Positive impact of dietary water on in vivo epidermal water physiology

Summary Background/purpose The importance of water in human physiology is well known, also for skin functionality. This study was conducted to assess the effects of dietary water on epidermal skin hydration in healthy females. Methods Thirty-four healthy females (mean 24.5 ± 6.34 years old) were selected and characterized according to their dietary daily habits, by a previously validated Food Frequency Questionnaire. For 1 month, these subjects were asked to add 2 L/day of water to their regular dietary habits. Measurements took place at day D0, D15, and D30, and involved general variables (body weight, blood pressure, Body Mass Index) and specific skin physiological variables in five anatomical sites (ventral forearm, anterior leg, dorsal hand, zygomatic area, and forehead) involving epidermal superficial and deep hydration, by capacitance and transepidermal water loss (TEWL). Results This water overload (2 L/day/30 days) did not change the blood volume or weight of the individuals. However, both superficial and deep skin hydration were clearly in those individuals that regularly consumed lees water per day. No significant effect was observed in the TEWL. Conclusions This study clearly suggests that dietary water intake seems to influence skin water content. Nevertheless further in vivo investigations involving other variables, such as biomechanical descriptors, should follow to look deeper into this aspect of skin physiology.