“Drinking lots of water gives me a better complexion.”
It is probably the universal “accepted truth”. The answer is yes, and no. Unless in extreme circumstances like severe dehydration and heat stroke, there is actually little to no research* to support the evidence that drinking plenty of water will directly cause your skin to be more moisturised than if you drank an average amount a day. When you constantly drink too much water, your kidneys will have difficulties getting rid of the excess water. The sodium (an important electrolyte) content of your blood becomes diluted. Hyponatremia can be a life-threatening process.
Of course, it is essential to drink adequate amounts of water for your body's survival and proper function, which does have an indirect consequence on your skin condition. Optimal water intake affects the blood circulation in the body and, ultimately, the amount of fluid, oxygen, and nutrients that nourish your skin. Water is also a strongly preferable alternative to caffeinated beverages, soft drinks, and bbt.
.
In TCM, Blood is Yin in nature, which embodies fluid, nourishing, moistening, substantial. In simple terms, when Yin and Yang do not balance, Yin-deficiency or Yang-excess occurs. Although prolonged lack of Yin will result in skin dehydration, Yin does not only equal blood (or water/fluids). It involves a complex mechanism to attain dewy complexion, which hardly includes drinking endless amounts of water. If you are with me long enough, "Everything in moderation" is my pet phrase.
Additionally, if your body does not absorb that huge amount of water, you'd just be running to the restroom more frequent than you'd like.
.
So, how much water should you drink in a day? Check the colour of your urine. If it is colourless, you won’t have to worry that you aren’t drinking enough.
If you suffer from chronic skin dryness (or skin problems like eczema and acne), it would be advisable to see a skin specialist to find out the cause of it rather than blindly gulping down bottles and bottles of water until you feel nauseous. If you are drinking water non-stop to lose weight, please stop it. See my previous post on Intermittent Fasting for weight loss.
Are you unnecessarily over-hydrated?
For your information, caffeine is mild diuretic. Interestingly, tea leaves contain 3.5% caffeine, while coffee beans 1.1–2.2%. But relatively hotter water is used for coffee brewing, which extracts more of the caffeine from the beans.
*Wolf R, Wolf D, Rudikoff D, Parish LC. Nutrition and water: drinking eight glasses of water a day ensures proper skin hydration-myth or reality? Clin Dermatol. 2010;28(4):380-3. doi:10.1016/j.clindermatol.2010.03.022