[Extracted from The Merck Manuals]
Minerals are necessary for the normal functioning of the body's cells. The body needs large quantities of calcium, chloride, magnesium, phosphate, potassium, and sodium. These minerals are called macrominerals. Bone, muscle, heart, and brain function depends on these minerals. The body needs small quantities of chromium, copper, fluoride, iodine, iron, manganese, molybdenum, selenium, and zinc. These minerals are called trace minerals. Except for chromium, all trace minerals are incorporated into enzymes or hormones required in body processes (metabolism). Chromium helps the body keep blood sugar levels normal. All trace minerals are harmful if too much is ingested.
Minerals are an essential part of a healthy diet. The recommended dietary allowance (RDA)—the amount most healthy people need each day to remain healthy—has been determined for most minerals. People who have a disorder may need more or less than this amount.
Consuming too little or too much of certain minerals can cause a nutritional disorder. People who eat a balanced diet containing a variety of foods are unlikely to develop a nutritional disorder or a major mineral deficiency, except for calcium, iodine, or iron deficiency. However, people who follow restrictive diets may not consume enough of a particular mineral (or vitamin). For example, vegetarians, including those who eat eggs and dairy products, are at risk of iron deficiency. Infants are more likely to develop deficiencies because they are growing rapidly (thus requiring large amounts of nutrients).
Consuming large amounts (megadoses) of mineral supplements without medical supervision may have harmful (toxic) effects.
Electrolytes
Some minerals—especially the macrominerals—are important as electrolytes. The body uses electrolytes to help regulate nerve and muscle function and to maintain acid-base balance and fluid balance.
To function normally, the body must keep fluid levels from varying too much in
the areas of the body that contain fluid (called compartments). The three main compartments are :
** Fluid within cells
** Fluid in the space around cells
** Blood
Electrolytes, particularly sodium, help the body maintain normal fluid levels in these compartments (called fluid balance), because how much fluid a compartment contains depends on the concentration of electrolytes in it. If the electrolyte concentration is high, fluid moves into that compartment. If the electrolyte concentration is low, fluid moves out of that compartment. To adjust fluid levels, the body can actively move electrolytes in or out of cells. Thus, having electrolytes in the right concentrations (called electrolyte balance) is important in maintaining fluid balance among the compartments.
The kidneys help maintain electrolyte concentrations by filtering electrolytes from blood, returning some electrolytes, and excreting any excess into the urine. Thus, the kidney help maintain a balance between daily consumption and excretion.
If the balance of electrolytes is disturbed, disorders can develop. An electrolyte imbalance can result from the following:
** Becoming dehydrated
** Taking certain drugs
** Having certain heart, kidney, or liver disorders
** Being given intravenous fluids or feedings in inappropriate amounts
Mineral
a) Calcium
Good Sources :
Milk and milk products, meat, fish eaten with the bones (such as sardines), eggs, fortified cereal products, beans, fruits, and vegetables
Main functions :
Required for the formation of bone and teeth, for blood clotting, for normal muscle function, for the normal functioning of many enzymes, and for normal heart rhythm
Recommended Dietary Allowance for adults :
1,000 milligrams (1,200 milligrams for people over 50 years)
Safe Upper Limit :
2,500 milligrams
b) Chloride
Good Sources :
Salt, beef, pork, sardines, cheese, green olives, corn bread, potato chips, sauerkraut, and processed or canned foods (usually as salt)
Main functions :
Involved in electrolyte balance
Recommended Dietary Allowance for adults :
1,000 milligrams
c) Chromium
Good Sources :
Liver, processed meats, whole-grain cereals, and nuts
Main functions :
Enables insulin to function (insulin controls blood sugar levels).
Helps in the processing (metabolism) and storage of carbohydrates, protein, and fat
Recommended Dietary Allowance for adults :
** 35 micrograms for men aged 50 and younger
** 25 micrograms for women aged 50 and younger
** 30 micrograms for men over 50
** 20 micrograms for women over 50
d) Copper
Good Sources :
Organ meats, shellfish, cocoa, mushrooms, nuts, dried legumes, dried fruits, peas, tomato products, and whole-grain cereals
Main functions :
Is a component of many enzymes that are necessary for energy production, for antioxidant action (antioxidants protect cells against damage due to reactive by-products of normal cell activity called free radicals), and for formation of the hormone epinephrine, red blood cells, bone, and connective tissue
Recommended Dietary Allowance for adults :
900 micrograms
Safe Upper Limit :
10,000 micrograms
e) Fluoride
Good Sources :
Seafood, tea, and fluoridated water
Main functions :
Required for the formation of bone and teeth
Recommended Dietary Allowance for adults :
3 milligrams for women
4 milligrams for men
Safe Upper Limit :
10 milligrams
f) Iodine
Good Sources :
Seafood, iodized salt, eggs, cheese, and drinking water (in amounts that vary by the iodine content of local soil)
Main functions :
Required for the formation of thyroid hormones
Recommended Dietary Allowance for adults :
150 micrograms
Safe Upper Limit :
1,100 micrograms
g) Iron
Good Sources :
Beef, poultry, fish, kidneys, and liver (these are heme iron)
Soybean flour, beans, molasses, spinach, clams, and fortified grains and cereals (these are non-heme iron - the body absorbs heme iron better than nonheme iron).
Main functions :
Required for the formation of many enzymes in the body. Is an important component of muscle cells and of hemoglobin, which enables red blood cells to carry oxygen and deliver it to the body's tissues
Recommended Dietary Allowance for adults :
** 8 milligrams for women over 50 and for men
** 18 milligrams for women aged 50 and younger (premenopause)
** 27 milligrams for pregnant women
** 9 milligrams for breastfeeding women
Safe Upper Limit : 45 milligrams
h) Magnesium
Good sources :
Leafy green vegetables, nuts, cereal grains, beans, and tomato paste
Main functions :
Required for the formation of bone and teeth, for normal nerve and muscle function, and for the activation of enzymes
Recommended Dietary Allowance for adults :
** 320 milligrams for women
** 420 milligrams for men
i) Manganese
Good Sources :
Whole-grain cereals, pineapple, nuts, tea, beans, and tomato paste
Main functions :
Required for the formation of bone and the formation and activation of certain enzymes
Recommended Dietary Allowance for adults :
** 2.3 milligrams for men
** 1.8 milligrams for women
Safe Upper Limit : 6 to 11 milligrams
j) Molybdenum
Good Sources :
Milk, legumes, whole-grain breads and cereals, and dark green vegetables
Main functions :
Required for metabolism of nitrogen, the activation of certain enzymes, and normal cell function. Helps break down sulfites (present in foods naturally and added as preservatives)
Recommended Dietary Allowance for adults :
45 micrograms
Safe Upper Limit :
1,100 to 2,000 micrograms
k) Phosphorus
Good Sources :
Dairy products, meat, poultry, fish, cereals, nuts, and legumes
Main functions :
Required for the formation of bone and teeth and for energy production. Used to form nucleic acids, including DNA (deoxyribonucleic acid)
Recommended Dietary Allowance for adults :
700 milligrams
Safe Upper Limit :
4,000 milligrams
l) Potassium
Good Sources :
Whole and skim milk, bananas, tomatoes, oranges, melons, potatoes, sweet potatoes, prunes, raisins, spinach, turnip greens, collard greens, kale, other green leafy vegetables, most peas and beans, and salt substitutes (potassium chloride)
Main functions :
Required for normal nerve and muscle function. Involved in electrolyte balance
Recommended Dietary Allowance for adults :
3.5 grams
m) Selenium
Good Sources :
Meats, seafood, nuts, and cereals (depending on the selenium content of soil where grains were grown). Acts as an antioxidant, with vitamin E
Main functions :
Required for thyroid gland function
Recommended Dietary Allowance for adults :
55 micrograms
Safe Upper Limit :
400 micrograms
n) Sodium
Good Sources :
Salt, beef, pork, sardines, cheese, green olives, corn bread, potato chips, sauerkraut, and processed or canned foods (usually as salt)
Main functions :
Required for normal nerve and muscle function. Helps the body maintain a normal electrolyte and fluid balance
Recommended Dietary Allowance for adults :
1,000 milligrams
Safe Upper Limit :
2,400 milligrams
o) Zinc
Good Sources :
Meat, liver, oysters, seafood, peanuts, fortified cereals, and whole grains (depending on the zinc content of soil where grains were grown)
Main functions :
Used to form many enzymes and insulin. Required for healthy skin, healing of wounds, and growth
Recommended Dietary Allowance for adults :
15 milligrams
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