Download Summary for Chapter 12 – Water and the Major Minerals

Summary for Chapter 12 – Water and the Major Minerals
Water makes up about 60 percent of the adult body’s weight. It assists with the transport of nutrients and waste
products throughout the body, participates in chemical reactions, acts as a solvent, serves as a shock absorber, and
regulates body temperature. To maintain water balance, intake from liquids, foods, and metabolism must equal
losses from the kidneys, skin, lungs, and GI tract. The amount and type of water a person drinks may have positive or
negative health effects.
In response to low blood volume, low blood pressure, or highly concentrated body fluids, these actions combine to
effectively restore homeostasis:
• ADH retains water.
• Renin retains sodium.
• Angiotensin constricts blood vessels.
• Aldosterone retains sodium.
These actions can maintain water balance only if a person drinks enough water.
Electrolytes (charged minerals) in the fluids help distribute the fluids inside and outside the cells, thus ensuring the
appropriate water balance and acid-base balance to support all life processes. Excessive losses of fluids and
electrolytes upset these balances, and the kidneys play a key role in restoring homeostasis.
The major minerals are found in larger quantities in the body, whereas the trace minerals occur in smaller amounts.
Minerals are inorganic elements that retain their chemical identities. They usually receive special handling and
regulation in the body, and they may bind with other substances or interact with other minerals, thus limiting their
absorption.
Sodium is the main cation outside cells and one of the primary electrolytes responsible for maintaining fluid balance.
Dietary deficiency is rare, and excesses may aggravate hypertension in some people. For this reason, health
professionals advise a diet moderate in salt and sodium. The accompanying table summarizes information about
sodium.
Sodium
Adequate Intake (AI)
Adults: 1500 mg/day (19–50 yr)
1300 mg/day (51–70 yr)
1200 mg/day (>70 yr)
Upper Level
Adults: 2300 mg/day
Chief Functions in the Body
Maintains normal fluid and electrolyte balance; assists in nerve impulse transmission and muscle contraction
Deficiency Symptoms
Muscle cramps, mental apathy, loss of appetite
Toxicity Symptoms
Edema, acute hypertension
Significant Sources
Table salt, soy sauce; moderate amounts in meats, milks, breads, and vegetables; large amounts in processed foods
Chloride is the major anion outside cells, and it associates closely with sodium. In addition to its role in fluid balance,
chloride is part of the stomach’s hydrochloric acid. The accompanying table summarizes information on chloride.
Chloride
Adequate Intake (AI)
Adults: 2300 mg/day (19–50 yr)
2000 mg/day (51—70 yr)
1800 mg/day (>70 yr)
Upper Level
Adults: 3600 mg/day
Chief Functions in the Body
Maintains normal fluid and electrolyte balance; part of hydrochloric acid found in the stomach, necessary for proper digestion
Deficiency Symptoms
Do not occur under normal circumstances
Toxicity Symptoms
Vomiting
Significant Sources
Table salt, soy sauce; moderate amounts in meats, milks, eggs; large amounts in processed foods
Potassium, like sodium and chloride, is an electrolyte that plays an important role in maintaining fluid balance.
Potassium is the primary cation inside cells; fresh foods, notably fruits and vegetables, are its best sources. The table
below summarizes facts about potassium.
Potassium
Adequate Intake (AI)
Adults: 4700 mg/day
Chief Functions in the Body
Maintains normal fluid and electrolyte balance; facilitates many reactions; supports cell integrity; assists in nerve impulse transmission and
muscle contractions
Deficiency Symptomsa
Irregular heatbeat, muscular weakness, glucose intolerance
Toxicity Symptoms
Muscular weakness; vomiting; if given into a vein, can stop the heart
Significant Sources
All whole foods: meats, milks, fruits, vegetables, grains, legumes
Most of the body’s calcium is in the bones where it provides a rigid structure and a reservoir of calcium for the blood.
Blood calcium participates in muscle contraction, blood clotting, and nerve impulses, and it is closely regulated by a
system of hormones and vitamin D. Calcium is found predominantly in milk and milk products, but some other foods
including certain vegetables and tofu also provide calcium. Even when calcium intake is inadequate, blood calcium
remains normal, but at the expense of bone loss, which can lead to osteoporosis. Calcium’s roles, deficiency
symptoms, and food sources are summarized on the next page.
Calcium
Adequate Intake (AI)
Adults: 1000 mg/day (19–50 yr)
1200 mg/day (>51 yr)
Upper Level
Adults: 2500 mg/day
Chief Functions in the Body
Mineralization of bones and teeth; also involved in muscle contraction and relaxation, nerve functioning, blood clotting, blood pressure
Deficiency Symptoms
Stunted growth in children; bone loss (osteoporosis) in adults
Toxicity Symptoms
Constipation; increased risk of urinary stone formation and kidney dysfunction; interference with absorption of other minerals
Significant Sources
Milk and milk products, small fish (with bones), calcium-set tofu, greens (bok choy, broccoli, chard, kale), legumes
Phosphorus accompanies calcium both in the crystals of bone and in many foods such as milk. Phosphorus is also
important in energy metabolism, as part of phospholipids, and as part of the genetic materials DNA and RNA. The
summary table on the next page lists functions of, and other information about, phosphorus.
Phosphorus
RDA
Adults: 700 mg/day
Upper Level
Adults (19–70 yr): 4000 mg/day
Chief Functions in the Body
Mineralization of bones and teeth; part of every cell; important in genetic material, part of phospholipids, used in energy transfer and in buffer
systems that maintain acid-base balance
Deficiency Symptoms
Muscular weakness, bone pain
Toxicity Symptoms
Calcification of nonskeletal tissues, particularly the kidneys
Significant Sources
All animal tissues (meat, fish, poultry, eggs, milk)
Like calcium and phosphorus, magnesium supports bone mineralization. Magnesium is also involved in numerous
enzyme systems and in heart function. It is found abundantly in legumes and leafy green vegetables and, in some
areas, in water. The table below offers a summary.
Magnesium
RDA
Men (19–30 yr): 400 mg/day
Women (19–30 yr): 310 mg/day
Upper Level
Adults: 350 mg nonfood magnesium/day
Chief Functions in the Body
Bone mineralization, building of protein, enzyme action, normal muscle contraction, nerve impulse transmission, maintenance of teeth, and
functioning of immune system
Deficiency Symptoms
Weakness; confusion; if extreme, convulsions, bizarre muscle movements (especially of eye and face muscles), hallucinations, and difficulty
in swallowing; in children, growth failure
Toxicity Symptoms
From nonfood sources only; diarrhea, alkalosis, dehydration
Significant Sources
Nuts, legumes, whole grains, dark green vegetables, seafood, chocolate, cocoa
Like the other nutrients, minerals’ actions are coordinated to get the body’s work done. The major minerals, especially
sodium, chloride, and potassium, influence the body’s fluid balance; whenever an anion moves, a cation moves—
always maintaining homeostasis. Sodium, chloride, potassium, calcium, and magnesium are key members of the
team of nutrients that direct nerve impulse transmission and muscle contraction. They are also the primary nutrients
involved in regulating blood pressure. Phosphorus and magnesium participate in many reactions involving glucose,
fatty acids, amino acids, and the vitamins. Calcium, phosphorus, and magnesium combine to form the structure of the
bones and teeth. Each major mineral also plays other specific roles in the body.