Water’s Balancing Act

Water’s Balancing Act

June 3, 2024

Joy Stepinski, MSN, RN-BC

I live by a river that winds through New Hampshire and Massachusetts. Especially during the summer months, the river has a certain rhythm. Ducks swim across its surface. Rising fish emerge with a small splash. Crew teams, kayakers, and canoers glide their boats forward with their oars. The water brings a sense of renewal when the river is calm and peaceful. Yet occasionally the river becomes quite low during drought, while at other times the water rises too high during an abundance of rain. When there is just enough water, the ecosystem stays in balance.

Our body is a lot like the earth’s waterways. We are dependent on water because it is vital for life. The etymology for the word “vital” is from Latin vitalis¸ which means “of or manifesting life.” The body experiences consequences if proper hydration is lacking. If too much, we can become overhydrated with negative effects of low sodium, confusion, seizures, or even death. More commonly, insufficient water intake leads to dehydration.

The body must maintain the proper balance between water intake and its elimination. Serum osmolality is a good indicator of this balance. Osmolality refers to the concentration of dissolved particles in a solution (blood), such as electrolytes like sodium [1]. With decreased water, osmolality increases. Water flows from inside the cell to the fluid outside (extracellular fluid) to compensate. Because of the shrinking cells, antidiuretic hormone is secreted by the pituitary gland so that the urinary system eliminates less water [2].

When the body requires more water, the sensation of thirst occurs. Detectors called osmoreceptors respond when fluid leaves the cell and other volume receptors are triggered when larger volume losses occur. Osmoreceptors are considered the first line of defense against dehydration. As a result, the hypothalamus stimulates thirst. These checks and balances are vital to the body. Unlike many beverages that add calories and cause dehydration, plain water hydrates the body. Approximately 64 ounces daily is recommended for adults and half a child’s weight in ounces for children.

References:

1.    Najem, O., Shah, M., Zubair, M., & De Jesus, O. (2024). Serum osmolality. StatPearls.

2.    Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Panel on Dietary Reference Intakes for Electrolytes, & Water. (2005). Dietary reference intakes for water, potassium, sodium, chloride, and sulfate. National Academies Press. https://nap.nationalacademies.org/catalog/10925/dietary-reference-intakes-for-water-potassium-sodium-chloride-and-sulfate