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.

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