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Weird Science: Salt is Essential to Life

NGSS Disciplinary Core Ideas:

Table salt, sodium chloride (NaCl), is a naturally occurring mineral essential for animal life. Salt is one of the most widely used and oldest forms of food seasoning (SF Fig. 2.2). Saltiness is one of the five basic human tastes in addition to sweetness, sourness, bitterness, and umami (a savory, meaty taste, such as that of cooked mushrooms, cheese, or soy sauce). As salt dissolves in a solution or on food, it breaks into its component ions: sodium and chloride (Na+ and Cl-, respectively). The salty flavor primarily comes from the sodium ions.

<p><strong>SF Fig. 2.2.</strong> (<strong>A</strong>) Table salt in a salt shaker.</p><br />
<p><strong>SF Fig. 2.2.&nbsp;</strong>(<strong>B</strong>) Individual sodium chloride (NaCl) table salt crystal as viewed under a powerful scanning electron microscope.</p><br />

Salt plays a crucial role in maintaining human health. It is the main source of sodium and chloride ions in the human diet. Sodium is essential for nerve and muscle function and is involved in the regulation of fluids in the body.  Sodium also plays a role in the body’s control of blood pressure and volume. Although sodium is essential, people who consume too much sodium may have hypertension or high blood pressure, a condition that can lead to serious illnesses such as heart disease, kidney disease, and stroke.

 

Chloride ions serve as important electrolytes by regulating blood pH and pressure. Electrolytes are compounds, often salts, which dissociate into their ionic components in solvents like water. Chloride is also a crucial component in the production of stomach acid (HCl). Humans excrete salt when sweating and must replenish these lost sodium and chloride ions through their diet.

 

All animals require some salt to survive. Humans consume foods that naturally contain salt (e.g., meat and seafood) or add salt as a seasoning. However, some terrestrial animals have diets deficient in salt. These animals must seek supplemental salt sources. Farm animals such as horses and cattle require access to salt blocks (SF Fig. 2.3 A). Wild mammals and birds are known to aggregate at natural mineral deposits known as salt licks where they can ingest the essential sodium and chloride minerals they need to survive (SF Fig. 2.3 B).

<p><strong>SF Fig. 2.3.</strong> (<strong>A</strong>) A cow and her calf licking a cube of salt.</p><br />
<p><strong>SF Fig. 2.3.&nbsp;</strong>(<strong>B</strong>) A wild herd of Indian bison, or gaur, at a natural salt lick, Rajiv Gandhi National Park, India.</p><br />


 

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Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.