Water, Minerals, and Body Fluids
Major concept of human physiology = Homeostasis:
A state of "dynamic (changing) equilibrium (balance)" in
which the body's internal environment is maintained within
narrow limits even when:
1) the external environment changes significantly
and
2) things are introduced into or removed from the
body
Food
Urine
Drinks
Feces
Drugs
Sweat
Air
Bleeding
Carbon dioxide
Two major components of fluid homeostasis:
1. Water balance – Keeping the right amounts of water in
the right places
2. Mineral balance – Keeping the right amounts of
minerals (also called “ions” and
“electrolytes”) in the right places
These fluid compartments are in equilibrium with each other
as
both water and all of the atoms and molecules dissolved in
that water (including minerals) move from one compartment
to another.
That exchange of water and minerals among compartments
is possible only because the cells and membranes lining
each of those compartments are permeable to them.
For example:
Fluid from the lumen of the intestine crosses its
epithelium to get into the extracellular space, then crosses
the epithelium of the blood vessels and lymphatic vessels.
o
That exchange of water and minerals among compartments
is possible only because the cells and membranes lining
each of those compartments are permeable to them.
For example:
Fluid from the lumen of the intestine crosses its
epithelium to get into the extracellular space, then crosses
the epithelium of the blood vessels and lymphatic vessels.
Fluid from the plasma of the blood crosses the epithelium
of capillaries to enter the extracellular/interstitial
compartment, and those fluids can cross the same
epithelium to enter the plasma or lymph compartments.
o
That exchange of water and minerals among compartments
is possible only because the cells and membranes lining
each of those compartments are permeable to them.
For example:
Fluid from the lumen of the intestine crosses its
epithelium to get into the extracellular space, then crosses
the epithelium of the blood vessels and lymphatic vessels.
Fluid from the plasma of the blood crosses the epithelium
of capillaries to enter the extracellular/interstitial
compartment, and those fluids can cross the same
epithelium to enter the plasma or lymph compartments.
Fluid from the extracellular/interstitial compartment
crosses the plasma membranes of all cells to enter the
intracellular compartment, and that fluid crosses the same
membrane to enter the extracellular/interstitial
compartment.
That equilibrium changes every time
- water and minerals are added (food, water, etc); or
- water and minerals are lost through sweat, urine, feces,
respiration, etc.
Terms we will be using: 1
Water: A specific molecule composed of one
oxygen atom and two hydrogen atoms.
Terms we will be using: 1
Water: A specific molecule composed of one
oxygen atom and two hydrogen atoms.
Mineral: Elements or atoms with certain
chemical characteristics (which,
fortunately, you do not need to
know)
Terms we will be using: 1
Water: A specific molecule composed of one
oxygen atom and two hydrogen atoms.
Mineral: Elements or atoms with certain
chemical characteristics (which,
fortunately, you do not need to
know)
Ion: Any atom that has either a positive or
negative electrical charge
Na+
PO4-3 Ca+2
Cl- +3
Fe
Terms we will be using: 1
Water: A specific molecule composed of one
oxygen atom and two hydrogen atoms.
Mineral: Elements or atoms with certain
chemical characteristics (which,
fortunately, you do not need to
know)
Ion: Any atom that has either a positive or
negative electrical charge
Cations have a postiive charge
Anions have a negative charge
Na+
PO4-3 Ca+2
Cl- +3
Fe
Terms we will be using: 2
Note:
Not all minerals are ions - some are electrically neutral
Not all ions are minerals – some have more than one atom
In physiology and nutrition, however, the terms
Mineral
Ion
are often used interchangably
Electrolyte
Water Balance:
Water = more than 60% of total body mass
Water Balance:
Water = more than 60% of total body mass
3 major compartments:
Plasma (in blood) ~8% of body water
Interstitial (between cells) ~25% of body water
Intracellular (inside cells) ~65% of body water
Water Balance:
Water = more than 60% of total body mass
3 major compartments:
Plasma (in blood) ~8% of body water
Interstitial (between cells) ~25% of body water
Intracellular (inside cells) ~65% of body water
Many smaller compartments: ~ 2%
Urine, Lymphatic fluid, Cerebrospinal fluid, Saliva,
Synovial fluid, Digestive system contents, Semen,
Respiratory system fluids, Peritoneal fluid, Tears,
Occular fluids, Pericardial fluid, Pleural fluid, etc.
Water Balance:
Movement of water from one compartment to another is
due to the concentration of minerals and other atoms or
molecules dissolved in it:
Forms
urine
Forms tears,
saliva, CSF,
synovial
fluid, semen,
lymph, etc.
Movement
among
Water Balance:
Water intake is primarily through food
and drink. Some water is gained from
metabolic processes like the synthesis
of proteins, lipids, and carbohydrates.
Water Balance:
Water intake is primarily through food
and drink. Some water is gained from
metabolic processes like the synthesis
of proteins, lipids, and carbohydrates.
Water output is primarily through urine,
sweat, transcutanous loss, respiration,
and feces. These are obviously
affected by such things as temperature,
exercise, humidity, etc.
Water Balance:
The FDA has set adequate intakes of
2.7 liters of water per day for women
3.7 liters of water per day for men,
but obviously
To remain healthy, water intake must be
balanced by water ouput. These can
vary from ~2 liters per day to over 5
liters per day.
Water Balance:
To regulate water
intake, the body
has a complex
system of creating
a sense of thirst.
Water Balance:
To regulate water
intake, the body
has a complex
system of creating
a sense of thirst.
Loss through the skin,
lungs, and feces can
not easily be
controlled, so the
kidneys are the
primary organs of water balance by
controlling how much water is lost in
the urine.
Water Balance:
Some things in our diet can act as diuretics – that is, they
interfere with the ability of the kidneys to keep water in the
body, thus increasing its loss in the urine.
-
Alcohol
Caffeine
Theobromines Found in tea, chocolate
Theophylline
Drugs used to control blood pressure, heart disease,
diabetes insipidus, edema, & other conditions
Water Balance:
Some conditions cause rapid water loss & dehydration:
-
Excessive diuretics
Extreme heat
Exercise without replenishing water
Vomiting
Diarrhea
Burns
This is almost always accompanied by loss of minerals
Nausea, diorientation, headaches, weakness
Muscle spasms, heart failure, kidney failure, death
Water Balance:
Although not currently common in the US, dehydration
from many diseases still kills millions of people each year
worldwide, mostly through diarrhea:
- Water contaminated with viruses and/or bacteria
- Infant malnutrition
- Cholera
- Shigellosis
- Giardiasis
- Celiac disease
Water Balance:
Although less common, the opposite extreme does exist:
water intoxication or overhydration is the intake of
excess amounts of water, diluting the minerals and other
molecules dissolved in body fluids
Let’s move on to discuss minerals:
Inorganic micronutrients
Not destroyed by heat, light, acidity, or alkalinity
Minerals:
Inorganic micronutrients
Not destroyed by heat, light, acidity, or alkalinity
Involved many ways in body structure and regulation:
For example:
Many = cofactors for enzymes
Sodium and potassium ions carry electrical signals
Sodium and potassium ions regulate blood pressure
Calcium ions regulates muscle contraction
Calcium provides bone rigidity
Iron binds oxygen in hemoglobin
Iodine is part of thyroid hormones
Sulfer is part of some amino acids
Phosphorus is part of DNA, RNA, ATP, phospholipids
etc.
Minerals:
Inorganic micronutrients
Not destroyed by heat, light, acidity, or alkalinity
Involved many ways in body structure and regulation:
Found in all plant and animal foods
Not all minerals are easily absorbed in the intestine
Major minerals and trace minerals
Minerals:
Minerals in the diet are often classified as
7 Major minerals and
10+ Trace minerals
Each mineral has its own
distributrions (where it is
found) and functions
(what it does) in the
body.
Minerals: Sodium (Na+)
By far:
The most common mineral in the American diet is sodium.
Adequate Intake for both men and women = 1,500mg/day
Tolerable Upper Intake Level = 2,300 mg/day
On average:
American men consume between 3,000 and 6,000 mg of
sodium per day, while women consume between 2,500
and 4,000 mg (due to their lower calorie intake, not
because of restricting sodium).
Minerals: Sodium (Na+)
Sodium is found naturally
in many foods, including
meat, fish, milk & cheese,
eggs, tomatoes, potatoes,
nuts, cereals, fruits
Minerals: Sodium (Na+)
Sodium is found naturally
in many foods, including
meat, fish, milk & cheese,
eggs, tomatoes, potatoes,
nuts, cereals, fruits
but our major source
of sodium is salt.
Minerals: Sodium (Na+)
Salt is sodium chloride, NaCl.
In body fluids the sodium ion (Na+)
and the chloride ion (Cl - ) separate,
leaving the sodium to function alone.
Minerals: Sodium (Na+)
Salt is sodium chloride, NaCl.
In body fluids the sodium ion (Na+)
and the chloride ion (Cl - ) separate,
leaving the sodium to function alone.
By weight, salt is 40% sodium and
60% chloride
One teaspoon of salt (5 grams = 5,000 mg)
contains about 2,000 mg of Na+
and
It is the most common additive
in American food
Minerals: Sodium (Na+)
Sodium is important in maintaining the composition of all
of the fluid compartments – primarily the interstitial
compartment and the blood plasma.
Like all ions, it attracts water, so cells
and organs can move water from one
place to another by transporting
sodium from place to another.
Minerals: Sodium (Na+)
Sodium is important in maintaining the composition of all
of the fluid compartments – primarily the interstitial
compartment and the blood plasma.
Like all ions, it attracts water, so cells
and organs can move water from one
place to another by transporting
sodium from place to another.
Sodium is also one of the two
major ions (potassium is the
other) which carries electrical
signals on the membranes of
nerve cells and muscle cells.
Minerals: Sodium (Na+)
While excess sodium can be
removed by the kidneys and
eliminated in the urine, this is not
a particularly efficient process
since the adrenal glands secrete
the hormone aldosterone which
causes the kidneys to reabsorb
Na+ back into the blood, thus
preventing its elimination through
the urine.
Another hormone, atrial natriuretic hormone produced by
the heart, has the opposite effect, stimulating Na+ loss
into the urine.
Minerals: Sodium (Na+)
The resulting high concentrations of sodium can cause a
number of problems because
- the excess sodium retains water,
- which raises blood pressure,
- which increases the risks of heart failure, kidney
failure, stroke, and vascular damage
- Accumulation of sodium in the interstitial fluid also
makes it more difficult for nerve and muscle cells to
produce electrical signals.
Minerals: Sodium (Na+)
The resulting high concentrations of sodium can cause a
number of problems because
- the excess sodium retains water,
- which raises blood pressure,
- which increases the risks of heart failure, kidney
failure, stroke, and vascular damage
- Accumulation of sodium in the interstitial fluid also
makes it more difficult for nerve and muscle cells to
produce electrical signals.
Sodium deficiency is essentially unknown in developed
countries.
Minerals: Chloride (Cl-)
The other part of salt, 60% by
weight, is chloride, (Cl-).
It also attracts water, so cells can
move water from one place to
another by transporting chloride ions
from one place to another
Cl- is also necessary for the formation of hydrochloric acid
(HCl) in the stomach and for maintaining the acid-base
balance of the different fluid compartments.
It is necessary for nerve cells and muscle cells to carry
electrical signals.
Minerals: Chloride (Cl-)
Adequate intake = 2,300 mg (2.3 g) per day
Tolerable Upper Intake Level = 3,600 mg (3.6 g) per day
Like sodium, the modern American diet contains much
more chloride than it needs.
The average American man consumes 4,500 to 9,000 mg
(4.5 to 9 g) of chloride per day, and the average American
woman consumes 3,800 to 6,000 mg (3.8 to 6 g) of
chloride per day.
Minerals: Chloride (Cl-)
Fortunately, the kidneys easily
remove excess chloride, so it
plays little if any role in disease.
Except in people with excessive
vomiting or sweating, chloride
deficiency is almost unheard of
in the American population.
In populations without excessive
salt consumption, it can cause nervous and circulatory
problems and can even be fatal.
Minerals: Potassium (K+)
Potassium is one of the two ions
(sodium is the other) which
move across the membranes of
nerve cells and muscle cells to
carry an electrical signal.
Because of the much larger mass of of muscles, most of
the potassium in the body is in the intracellular fluid.
Like all other ions, it attracts water and
thus plays a role in maintaining the
volume of that fluid compartment
Minerals: Potassium (K+)
Adequate intake = 4,700 mg (4.7 g) per day
No Tolerable Upper Intake Level has been set
Dietary sources: dairy products
meat, fish, poultry
bananas
lima beans
spinach
melons
fruits
Minerals: Potassium (K+)
Most Americans consume only 2,500 to 3,000 mg/day of
potassium, below the Adequate Intake of 4,700 mg/day.
It can also be lost in the urine, sweat, and feces;
and vomiting and diarrhea can cause critical deficiencies.
- muscle weakness or cramps
- nervous disorders
- cardiac arrhythmias
- Also linked with bone loss, kidney stones, and
acid-base imbalance
Minerals: Potassium (K+)
The concentration of K+ in the body is
primarily regulated by the hormone
aldosterone:
- it helps retain Na+, but
- it stimulates loss of K+
by the kidneys
Because the kidneys easily remove excess potassium,
the risk of toxicity is low.
- cardiac arrhythmias
- muscle weakness
Minerals: Calcium (Ca2+)
Because it is part of bones and teeth,
calcium is the most abundant mineral
in our body. Forms a large molecule
called calcium hydroxyapatite.
It also regulates the contraction of
muscle (including the heart and
smooth muscle in the walls of
hollow organs).
It is necessary for clotting of the blood,
and plays a role in conducting electrical
signals in nerves.
Minerals: Calcium (Ca2+)
Even though calcium is the most
abundant mineral in the body,
99% of it is in bones so its turnover
is similar to that of other minerals.
Minerals: Calcium (Ca2+)
Even though calcium is the most
abundant mineral in the body,
99% of it is in bones so its turnover
is similar to that of other minerals.
Its concentrations in the blood and in bone tissue are
regulated by three hormones:
- Calcitriol (made in the kidneys from vitamin D)
increases absorption of Ca++ from the intestine
into the blood
- Calcitonin (from the thyroid gland) moves Ca++ from
blood into bone tissue
- Parathyroid hormone (from the parathyroid glands)
moves Ca++ from bone tissue into the blood
Minerals: Calcium (Ca2+)
Adequate intake = 1,000 to 1,300 mg (1 to 1.3 g) per day
Tolerable Upper Intake Level = 2,500 mg (2.5 g) per day
Most people do not get adequate amounts in the diet,
even though it is a common supplement in dairy products.
Dietary sources: dairy products
califlower, cabbage
soybeans
some seeds
anything with bones
Minerals: Calcium (Ca2+)
Inadequate intake/absorption or
increased loss of Ca++ leads to
- loss of bone density (osteoporosis)
- muscle weakness
- nerve damage
- increased risk of hypertension
In fetuses and children, inadequate Ca++ can cause
permanent bone and muscle damage.
Minerals: Calcium (Ca2+)
Inadequate intake/absorption or
increased loss of Ca++ leads to
- loss of bone density (osteoporosis)
- muscle weakness
- nerve damage
- increased risk of hypertension
In fetuses and children, inadequate Ca++ can cause
permanent bone and muscle damage.
Excess:
interferes with iron absorption = anemia
muscle weakness
kidney stones
Minerals: Phosphorus (P3-)
Almost all phosphorus in the
body is combined with oxygen
to form phosphate
which is:
- A major component of bone in the form of the
calcium phosphate salt called hydroxyapatite (85%)
- The hydrophilic component of phospholipids
- Part of energy storage molecules
adenosine triphosphate, creatine phosphate
- Part of nucleic acids (DNA and RNA)
- Parts of many hormones, enzymes
- One of the major buffers that control pH of body fluids
Minerals: Phosphorus (P3-)
Recommended Dietary Allowance = 700 mg per day
Tolerable Upper Intake Level = 4,000 mg (4 g) per day
Dietary sources: dairy products
meat, fish, poultry
eggs
legumes
nuts
Often used as a supplement
High in carbonated drinks
Minerals: Phosphorus (P3-)
Recommended Dietary Allowance = 700 mg per day
Tolerable Upper Intake Level = 4,000 mg (4 g) per day
Dietary sources: dairy products
meat, fish, poultry
eggs
legumes
nuts
Often used as a supplement
High in carbonated drinks
Because 85% of phosphorus is bonded to calcium in
bone, they are regulated together by calcitonin, calcitriol,
and parathyroid hormone
Minerals: Phosphorus (P3-)
Deficiency: very rare in healthy individuals
may occur in hormone deficiencies
or calcium deficiency
Minerals: Phosphorus (P3-)
Deficiency: very rare in healthy individuals
may occur in hormone deficiencies
or calcium deficiency
Excess: very rare in healthy individuals with normal diet
may occur with supplement megadoses
or kidney failure
- muscle spasms
- neurological dysfunctions
Minerals: Magnesium (Mg2+)
Helps regulate nerve impulses and muscle contractions
Cofactor for hundreds of enzyme reactions, particularly
those of carbohydrate, protein, and fat metabolism
Helps regulate the movement of potassium calcium
into and out of cells
Helps regulate blood clotting
60% is in bone tissue
25% is in muscle cells
Minerals: Magnesium (Mg2+)
Recommended Dietary Allowances:
400-420 mg per day for men
310-320 mg per day for women
Tolerable Upper Intake Level = 350 mg per day
Dietary sources: nuts
seafood
leafy vegetables
legumes
Often used as a supplement
Minerals: Magnesium (Mg2+)
Deficiency: rare in healthy individuals with normal diets
may occur from diarrhea, vomiting
- nausea
- bone loss
- muscle weakness or cramps
- cognitive problems
- cardiac arrhythmias
Minerals: Magnesium (Mg2+)
Deficiency: rare in healthy individuals with normal diets
may occur from diarrhea, vomiting
- nausea
- bone loss
- muscle weakness or cramps
- cognitive problems
- cardiac arrhythmias
Excess: very rare in healthy individuals with normal diet
may occur in kidney failure
- diarrhea
- muscle weakness or cramps
- cognitive problems
- cardiac arrhythmias
Minerals: Sulfer (S2-)
Does not have a function alone.
Part of two amino acids (and therefore proteins)
Cysteine, Methionine
Part of two vitamins
Thiamin, Biotin
Minerals: Sulfer (S2-)
Dietary sources: foods rich in protein
eggs (yolk is very high)
meat
poultry
seafood
also found in onions
peppers
radishes
No adequate intake
have been established
tolerable upper intake level
Minerals: Sulfer (S2-)
Excess intake: very rare – no common symptoms
Deficiency: very rare except in people who are
protein deficient: weak nails
joint problems
skin problems
muscle weakess
Trace Minerals
Needed only in very small amounts
Cofactors for enzymes
Components of hormones
Regulate many reactions
Trace Minerals: Iron (Fe2+, Fe 3+)
Oxygen transport as part of hemoglobin and myoglobin
Cofactor for enzymes
Required for normal immune function
Required for normal brain function
Trace Minerals: Iron (Fe2+, Fe 3+)
Recommended Dietary Allowance
18 mg per day for women before menopause
8 mg per day for men & women after menopause
Tolerable Upper Intake Level = 45 mg per day
Trace Minerals: Iron (Fe2+, Fe 3+)
Dietary sources:
Meat, liver, poultry, fish – both “heme” and
“non-heme” iron
Eggs
non-heme
Legumes
iron
Leafy vegetables
Often used as a supplement
Trace Minerals: Iron (Fe2+, Fe 3+)
Not all iron in the diet is absorbed - up to 50% or 60%
- Higher when iron status is low
- Lower when iron status is high
- Stomach acid required
- Fiber decreases absorption
- Heme iron absorbed more easily
- Other minerals (calcium, zinc) decrease absorption
- Vitamin C increases absorption
Trace Minerals: Iron (Fe2+, Fe 3+)
Body conserves iron,
distributing it where needed
Stored in liver
Small amounts lost in sweat and feces
Larger amounts lost in bleeding and menstruation
Trace Minerals: Iron (Fe2+, Fe 3+)
Excess intake:
- Can cause acute poisoning, especially in children
vomiting, diarrhea, cardiac arrhythmias, death
- Chronic excess: liver damage
deposition in tissues around body
Trace Minerals: Iron (Fe2+, Fe 3+)
Excess intake:
- Can cause acute poisoning, especially in children
vomiting, diarrhea, cardiac arrhythmias, death
- Chronic excess: liver damage
deposition in tissues around body
Deficiency:
- Most common in children
growth deficits, nerve damage & cognitive deficits
- Adults: anemia
Trace Minerals: Zinc (Zn2+)
Cofactor for numerous enzymes
Helps proteins fold and retain shape
Helps regulate gene expression
Helps regulate immunity
Minor roles in nerve impulse transmission and
muscle contraction
Trace Minerals: Zinc (Zn2+)
Recommended Dietary Allowance
8 mg per day for women
Higher when pregnant or breastfeeding
11 mg per day for men
Tolerable Upper Intake Level = 34-40 mg per day
Trace Minerals: Zinc (Zn2+)
Dietary sources:
Meat, liver, poultry, seafood
May be used to supplement cereals
Trace Minerals: Zinc (Zn2+)
Not all zinc in the diet is absorbed - 10%-35%
- Higher when zinc status is low
- Lower when zinc status is high
- Fiber decreases absorption
- Other minerals (calcium, iron) decrease absorption
- Other chemicals in food can decrease absorbtion
Trace Minerals: Zinc (Zn2+)
Excess intake: rare in healthy individuals with normal diets
- vomiting,
- abnormal immune function
Deficiency: rare in healthy individuals with normal diets
- abnormal immune function
- muscle and nerve dysfunction
- skin problems and hair loss
- growth problems in children
Other Trace Minerals:
Iodine
Copper
Manganese
Floride
Nickel
Selenium
Chromium
Silicon
Molybdenum