Download Perspectives in Nutrition, 8th Edition

Perspectives in Nutrition, 8th Edition
Chapter 14 Outline: Water and Major Minerals
After studying this chapter, you will be able to:
1.
2.
3.
4.
5.
Describe the factors that influence water balance and how it is maintained in the body.
Discuss how both dehydration and water intoxication develop and how to prevent them.
Identify food sources of water and major minerals.
Explain the functions of water and major minerals in the body.
Discuss the problems with low and high intakes of major minerals and how to avoid
inadequate or excessive intakes.
6. Explain the role of nutrition in the prevention and treatment of hypertension.
7. Estimate and evaluate adequacy of dietary calcium intake.
8. Describe the role of nutrition in bone health and in the prevention of osteoporosis.
14.1
Water
A.
Water in the Body: Intracellular and Extracellular Fluid
1.
Body has no storage site for water; death occurs within a few days with no water
2.
Water makes up 50 - 75% of body weight, depending on age and body fat content
a.
Lean tissue is 73% water
b.
Adipose tissue is only 20% water
3.
Compartments
a.
Intracellular compartment: inside cells, makes up 2/3 body water
b.
Extracellular compartment: outside cells
i.
Interstitial fluid: between cells
ii.
Intravascular fluid: in blood and lymph
4.
Fluid contains solutes
a.
Electrolytes form when salts dissociate in solution to form ions
b.
Cations: positively charged ions
i.
Intracellular cations: potassium, magnesium
ii.
Extracellular cations: sodium, calcium
c.
Anions: negatively charged ions
i.
Intracellular anions: phosphate, sulfate
ii.
Extracellular anions: chloride, bicarbonate
5.
Maintenance of Water Balance
a.
Water balance is controlled by electrolyte concentrations, which are
regulated by pumping mechanisms that use energy to move ions against
a concentration gradient (see Figure 14-3)
b.
Water is attracted to ions
c.
Osmosis: passive diffusion of water across a semipermeable membrane
(cell membrane) from an area of low concentration to an area of high
concentration (see Figure 14-4)
d.
In cells, water cannot move easily through lipid membranes, but moves
through aquaporins, made of proteins
e.
B.
C.
Tight regulation of water balance is necessary because shifts in cellular
water volume can disrupt function
Functions of Water
1.
Maintenance of blood volume
2.
Transport of nutrients and oxygen
3.
Basis for saliva, bile, amniotic fluid
4.
Lubricates joints
5.
Solvent for and participant in many metabolic processes
6.
Temperature Regulation
a.
Maintenance of body temperature within a narrow range ensures normal
enzyme function
b.
Water has high heat capacity (specific heat): resists temperature changes
because polar water molecules are strongly attracted to each other,
requiring large amount of energy to change state
c.
Perspiration and subsequent evaporation releases excess heat, cools the
body
7.
Waste Product Removal
a.
Most wastes are water soluble and excreted in urine
b.
Liver converts many fat-soluble compounds into water-soluble
compounds for excretion in urine
c.
Urine production depends upon
i.
Protein intake (i.e., urea excretion)
ii.
Sodium intake
iii.
Fluid intake
d.
Normal urine output: 1 - 2 L
i.
Minimal required urine output: 600 ml
ii.
Low urine output (i.e., concentrated solutes) increases risk for
kidney stones in susceptible people
Water in Foods
1.
Beverages and liquid foods
2.
Fruits and vegetables (75 - 95% water)
3.
Potatoes, meats (50 - 75% water)
4.
Jam, honey, crackers, fats (low water)
5.
Sweetened beverages also supply calories (13 - 22% of total kcal; soft drinks are
single largest source of calories in U.S. diet)
a.
Liquid calories do not promote satiety
b.
No compensation by eating less
c.
Low nutrient density
6.
Caffeine is a mild diuretic, but intakes up to 500 mg/d (4 - 5 c/d of brewed
coffee) do not lead to water imbalance or dehydration
7.
Alcohol increases urine output by inhibiting antidiuretic hormone, which leads to
dehydration
8.
Bottled versus tap water
a.
b.
c.
d.
D.
Bottled water is no safer than tap water
Bottled water may not contain fluoride
Bottled water is more expensive than tap water
Producing and disposing of plastic bottles has negative environmental
impact
Water Needs
1.
Individual variances
a.
Body size
b.
Physical activity
c.
Environmental conditions
d.
Dietary intake
2.
AI for total water intake (water from liquids and foods)
a.
Adult men: 15 cups (13 cups from fluids)
b.
Adult women: 11 cups (9 cups from fluids)
3.
Components of water intake
a.
Fluids
b.
Foods
c.
Water is produced as a byproduct of metabolism (1 - 1.5 c/d)
4.
Components of water output
a.
Urine (600 - 1000 ml/d)
b.
Skin (450 - 1900 ml)
c.
Lungs (250 - 350 ml)
d.
Feces (100 - 200 ml)
5.
GI tract is efficient at conserving water
a.
GI secretions: 32 c
b.
Diet: 8 - 13 c
c.
Losses in feces: ½ - ¾ c
6.
Kidneys conserve water: reabsorb 97% of filtered water
7.
Dehydration
a.
Causes
i.
Diarrhea or vomiting
ii.
Fever
iii.
Heavy exercise
iv.
Hot weather
v.
Dry environments
vi.
High altitudes
b.
Thirst mechanism does not always work well
i.
Intense exercise (consume 2.5 - 3 c for every pound of weight
lost)
ii.
Illness
iii.
Infancy
iv.
Old age
c.
Signs of mild - moderate dehydration (see Figure 14-9)
8.
14.2
i.
Dry mouth and skin
ii.
Fatigue
iii.
Muscle weakness
iv.
Decreased urine output
v.
Deep yellow urine
vi.
Headache
vii.
Dizziness
d.
Severe dehydration
i.
Concentrated blood
ii.
Decreased blood volume and blood pressure
iii.
Increased heart rate
e.
Antidiuretic hormone: released by pituitary gland in response to
increased concentration of blood and decreased blood pressure; signals
kidneys to reduce urine output
Water Toxicity
a.
Overconsumption of water dilutes blood, leading to hyponatremia (low
serum sodium)
b.
Symptoms
i.
Headache
ii.
Blurred vision
iii.
Muscle cramps
iv.
Convulsions
v.
Death
c.
High-risk populations
i.
Mental disorders
ii.
Infants given extra water or overdiluted formula
iii.
Endurance athletes
d.
Prevention for endurance athletes: consume sports drinks, which contain
electrolytes, instead of plain water
Overview of Minerals
A.
General
1.
Essential, inorganic elements needed in small amounts in the diet for normal
function, growth, and maintenance of body tissues
a.
Cannot be synthesized by the body
b.
Health declines when substance is not consumed
c.
Deficiency symptoms are alleviated by restored intake
2.
Classified by needs
a.
Major (macro) minerals: 100 mg or more
b.
Trace (micro) minerals: less than 100 mg
3.
Functions of minerals and water (see Figure 14-1)
a.
Cell metabolism
i.
Calcium
b.
c.
d.
e.
f.
g.
h.
ii.
Phosphorus
iii.
Magnesium
iv.
Zinc
v.
Chromium
vi.
Iodide
vii.
Water
Bone health
i.
Calcium
ii.
Phosphorus
iii.
Iron
iv.
Zinc
v.
Copper
vi.
Fluoride
vii.
Magnesium
Growth and development
i.
Calcium
ii.
Phosphorus
iii.
Zinc
Blood formation and clotting
i.
Iron
ii.
Copper
iii.
Calcium
Nerve impulses
i.
Sodium
ii.
Potassium
iii.
Chloride
iv.
Calcium
Muscle contraction and relaxation
i.
Sodium
ii.
Chloride
iii.
Potassium
iv.
Calcium
v.
Magnesium
Antioxidant defenses
i.
Selenium
ii.
Zinc
iii.
Copper
iv.
Manganese
Water and ion balance
i.
Sodium
ii.
Potassium
iii.
Chloride
iv.
Phosphorus
B.
C.
D.
E.
F.
v.
Water
Food Sources of Minerals
1.
Some minerals are most bioavailable from animal sources
a.
Calcium
b.
Iron
c.
Zinc
2.
Some minerals are found mainly in plant sources, although bioavailability may
be hindered by plant compounds
a.
Potassium
b.
Magnesium
3.
Factors that affect mineral content of foods
a.
Genetic variations
b.
Mineral composition of animal feed and medications
c.
Soil and water mineral content
d.
Mineral content of fertilizers and pesticides
e.
Food processing (e.g., equipment, additives, refinement)
f.
Fortification
i.
Salt - iodine
ii.
Some types of orange juice - calcium
iii.
Breakfast cereals - variety of vitamins and minerals
Absorption of Minerals
1.
Factors that affect absorption of minerals
a.
Physiological need for mineral (higher needs increase absorption)
b.
Nutrient competition: minerals of same weights and charges may
compete for absorption (e.g., magnesium, calcium, iron, and copper)
c.
Non-mineral dietary substances
i.
Phytic acid (phytate) in wheat grain fiber, although leavening
with yeast improves mineral bioavailability
ii.
Oxalic acid (oxalate) in leafy green plants
iii.
Polyphenols in tea, chocolate, and wine
d.
Some vitamins enhance mineral bioavailability
i.
Vitamin C - iron
ii.
Vitamin D hormone - calcium, phosphorus, and magnesium
e.
Gastric acidity: HCl dissolves and maintains minerals in reduced state
Transport of Minerals
1.
Free form: some can be reactive and/or toxic if unbound
2.
Bound to proteins
Excretion of Minerals
1.
Urine
2.
Bile
Functions of Minerals
1.
Water balance
2.
Transmission of nerve impulses
G.
H.
14.3
3.
Enzyme cofactors
4.
Components of body compounds (e.g., hemoglobin, bone)
Mineral Deficiencies
1.
Calcium
2.
Potassium
3.
Magnesium
4.
Iron
5.
Zinc
6.
Iodide
Mineral Toxicity
1.
Excess supplemental intake may lead to toxicity
2.
Competition may limit absorption of some minerals
3.
Supplements may be contaminated (e.g., with lead) - select brands with USP
label
Sodium (Na)
A.
General
1.
Produced by mining inland salt deposits or evaporating sea water
2.
Historically valued (root of the word “salary”)
3.
Used in food processing
a.
Flavorings/flavor enhancers
b.
Preservatives
c.
Leavening agents
d.
Curing agents
e.
Wetting agents
f.
Color preservatives
g.
Anticaking agents
4.
Most North Americans consume excess sodium (2300 - 4700 mg/d)
B.
Sodium in Foods
1.
Sodium chloride
a.
40% sodium (1 tsp, or 6 g, provides 2300 mg sodium)
b.
60% chloride
2.
Food processing (75 - 80% of intake)
a.
White bread and rolls
b.
Processed meats
c.
Cheese
d.
Dried and canned soups
e.
Tomato sauce
f.
Condiments and sauces
g.
Seasoned pasta mixes
h.
Canned and frozen entrees
i.
Restaurant foods
3.
C.
D.
E.
F.
G.
Naturally present in foods (10% of intake); without added salt or food
processing, daily sodium intake would be about 500 mg
4.
Added in cooking and at table (10 - 15% of intake)
5.
Softened tap water
6.
Medicines
Sodium Needs
1.
AI
a.
Adults under age 51: 1500 mg
b.
Adults 51 - 70: 1300 mg
c.
Adults over 70: 1200 mg
2.
DV: 2400 mg
3.
UL: 2300 mg
4.
Only 200 mg/d is needed to maintain body functions, but AI is set above needs to
allow for more varied diet
Storage of Sodium: extracellular fluid sodium content is tightly regulated by kidneys
Excretion of Sodium
1.
Urine
2.
Feces
3.
Perspiration
Functions of Sodium
1.
Absorption of glucose and some amino acids from the small intestine
2.
Muscle and nerve function: electrical charge resulting from shift in sodium and
potassium ions into and out of cells
3.
Water balance
a.
When excess sodium is ingested, more water is retained until sodium is
excreted
b.
Faulty sodium excretion by the kidneys, leading to fluid retention
i.
Nephrotic syndrome
ii.
Congestive heart failure
Sodium Deficiency
1.
Rare due to abundance of sodium in food supply compared to low requirements
2.
Deficiency (hyponatremia) occurs when losses exceed intake (e.g., excessive
perspiration)
a.
>2% of body weight
b.
Perspiration contains only 2/3 the sodium content of blood, but seems
salty due to evaporation of water
3.
Symptoms
a.
Headache
b.
Nausea/vomiting
c.
Fatigue
d.
Muscle cramps
e.
Seizures, coma, death in severe cases
4.
Prevention/treatment
H.
14.4
a.
Salting foods
b.
Sports drinks
Excess Sodium and Upper Level
1.
UL: 2300 mg
2.
95% of North American adults exceed the UL
3.
Consequences
a.
Hypertension, heart disease, stroke
b.
Increased calcium losses in urine (although not linked to osteoporosis
risk)
c.
Increased risk of calcium oxalate kidney stones
4.
American Medical Association and World Health Organization call for 50%
reduction in sodium content of processed and restaurant foods
5.
Reducing sodium intake by 50% will reduce prevalence of hypertension by at
least 20% and reduce mortality from coronary heart disease and stroke
6.
Food labels help consumers identify sodium content of food
a.
Nutrition Facts panel
b.
Salt-free, sodium-free, low sodium
7.
Taste preferences adjust with low-sodium diet
8.
Table 14-5 provides tips for decreasing sodium intake
Potassium (K)
A.
Potassium in Foods
1.
Unprocessed foods are best sources of potassium
2.
Fruits
3.
Vegetables
4.
Milk
5.
Whole grains
6.
Dried beans
7.
Meats
8.
Coffee
9.
Salt substitutes (potassium chloride)
10.
Food additives
B.
Potassium Needs
1.
AI: 4700 mg
2.
DV: 3500 mg
3.
Average potassium intakes range from 2100 - 3300 mg/d
C.
Storage of Potassium: 95% of potassium is found in cells
D.
Excretion of Potassium: urine
E.
Functions of Potassium
1.
Fluid balance
2.
Transmission of nerve impulses
3.
Contraction of muscles
4.
High potassium decreases calcium excretion in urine
5.
F.
G.
14.5
High potassium suppresses renin-angiotensin system and promotes excretion of
excess sodium and water
Potassium Deficiency
1.
Hypokalemia is life-threatening
2.
Consequences
a.
Weakness
b.
Fatigue
c.
Constipation
d.
Arrhythmia
e.
Increased blood pressure
f.
Increased risk of stroke
3.
Causes
a.
Losses via urine (e.g., due to diuretics)
b.
Losses via GI tract (e.g., excessive vomiting)
c.
Low dietary intake (e.g., eating disorders or alcoholism)
d.
Heavy perspiration
Excess Potassium and Upper Level
1.
Hyperkalemia is also life-threatening
2.
Causes
a.
Not likely due to high dietary intake; excess would be excreted in urine
b.
Kidney disease impairs excretion
3.
Consequences
a.
Irregular heartbeat
b.
Cardiac arrest
c.
Intestinal upset
Chloride (Cl)
A.
General
1.
Main anion in the extracellular fluid
2.
Chlorine (Cl2) is toxic
B.
Chloride in Foods
1.
Table salt
2.
Processed foods
3.
Restaurant foods
4.
Seaweed
5.
Olives
6.
Rye
7.
Lettuce
8.
Fruits
9.
Vegetables
10.
Salt substitutes
C.
Chloride Needs
1.
AI: 2300 mg, based on AI for sodium
D.
E.
F.
G.
H.
14.6
2.
DV: 3400 mg
3.
Average intake: 5400 mg
Storage of Chloride: extracellular fluid, associated with sodium
Excretion of Chloride: urine
Functions of Chloride
1.
Major anion in extracellular fluid; maintains extracellular fluid volume and
balance
2.
Transmission of nerve impulses
3.
Component of HCl
4.
Immune response
5.
Acid-base balance
6.
Excretion of CO2 via lungs
Chloride Deficiency
1.
Causes
a.
Unlikely due to high salt intake
b.
Frequent and lengthy bouts of vomiting coupled with nutrient-poor diet
2.
Consequences
a.
Weakness
b.
Anorexia
c.
Lethargy
d.
Disruption of acid-base balance
Upper Level for Chloride
1.
UL: 3.6 g, based on UL for sodium
2.
Dietary chloride has been implicated along with sodium as a culprit for
hypertension
Calcium (Ca)
A.
Calcium in Foods
1.
Dairy products are most bioavailable dietary source of calcium, provide ½
calcium in American diets
2.
White bread, rolls, crackers
3.
Leafy greens (e.g., collards, kale, turnip greens), although bioavailability in some
foods is limited by oxalic acid
4.
Broccoli
5.
Calcium-fortified foods (e.g., orange juice, breakfast cereals)
6.
Canned fish with bones
7.
Soybean curd made with calcium carbonate
B.
Calcium Needs
1.
AI
a.
Adults up to age 50: 1000 mg
b.
Adults 51+: 1200 mg
c.
Adolescents: 1300 mg
2.
DV: 1000 mg
3.
4.
C.
D.
E.
F.
Average intake is adequate for men, but inadequate for women
Calcium supplements are helpful for those with restricted calorie intakes and
those who avoid dairy products
a.
Made of calcium salts
i.
Calcium carbonate (40% calcium)
ii.
Calcium citrate: better for those with low stomach acid
iii.
Calcium gluconate (9% calcium)
b.
May contain vitamin D to boost calcium absorption
c.
Dose should be no more than 500 mg at a time
d.
Consuming with meals improves absorption due to higher acid
concentration in stomach
e.
Interactions with other minerals; do not take calcium supplements at the
same time as other mineral supplements
i.
Zinc
ii.
Iron
iii.
Magnesium
f.
Contamination with lead
i.
Most likely in supplements made with bone meal or oyster shell
ii.
Look for USP label to lessen risk of contamination
Calcium Absorption
1.
Factors that increase calcium absorption
a.
Active vitamin D hormone (in upper GI tract)
b.
Increased need (e.g., infancy, pregnancy), absorption increases to 75%
c.
Lactose and other sugars
d.
Protein
2.
Factors that decrease calcium absorption
a.
Age
b.
Phytic acid
c.
Oxalic acid
d.
Excessive phosphorus
e.
Polyphenols
f.
Vitamin D deficiency
g.
Diarrhea
h.
Fat malabsorption: fatty acids bind to calcium to form unabsorbable
soaps
Calcium Transport
1.
Free ionized calcium
2.
Bound to proteins
Calcium Storage
1.
99% in skeleton and teeth
2.
Small, regulated amount in blood
Calcium Regulation
1.
Because of tight regulation, blood calcium is a poor indicator of calcium status
2.
G.
H.
I.
When blood calcium is low, parathyroid gland releases parathyroid hormone
(PTH):
a.
Works with 1,25 (OH)2 vitamin D to increase kidney’s reabsorption of
calcium
b.
Increases calcium absorption by increasing synthesis of 1,25 (OH)2
vitamin D
c.
Works with 1,25 (OH)2 vitamin D to increase release of calcium from
bones
3.
When blood calcium is high, release of PTH falls
a.
Urinary calcium excretion increases
b.
Synthesis of 1,25 (OH)2 vitamin D decreases, leading to decreased
absorption of calcium
c.
Thyroid gland secretes calcitonin, which blocks calcium loss from bones
Calcium Excretion
1.
Urine
2.
Skin
3.
Feces (intestinal secretions)
Functions of Calcium
1.
Bone Development and Maintenance
a.
Calcium and phosphorus are main bone minerals, form hydroxyapatite,
which imparts strength and resilience
b.
Collagen forms bone matrix, allows absorption of impact
c.
Cortical bone
d.
Trabecular bone
i.
Site of mineral exchange
e.
Remodeling: continuous building, breaking down, and replacing bone
i.
Repairs damaged and brittle areas
ii.
Allows withdrawal of stored minerals
iii.
Bone mass declines 25% with aging, or more for women with
low estrogen (e.g., menopause, amenorrhea, oophorectomy)
because estrogen inhibits osteoclast activity
f.
Other nutrients involved in bone metabolism
i.
Magnesium
ii.
Potassium
iii.
Sodium
iv.
Fluoride
v.
Vitamin K
vi.
Sulfur
2.
Blood Clotting: calcium ions participate in formation of fibrin
3.
Transmission of Nerve Impulses to Target Cells
4.
Muscle Contraction
Potential Health Benefits of Calcium
1.
Bone health
2.
3.
4.
5.
J.
14.7
Protection against colon cancer
Protection against some forms of kidney stones
Decreased blood pressure
Possible link between calcium intake, metabolism, and body weight;
epidemiological evidence is not strongly supported by clinical trials
6.
May reduce risk for high blood pressure during pregnancy in women with low
calcium intake
Upper Level for Calcium
1.
UL: 2500 mg, based on increased risk of kidney stones at higher intakes
2.
High blood calcium is usually the result of hyperparathyroidism (overproduction
of PTH, usually caused by tumor) or high supplemental doses of calcium
3.
Consequences of excessive blood calcium
a.
Calcification of kidneys and other organs
b.
Irritability
c.
Headache
d.
Kidney failure
e.
Kidney stones
f.
Decreased absorption of other minerals
Phosphorus (P)
A.
General
1.
Major component of bones and teeth
2.
Glowing material
3.
Required by every body cell
B.
Phosphorus in Foods
1.
Milk
2.
Cheese
3.
Meat
4.
Bakery products
5.
Cereals
6.
Bran
7.
Nuts
8.
Fish
9.
Food additives (may not be included in nutrient databases)
10.
Nutrients used for fortification
C.
Phosphorus Needs
1.
RDA: 700 mg
2.
DV: 1000 mg
3.
Average intake: 950 - 1650 mg
D.
Storage of Phosphorus
1.
80% found in bones and teeth as a component of hydroxyapatite
2.
Extracellular fluid
3.
Body cells
E.
F.
G.
H.
14.8
Excretion of Phosphorus: urine
Functions of Phosphorus
1.
Major component of bones and teeth
2.
Main intracellular anion (HPO42- or H2PO4-)
3.
Component of ATP and creatine phosphate
4.
Component of DNA and RNA
5.
Component of phospholipids in cell membranes
6.
Takes part in enzyme and cellular message systems (phosphorylation activates
many hormones and enzymes)
7.
Regulation of acid-base balance
8.
Possibly protective against hypertension
Phosphorus Deficiency
1.
Rare
2.
Consequences
a.
Bone loss
b.
Decreased growth
c.
Poor tooth development
d.
Symptoms of rickets due to insufficient bone mineralization
e.
Anorexia
f.
Weight loss
g.
Weakness
h.
Irritability
i.
Stiff joints
j.
Bone pain
3.
High-risk populations
a.
Premature infants
b.
Alcoholics
c.
Older adults with nutrient-poor diets
d.
Chronic diarrhea or weight loss
e.
Frequent use of aluminum-containing antacids (bind phosphorus in small
intestine)
Toxicity and Upper Level for Phosphorus
1.
Rare
2.
Hyperphosphatemia is usually due to compromised kidney function
3.
Consequences: calcium-phosphorus deposits in body tissues
4.
UL: 3 - 4 g, based on development of high blood [P]
Magnesium (Mg)
A.
Magnesium in Foods
1.
Component of chlorophyll; richest sources are plant foods
a.
Green leafy vegetables
b.
Broccoli
c.
Squash
B.
C.
D.
E.
F.
d.
Beans
e.
Nuts
f.
Seeds
g.
Whole grains
h.
Chocolate
2.
Animal products supply some Mg
a.
Milk
b.
Meats
3.
Hard tap water
4.
Magnesium oxide (in supplements) is not well absorbed
Magnesium Needs
1.
RDA
a.
Adult men (age 19 - 30): 400 mg
b.
Adult women (age 19 - 30): 310 mg
c.
Needs slightly increase beyond age 30
2.
DV: 400 mg
3.
Average intakes are 80% RDA
Storage of Magnesium
1.
Bones (about 50%)
2.
Other tissue (particularly muscle)
Excretion of Magnesium: kidneys
Functions of Magnesium
1.
Stabilizes ATP by binding phosphate groups
2.
Cofactor for more than 300 enzymes that utilize ATP
a.
Energy metabolism
b.
Muscle contraction
c.
Protein synthesis
3.
Required for activity of cellular sodium-potassium pump
4.
DNA and RNA synthesis
5.
Role in calcium metabolism, contributes to bone structure and mineralization
6.
Nerve transmission
7.
Heart and smooth muscle contraction
8.
Insulin release from pancreas
9.
Insulin action on cells
10.
Decreased blood pressure due to vasodilation
11.
Prevention of arrhythmias
12.
Protective against gallstone formation
Magnesium Deficiency
1.
Consequences, likely due to impaired function of Na/K pump
a.
Irregular heartbeat
b.
Weakness
c.
Muscle spasms
d.
Disorientation
G.
e.
Nausea
f.
Vomiting
g.
Seizures
h.
Decreased PTH release, resulting in low blood calcium
i.
Blunted action of 1,25 (OH)2 vitamin D
j.
Increased risk of metabolic syndrome
2.
Slow to develop due to body storage
3.
Causes
a.
Excessive GI tract losses (e.g., prolonged diarrhea or vomiting)
b.
Excessive urinary losses (e.g., use of diuretics)
c.
Alcoholism
d.
Poorly controlled diabetes
e.
Low dietary intake
f.
Heavy perspiration
Upper Level for Magnesium
1.
UL: 350 mg from supplement and other nonfood sources (e.g., antacids or
laxatives)
2.
Causes
a.
Excessive supplementation
b.
Chronic antacid or laxative use
c.
Kidney failure
3.
Consequences
a.
Weakness
b.
Nausea
c.
Slowed respiration
d.
Malaise, coma, death
4.
High-risk population: older adults, due to declines in kidney function
14.9
Sulfur (S)
A.
Sources
1.
Protein-rich foods (component of methionine and cysteine)
2.
Preservative used to protect color of dried fruit and white wines
B.
Requirements
1.
No AI or RDA established because of ample consumption from protein foods
2.
No UL established, no toxicity symptoms
C.
Functions
1.
Synthesis of sulfur-containing compounds
2.
Stabilize protein structure
3.
Acid-base balance
14.10
Global Perspective: Water for Everyone
A.
Water supply
1.
Average per capita daily water use in U.S. and Europe = 52 - 160 gallons
2.
3.
B.
14.11
Minimum daily clean water need per person (United Nations): 5 ½ gallons
In addition to personal water usage, water is also needed for agriculture (70% of
world’s water consumption), energy production, and industry
4.
Millions of people rely on water for income and food production (e.g., fishing,
farming)
5.
Inadequate water supply leads to poverty, malnutrition, and illness
6.
1 in 3 people worldwide faces water shortage due to arid climate or lack of
infrastructure
7.
Inequitable water distribution may cause civil unrest
Water sanitation
1.
Contamination with sewage, herbicides, pesticides, and toxins causes diseases
(e.g., diarrheal disease), which lead to death, especially among malnourished
children
2.
Water purification and wastewater treatment are needed
Medical Perspective: Hypertension and Nutrition
A.
General
1.
1 in 3 adults has hypertension
2.
Measurement of blood pressure
a.
Systolic: pressure in arteries when heart contracts
b.
Diastolic: pressure in arteries when heart relaxes
3.
Classifying blood pressure (see Table 14-6)
a.
Normal: <120/<80
b.
Prehypertenion: 120 - 139/80 - 89
c.
Hypertension, stage 1: 140 - 158/90 - 99
d.
Hypertension, stage 2: ≥160/≥100
B.
Causes of Hypertension
1.
Secondary hypertension (5 - 10% of cases)
a.
Kidney disease
b.
Liver disease
c.
Diabetes
2.
Primary hypertension
a.
Actual cause is not fully known
b.
Develops over a period of years as arteries narrow and harden
(arteriosclerosis)
c.
Endothelial cells release vasoconstrictors in response to arterial damage
d.
Increased production of renin by kidneys, leading to increased
angiotensin II, a powerful vasoconstrictor that triggers sodium and water
retention
C.
Risk Factors for Hypertension
1.
Age: 90%+ over age 55 develop hypertension
2.
Race: African-Americans develop hypertension more often and at younger age
than whites
Obesity: increased fat mass adds blood vessels, increasing heart’s workload
Diabetes: elevated insulin increases sodium retention; 65% of diabetics also have
hypertension
Effects of hypertension
1.
Damage to arteries
2.
Heart attack
3.
Stroke
4.
Kidney failure
5.
Vision loss
Lifestyle Modifications to Prevent and Treat Hypertension
1.
Many recommendations for lowering hypertension are also part of Dietary
Guidelines
2.
Modest weight loss (10 lbs) for overweight person
3.
DASH eating plan: high in fruits, vegetables, low-fat dairy; low in sodium and
saturated and total fat
4.
Moderate physical activity, particularly aerobic exercise
5.
Improve insulin sensitivity
6.
Control alcohol intake
7.
Control sodium intake
Minerals, Phytochemicals, and Hypertension
1.
Sodium
a.
Intersalt study: as urinary sodium excretion increases, blood pressure
increases
b.
Salt sensitivity
i.
Only 25-50% of people experience high blood pressure with
high salt intake
ii.
Trial of sodium restriction is only way to determine salt
sensitivity
iii.
African-Americans, overweight people, those with diabetes, and
the elderly are more likely to be salt sensitive
2.
High potassium, low sodium diet offers best protection against hypertension
3.
High calcium linked to lower blood pressure
4.
High magnesium linked to lower blood pressure
5.
High fiber linked to lower blood pressure
6.
Dark chocolate (6 g/d) causes modest reduction in blood pressure due to
polyphenols that cause vasodilation
7.
Caffeine temporarily increases blood pressure, but chronic intake is not
associated with increased blood pressure
The Dietary Approaches to Stop Hypertension (DASH) Diet
1.
Food plan
a.
Grains: 6 - 8 servings/d (emphasize whole grains)
b.
Vegetables: 4 -5 servings/d
c.
Fruits: 4 - 5 servings/d
3.
4.
D.
E.
F.
G.
H.
14.12
d.
Fat-free or low-fat milk products: 2 - 3 servings/d
e.
Lean meats, poultry, and fish: 6 or less servings/week
f.
Nuts, seeds, and legumes: 4 - 5 servings/week
g.
Fats and oils: 2 - 3 servings/d
h.
Sweets and added sugars: 5 or less per week
2.
Nutrient goals
a.
Low in fat (27% of kcal)
b.
Low in saturated fat (6% of kcal)
c.
Moderate in protein (18% of kcal)
d.
Moderate in carbohydrates (55% of kcal)
e.
Low in cholesterol (150 mg/d)
f.
Low in sodium (2300 mg/d is effective, 1500 mg/d shows better
reductions in blood pressure)
g.
High in potassium (4700 mg/d)
h.
High in calcium (1250 mg/d)
i.
High in magnesium (500 mg/d)
j.
High in fiber (30 g/d)
3.
Works as well as medications for those with hypertension
4.
Health benefits of DASH diet
a.
Reduced blood pressure
b.
Cancer prevention
c.
Heart disease prevention
Drug Therapy for Hypertension
1.
Usually initiated when blood pressure exceeds 140 mmHg systolic and/or 90
mmHg diastolic on 3 or more occasions
2.
Diuretics: increase water and salt excretion; may increase potassium excretion
(e.g., furosemide and hydrochlorothiazide)
3.
Beta-blockers: slow heart rate and decrease force of heart contraction (e.g.,
metropolol)
4.
Angiotensin-converting enzyme (ACE) inhibitors: reduce conversion of
angiotensin I to angiotensin II in the lung, leading to vasodilation (e.g., captopril)
5.
Calcium channel blockers: prevent calcium from entering cells of heart and blood
vessels, leading to vasodilation (e.g., nifedipine)
Medical Perspective: Osteoporosis
A.
General
1.
Low calcium intake is most common cause; calcium is withdrawn from bone to
maintain blood calcium levels
2.
Develops over many years
3.
Osteopenia: low bone mass caused by vitamin D deficiency, medications, cancer,
anorexia nervosa, or other conditions
4.
B.
C.
Diagnosis of osteoporosis occurs when bone mass has declined to the extent that
bone strength is compromised and bones are likely to break (e.g., hip, wrist,
vertebrae)
5.
Kyphosis (dowager’s hump): compression fractures in vertebrae lead to loss of
height
6.
8 million women and 2 million men suffer from osteoporosis; 34 million have
low bone mass
7.
Ethnic/racial disparity
a.
African-Americans are least likely to develop osteoporosis
b.
Highest rates in Caucasian and Asian populations
8.
Risk factors for osteoporosis
a.
Family history
b.
Small, thin skeletal frame
c.
Low peak bone mass
d.
Advancing age
e.
Caucasian or Asian ancestry
f.
Menopause
g.
Amenorrhea
h.
Oophorectomy: removal of ovaries
i.
Smoking
j.
Low calcium intake
k.
Vitamin D deficiency
l.
Low physical activity
m.
Excessive alcohol consumption
n.
Diseases that impair nutrient absorption, metabolism, or utilization of
bone-forming nutrients or increase their excretion (e.g., cystic fibrosis,
anorexia nervosa, type 1 diabetes mellitus, inflammatory bowel disease,
celiac disease, multiple sclerosis, epilepsy)
o.
Some medications (e.g., glucocorticoids)
Osteoporosis Diagnosis
1.
Dual energy X-ray absorptiometry (DEXA) bone scan measures ability of bone
(spine, hips, and whole body) to block the path of radiation; compare with bone
density of person at peak bone density
2.
Peripheral DEXA or ultrasound: measure bone density at one site (e.g., wrist or
heel); faster than DEXA, but not as accurate
Osteoporosis Prevention and Treatment
1.
Consume ample calcium, vitamin D, phosphorus, magnesium, vitamin K, and
potassium
2.
Vitamin D requirements may be much higher than current AI for older adults and
those with osteopenia or osteoporosis
3.
1200 mg/d calcium + 800 IU/d vitamin D
4.
Physical activity, including weight-bearing activity; also improves balance and
strength to reduce risk of falling
D.
5.
Smoking cessation
6.
Limited alcohol intake
7.
Moderate intakes of caffeine, sodium, and protein to decrease calcium excretion
Drug Therapy for Osteoporosis Prevention
1.
Decrease of more than 1 ½ inches from pre-menopausal height is a sign of
significant bone loss among postmenopausal women
2.
Estrogen: slows osteoclast activity, but may increase risk of CVD and certain
cancers
3.
Bisphosphonates: bind to hydroxyapatite crystals and osteoclasts to slow bone
resorption (e.g., alendronate and ibandronate)
4.
Selective estrogen receptor modulators (SERMS): increase utilization of existing
estrogen to slow osteoclast activity (e.g., raloxifene)
5.
Calcitonin: inhibits osteoclast activity and bone resorption
6.
PTH: stimulates osteoblast activity and new bone formation