Water: An Overview
Your body is 60% water.
Your brain and heart are 73% water.
Your lungs are 83% water.
Your muscles are 79% water.
Your blood is 90% water.
Water is the most important nutrient on planet earth. It’s a simple molecule made of 3 atoms - 2 hydrogen and 1 oxygen - that plays a profound role in every cell in the body. Water is used to generate energy, transport nutrients to cells, deliver oxygen, eliminate cellular toxins and waste, lubricate joints, maintain healthy blood pressure, assist in proper digestion, and more.
The body uses large amounts of water on a daily basis. It is estimated that an average of 1 liter (almost 34 ounces) is lost through breathing, sweating, and bowel movements, and the average adult urine output is around 1.5 liters (almost 52 ounces) per day. Large water output requires large input to maintain overall health and well-being.
How Much Water Do You Need?
The Institute of Medicine recommends the following “Adequate Intake” to prevent the harmful effects of dehydration [1]:
- 3.3 liters (125 ounces) for males
- 2.3 liters (91 ounces) for females
While these intakes can help prevent dehydration, your hydration needs are personal based on height, weight, activity level, and even climate. For example, living in warmer, more humid climates or at elevation increases hydration needs due to increased fluid loss. Your level of physical exercise is another important factor for water intake. Vigorous exercise in a hot, humid climate can lead to a sweat loss of over 100 ounces per hour [2]. You have to rehydrate accordingly.
A simple equation to find your optimal water intake range:
Water need: 1/2-1 ounces X pound of body weight
Example: If you weigh 150 pounds, drink 75-150 ounces per day
Remember, if you live in a warmer climate, have a physically strenuous job, sweat more, or exercise intensely, you should shoot for the upper range of this formula.
Another factor that can impact your hydration is your stress levels.
Signs of Dehydration
Thirst
Fatigue
Headache
Dizziness
Weakness
Lightheadedness
Muscle cramps
Dark urine
Sunken eyes
Low blood pressure
Dry Skin
Heart palpitations
Stress and Dehydration: Why Hydration is Key Under Stress
When under stress, your body releases hormones that increase your heart rate and respiration rate. These physical changes increase the need for water. That said, it is believed that thirst signals from the brain may be down-regulated under stress. This means you don’t feel thirsty when you’re stressed. And this is a major problem. [4]
This can create a catch-22. Under stress, you need more water but consume less. This state of dehydration compounds stress in the body. A simple loss of 16 ounces of water can increase the body’s main stress hormone, cortisol. In fact, in animal studies, dehydration DOUBLED cortisol [5]!
While the body maintains total body water (TBW) within 0.22% [4], researchers have found that the thirst signal is not strongly activated until 1-2% of total body water (TBW) is lost. At just a 2% TBW loss, cognitive performance and psychomotor function start to decline [6]. This level of water loss also results in headaches, fatigue, impaired memory, and mood changes.
This all happens right around the level where most individuals begin to feel thirsty. That should serve as a good reminder that you need to be drinking water BEFORE you feel thirsty. If you are thirsty, your body is already dehydrated.
The Bottom Line
If you are under stress, you need to be extra diligent about consuming enough water. Drinking water while under stress can help your body become more resilient to symptoms of stress - headache, fatigue, nausea, anxiety, and depression. Research published in the Journal of Neuroscience reported that hydration status directly impacts how well the body handles stress, both mentally and emotionally [8]. Staying hydrated may also help improve the production of your feel-good neurotransmitter, serotonin, which also helps combat stress [5].
Last but not least, micronutrients also play a role in hydration. Zinc helps assist with water absorption at the gut lining [8], and electrolytes such as magnesium, potassium, and sodium regulate fluid balance across cellular membranes. It is important to ensure your micronutrient needs are met to support whole-body hydration.
Sources
- Gandy, Joan. Water intake: validity of population assessment and recommendations. Eur J Nutr. 2015; 54(Suppl 2): 11–16. doi: 10.1007/s00394-015-0944-8
- Murray, Bob. Hydration and physical performance. J Am Coll Nutr. 2007 Oct;26(5 Suppl):542S-548S. doi: 10.1080/07315724.2007.10719656.
- Kory Taylor; Elizabeth B. Jones. Adult Dehydration. https://www.ncbi.nlm.nih.gov/books/NBK555956/
- Lawrence E. Armstrong, Stavros A. Kavouras. Thirst and Drinking Paradigms: Evolution from Single Factor Effects to Brainwide Dynamic Networks. Nutrients. 2019 Dec; 11(12): 2864. doi: 10.3390/nu11122864
- N. K. Popova, L. N. Ivanova, T. G. Amstislavskaya. Brain Serotonin Metabolism during Water Deprivation and Hydration in Rats. Neuroscience and Behavioral Physiology volume 31, pages327–332 (2001)
- Ann C Grandjean, Nicole R Grandjean. Dehydration and cognitive performance. J Am Coll Nutr. 2007 Oct;26(5 Suppl):549S-554S. doi: 10.1080/07315724.2007.10719657.
- Eric G. Krause, Annette D. de Kloet, et al. Hydration State Controls Stress Responsiveness and Social Behavior. J Neurosci. 2011 Apr 6; 31(14): 5470–5476. doi: 10.1523/JNEUROSCI.6078-10.2011
- Sonja Skrovanek, Katherine DiGuilio, et al. Zinc and gastrointestinal disease. World J Gastrointest Pathophysiol. 2014 Nov 15; 5(4): 496–513. doi: 10.4291/wjgp.v5.i4.496