4.11: Minerals

The human body is mostly carbon, hydrogen, oxygen, and nitrogen. These four elements make up about 99% of the atoms in the body. We get enough carbon, hydrogen, and oxygen by breathing and by meeting energy and water needs. We get nitrogen (and sulfur) as a part of the protein we eat. We need cobalt only because we need vitamin B₁₂ (cobalt is a part of B₁₂). Thus, specific dietary requirements aren’t given for these elements because we automatically get them by meeting other requirements.

Fifteen minerals are known to be essential in our diet (Table 4-1). Some are listed in Appendix A-5 along with some of their functions, food sources, and symptoms of deficiency and toxicity.

The body protects itself from accumulating too much of a mineral by getting rid of excesses in the urine or by controlling the amount absorbed in the intestine in the first place. Sodium is easily absorbed, and excesses are excreted in the urine. Water is needed to get rid of sodium, so we need more water if we ingest excess sodium. In other words, if we eat a lot of salty food (table salt is sodium chloride), we feel thirsty, drink more, and urinate more. Pubs that sell beer don’t lose money on free bowls of salty nuts, pretzels, or tortilla chips!

In contrast, excess iron can be toxic and isn’t excreted in the urine. So the intestine acts as a gatekeeper and doesn’t let much in. But it can increase absorption a bit when a person’s need goes up, e.g., during pregnancy.