Transcript Chapter 4: The Human Body: From Food to Fuel

Water & the Minerals
Readings
– Chapter 11 & Chapter 12
– Omit details p 463 - 465
– Omit details in figs
11.4,11.6, 11.7, 11.10,
11.11, 11.21
– Omit the sections on
“Manganese”,
“Molybdenum”, and
“Other Trace Elements
and Ultratrace Elements”
Water
99 lb water
Water is the most
indispensable nutrient.
Our bodies are made of 27 lb protein
about 50 - 75% water.
24 lb fat
10 lb minerals
& glycogen
160 lb man
Functions of Water
• transport of nutrients & waste compounds
throughout body
• maintains the structure of large molecules
• participation in metabolic reactions
• solvent for minerals, vitamins, amino acids,
glucose, and other small molecules
• lubrication and cushioning of joints, eye,
spinal cord
• regulates body temperature
• maintains blood volume & blood pressure
Functions of Water
Water in the Body
extracellular fluid
intracellular
fluid
interstitial fluid
plasma
Water Sources
Liquids
550 - 1500 ml
Metabolism
200 - 300 ml
Foods
700 - 1000 ml
Total = 1450 - 2800 ml
Water in Selected Foods
•
•
•
•
chicken breast or salmon = 60%
cooked white rice = 70%
bread = 40%
pears = 85%
Water Intake
Recommendations
• 1–1.5 ml water/kcal of energy expended
Example
• energy expenditure = 2000 kcal/day
• water needs = 2000 - 3000 ml water/day
Note
• alcoholic beverages, soft drinks, and
beverages containing caffeine are NOT good
substitutes for water
• act as diuretics
Water Intake
Healthy choices…
Less healthy choices…
Tap vs. Bottled Water?
• in NA, bottled water is regulated by similar
standards as for tap water
• in fact, some tap regulations aren’t imposed on
bottled water
• ~40% of bottled water is just processed tap water
• it costs ~10,000 times more to produce bottled
than it does tap water
• Some people do not like taste of tap water.
– Leave on counter to allow chlorine to evaporate
• GVRD recommends letting tap water run for a
minute if it has been off for several hours.
Is bottled water better?
Water Excretion
Feces
150 ml
Kidneys
500 - 1,400 ml
Lungs
350 ml
Skin
450 - 900 ml
Total = 1450 - 2800 ml
Dehydration
• occurs when water loss exceeds water intake
• may result from excessive water loss or
inadequate intake
• onset & severity of symptoms depend on
activity, fitness level, acclimatization,
temperature, & humidity
• leads to failure to regulate body temperature,
causing hyperthermia
• electrolyte imbalances contribute to cardiac
arrhythmias & death
Dehydration
% Weight Lost
Symptoms
1-2%
• thirst, fatigue, vague discomfort, loss of appetite
3-4%
• impaired physical performance, dry mouth, reduction in
urine, flushed skin, impatience, apathy
5-6%
• difficulty concentrating, headache, irritability,
sleepiness, impaired temperature regulation, increased
respiratory rate
7-10%
• dizziness, muscle spasms, loss of balance, delirium,
exhaustion, collapse
Water Intoxication
• excess consumption of water may lead
to dilution of the sodium concentration
in the blood causing hyponatremia
• children, elderly are most at risk;
problem also has a higher incidence in
endurance athletes
Thirst
• most important stimulus for drinking
• stimuli for thirst are:
reduced blood volume & blood pressure
- Athletics, infants, elderly, air travel, illness (fever,
diarrhea)
- Also triggered with high salt intake
- dryness of the mouth & mucous
membranes lining the esophagus
• Response:
– ADH (anti diuretic hormone)
•
•
Triggers kidneys to conserve water
Strong alcohol inhibits ADH, lose water, manifest
symptoms of low water.
Substances that Affect Fluid Balance
Alcohol
• suppresses ADH secretion, increasing fluid
loss
• excessive consumption can lead to
dehydration, a key contributing factor to many
of the symptoms of a hangover
- Aspirin does not help hangovers
• Drinking less alcohol does
Caffeine
• inhibits the activity of ADH, increasing fluid
loss (still net gain of fluid)
Introduction to the Minerals
• inorganic elements
• some travel freely,
others require
transporters
• often interact with each
other
• have many and
various functions
Mineral Bioavailability
Nutritional status
(needs)
Interactions with
other minerals
Fibers, Phytates,
Oxalates
Factors that
affect mineral
bioavailability
Intestinal
Acidity
Polyphenols
Sodium (Na+)
Functions
• principle cation of the ECF & primary regulator
of ECF volume
• helps maintain acid-base balance
• essential for electrical signaling in nerves and
muscles
Recommendations
• Can: 115 mg/day minimum; US: 500 mg/day
• AI = 1500 mg; Daily Value = 2400 mg
• 1 tsp table salt = 2000 mg sodium
Sodium in Foods
• processed foods contain the most sodium
– 75% of sodium in average North American diet
from processed foods
– 15% from salt added during cooking & at table
– only 10% from sodium naturally present in food
– 1 oz Cornflakes contains more sodium than 1 oz
salted peanuts
– ½ cup instant chocolate pudding contains more
sodium than either the cornflakes or the peanuts
Sodium in Foods
Sodium (Na+)
Deficiency
• does not result from inadequate intake!
• may occur due to excessive loss caused by:
– vomiting
– diarrhea
– heavy sweating during physical activity
• may lead to hyponaturemia
– symptoms include muscle cramps, mental apathy, loss of
appetite
• replaced through food or beverages containing
both sodium & glucose
Sodium (Na+)
Toxicity
• acute symptoms include edema &
hypertension
• prolonged excessive intake MAY contribute to
hypertension in salt-sensitive individuals
• salt restriction in combination with a diet rich
in fruits & vegetables decreases blood
pressure in these individuals
• high sodium intake also linked with an excess
of calcium excretion in the urine
Potassium (K+)
• principle cation of the intracellular fluid
• important for electrical signaling of nerves
and muscles
• helps regulate heart rate & blood pressure
• a diet LOW in potassium is associated with
an INCREASED risk of hypertension
• potassium rich fruits and vegetables linked to
a decreased risk of stroke
• AI = 4700 mg; Daily Value = 3500 mg
Potassium (K+): Food Sources
• best food sources:
– fresh foods, especially fruits and
vegetables
• potassium is LOST with food
processing
Potassium (K+)
Deficiency
• rare as a result of dietary insufficiency!
• hypokalemia = most common electrolyte
imbalance
– may result from excessive loss associated with heavy
sweating, vomiting, or diarrhea
– symptoms include muscular weakness, paralysis,
confusion
Toxicity
• result of consumption of supplements
Effect of Food Processing on
the Mineral Composition of
Foods
Chloride (Cl-)
• important ion in the extracellular fluid
• maintains fluid and electrolyte balance
• forms part of hydrochloric acid (HCl) in the
stomach
• diets rarely lack chloride
• losses may occur with excess sweating, chronic
diarrhea, or vomiting
– loss of Cl- & H+ produces metabolic alkalosis
• blood concentrations may rise with severe
dehydration
Calcium (Ca2+)
• most abundant mineral in the body (99% of
calcium is contained within our bones)
– maintains bone structure
– serves as a pool to maintain calcium levels
elsewhere in the body
Recommendations
• Adolescents: 1300 mg/day
• Adults: 1000 mg/day
trabecular bone
Calcium: Functions
• with phosphorous
forms a crystal called
hydroxyapatite
– attaches to a collagen
matrix to mineralize
bones and teeth
– gives bones their
strength and rigidity cortical bone
Calcium: Functions
• ionized calcium also important for:
– muscle contraction
– heart function
– nerve function: transmission of nerve impulses,
release of neurotransmitters from nerve cells
– blood clotting: formation of fibrin
– regulation of blood pressure
– intracellular signaling: binds with calmodulin
• activating enzymes and regulating various
processes ie. hormone secretion
Calcium: Sources
• most abundant in milk and other dairy
products
• non-dairy sources include:
–
–
–
–
–
–
cauliflower
bok choy
broccoli
fortified soy products
canned fish with bones
bone soup stock
 50%
absorbed
cauliflower, watercress, Chinese
cabbage, head cabbage, brussels
sprouts, rutabaga, kolhrabi, kale,
mustard greens, bok choy, broccoli,
turnip greens, calcium fortified foods
and beverages
 30%
absorbed
milk, calcium-fortified soy milk,
calcium-set tofu, cheese, yogurt
 20%
absorbed
almonds, sesame seeds, pinto beans,
sweet potatoes
 5%
absorbed
spinach, rhubarb, Swiss chard
Calcium: Deficiency
• low calcium intake during growth prevents
bone from reaching optimal mass and density
 development of osteoporosis later in life
• with inadequate calcium intake, blood calcium
concentrations are maintained at the expense
of bones
• low blood calcium = hypocalcemia
– not a result of low calcium intake!
– causes include kidney failure, parathyroid
disorders, Vitamin D deficiency
– may lead to muscle spasms, convulsions
Calcium: Toxicity
• symptoms include constipation and increased
risk of kidney stones
• excess calcium also interferes with the
absorption of other minerals
– e.g. iron, magnesium, zinc
• high blood calcium = hypercalcemia
– not caused by excessive intake!
– primary causes usually cancer, overproduction of
PTH, or excess Vitamin D
– effects include fatigue, confusion, loss of appetite,
constipation, and calcification of tissues
Phosphorous (P)
• second most abundant mineral in the body
• with calcium forms hydroxyapatite crystals of
bones and teeth
• other important functions include:
– buffers pH
– part of DNA, RNA, phospholipids, and some
proteins
– assists in energy metabolism: part of ATP
– activation and deactivation of enzymes through
phosphorylation reactions
• deficiency and toxicity are rare
Phosphorous: Sources
Milk and
dairy
products
Steak,
liver, and
other
meats
Chick peas
and other
legumes
Salmon,
tuna, cod
and other
fish
Hypophosphatemia
• = low blood phosphate
• not a result of dietary insufficiency!
• common causes include:
– hyperparathyroidism, Vitamin D deficiency,
overuse of antacids that bind phosphate
• symptoms may include:
– anorexia, dizziness, bone pain, muscle weakness,
waddling gait
• chronic hypophosphatemia leads to:
– muscle weakness and damage, respiratory
problems, rickets, osteomalacia
Hyperphosphatemia
•
•
•
•
= high blood phosphate
not a result of excess consumption
commonly a consequence of kidney disease
may also result from:
– an underactive parathyroid gland, excess Vitamin
D supplements, or overuse of phosphatecontaining laxatives
• excess phosphate may bind calcium leading
to muscle spasms and convulsions
Magnesium: Functions
• important as a cofactor for metabolism and
required for protein synthesis
– essential for the production of ATP by the electron
transport chain
• holds calcium in tooth enamel
• participates in muscle contraction and blood
clotting
• protects against hypertension & heart disease
• supports normal functioning of the immune
system
Magnesium: Sources
Legumes
Oysters
Spinach
Sunflower
seeds
Figs
Potatoes
Magnesium: Sources
• refined foods lose Mg2+ during processing
– not added back with enrichment
• “hard” tap water may be a significant source
• about 50% of magnesium is absorbed
– high fiber foods containing fermentable
carbohydrates (resistant starches,
oligosaccharides, and pectin) increase
magnesium absorption
• high Ca2+ intake (e.g. from supplements) can
interfere with absorption of Mg2+
Hypomagnesia
• usually only occurs with disease (e.g. kidney,
alcoholism, prolonged diarrhea)
• symptoms include weakness, tetany, impaired
functioning of the central nervous system,
cardiac arrhythmias
Hypermagnesia
• uncommon in the absence of kidney disease
• results in nausea, weakness, diarrhea,
dehydration and alkalosis
Sulfur
• not found alone as a nutrient
• in body, exists as a component of other
organic compounds (e.g. thiamin, biotin,
methionine, cysteine)
• important for protein structure
– permits the formation of disulfide bridges that
help proteins fold in specific ways
• obtained in diet through consumption of sulfur
containing amino acids
– deficiency is unknown in humans
Trace Minerals: An Overview
• only in miniscule amounts
• content in foods depends on soil content,
water composition, & food processing
• interactions among trace minerals are
common
• the trace minerals include: iron, zinc, iodine,
selenium, copper, fluoride, chromium,
molybdenum & manganese
Iron
• exists in two forms:
– “reduced” or ferrous iron (Fe2+)
– “oxidized” or ferric iron (Fe3+)
Functions
• forms part of electron carriers called
cytochromes in the ETC (metabolism)
• forms part of proteins hemoglobin &
myoglobin
• required by enzymes that synthesize
collagen, hormones, neurotransmitters,
and amino acids
• important for immune function
Iron in Foods
Types of Iron
• heme
– from food derived from animal food
sources
– 25% absorption
• non-heme
– from both animal and plant derived foods
– only 10% is absorbed
Iron: Sources
3 oz steak = 3 mg
3 oz liver = 3 mg
½ cup clams = 22 mg
3 oz shrimp = 2 mg
Best source per kcal
Iron: Sources
Others
• broccoli, spinach, dried fruits, eggs, legumes,
enriched grains and cereals
Contamination Iron
• iron found in foods as the result of
contamination by inorganic iron salts from
iron cookware or iron containing soils
Recommendations
• Men:
8 mg per day
• Women: 18 mg per day
Iron Absorption
Factors Enhancing
Absorption
• MFP factor
• Vitamin C
• citric, malic & lactic
acid
• HCl acid
• sugars
Factors Inhibiting
Absorption
•
•
•
•
high fiber diet
phytates
oxalates
calcium and
phosphorous
• EDTA
• Tannins (found in tea)
Iron: Absorption & Metabolism
• iron is not readily
excreted
• balance is
maintained by
adjusting
absorption
•  iron stores, 
iron absorption
Iron: Transport & Storage
• the intestine absorbs iron and stores it in
protein called mucosal ferritin
– iron that is not needed is lost when intestinal cells
are shed
• when body needs iron, it is moved to another
protein transferrin
– transports iron to the rest of the body where it is
needed, such as the bone marrow where red
blood cells are synthesized
– think “transferrin” = “transport”
Iron: Transport & Storage
cont.
• surplus is stored in ferritin in the liver,
bone marrow and spleen
• even greater concentrations of iron lead
to storage of iron in another protein
called hemosiderin
• storage important to prevent free iron
from acting as a free radical
Iron: Deficiency
• most common nutrient deficiency world wide
Ways Iron is Lost from the Body…
• some iron is lost daily from the digestive tract
• only tiny amounts lost through feces, urine,
sweat and shedding skin
• blood loss
Iron: Deficiency cont.
Stages in the Development of Deficiency
• iron stores diminish
– measured by assessing serum ferritin
• levels of functional iron decrease
– decreased transferrin saturation
– accumulation of erythrocyte protoporphyrin
• iron deficiency anemia: “microcytic
hypochromic anemia”
– production of hemoglobin decreases
– decrease in hematocrit
– decrease in red blood cell size
Iron: Deficiency cont.
Symptoms
• microcytic hypochromic anemia
– red blood cells are small and pale
– results in fatigue, weakness, headaches, pallor,
poor resistance to cold
Normal
Anemic
• cognitive impairment, behavioural changes,
reduced learning ability
Iron: Toxicity
• iron absorption decreases when body needs
decrease
• excess iron is referred to as “iron overload”
– Hemochromatosis
• hereditary disorder characterized by enhanced
iron absorption
– Hemosiderosis
• due to long-term overconsumption of iron
• characterized by deposits of hemosiderin in
tissues
Iron: Toxicity cont.
Symptoms & Consequences
• tissue damage, deposits of iron
• apathy, lethargy and fatigue
• increased infections
• increased risk of heart disease:
– free iron acts as a pro-oxidant
– may oxidize LDL and contribute to development
of atherosclerosis
• increased risk of cancer
– increased free radical formation may contribute to
DNA damage
Iron: Toxicity cont.
Symptoms & Consequences
• poisoning in children if ingest
supplements
Which are candies and
which are supplements?
Iron Supplements
Zinc: Functions
• acts as a cofactor for many enzymes
Example: metalloenzymes
• assists in immune function
• important for growth and development
– required for DNA and RNA synthesis
• synthesis of heme in hemoglobin
• releases Vitamin A from stores and converts
to its active form
• forms part of an antioxidant enzyme that
protects from free radicals = zinc superoxide
dismutase
Zinc: Functions cont.
• stabilizes cell membranes and helps
protect them from free radical attack
• interacts with platelets in blood clotting
• required for the synthesis, storage, and
release of the hormone insulin
• regulates thyroid hormone function
• influences behaviour and learning
performance
• plays important role in protein synthesis
• participates in carbohydrate, fatty acids
and alcohol metabolism
• others: sperm production, fetal
development, taste
Zinc: Absorption & Metabolism
• absorption rate varies between 15 - 35%
– dependant on zinc status
– absorption inhibited by fibers and phytates
• after absorption may be stored by the protein
metallothionein
• transported in the blood by several proteins
including:
– albumin
– alpha2-macroglobulin
– transferrin
Zinc
Interactions
• an excess of dietary iron may reduce
zinc absorption
– a dietary iron : zinc ratio > 2 : 1 decreases
zinc absorption
• large doses of zinc:
– inhibit iron absorption
– interferes with copper absorption
Zinc: Sources
• richest sources are protein rich foods
Examples
oysters 3 oz > 12 mg
crab 3 oz = 4.5 mg
lean ground beef 3 oz = 4 mg
yogurt 1 cup = 2 mg
Recommendations
Men = 11 mg/day
Women = 8 mg/day
Zinc: Deficiency
• most vulnerable: pregnant
women, young children,
the elderly, poor
• may result from other
disease conditions that
affect absorption or
excretion
Symptoms
• extreme deficiency leads to
severe growth retardation
and arrested sexual
development during growth
= dwarfism
Zinc: Deficiency cont.
Symptoms cont.
• impaired immune function
• altered taste perception
• diarrhea
• symptoms of a Vitamin A deficiency
• impaired thyroid function
• anorexia
• impaired glucose tolerance
• slowed wound healing
Zinc: Toxicity
• toxicity from a high dietary intake is rare
• acute excessive doses may result in
nausea, vomiting, abdominal cramps,
diarrhea, headaches
• may interfere with iron and copper
absorption and metabolism
• chronic elevated intake may depress
immune function in elderly individuals
Selenium
Functions
• forms part of the enzyme glutathione
peroxidase
– an antioxidant
– important for protection from OFR
• important for thyroid hormone function
Food Sources
• protein rich foods such as tuna, lobster, pork,
eggs, also grains such as oatmeal, whole
wheat bread, brown rice and others
Selenium
Deficiency
• associated with a predisposition to a type of
heart disease called Keshan disease
Toxicity
• chronic high doses lead to brittle hair and
nails
• high doses produce vomiting, diarrhea, hair
loss, skin lesions and neurological problems
Iodine
• iodine in foods is converted to its ionic form
iodide by the body
Functions
• an integral part of thyroid hormone
• thyroid hormone has many important
functions including:
– regulation of basal metabolic rate
– regulation of body temperature
– necessary for reproduction and growth
Iodine: Sources
• iodized salt, ocean fish,
plants grown in iodine
rich soil, milk
• average intake of North
Americans is above
recommendation but
below toxic levels
Iodine: Deficiency
• results in hypothyroidism
• causes enlargement of the
thyroid gland called a goiter
• maternal iodine deficiency
during pregnancy leads to
cretinism in the developing
fetus
Iodine: Toxicity
• also enlarges the thyroid gland causing a
goiter
• poses risk of suffocation for a fetus if excess
consumed during pregnancy
– goiter may block airways
• upper limit is 1000 mg per day
Note
• a goiter may also develop from excess
consumption of goitrogens, an anti-thyroid
substance found in plants of the cabbage
family
Copper
Functions
• forms part of several enzymes
– e.g. superoxide dismutase, which functions as
an antioxidant enzyme
• important for the synthesis of hemoglobin
Sources
• legumes, whole grains, nuts, shellfish, organ
meats, seeds, water
Copper
Deficiency
• rare, may be associated with excess Vitamin
C or zinc which interfere with absorption
• symptoms include microcytic anemia
• in animals leads to increased blood
cholesterol and damage to blood vessels
Toxicity
• rare, may interfere with iron and zinc
metabolism
Fluoride
Functions
• forms fluorapatite crystals in teeth
– replaces the hydroxyl (OH-) in hydroxyapatite
crystals
Deficiency
• associated with dental decay
• 1 part fluoride to 1 million parts water =
best protection
• primary source of fluoride is drinking water;
also in tea and seafood
Fluoride
Toxicity
• fluorosis: damage to teeth that pits and
stains the enamel
• also leads to nausea, vomiting,
diarrhea, chest pain, and itching
Chromium
Functions
• regulates carbohydrate & lipid metabolism
• enhances insulin activity
Sources
• present in a wide variety of foods (e.g. liver,
brewer’s yeast, whole grains, nuts and seeds)
Deficiency
• produces a diabetes-like condition marked
by an inability to use glucose normally