The improvement is more drastic for people who typically drink little water.
- TEWL does not change.
For the longer answer, we’ll refer you to her post.
Conclusion: Similar findings; the main point being that proper hydration is important. If you are dehydrated, water will both help you function, and make your skin look better. If you are already hydrated, little to no effect can be seen. There are no in-depth studies on the benefit of water overloading for cosmetic reasons (or health reasons).
It seems clear that for people who are already adequately hydrated, there is little scientific evidence to support drinking even more water. The benefits are marginal at best, and quite likely non-existent. If you are healthy, under normal conditions (no vigorous exercise, no medical conditions, not exposed to extreme heat) you can simply drink when you are thirsty; no need to go overboard.
This, of course, assumes that you are in fact, well hydrated. That the subjects who saw the most improvement were people who typically drank little water adds weight to this. Good-looking skin is only one of the reasons to adequately hydrate – and in the big picture, probably the least important one. Water keeps your energy and brain function high, boosts mood, concentration, and keeps you from overeating as it provides satiety. It also keeps physical performance high. Your body is incredibly smart; give it some credit! When you are dehydrated, your body will know enough to retain most of the water you drink. You will sweat less, and urinate less. When you have adequate hydration, most of the extra water you drink will be followed by frequent trips to the washroom and excreted through urine.
One last note: Overhydration (hyponatremia) can be a thing under very unusual circumstances such as endurance sports like marathons or water drinking competition, but usually, it’s very difficult to drink water to the point of water poisoning. Dehydration, on the other hand, is far more common and can have serious consequences. The advice to drink more water will still apply to the vast majority of people.
1Which is mostly but not completely true; it depends heavily on the environment. Nonetheless, the gist of it is true – humans don’t last very long without constant access to fresh water.
3Which are likely much more important factors in skin hydration.
4As is true of most health and lifestyle-related advice, unfortunately, the people most likely to read or take that advice to heart probably least need it.
5It’s generally accepted that our sense of thirst decreases with age.