Transcript chapter 8 Water and Minerals

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Water makes up ≈60%
of an adult’s body weight
Water is found in
◦ Blood vessels
◦ Cells
◦ Chemical structure of cells, tissues, organs
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Water participates in many chemical reactions
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Delivers nutrients and removes waste from
cells
Water is a, nearly, universal solvent
Water is the body’s cleansing agent
Water’s incompressibility
Water plays a role in thermoregulation
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Water balance
◦ Water intake needs to equal water loss
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Dehydration
◦ Water loss
◦ Progression of symptoms: thirst  weakness 
exhaustion and delirium  death
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Water intoxication
◦ Dangerous dilution of body fluids resulting from
excessive water ingestion
◦ Symptoms: headache, muscular weakness, lack of
concentration, poor memory, loss of appetite
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A disturbed fluid balance can cause a severe
illness
◦ In vomiting or diarrhea
 Result: fluid and electrolyte imbalance
 Life-threatening disruption of heartbeat
◦ Minerals also play a role in acid-base balance
 In pure water H+ and OH- ions exist in equilibrium
 When dissolved in water
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The maintenance of a nearly constant pH is
critical to life
◦ Slight changes in pH can change the structure and
function of most biologically important molecules
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DRI meets ≈80% of day’s need for water
◦ Men: 13 cups of fluid from beverages and drinking
water
◦ Women: 9 cups of fluid from beverages and
drinking water
◦ Remaining water need is met from consumed foods
◦ Body produces water from the breakdown of
energy-yielding nutrients
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Minerals
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Naturally occurring
Inorganic
Homogenous
Chemical elements
Major minerals
◦ Essential nutrients
◦ Found in the body in amounts exceeding 5 grams
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Trace minerals
◦ Essential nutrients
◦ Found in the body in amounts less than 5 grams
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Role: Most abundant mineral in the body
◦ ≈99% stored in bone and teeth
◦ Calcium & phosphorous for bone formation
 Calcium phosphate salt forms hydroxyapatite crystals to
add rigidity to bone
 Integral part of bone structure & building
 Bone serves as a calcium reserve, releasing or removing
calcium from the blood
◦ Essential for muscle contraction and therefore
heartbeat
◦ Allows secretion of hormones, digestive enzymes,
and neurotransmitters
◦ Activates cellular enzymes that regulate many
processes
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Despite adjustments, some bone loss in an
inevitable consequence of aging
◦ By the late 20s, or 10 years after adult height is
reached, skeleton no longer adds to bone density
◦ After ≈40 years of age, regardless of calcium
intake, bones begin to reduce density
 Loss can be slowed by a diet high in calcium along
with sufficient physical activity
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Low intakes of calcium are associated with an increased
risk of colon and rectal cancer as compared to higher
calcium intakes
To protect against bone loss, high calcium
intakes early in life are recommended
◦ A calcium-poor diet during the growing years may
prevent a person from achieving peak bone mass
◦ Insufficient bone calcium increases the risk of
osteoporosis (adult bone loss)
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How Much Calcium Do I Need?
◦ Setting recommended intakes is difficult
◦ Absorption varies with: age, vitamin D status,
dietary calcium intake
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Recommended intakes are high for children
and adolescents along with Vitamin D
◦ People develop their peak bone mass during their
growing years
◦ Average intakes among growing individuals are too
low to meet recommendations
© 2006 Thomson-Wadsworth
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Calcium consumption
 Average woman consumes 1/3 of RDA
 Average man consumes ~3/4 of RDA
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Deficiency
◦ Associated with all sorts of major illnesses
including
 Adult bone loss
 High blood pressure
 Kidney stones
◦ Consumption of milk, one of the best sources of
calcium, has declined
 While the consumption of beverages such as soft
drinks has dramatically increased
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Milk, Yogurt, and Cheese Group
◦ Children who don’t drink milk often have lower
calcium intakes and poorer bone health than those
who drink milk regularly
◦ People with lactose intolerance, dislike, or allergy
can obtain calcium from other sources
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Other non-milk choices
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Yogurt
Kefir
Buttermilk
Cheese--Especially low-fat or fat-free varieties
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Vegetables: Dark greens of all kinds
◦ Superb sources of riboflavin
◦ Indispensable for the vegan or anyone else who does
not drink milk
◦ Good sources of calcium
 Rutabaga, Broccoli, Beet and collard greens, Turnip
greens, Bok Choy & Kale
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EXCEPTIONS: Spinach, Swiss chard, rhubarb
◦ Equal to milk in calcium content
◦ Provide little to the body because they contain binders
that prevent calcium absorption
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Causes of Osteoporosis
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Gender
Advanced age
Genetics
Environmental factors
Environmental factors
 Poor nutrition
 Involving calcium and vitamin D
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Estrogen deficiency in women
Lack of physical activity
Being underweight
Use of tobacco and alcohol
Possibly: excess protein, sodium, caffeine, soft drinks
Inadequate vitamin K intake
© 2006 Thomson-Wadsworth
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Second most abundant mineral in the body
Role
≈85% in the crystals of the bone and teeth
Maintain the acid-base balance of cellular fluids
Part of DNA and RNA
Phosphorus compounds carry, store, and release
energy in the metabolism of energy nutrients
◦ Phosphorous compounds assist many enzymes and
vitamins extracting the energy from nutrients
◦ Forms part of phospholipids
◦ Present in some proteins
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Barely qualifies as a major mineral
◦ Only ≈1 ounce in the body of a 135-pound person
 Over half in the bones
 The rest in muscles, heart, liver, other soft tissues
 Only 1% in body fluids
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Critical to many cell functions: 300+ enzymes
Release and use of energy from nutrients
Directly affects the metabolism of K+, Ca++ & Vit D
Acts in the cells of all soft tissue
Needed for the proper functioning of muscles
Promotes resistance to tooth decay by holding calcium
in tooth enamel
Needs and deficiency
◦ Needs are easily met by almost any diet
 Therefore, deficiencies are unknown
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Source
◦ Animal protein is the best source
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Deficiency
◦ May occur as a result of
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Inadequate intake
Vomiting & Diarrhea
Alcoholism & Protein malnutrition
Diuretic use
Deficiency symptoms
◦ Causes hallucinations
◦ Overt deficiency symptoms are rare in normal,
healthy people
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Low intake is common
◦ Most Americans receive only ≈75% of the
recommended magnesium from their diets
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Sources
 Easily washed and peeled away from foods during
processing
 In some parts of the country, water contributes
significantly to magnesium intake
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Toxicity
 Rare but can be fatal
 Only occurs with high intakes from: Supplements or
magnesium salts
 Accidental poisonings
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Toxicity symptoms
 Severe diarrhea
 Acid-base imbalance
 Dehydration
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Positive ion in sodium chloride (table salt)
◦ 40% of the weight of sodium chloride
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Role
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Fluid balance
Electrolyte balance
Maintenance of extracellular fluid balance
Acid-base balance
Muscle contraction
Nerve transmission
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Deficiency
◦ No known human diets lack sodium
 Most foods include more salt than is needed
◦ Body absorbs sodium freely
◦ Kidneys filter excess sodium out of the blood into
the urine
◦ Kidneys will also conserve sodium
◦ Small sodium losses occur in sweat
◦ The amount of sodium excreted in a day equals the
amount ingested that day
© 2006 Thomson-Wadsworth
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Sodium Intakes
◦ Adults in the U.S. exceed the Tolerable Upper Intake
Level by more than a third
◦ Asian peoples, whose staple sauces and flavorings
are based on soy sauce and MSG, may consume the
equivalent of 30 to 40 grams of salt per day
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A dietary that may help salt-sensitive and
non-salt-sensitive people is the DASH diet
◦ This diet often achieves a lower blood pressure
than restriction of sodium alone
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DASH diet
◦ Greatly increased intake of fruits and vegetables
◦ Adequate amounts of nuts, fish, whole grains,
low-fat dairy products
◦ Occasional small portions of red meat, butter,
and other high-fat foods and sweets
◦ Import role of potassium as a sodium antagonist
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Other reasons for reducing salt intake
◦ Older people without clinical hypertension often die
of stroke
 Reducing dietary sodium may lower their blood
pressure enough to reduce stroke risks
◦ Excess dietary sodium increases calcium excretion
 This may compromise the integrity of the bones
◦ Excessive salt may stress a weakened heart,
aggravate kidney problems, may be a cause of
stomach cancer
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The principal positively charged ion inside the
body’s cells
Role
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Maintenance
Maintenance
Maintenance
Maintenance
of
of
of
of
fluid balance
electrolyte balance
cell integrity
heartbeat
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Deficiency
◦ Sudden deaths occur during fasting or severe
diarrhea due to heart failure caused by potassium
loss
◦ Dehydration leads to a loss of potassium from
inside cells
 When cells of the brain lose potassium, the brain loses
the ability to notice the need for water
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With low potassium intake
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Salt-sensitive hypertension becomes worse
Glucose tolerance is impaired
Metabolic acidity increases
Calcium losses from bones accelerates
Kidney stone risk increases
◦ **In healthy people, any reasonable diet provides
enough potassium to prevent dangerously low
blood potassium
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Toxicity
◦ Potassium from food is safe
◦ Potassium injected into a vein can stop the heart
◦ Over-the-counter potassium chloride pills should
not be used except on a physician’s advice
 Even though they are sold without a warning label
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Major negative ion in the body
Role
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Accompanies sodium in fluids outside cells
Acid-base balance
Electrolyte balance
Component of hydrochloric acid
Source
◦ Salt
 Both added and naturally occurring
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Deficiency
◦ No known diet lacks chloride
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Role
◦ Required for the synthesis of many important
sulfur-containing compounds
 Certain antioxidants
 Thiamin
 Sulfur-containing amino acids
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Deficiencies
◦ Unknown
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Toxicity
◦ From too much sulfate in water, either naturally
occurring or from contamination
◦ Diarrhea
◦ Colon damage
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Difficult to determine the precise roles of
trace elements
Intake recommendations have been
established for nine trace minerals
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Role
◦ Component of thyroxine
 Manufactured by the thyroid gland that is responsible
for the regulation of basal metabolic rate
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Sources
◦ Amount in food varies with amount in soil in which
plants are grown or on which animals graze
◦ Seafood
 Iodine is plentiful in the ocean; sea salt, very little
◦ Iodized salt: <half-teaspoon meets RDA
◦ Use of iodized salt in fast-food andrestaurant
◦ Bakery products & Milk
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Deficiency
◦ Enlarged thyroid
(goiter)
◦ Sluggishness
◦ Weight gain
© 2006 Thomson-Wadsworth
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Severe deficiency during pregnancy
◦ Cretinism
 Extreme irreversible mental and physical retardation
 Can be averted if the woman’s deficiency can be
detected and treated within the first six months of
pregnancy
◦ Iodine deficiency is one of the most treatable and
preventable causes of mental retardation
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Potassium iodide
◦ Effectively blocks damage to the thyroid gland
caused by radioactive iodine from nuclear
emergencies
◦ Given at the right time and at the right dosage
potassium iodide will greatly reduce the risk of
thyroid cancer
◦ Given at the wrong dosage or at the wrong time,
potassium iodide is useless or toxic
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Most of the iron in the body is a component
of either hemoglobin or myoglobin
◦ Hemoglobin is the oxygen-carrying protein RBCs
◦ Myoglobin is the oxygen-holding muscle protein
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Body cells combine oxygen with the carbon
and hydrogen they release as they break
down nutrients
◦ Therefore, the body needs a continuous supply of
oxygen
 Red blood cells supply this oxygen
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Additional roles of iron
◦ Helps many enzymes use oxygen
◦ Needed to make
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New cells
Amino acids
Hormones
Neurotransmitters
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What Happens to a Person Who Lacks Iron?
◦ Iron deficiency
 Result of absorption not compensating for losses or
low dietary intakes
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Iron deficiency anemia
◦ Often occurs with iron deficiency
◦ A person can be iron deficient without being anemic
◦ Anemia refers to depletion of iron stores resulting
in low blood hemoglobin
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Severe iron deprivation  insufficient
hemoglobin production to fill new blood cells
 anemia (cells are smaller and lighter red
than normal)
◦ Cells contain too little hemoglobin and thus deliver
too little oxygen  limits cell’s energy metabolism
 tiredness, apathy, a tendency to feel cold
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Fatigue and can impair physical work capacity
and productivity
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Causes of Iron Deficiency and Anemia
◦ Women are at greater risk of an iron deficiency than
men
 Need more iron
 On average, eat less food
◦ Infants over 6 months of age, young children,
adolescents, menstruating and pregnant women
have increased iron needs
 To support growth of new tissue and/or to replace iron
loss
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Most common nutrient deficiency(1.2B people)
 Parasitic infections cause people to lose blood daily
 In digestive tract, ulcers, sores, and inflammation can
cause sufficient blood loss to cause anemia
 In developing countries, ~1/2 of preschool children &
pregnant women suffer iron-deficiency anemia
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In the US ~10% of toddlers, adolescent girls &
women of childbearing age
◦ The iron status of U.S. infants and young children
has improved over the last decade
 Increased breastfeeding, which promotes iron
absorption & iron-fortified infant formula /cereals
 WIC provides coupons redeemable for foods high in iron
© 2006 Thomson-Wadsworth
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Can a Person Take In Too Much Iron?
◦ Iron is toxic in large amounts
◦ Once absorbed it is difficult to excrete
◦ The body defends against iron overload
(hemochromatosis) by controlling its entry
 Intestinal cells trap some of the iron and hold it within
their boundaries; when these cells are shed the excess
iron they collected is lost from the body
 When iron stores fill up, less iron is absorbed
◦ The danger of iron overload is an argument
against high-level iron fortification of foods
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Iron supplements can reverse iron-deficiency
anemia from dietary causes
◦ May create oxidative reaction in the digestive tract
that may damage its linings
 Especially in those suffering with inflammation of
these tissues
◦ Iron supplements are a leading cause of fatal
accidental poisonings among U.S. children under 6
years old
© 2006 Thomson-Wadsworth
© 2006 Thomson-Wadsworth
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Iron Recommendations and Sources
◦ Adult men rarely experience iron-deficiency anemia
 If a man has a low hemoglobin concentration, his
health-care provider should examine him for a bloodloss site
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Iron Recommendations and Sources
◦ Vegetarians, because the iron in their foods is not
well absorbed and because their diets lack factors
from meat that enhance iron absorption, are
advised to obtain 1.8 times the normal requirement
◦ To meet iron needs, is best to rely on foods
 Iron from supplements is much less well absorbed
than iron from food
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The usual Western diet provides only about 5
to 6 mg iron/1,000 calories
◦ For an adult male this does not pose a problem
◦ A female who eats fewer calories and needs more
iron needs to select high-iron, low-calorie foods
from each food group
◦ Pregnant women need an iron supplement
◦ Iron supplements should only be taken when
recommended by a physician
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Absorbing Iron
◦ Iron occurs in two forms in foods
 Some is bound into heme
 The iron-containing part of hemoglobin and myoglobin in
meat, poultry and fish
 Some is nonheme iron
 Found in foods from plants and in nonheme iron of meats
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Absorbing Iron
◦ Heme iron is more reliably absorbed than nonheme
iron
 Healthy people with adequate iron stores absorb heme
iron at a rate of ≈23%
 People absorb nonheme iron at rates of 2%-20%
 Depending on dietary factors and iron stores
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Absorbing Iron
(continued)
◦ MFP factor
 Found in meat,
fish and poultry
 Promotes the absorption of nonheme iron from other
foods eaten at the same time
◦ Vitamin C can triple absorption of nonheme iron
from foods eaten in the same meal
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Impairment of iron absorption
 Tannins
 Found in tea and coffee
 Calcium and phosphorus
 Milk
 Phytates
 Found in the fiber of lightly processed legumes and wholegrain cereals
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Impairment of iron absorption (continued)
◦ Black tea is exceptional in reducing iron absorption
◦ Clinical dieticians advise people with iron overload
to drink it with their meals
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The amount of iron
absorbed from a meal
depends partly on the
interaction between
promoters and inhibitors
of iron absorption
Cooking in an iron pan
adds iron to food
◦ This iron is in the form of
iron salts somewhat like
those in supplements
◦ The iron content of 100
grams of spaghetti sauce
 Simmered in a glass dish =
3mg
 Cooked in a black iron skillet
= 87mg
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Role
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Helps nearly 100 enzymes
Regulation of gene expression in protein synthesis
Affects behavior and learning
Assists in immune function
Wound healing
Sperm production
Taste perception
Fetal development
Growth and development in children
Produces the active form of vitamin A
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Even a mild deficiency can result in:
◦ Impaired immunity
◦ Abnormal taste
◦ Abnormal vision in the dark
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Problem: Too Little Zinc
◦ First reported in the 1960s from studies of growing
and adolescent boys in the Middle East
 Diets were low in animal protein and high in whole
grains and beans
 The breads were not leavened
 In leavened bread, yeast breaks down phytates as the
bread rises
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Deficiency symptoms
◦ Adverse affects on growth
◦ Profoundly alters digestive function
 And causes diarrhea, which worsens the malnutrition
already present with regard to all nutrients
◦ Drastically impairs the immune response
 Making infections likely
◦ Infections of the intestinal tract
worsen malnutrition
 Including zinc malnutrition
◦ Zinc deficiency disturbs
thyroid function
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Symptoms are so pervasive that when
confronted with zinc deficiency, a physician is
more likely to diagnose it as general
malnutrition and sickness
Severe zinc deficiencies are not widespread in
developed countries
◦ At risk:
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Pregnant women
Young children
Elderly
Poor
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Problem: Too Much Zinc
◦ Toxic in large quantities
 In high enough doses, supplements can cause serious
illness or death
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Over time, regular doses a few milligrams
above the recommended intake can block
copper absorption and lower the body’s
copper content
◦ In animal studies, this has lead to degeneration of
heart muscle
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In high doses
◦ May reduce blood concentrations of HDLs
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High doses can also inhibit iron absorption
A protein that carries iron from the
digestive tract to tissues also carries zinc
◦ If there is excess zinc, there is little room left for
this protein to pick up iron from the digestive
tract
◦ If there is too much iron, there is little room for
this protein to pick up zinc from the digestive
tract
 Thus impairing zinc absorption
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Zinc and iron are are often found together in
foods
◦ Food sources never cause imbalances in the body
◦ Zinc from lozenges and spray, sold for the
treatment of the common cold, may or may not
provide the intended relief
 But contributes supplemental zinc to the body
◦ Unlike iron, excess zinc has a normal escape route
from the body
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Food Sources of Zinc
◦ Major sources
 Meats
 Shellfish
 Poultry
◦ Plant sources of zinc are not absorbed as well as
animal sources
 Some legumes
 Whole grains
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Most people meet the recommended intake
levels
◦ Men: 11 mg/day
◦ Women: 8 mg/day
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Vegetarians are advised to eat a varied diet
that includes whole-grain breads well
leavened with yeast
◦ Leavening helps make the zinc available for
absorption
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Role
◦ Protects vulnerable body chemicals against
oxidative destruction
 Assists a group of enzymes that, in concert with
vitamin E, work to prevent the formation of free
radicals and prevent oxidative harm to cells and
tissues
◦ Plays roles in activating thyroid hormone
◦ Low blood selenium correlates with the
development of some forms of cancer
 Especially prostate cancer
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Low intake and Deficiency
Prostate cancer
◦ 4th leading cancer in men worldwide
 Black men in the U.S. suffer the highest rates of all
◦ Men with adequate selenium in their blood have a
lower incidence of prostate cancer than men whose
blood measures are low
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Heart disease
◦ A type first identified in China among people from
areas with selenium-deficient soils
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Sources
◦ No need to worry about a selenium deficiency if you
eat a normal diet composed of unprocessed foods
◦ Widely distributed in foods such as
 Meats
 Shellfish
 Vegetables and grains grown in selenium-rich soils
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Toxicity
◦ Long-term supplementation
◦ UL: 400 micrograms/day
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Not essential: only trace amounts in human
body
Role
◦ Crystalline deposits in bone and teeth
 Forms more decay-resistant fluorapatite in
developing teeth
◦ Helps prevent dental caries
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Sources
◦ Primary source: fluoridated drinking water
 65+% of U.S. population has access to water with
optimal fluoride concentration
 Such water typically delivers ≈1 mg/day (≈1 part per
million)
 Rarely present in bottled water
 Unless it was added at the source
 As in bottled municipal tap water
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Deficiency
◦ Where fluoride is missing, the incidence of dental
decay is very high
 Fluoridation of water is recommended for public dental
health
◦ Fluoridation is a practical, safe, and cost-effective
way to help prevent dental caries in the young
◦ Sufficient fluoride during the tooth-forming years
of infancy and childhood gives lifetime protection
against tooth decay
Percent of
population
in each
state with
access to
fluoridated
water
© 2006 Thomson-Wadsworth
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Toxicity
◦ Discoloration of teeth (fluorosis) may occur
 Occurs only during tooth development, never after
teeth have formed. Irreversible
◦ Widespread availability of fluoridated toothpaste
and mouthwash, foods made with fluoridated
water, and fluoride-containing supplements
 Mildest form of fluorosis
 Characteristic white spots form in the tooth enamel
◦ No evidence connecting fluoridation of with cancer
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Role
◦ Works closely with insulin to regulate and release
energy from glucose
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Deficiency
◦ Impaired insulin action
 Resulting a a diabetes-like condition of high blood
glucose
 Resolves with chromium supplementation
◦ Supplements cannot cure the common forms of
diabetes
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Chromium supplements
◦ Will not build extra muscle mass or melt off fat
◦ Does not lower blood cholesterol
◦ Diets high in simple sugars and low in whole,
nutrient-dense foods deplete the body’s supply of
chromium
◦ Becomes more common as people become more
dependent on heavily refined foods
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Toxicity
◦ Chromium compounds used in various industrial
processes are known carcinogens
 The form found in foods and supplements is nontoxic
by comparison
 Amount up to 200 micrograms/day seems to be safe
◦ Supplementation may cause skin eruptions
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Source
◦ Widely distributed in the food supply
 Especially in unrefined foods and whole grains
 Lost during food processing
◦ Exists in foods in complexes with other compounds
that make it easily controlled and used by the body
 These chromium-containing compounds are termed
biologically active chromium or glucose tolerance
factor
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Source
◦ Widely distributed in the food supply
 Especially in unrefined foods and whole grains
 Lost during food processing
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Best chromium sources
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Liver
Whole grains
Nuts
Cheeses