Principal mineral elements that animals require are listed in Table 50.1. Elements required in large amounts are called macronutrients; those required in only tiny amounts (generally less than 100 mg/day) are called micronutrients. Some micronutrients are required in such minute amounts that deficiencies are never observed, but they are nevertheless essential elements.
| Element | Source in human diet | Major functions |
|---|---|---|
| MACRONUTRIENTS | ||
| Calcium (Ca) | Dairy foods, eggs, green leafy vegetables, whole grains, legumes, nuts, meat | Found in bones and teeth; blood clotting; nerve and muscle action; enzyme activation |
| Chlorine (Cl) | Table salt (NaCl), meat, eggs, vegetables, dairy foods | Water balance; digestion (as HCl); principal negative ion in extracellular fluid |
| Magnesium (Mg) | Green vegetables, meat, whole grains, nuts, milk, legumes | Required by many enzymes; found in bones and teeth |
| Phosphorus (P) | Dairy, eggs, meat, whole grains, legumes, nuts | Component of nucleic acids, ATP, and phospholipids; bone formation; buffers; metabolism of sugars |
| Potassium (K) | Meat, whole grains, fruits, vegetables | Nerve and muscle action; protein synthesis; principal positive ion in cells |
| Sodium (Na) | Table salt, dairy foods, meat, eggs | Nerve and muscle action; water balance; principal positive ion in extracellular fluid |
| Sulfur (S) | Meat, eggs, dairy foods, nuts, legumes | Found in proteins and coenzymes; detoxification of harmful substances |
| MICRONUTRIENTS | ||
| Chromium (Cr) | Meat, dairy, whole grains, legumes, yeast | Glucose metabolism |
| Cobalt (Co) | Meat, tap water | Found in vitamin B12; formation of red blood cells |
| Copper (Cu) | Liver, meat, fish, shellfish, legumes, whole grains, nuts | Found in active site of many redox enzymes and electron carriers; production of hemoglobin; bone formation |
| Fluorine (F) | Most municipal water supplies | Found in teeth; helps prevent tooth decay |
| Iodine (I) | Fish, shellfish, iodized salt | Found in thyroid hormones |
| Iron (Fe) | Liver, meat, green vegetables, eggs, whole grains, legumes, nuts | Found in active sites of many redox enzymes and electron carriers, hemoglobin, and myoglobin |
| Manganese (Mn) | Organ meats, whole grains, legumes, nuts, tea, coffee | Activates many enzymes |
| Molybdenum (Mo) | Organ meats, dairy, whole grains, green vegetables, legumes | Found in some enzymes |
| Selenium (Se) | Meat, seafood, whole grains, eggs, milk, garlic | Fat metabolism |
| Zinc (Zn) | Liver, fish, shellfish, and many other foods | Found in some enzymes and some transcription factors; insulin physiology |
Calcium is an example of a macronutrient. It is the fifth most abundant element in the body; a 70-
*connect the concepts Many physiological processes are affected by Ca2+; therefore it is essential that the blood levels stay between 9 and 11 mg/100 mL. This is only 0.1 percent of the Ca2+ in the body. About 1 percent is intracellular and 99 percent is in the bones, thus it is a challenge to maintain tiny, but critical, blood levels in the face of such huge reservoirs. Hormonal regulation of blood calcium is discussed in Key Concept 40.4, and the cellular mechanisms are discussed in Key Concept 47.1.
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Iron is an example of a micronutrient. It is found throughout the body because it is the oxygen-
Activity 50.1 Mineral Elements Required by Animals
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