The first question we must answer is ‘why do we need water in the skin?’. Water is the main component of all body cells, and without it we would experience dehydration, which can be life-threatening when severe 4, 5. The outer layer of the skin, called the stratum corneum, forms the barrier protection between our body and the environment. To be an effective barrier, the skin needs water to transport essential substances to this top layer, while also giving it strength and pliability so that when pressure is applied, it can change shape and move with the body so that it does not become damaged. Research tells us that hydrated skin is stronger and a more effective barrier than dehydrated skin 1, 2, 4. To summarise, without water in our skin it would become brittle, and every movement, touch or stressor would damage it and we would not be protected any longer. Without an effective skin barrier, we would have skin disease, and in severe cases, become unwell or not survive!
The stratum corneum is influenced heavily by our environment: a dry environment (like we experience in Moranbah) tends to steal water from our skin making the outer layer prone to dehydration. Conversely, a humid environment (like Mackay or Airlie Beach) transfers water into our skin increasing the hydration of the outer layer, consequently plumping it up. The plumping occurs because the skin cells have the ability to increase up to 50% or more in size when saturated with water molecules. This is why your skin can look so healthy with a reduction in fine lines when you travel to humid climates from a dry climate, or why you look so fresh after a bath or shower 2, 8, 9. Photo by Anthony Tran on Unsplash
Skin hydration also helps skincare ingredients penetrate further and more effectively into the skin. This is why your skin therapist is always aiming to enhance your skin hydration, so that your skincare products have a greater capability to penetrate the skin and produce desirable results. It is also important to note at this point why we use a moisturiser. Moisturisers are placed on top of serums to occlude the skin, which reduces the amount of water that can escape the skin by trapping it in while also trapping in the serums to enhance their penetration 2, 6, 7. Photo by Anna Shvets from Pexels
Within the skin, the dermis (the second layer) is the main compartment for water storage in humans. The reason is because this section contains molecules called proteoglycans and glycosaminoglycans, including hyaluronic acid, which have the ability to bind to and hold large amounts of water. The stratum corneum holds much less water, however without enough water volume in this section the skin elasticity and surface texture are impacted, along with crucial biophysical processes which help the skin to function optimally 1, 10.
The Australian Dietary Guidelines state that the estimated daily water intake for males and females should be between 2.6L (10 cups) and 2.1L (8 cups) respectively. However, if the individual is in a hot climate, pregnant, has a high BMI or is sweating excessively through exercise, consumption should increase. Therefore, the exact volume of water we need to drink per day for optimal health is individually based, and an exact figure cannot be presented 3. As our bodies are designed to alert us when we need to consume water through the thirst reflex, the best advice may be if you feel thirsty, drink water until you don’t feel thirsty anymore 1. Photo by Wagner Soares from Pexels
Research into determining how much water we need to drink for skin health is few and far between, with a lot of the studies produced being low in quality. What we do know from research is that individuals who are dehydrated internally are likely to have skin dehydration, and therefore, an increase in water intake to meet the needs of the body enhances skin hydration. This is because with an increased intake, the body has the volume of water it needs to perform its essential functions and does not need to withhold it from the skin. As the individual gets closer to drinking enough water to hydrate the body, the hydration impacts of increased water intake within the skin are less noticeable 4, 5.
Studies have also identified that drinking increased volumes of water does not keep the skin hydrated in situations where water is escaping out from the surface of the skin, for example environmental water loss in hot dry environments and poor skin barrier function 5. Therefore, if your skin barrier is compromised, drinking extra water is not going to hydrate your skin. Rather you need to fix the skin barrier to keep the water in!
Research also indicates that there may not be a benefit to drinking higher volumes of water beyond the needs of our body. And ironically, there is no evidence to suggest that drinking 8 glasses of water per day is required to maintain optimal health 1.
To conclude, there is no evidence to suggest that a sharp increase in water intake throughout the day or over long periods of time can influence skin hydration if you are already drinking enough water to support your body. The only people who notice benefits are those who are internally dehydrated enough to impact the skin when water intake increases to meet the needs of the body (1, 5). So, the statement of you must drink 8 glasses of water a day for your skin to be hydrated and healthy’ is a myth! The correct statement may be ‘you must drink enough water to prevent yourself from being internally dehydrated, and maintain your skin barrier to keep your skin hydrated and healthy’. As to how much water you need to drink – this is entirely individual! Start with the Australian Dietary Guidelines and increase your intake based on your personal circumstances if required, and make sure you drink when you are thirsty until you no longer feel thirsty! Photo by Daria Shevtsova from Pexels
- Wolf, R., Wolf, D., Rudikoff, D., & Parish, L. C. (2010). Nutrition and water: drinking eight glasses of water a day ensures proper skin hydration – myth or reality? Clinics in Dermatology, 28(), 380-383. http://dx.doi.org/10.1016/j.clindermatol.2010.03.022
- Mojumdar, E. H., Pham, Q. D., Topgaard, D., & Sparr, E. (2017). Skin hydration: interplay between molecular dynamics, structure and water uptake in the stratum corneum. Scientific Reports, 7,1-13 . 10.1038/s41598-017-15921-5
- National Health and Medical Research Council. (2013). Australian Dietary Guidelines.https://www.eatforhealth.gov.au/sites/default/files/files/the_guidelines/n55_australian_dietary_guidelines.pdf
- Palma, L., Marques, L. T., Bujan, J., & Rodrigues, L. M. (2015). Dietary water affects human skin hydration and biomechanics. Clinical, Cosmetic and Investigational Dermatology, 8, 413-421.http://dx.doi.org/10.2147/CCID.S86822
- Akdeniz, M., Tomova-Simitchieva, T., Dobos, G., Blume-Peytavi, U., & Kottner, J. (2018). Does dietary fluid intake affect skin hydration in healthy humans? A systematic literature review. Skin Research and Technology, 24(3),459-465.
- Tan, G. T., Xu, P., Lawson, L.B., He, J., Freytag, L. C., Clements, J. D., & John, V. T. (2009). Hydration effects on skin microstructure as probed by high-resolution cryo-scanning electron microscopy and mechanistic implications to enhanced transcutaneous delivery of biomacromolecules. Journal of Pharmaceutical Sciences, 99(2), 730-740. https://doi-org/10.1002/jps.21863
- Wiedersberg, S., Leopold, C. S., & Guy, R. H. (2009). Effects of various vehicles on skin hydration in vivo. Skin Pharmacology and Physiology, 22(3), 120-130. 10.1159/000189801
- Cravello, B., & Ferri, A. (2007). Relationships between skin properties and environmental parameters. Skin Research and Technology, 14(2), 180-186. https://doi-org/10.1111/j.1600-0846.2007.00275.x
- Bari, D. S., Aldosky, H. Y. Y., Tronstad, C, Kalvoy, H., & Martinsen, O. G. (2018). Influence of relative humidity on electrodermal levels and responses. Skin Pharmacology and Physiology, 31(6), 298-307. 10.1159/000492275
- Papakonstantinou, E., Roth, M., & Karakiulakis, G. (2012). Hyaluronic acid: A key molecule in skin aging. Dermato-endocrinology, 4(3), 253-258. 10.4161/derm.21923