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11
WATER AND THE MAJOR MINERALS
CHAPTER OVERVIEW
Part three of the text, “The Vitamins and Minerals,” continues with a discussion of water and the
major minerals. First, water is discussed with respect to its unique chemical properties and roles in the
body. Next, the major minerals, sodium, potassium, chloride, calcium, phosphorus, magnesium, and sulfur,
are reviewed. The absorption, transport, and excretion of each mineral is introduced to the learner, as are
the functions, food sources, recommended intakes, and deficiency/toxicity concerns. The Expert Opinion
discusses “Assessing the Risks and Benefits of Estrogen Replacement Therapy.” Finally, the Nutrition
Perspective reviews “Minerals and Hypertension,” including the DASH diet.
CHAPTER OBJECTIVES
By the end of this chapter, the student should be able to:
1.
State the key roles of water in the body.
2.
Discuss the daily water needs of humans.
3.
List the primary functions, recommended intakes, and deficiency/toxicity issues for each
macromineral.
4.
Understand how each macromineral is absorbed, transported, and excreted.
5.
Select foods that are concentrated sources of each mineral.
6.
Understand the dietary factors that affect blood pressure.
LECTURE NOTES
I.
Water
A. Structure
B. Water in the Body – Intracellular and Extracellular Fluid
1. Amount of water in each compartment primarily controlled by electrolyte concentration
in each
a. Water is attracted to ions.
2. Osmosis
a. Passage of solvent through a semipermeable membrane.
b. Osmotic Pressure
3. Water and Ions in the Body – a Balancing Act
a. Cells maintain their intracellular water volume and electrolyte concentrations within
narrow ranges.
b. Mechanisms
c. Both ion concentrations and charges are balanced.
C. Functions of Water
1. Solvent
2. Water Contributes to Temperature Regulation
a. High heat capacity (specific heat)
i. Molecules are strongly attracted to each other.
As amount of heat energy within body increases, water in surrounding tissues
absorbs excess heat energy
c. Perspiration secreted evaporates through skin pores
d. Fever increases energy needs
3. Water Helps Remove Waste Products
a. Most waste products leave via urine
b. Typical urine volume is 1-2 liters daily
4. Other Functions of Water
a. Joint lubricant.
b. Basis of saliva, bile, and amniotic fluid
D. Water Needs
1. Adults: 1 mL/kcal expended
2. Sources of Water
a. Liquids
i. Fruit Juices
ii. Coffee
iii. Tea
iv. Soft Drinks
v. Water
b. Foods
i. Fruits
ii. Vegetables
c. Metabolism
i. About 350 mL/day
3. Insensible Water Losses
4. Water Deficiency
a. Thirst
i. Signal to brain…drink!
ii. Not always reliable
b. Obtain weight before and after physical activity
i. Two cups of water = 0.5 pounds
ii. Replace about 75% of weight lost
c. Symptoms
i. Fever
ii. Vomiting
iii. Diarrhea
iv. Increased Perspiration
5. What if the Thirst Message Is Ignored?
a. Body registers an increase in blood concentration to increase fluid conservation
i. Kidney
b.

ii.
Pituitary gland releases ADH
 Kidney reduces urine flow to conserve water
Blood Pressure

BP decreases

Kidneys release renin

Renin activates angiotensinogen to form angiotensin I

Angiotensin I converted to angiotensin II

Triggers adrenal glands to release aldosterone

II.
Signals kidneys to retain more sodium and chloride…consequently,
more water retained
b. Dehydration will result without fluid replacement of losses
E. Water in Foods
F. Water Safety: How Safe Is the Water We Consume?
1. Most individuals in the US enjoy safe water
2. Some rural communities have polluted water from agricultural runoff
3. Chlorine and ammonia are added to water to kill bacteria
a. Techniques for removing chlorine from water
G. Water Toxicity
1. Usually occurs with insufficient electrolyte consumption
2. Very few people are at risk
3. Symptoms
a. Headache
b. Blurred vision
c. Cramps
d. Convulsions
e. (Ultimately) Death
Minerals
A. Definition of Major Mineral Versus Trace Mineral
1. Major Mineral
a. 100 mg or more/day
2. Trace Mineral
a. Less than 100 mg/day
B. Absorption, Transport, and Excretion of Minerals
1. Factors that influence absorption
a. Physiological need for the mineral
b. Bioavailability
i. Factors that influence

2.
3.
Size
 Charge
c. Fiber
i. Phytic acid
d. Oxalic Acid
Transport
a. Free
b. Bound to protein
Excretion
a. Primarily in urine
III.
b. Feces
C. Functions of Minerals
1. Diverse
2. Play important roles in maintaining body functions
D. Food Sources of Minerals
1. Both plants and animals
2. Animal sources are more easily absorbed, in general
3. More refined plant foods are lower in mineral content, in general
4. Only iron is enriched into grains…emphasize consumption of whole grains
E. North Americans at Risk for Mineral Deficiencies
1. Major minerals
a. Calcium
2. Trace Minerals
a. Iron, Zinc
F. Toxicity of Minerals
1. Trace minerals most likely to pose problems, especially with supplement usage
2. UL should not be exceeded except under the guidance of a physician
Sodium (Na)
A. Absorption, Transport, Storage, and Excretion of Sodium
1. Absorption
a. 95% of ingested is absorbed
b. Easily absorbed from stomach, small intestine, and colon
2. Storage
a. Some in bones
3. Excretion
a. Blood filtered by kidney to maintain concentration of blood
b. Excretion maintained by mechanism involving glomerular filtration, the renninangiotensin system, catecholamines, and blood pressure
c. Three routes of excretion
i. Kidneys (major route)
ii. skin
iii. GI tract
B. Functions of Sodium
1. Major cation in extracellular fluid
2. Key factor in retaining body fluids
3. Muscle contraction
4. Nerve impulse transmission
5. Participates in absorption of other nutrients (glucose)
C. Sodium Deficiency
1. Results from a low sodium diet coupled with excessive perspiration, persistent vomiting,
or diarrhea
2. Results in
a. Muscle cramps
b. Nausea
c. Vomiting
IV.
d. Dizziness
e. Shock and coma (late stages)
3. Unlikely to happen
D. Sodium in Foods
1. Primarily added during processing or during cooking/consumption
2. Nutrient-dense sources
a. Table salt
b. Processed foods
c. Condiments
d. Sauces
e. Soups
f. Chips/snack foods
E. Sodium Needs
1. Only about 100 mg/day
2. 1989 RDA/Labeling Guidelines
a. Minimum requirement for health = 500 mg/day
b. Daily value = 2400 mg
3. How Much Sodium Do You Consume?
4. Adapting to a Lower Sodium Intake
F. North Americans at Risk for a Sodium Deficiency
1. Only when weight loss exceeds 2-3% of body weight
G. Toxicity of Sodium
1. Humans can adapt to various dietary sodium intakes
2. When kidneys cannot excrete excess in urine or water intake is lacking
Potassium (K)
A. Absorption, Transport, and Excretion of Potassium
1. Body absorbs about 90% of that consumed
2. Balance achieved primarily via kidneys
3. Primary regulatory hormone = aldosterone
B. Functions of Potassium and the Effect of a Deficiency
1. Shares many of the same functions as sodium, including fluid balance and nerve-impulse
transmission
2. Influences contractility of smooth, skeletal, and cardiac muscle
3. Major cation inside the cell
4. Low blood potassium is life threatening
a. Symptoms include loss of appetite, muscle cramps, confusion, and constipation
b. Heart’s capacity to pump blood decreases
C. Potassium in Foods
1. Not generally added to foods
2. Fresh fruits and vegetables are most nutrient-dense sources
D. Potassium Needs
1. 1989 RDA Minimum Requirement for Health = 2000 mg/day
2. Daily Value = 3500 mg
E. North Americans at Risk for a Potassium Deficiency
1. Those taking potassium-wasting diuretics
2.
V.
VI.
Continual deficient diet
a. Alcoholism
b. Eating disorders
c. Very low kcal diets
F. Toxicity of Potassium
1. Harmless with normal kidney function
2. Hyperkalemia
a. Inhibits heart function
b. Can be fatal
Chloride (Cl-)
A. Absorption, Transport, and Excretion of Chloride
1. Near 100% absorption in small intestine and colon
2. Excretion via three routes
a. Kidneys (main route)
b. Skin
c. GI tract
B. Functions of Chloride and the Effects of a Deficiency
1. Electrolyte balance
2. Component of HCl
3. Used during immune responses as WBCs attack foreign cells
4. Aids in transport of carbon dioxide from cells to lungs and disposal of carbon dioxide via
exhaled air
C. Chloride in Foods
1. Seaweed, olives, rye, lettuce, some fruits/vegetables
2. Chlorinated water
3. Foods with added salt
D. Chloride Needs
1. 1989 Minimum Requirement for Health = 700 mg/day
E. North Americans at Risk for Deficiency
1. Unlikely
2. May be precipitated by frequent and lengthy bouts of vomiting if coupled with a nutrientpoor diet
3. Convulsions in infants
F. Chloride Toxicity
1. May increase blood pressure
2. Fluid retention
Calcium (Ca)
A. Absorption, Transport, Storage, and Excretion of Calcium
1. Absorption
a. occurs primarily in upper part of small intestine
b. depends greatly on active vitamin D hormone
c. between 25-60% absorbed
1. enhanced by parathyroid hormone, dietary glucose and lactose, and normal intestinal
flow
2.
limited by phytic acid (wheat bran), excess phosphorus, polyphenols (tea), vitamin D
deficiency, and diarrhea
2. Transport, Storage, and Excretion
a.
much is stored in bones
b.
released from bones by activity of osteoclasts
c.
excretion through kidneys (urine), skin and feces
B. Functions of Calcium
1. Bone Development and Maintenance
a. osteoblasts form the support structure of the bones
i. mature to osteocytes then secrete bone mineral, which then matures
(hydroxyapatite)
b. osteoclasts continually break down in areas where calcium is not needed
i. stimulated by parathyroid hormone
c. bone turnover = bone remodeling
d. during growth, osteoblast activity > osteoclast activity
e. bone mass peaks around age 30
i. levels effected by many factors
f. structural types of bones
i. cortical (compact) – outer surface of bones, long bones
ii. trabecular (cancellous or spongy) – ends of long bones, spinal vertebrae, pelvis,
internal network of bones
2. Blood Clotting
a.
calcium ions participate in formation of fibrin, main component of blood clot
3. Transmission of Nerve Impulses to Target Cells
a.
arrival of impulse to target site stimulates influx of calcium ions into nerve,
leading to
release of neurotransmitters
b.
tetany
c.
hypocalcemia
4. Muscle Contraction
a. skeletal muscles
b. increased concentration of calcium ions and ATP
c. return to intracellular stores following contraction
5. Cell Metabolism
a. calmodulin system
6. Other Attributes of a Diet Rich in Calcium
a. lower blood pressure
b. lower risk of colon cancer
c. decreased PMS symptoms
d. lower cholesterol
e. reduced risk of kidney stones
C. Calcium Deficiency
1.
Osteoporosis
a. may be preceded by osteopenia
b. especially common among post-menopausal women
c. exacerbated by smoking, excessive alcohol intake, inactivity
2. Estrogen replacement and related therapies
VII.
VIII.
b.
3. Maintain physical activity
4. Minimize risk for falls
D. Calcium in Foods
1.
Dairy products, especially nonfat dry milk
2.
Leafy greens – have high nutrient density of calcium, but absorption hindered by
oxalic acid
3.
Fortified foods
4.
Canned fish
5.
Tofu made with calcium carbonate
E. Calcium Supplements
1.
Calcium carbonate has highest concentration by weight (40%)
2.
Calcium citrate (21%)
3.
Calcium phosphate (8%)
4.
Calcium gluconate, calcium lactate
5.
Avoid bonemean – lead toxicity
6.
500 mg 2X day
F. Calcium Needs
1.
1000-1200 mg/day for adults
2.
Slightly higher for ages 9-18
G. North Americans at Risk for a Calcium Deficiency
1. Current intakes: 600-800 mg for women; 800-1000 mg for men
2. Young women
3. Vegetarians
4. Adolescents
5. Older adults
H. Calcium Toxicity
1. Excess prevented from absorption by small intestine
2. Upper Level is 2500 mg/day
a. risk of kidney stones
Expert Opinion: Assessing the Risks and Benefits of Estrogen Replacement Therapy
Phosphorus (P)
A. Absorption, Transport, and Excretion of Phosphorus
1. 70-90% of dietary intake absorbed
a. enhanced by vitamin D
based on P concentration in lumen of small intestine and colon
2. Excretion via kidneys
B. Functions of Phosphorus and the Effects of a Deficiency
1.
80% found in bones and teeth as calcium phosphate
2.
Cells and extracellular fluid
3.
Component of enzyme systems and acid-base balance
4.
Deficiency can contribute to bone loss, decreased growth, poor tooth development
C. Phosphorus in Foods
1. Dairy, bakery products and meats
a.
20-30% comes from food additives
b. soft drinks
Phosphorus Needs
1. 580 mg/day for men and women over 19
2. RDA is 700 mg/day
3. Deficiency is unlikely; consumptions average 1000-1600 mg/day
E. North Americans at Risk for a Phosphorus Deficiency
1.
Premature infants
2.
Vegans
3.
Alcoholics
4.
Elderly
5.
Using aluminum-containing antacids
F. Toxicity of Phosphorus
1. Problems if certain kidney diseases present
2. Can contribute to bone loss
3. Upper Lever is 3-4 g/day
Magnesium (Mg)
A. Absorption, Transport, Storage, and Excretion of Magnesium
1.
40-60% of dietary intakes absorbed
2.
Both passive and active absorption in small intestine
3.
Kidneys regulate blood concentration
4.
Alcohol increases Mg loss in urine
5.
Stored in bones, some tissues
B. Functions of Magnesium and the Effects of a Deficiency
1.
Required in more than 300 enzyme-catalyzed reactions
a.
active ATP
b.
DNA, RNA synthesis
c.
nerve, heart function
d.
insulin
2. Deficiency Effects
a.
rapid heartbeat with weakness, muscle spasms, disorientation, nausea/vomiting,
seizures
b.
fall in blood calcium
3. Deficiency develops very slowly
C. Magnesium in Foods
1.
Plant products are best
2.
Animal products supply some
3.
Hard tap water
D. Magnesium Needs
1.
Based on a daily intake that equals daily losses
2.
330 mg/day (adult males); 255 mg/day (adult females)
3.
RDA of 400 mg (men); 310 mg (women)
4.
Slightly higher for men/women over 30
E. North Americans at Risk of a Magnesium Deficiency
1.
Users of diuretics
2.
Heavy perspiration, long bouts of vomiting/diarrhea
D.
IX.
X.
XI.
3.
Alcoholics
4.
Diabetics
F. Toxicity of Magnesium
1. Rare
2. Upper Level is 350 mg for nonfood sources
a.
>350 mg may lead to diarrhea
3. Seen in kidney failure
Sulfur (S)
A. Functions
1.
Part of vitamins and amino acids
2.
Aids drug detoxification
3.
Part of acid-base balance
B. Sources
1. Protein foods
Nutrition in Perspective: Minerals and Hypertension
A. Definition
B. Why Control Blood Pressure?
C. Causes of Hypertension
D. Salt and Blood Pressure
E. Other Minerals and Blood Pressure
F. Prevention of Hypertension
G. Medications to Treat Hypertension
ACTIVITIES, EXERCISES, AND ASSIGNMENTS (Additional Activities in
Text)
1.
Assign students to visit supermarkets, beverage outlets, and pharmacies to take a census and "cost
out" the various bottled waters for sale. If possible, have students interview the owner of the
establishment to determine the most and least popular brands. Determine the source of the bottled
water. (Have students consult publications such as Consumer Reports for an update on the safety
and flavor qualities of these waters.)
2.
Assign students to select several multivitamin/mineral supplements at a local supermarket or
pharmacy and identify the major minerals included in the supplement. Have students compare the
potency of the various mineral with the U.S. RDA. What is cost per capsule of these various
supplements?
3.
Assign students to identify the calcium supplements available at a local supermarket or pharmacy.
Compare the cost, absorbability, and directions for use on the package.
4.
Assign students to make a list of common foods (such as cereals, dairy products and orange juice)
that are fortified with calcium. Identify the various calcium salts used and compare prices among the
various products. Which calcium salts are most absorbable?
5.
Have students visit supermarkets and other food outlets to select foods that are advertised as
“reduced in sodium,” “sodium free” and “lite.” Compare the sodium content in these products with
the normal product it is imitating. What is the difference in cost? What kind of promotion is the
manufacturer using to entice the shopper to select these products?
6.
Using the printout from a previous nutrition analysis assignment, have students compare their
menu(s) with their RDA for calcium, phosphorus, and magnesium. Also, have students identify the
foods providing the largest amounts of sodium and potassium.
7.
Assign students to prepare a menu for an adolescent girl that delivers 1200 milligrams of calcium.
8.
Assign students to prepare a menu for a patient with hypertension delivering no more than 4 grams
of sodium.
9.
Have student conduct a review of current literature about hormone replacement therapy. Have them
report on the pros and cons of this treatment.
10.
Assign students to gather a list of phytoestrogenic food sources. Organize a discussion of these
substances and suggested intake amounts.
ANNOTATED REFERENCES AND READINGS (Annotated References in
Text)
1.
Sowers M (1996): Nutritional Advances in Osteoporosis and Osteomalacia. In Ziegler EE and Filer
LJ (eds.), Present Knowledge in Nutrition, 7th ed., International Life Sciences Institute, Washington
DC pp. 456-463.
2.
Knapp HR (1996): Nutritional Aspects of Hypertension. In Ziegler EE and Filer LJ (eds.), Present
Knowledge in Nutrition, 7th ed., International Life Sciences Institute, Washington, DC pp. 438-444.
3.
Calcium supplementation prevents hypertensive disorders of pregnancy, Nutrition Reviews 50:233,
1992.
4.
Wood, RJ, and C Serfaty-Lacrosniere: Gastric acidity, atrophic gastritis, and calcium absorption,
Nutrition Reviews 50:33, 1992.
5.
Law, MR, CD Frost, and NJ Wald: By how much does dietary salt reduction lower blood pressure?
I. Analysis of observational data among populations II. Analysis of observational data within
populations, III. Analysis of data from trials of salt reductions, British Medical Journal 302:819,
1991.
6.
Mazess, RB and HS Barden: Bone density in premenopausal women: effects of age, dietary intake,
physical activity, smoking, and birth control pills, The American Journal of Clinical Nutrition
53:132, 1991.
7.
Orwoll, ES and S Oviatt: Relationship of mineral metabolism and long-term calcium and
cholecalciferol supplementation to blood pressure in normotensive men, The American Journal of
Clinical Nutrition 52: 717, 1990.
8.
Johnson, CC and others: Calcium supplementation and increases in bone mineral density in
children, The New England Journal of Medicine 327:82, 1992.
9.
The effects of nonpharmacologic interventions on blood pressure of persons with high normal
levels. Results of the Trials of Hypertension Prevention, Phase I., The Journal of the American
Medical Association 267:1221, 1992.
MEDIA RESOURCES
Videos:
1.
Living with High Blood Pressure. Creative Street, Hosted by Arthur Ashe. NCES, 1904 East 123rd
Street, Olathe, KS 66061-5886.
2.
Milk for More Nutra-Ed's Live Action Videos and Lesson Plans #7027. NCES, 1904 East 123rd
Street, Olathe, KS 66061-5886.
3.
Nutrient Needs: Water and Minerals. Health Sciences Consortium, 103 Laurel Ave., Carrbora, NC
27510.
4.
Body Fluids. Audio-Visual Services, The Pennsylvania State University, University Park, PA
16803.
5.
Minerals (MVCS). Audio-Visual Services, The Pennsylvania State University, University Park, PA
16S03.
6.
Osteoporosis Patient Education Media, Inc., Time and Life Bldg., 1271 6th Ave., NY, NY
10020.