WATER
The water in body fluids:
• Carries nutrients and waste products throughout
the body
• Maintains the structure of large molecules such as
proteins and glycogen
• Participates in metabolic reactions
• Aids in regulation of body temperature
• Maintains blood volume and pH balance
• Acts as a lubricant and cushion around joints and
inside eyes, and the spinal cord
ELECTROLYTES
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Water in the body contains numerous
dissolved minerals, called electrolytes, that
are kept in constant balance
When salts, such as NaCl, dissolve in water,
they break apart into + and – ions
+ = cations (sodium and potassium)
- = anions (chloride and phosphate)
Unlike pure water which conducts
electricity poorly, ions dissolved in water
carry an electrical current, hence they are
called electrolytes
ELECTROLYTES
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Na+ is the major cation in the extracellular
fluid, K+ is the predominant cation in the
intracellular fluid
ELECTROLYTES
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The balance of body fluids and the amount
of electrolytes are controlled precisely
In an electrolyte solution, the amount of +
charges always equals the amount of
negative charges
Whenever Na+ leaves a cell, other +ions
enter (like K+)
Whenever electrolytes move across the cell
membrane, water follows
WATER EXCRETION
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Our body loses water through: the skin, lungs,
feces (very little), urine
Depending upon the amount of protein, water, and
sodium consumed, we lose 1-2L each day through
the urine
Insensible water loss accounts for ~ ¼ to ½ of
daily fluid loss
Losses increase in: exercise, high altitude, low
humidity, high temperatures, illness (coughing,
fever, rapid breathing, and watery nasal
secretions)
Regulation of Fluid Excretion
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The kidneys adjust the amount and concentration
of urine in response to the body’s hydration status
Low water intake = low volume of concentrated
urine
High water intake = high volume of diluted urine
Osmoreceptors and antidiuretic hormone (ADH)
work together to regulate water excretion
THIRST
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Thirst is not always a reliable guide to
avoiding dehydration
Athletes, elderly people, and infants are
vulnerable to dehydration
How can we avoid dehydration?
From the International Journal of
Sports Nutrition
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Researchers concluded that “urine color
may be used in athletic/industrial settings to
determine whether a subject is adequately
hydrated”
Suggested that athletes (and others) should
seek to produce urine that is “very pale
yellow” or “straw-colored”
WATER INTAKE
RECOMMENDATIONS
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There is no RDA for water
General recommendation: 1 to 1.5 mL per
kcals expended (2400 kcal = 2400 mL or
2.4 litres)
Equals ~ 9.6 cups of water per day
WATER SOURCES
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Hydrating beverages: water, milk, fruit
juice, herbal tea, most foods (especially
fruits and vegetables)
Dehydrating beverages: alcohol, caffeinated
beverages (coffee, tea, some soft drinks)
Are Americans chronically dehydrated?
Per capita median intake of
water
672 ml (2.8 cups)
Per capita milk intake
312 ml (1.3 cups)
Per capita coffee and tea
intake
360 ml (1.5 cups)
Per capita soft drink intake
420 ml (1.75 cups)
Total per capita fluid
comsumption
1764 ml (7.35 cups)
What are the effects of chronic
dehydration?
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Diminished physical performance
Diminished mental performance
Diminished salivary gland function
Increased risk of urinary tract, colon, and
breast cancer*
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Is it possible to take in too much water?
HYPONATREMIA: Low concentration of
sodium in the blood
• Symptoms: can range from mild to severe
and can include nausea, muscle cramps,
disorientation, slurred speech, confusion,
and inappropriate behavior
• Seizures or coma, and death can occur
Do we need to replace
electrolytes during exercise?
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Plus approximately 30mg potassium
DIURETICS
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A diuretic is any substance that increases
fluid loss through increased urination
Alcohol and caffeine act as diuretics by
inhibiting ADH activity
MAJOR MINERALS: Sodium
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Sodium acts in concert with potassium
and chloride to maintain proper body
water distribution and blood pressure
Sodium also helps to maintain acidbase balance, nerve transmission,
muscle function, and absorption of
nutrients such as glucose
SODIUM: Sources
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Most of the sodium in our diet comes from
processed foods (75%)
The other sources are natural sodium in
foods (10%) and salt added during cooking
and eating (15%)
SODIUM: Requirements
Estimated minimum requirement for
sodium: 500 mg/day
 Recommended maximum intake of salt: 6
g/day (2400 mg sodium).
– 5 g salt = about 2 g sodium
– 3 g salt = 1.2 tsp
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HYPERTENSION
Chronic High Blood Pressure
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Hypertension injures the artery linings and
accelerates plaque formation
Plaques and reduced blood flow induce a further
rise in blood pressure, and HTN and
atherosclerosis become mutually aggravating
conditions
Diagnosis: diastolic pressure >90mmHg and/or
systolic pressure >140mmHg (men) and
>160mmHg (women)
These values are associated with an increase in
mortality of over 50%
SODIUM and HYPERTENSION
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Our bodies are poorly adapted to handle our
modern high sodium, low potassium diets. (The
diet of our ancestors is estimated to have
contained 16 times more potassium than sodium.)
About 10-15% of people with hypertension are
“salt-sensitive”. If these people decrease their
sodium intake, their BP decreases
For non “salt-sensitive” people, reducing salt
intake has a minimal effect on BP
HYPERTENSION
Other Dietary Factors:
• Excess weight tends to raise BP, exercise
and weight loss help to reduce it
• Alcohol consumption can increase BP
• Diets rich in calcium, magnesium, and
potassium help to reduce BP
POTASSIUM
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Like sodium, potassium is important in
regulation of blood pressure, nerve
transmission, muscle contractions,
electrolyte balance, and cell integrity
POTASSIUM: Sources
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Good sources include fresh fruits and
vegetables, especially bananas, potatoes,
spinach, legumes, squash, and melons
Fresh meat, milk and yogurt, coffee and tea
are other good sources
FUNCTIONS of IRON
OXYGEN TRANSPORT
• Most of the body’s iron is found in two
proteins: hemoglobin and myoglobin
• In both, iron helps to accept, carry, and
then release oxygen
• Hemoglobin in RBCs transports
oxygen to the blood
• Myoglobin facilitates the movement of
oxygen into muscle cells
FUNCTIONS of IRON
ENZYMES
• Iron is a component of enzymes involved in
energy metabolism (cytochromes are hemecontaining compounds in the ETC)
• Iron is also required by enzymes involved in
the making of amino acids, collagen,
hormones, and neurotransmitters
• It is also a cofactor for antioxidant enzymes
FUNCTIONS of IRON
IMMUNE FUNCTION
• Iron is necessary for optimal immune
function
• Iron deficiency decreases concentrations of
lymphocytes, natural killer cells, and other
immune factors
• Iron overload can worsen an infection
because it serves a nutrient for bacteria
FUNCTIONS of IRON
OTHER
• Iron is used by brain cells for normal
function at all ages: in the synthesis of
neurotransmitters, and possibly a role in
myelinization
• Synthesis of niacin from tryptophan,
carnitine synthesis
IRON IN THE BODY
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More than 80% of the body’s functional
iron is found in the RBCs, and the rest is in
myoglobin and enzymes
The body regulates its iron status by
balancing absorption, transport, storage, and
losses
IRON ABSORPTION
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Iron absorption in the gastrointestinal tract
is the primary regulator of iron levels
It depends upon:
Normal GI function
The amount and kind of iron consumed
Dietary factors that effect iron absorption
IRON ABSORPTION
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Absorption can vary from less than 1% to
greater than 50% depending upon:
Body iron stores
Certain conditions – pregnancy, blood loss,
menstruation
Gender – men absorb less than women
IRON ABSORPTION
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Foods contain two types of iron – heme and
non-heme
Heme iron is supplied by animal foods which
also contain non-heme iron (~40% heme, 60%
non-heme)
Plant based foods contain only non-heme iron
Heme iron is 2 to 3 times more absorbable than
non-heme iron
People with severe iron deficiency absorb both
heme and non-heme iron more efficiently
IRON ABSORPTION
Dietary Factors
• Organic acids (like Vitamin C) and
meat boost absorption of non-heme
iron
• Phytates, polyphenols (found in tea and
coffee), oxalates (spinach), calcium
and phosphorus, EDTA (food
additive), and fiber inhibit non-heme
absorption
IRON TURNOVER and LOSS
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The body recycles iron, and adjusts
absorption and excretion as needed
In adult men, the breakdown of older RBCs
supplies ~95% of the iron required to
produce new RBCs
Adults lose ~1mg per day in the feces,
intestinal cells, and skin
Women require additional iron to
compensate for blood loss during
menstruation
SOURCES of IRON
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Good sources include beef, clams, oysters,
tofu, legumes, and liver
Fortified cereals provide iron in the
American diet
Foods cooked in iron cookware take up iron
salts. The more acidic the food, and the
longer it is cooked, the higher the iron
content. However, the absorption may be
poor
IRON DEFICIENCY
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Stages of Iron Deficiency: depletion of iron
stores – depletion of functional iron – iron
deficiency anemia
Iron-deficiency anemia is characterized by
microcytic, hypochromic RBC
IRON TOXICITY
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Iron poisoning is the leading cause of accidental
death in small children
In a condition called Hemochromatosis, a genetic
defect causes excessive iron absorption. Iron
builds up in many parts of the body, leading to
severe organ damage and even death
An intake in excess of the RDA by adult men and
postmenopausal women may increase risk for
heart disease and cancer
Excessive iron helps to generate large amounts of
free radicals that attack cellular molecules
CALCIUM: Functions
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Bone Structure: as bones begin to form,
calcium salts form crystals called
hydroxyapatite, on a matrix of collagen.
During mineralization, as the crystals become
denser, they give strength and rigidity to
maturing bones
The calcium in bones serves as a calcium
“bank”
Peak bone mass occurs at ~ 30 years of age
CALCIUM: Functions
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Nerve function
Blood clotting
Muscle contraction
Cellular metabolism
CALCIUM: Sources
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Dairy products, blackstrap molasses, canned fish with
bones, almonds, sesame seeds, some dark green leafy
vegetables
Depends on bioavailability:
>50% absorbed – kale, mustard greens, bok choy,
turnip greens, broccoli, calcium-fortified foods and
beverages
~30% absorbed – dairy foods, calcium set tofu
~20% absorbed – almonds, sesame seeds, pinto beans
<5% absorbed – swiss chard, spinach, rhubarb
CALCIUM ABSORPTION
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The body normally absorbs 25 to 75% of
dietary calcium, depending upon Vitamin
D, the body’s need, and calcium intake
Calcium absorption is highest during
pregnancy and infancy, lowest in old age
Phytates, high levels of phosphorus and
magnesium, and low estrogen levels can
decrease absorption
OSTEOPOROSIS
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Osteoporosis is one of the most prevalent
disease of aging, affecting more than 25
million people in the US – most of them
women
The disease occurs when the bone mineral
density becomes so low that the skeleton is
unable to sustain ordinary strains, a
condition marked by the occurrence of
fractures
BONE BUIDLING NUTRIENTS
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Calcium, phosphorus, fluoride, magnesium,
potassium, Vitamin A, Vitamin D, Vitamin K
Possibly iron, copper, zinc, manganese, and
boron - function in bone metabolism, but
their roles in preventing bone loss are not well
established
OSTEOPOROSIS
Dietary Factors
• Excessive dietary fiber may interfere with calcium
absorption
• Excessive animal protein consumption may lead to
increased urinary calcium excretion
• High sodium intakes, especially in association with
low calcium intakes, can result in increased urinary
calcium excretion
• Caffeine can reduce calcium absorption and increase
excretion rates
• High phosphorus intake, in association with low
calcium intake may increase bone loss
PREVENTION of
OSTEOPOROSIS
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Increase intake of bone-building nutrients
Reduce consumption of alcohol, tobacco,
caffeine, sodium, and animal protein
Engage in regular weight-bearing exercise
OSTEOPOROSIS
Risk Factors:
• Aging, female sex, limited intake of bone
building nutrients, excessive consumption
of potentially damaging substances
(alcohol, tobacco), sedentary lifestyle, lack
of sunlight, decreased estrogen levels,
genetics, and race
REGULATION of BLOOD
CALCIUM
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Vitamin D
Parathyroid Hormone
Calcitonin
Figure 11.19
CALCIUM ABSORPTION
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The body normally absorbs 25 to 75% of
dietary calcium, depending upon Vitamin
D, the body’s need, and calcium intake
Calcium absorption is highest during
pregnancy and infancy, lowest in old age
Phytates, high levels of phosphorus and
magnesium, and low estrogen levels can
decrease absorption