Hydration: Why It’s So Important

This week we will examine how our body regulates and balances our fluids and hydration. All cells, organs and tissues in our bodies use water and water makes up around 55-60% of who we are. 

• Brain and muscle tissue are about 75% water

• Blood is about 83% water

• Bones are about 22% water

Fluid or water in our bodies has many important jobs from regulating body temperature, keeping joints lubricated, starting chemical reactions, and delivering nutrients to our cells. Being well hydrated also improves cognition, mood, and sleep quality. Fluid balance is the relationship between fluid coming in and fluid going out and there are many factors that can affect fluid input and output. 

Here are some ways we take in fluid:

• Food

• Drinks

• Absorbed through the skin (though it stays in the skin and does not get absorbed into the rest of the body)

• and we also “create” water through metabolic reactions (in very small amounts)

Here are some ways we lose fluid:

• Sweating

• Breathing

• Excretion (urine and feces)

• Vomiting (if we are ill)

• Tears

• Saliva 

The question many of us find ourselves asking is “how much fluid do I need?” The simple answer is; it depends.

Most adults need around 3 liters of fluid each day. Now you might recall in the previous article, general recommendation is 64 ounces of water a day. If you enjoy math you may notice a discrepancy. On average we consume 1 liter of fluid (4 cups) or 32 ounces from our food. This means 2 liters (8 cups) or 64 ounces come from drinking water. Our body regulates our thirst so that we can take in more fluid when we need it. We get thirstier when: 

• it’s warmer;

• we have eaten something salty; 

• the air is dry;

• we have been sweating; and/or

• we have consumed alcohol

Now for the flip side. Our daily fluid intake balances our daily fluid loss. On average our daily fluid loss is 1500 mL or 50 fluid ounces. Breathing and skin evaporation generally make up for 800 mL, 100 mL through feces, 500 mL through urine, and 100 mL through sweating without exercise (Scott-Dixon, Berardi, St. Pierre, Kollias, DePutter, 2019, pg. 203)

Dehydration is simply not having enough water in the body for daily function. We can, to some degree, control the effect of dehydration. However, the body is unable to adapt to dehydration, we cannot “train” to become better at being dehydrated. It isn’t until we have lost 1-2% of our body water that we begin to feel thirsty. At this point, our performance has started to suffer, hence the saying “if you’re thirsty you are already dehydrated”. Some symptoms of dehydration include:

• headache

• nausea

• fatigue

• dizziness

• and rapid heart rate

Dehydration effects physical performance.  It can cause a reduction in blood volume, decreased blood flow to the skin, decreased sweat rate, decreased heat dissipation, and increased core temperature. Athletes/exercisers should be careful to drink regularly and anticipate needing more fluid then you expect. 

It is important to build hydration habits. This will help provide a foundation for fluid balance. Instead of focusing on specific amounts try instead focusing on behaviors that promote positive hydration habits. For example, have a glass of water with every meal or put a glass near the bathroom sink and when you visit the bathroom fill up the glass and drink it.