HLSC-2P92 Lecture 5: Water and Electrolyte Balance

intracellular

intracellular

area inside the cells 2/3

extracellular

outside the cell 1/3

intercellular or inter

found between cells

body tissue varies by:

- tissue type - lean tissues have higher fluid content than fat tissues
- age - lean tissue is lost with age and body fluid is lost with it
- sex - males have more lean tissue and therefore more body fluid

what do body fluid contain?

- Solutes
- Electrolytes such as sodium, potassium etc
- Non-electrolytes such as glucose, urea, proteins etc

roles of water

- Dissolves and transports nutrients (e.g. glucose) and waste products
- Maintain structure of large molecules (e.g. glycogen)
- Involved in metabolic reactions (hydrolysis and condensation)
- Acts as lubricant (e.g. saliva) and cushion around joints, in the spinal cord and in the brain
- Aids in thermoregulation (i.e. sweat)
- Maintains blood volume

body fluid electrolytes contain:

sodium (Na+)
potassium (K+)
magnesium (Mg+)
calcium (Ca+)
chloride (Cl-)
phosphate (HPO42-)

intracellular fluid contain:

potassium (K+ ) and phosphate (HPO42-) are the predominant electrolytes.

extracellular fluid contain:

sodium (Na+ ) and chloride (Cl- ) are the predominant electrolytes.

roles of electrolytes

- Action potential (electrochemical gradient involving Na+ and K+)
- Nerve impulse transmission (action potential, Na+ and K+)
- Muscle contraction (action potential, movement of Ca2+)
- Regulate fluid balance by maintaining the appropriate distribution of body fluids
- Regulate the acidity of body fluids (acid-base balance)

Water homeostasis needs to control:

- total body water
- water location (ratio)

sources:

- metabolic reactions (e.g. C6H12O6 + 6O2 = 6CO2 + 6H2O+Energy ATP) accounts for ~10%
- dietary makes up the rest

losses:

~60% through excretion (urine, feces)
~30% through thermoregulation (sweat)
~10% through respiration (lungs)

health canada: water

Needs dependent on
- diet (intake)
- activity (loss)
- environment (temperature and humidity - loss)
- body size (loss)
- 1.0-1.5 ml/kcal expended (adult)
- ~2-4 L/day for adults
- 1.5 ml/kcal expended (infants)

water sources:

- Water and beverages
- Caffeinated beverages increase water loss since caffeine is a diuretic
- Foods
- Fruits and vegetables (95% water)
- Meats and cheeses (50% water)

some areas of water homeostatis that need more attention:

- illness
- injury/trauma (blood loss)
- diuretics
- physical activity
- environment
- pregnancy
- lactation

how much should the body excrete each day?

500ml

homeostasis imbalances

-Dehydration caused by not drinking enough water
-Water intoxication
•Rare condition in which body water content is too high

thirst

sensed by brain's hypothalamus via signals such as:
•concentration of solutes, electrolytes in the blood
•for example when blood sodium concentration increases from eating salty snacks, the hypothalamus sends out a strong message to drink something.

kidney

central to fluid maintenance
functional unit is a nephron
utilize electrolyte concentration gradients to move water

regulated by: antidiuretic hormone (ADH), renin, angiotensin, aldosterone

Antidiuretic hormone

•Response to high electrolyte concentration in blood (e.g. sodium due to dehydration) or to low blood volume or blood pressure (sensed by hypothalamus)
•Secreted by pituitary gland (hypothalamus stimulation)
•Triggers kidneys to reabsorb water
•Increases blood volume and blood pressure

Renin

- Response to low blood pressure (due to low blood volume)
- An enzyme secreted by kidney
- Triggers activation of angiotensin I

Angiotensin I/II

blood (plasma) protein activated by renin converts into _____________ __ which triggers:
-secretion of aldosterone
-vasoconstriction of blood vessels and increase of blood pressure

aldosterone

- A hormone secreted by adrenal glands in response to angiotensin II
- Triggers kidneys to reabsorb more sodium and chloride and, in turn, retain water and increases blood volume and blood pressure

water location homeostasis

- Maintain ~2/3 water inside cells (intracellular) and ~1/3 outside cells (extracellular)
- Electrolytes dissolved in water
- cations (positive, e.g. Na+)
- anions (negative, e.g. Cl-)
- Move electrolytes and water will follow

osmosis

Osmosis is a process where water moves through the wall of a cell membrane from a dilute solution (more water and fewer electrolytes) toward a more concentrated solution (less water and more electrolytes)

Sodium-Potassium Pump

- Sodium and chloride outside cell
- Potassium and other ions inside cell
- Cells can regulate the exact amount of water inside and outside their boundaries, by maintaining specific amounts of sodium outside and potassium inside

acid base balance

- Ions help regulate acidity (pH) of fluids
- By acting as buffers
- Substances that can accommodate excess acids or bases
- First line of defense against changes in acid-base balance
- Kidneys play the primary role in maintaining acid-base balance

sodium

Easily obtained, digested, & absorbed
~10% naturally occurring in foods
~15% added during cooking
~75% added by manufacturers
Most dietary ______ comes from salt added into processed foods

Deficiencies unlikely
AI = 1500 mg/day
UL = 2300 mg/day (1 teaspoon of salt)
- Certain group of people (e.g. with hypertension) should not exceed 1500mg per day

sodium roles

-Principle electrolyte in extracellular fluid (ECF, the fluid outside the cells),
primary cation regulator of extracellular volume
-Helps maintain acid-base balance
-Essential to muscular contraction and nerve transmission
•Excesses ________ in our diet can contribute to high blood pressure (hypertension)

hyponatremia

- abnormally low blood sodium level (result from prolonged vomiting, diarrhea, or sweating e.g. during exercise)
- Hyponatremia in athletes that consume too much water (hyperhydration)

hypernatremia

abnormally high blood sodium concentration (high blood pressure)

chloride roles

- primary anion (negative ion) regulator of extracellular volume
- can move freely to the intracellular space
- critical in maintaining fluid, electrolyte, acid-base balance
- make up part of stomach acid (HCl); maintains acidity of - gastric fluids

- salt & processed foods are main source

potassium roles

- Major positive ion inside the body cells;
- primary cation regulator of intracellular volume
- Major role in maintaining fluid and electrolyte balance
- Involved in maintaining a steady heartbeat, transmitting nerve impulses, and contracting muscles

- deficiencies:

• Usually related to excessive losses rather than low intakes

• Inadequate intake possible in diets low in fresh fruits and vegetables

• Unlikely in healthy people

potassium toxicity

- Can result from excessive intake of potassium salts or supplements
- Related to specific diseases and medications
- Kidneys accelerate excretion in times of excess

potassium AI

= 4700 mg/day
- Good food sources include fresh fruit and vegetables
- Low intake, especially when combined with high sodium intake, increases blood pressure and the risk of death from stroke
- Hypertension risk is associated with the ratio of sodium and ___________, rather than their individual absolute values

dietary requirements: sodium and potassium

- Key is balance between sodium and potassium
- 3:1; K:Na
- Dietary changes may include both decreased sodium and/or increased potassium

phosphorus role:

- Body's second most abundant mineral

- bone structure (85%)
- primary anion regulator of intracellular volume-HPO42-
- important role in bone and teeth formation
- key role in energy metabolism (part of ATP)
- part of DNA and RNA
- lipids w/ this are principal components of all cell membranes (phospholipids)
- part of lipoproteins; help transport other lipids in the blood

- best sources are animal protein

role of blood in health

- Transports nutrients such as glucose, oxygen
- Removes carbon dioxide and waste products
- Immune function (white blood cells)
- Regulates body temperature

plasma

fluid portion of blood 55-60%

white blood cells WBC (leukocytes)

immune function <1%

plateletes

blood clotting <1%

red blood cells RBC (ethrocytes)

oxygen carrier 45%

nutrients that contribute to blood health

- Iron
- Zinc
-Copper
- Vitamin K
-Folate
- Vitamin B12

iron

All Cells CONTAIN ______

- Most is component of hemoglobin (in red blood cells) and myoglobin (in muscle cells)
- Assists with carrying and release of oxygen
- Recycled when red blood cells die (the liver saves the ___ and returns it to the bone marrow, which uses it to build new red blood cells)
- Normally only about 10-15 percent of dietary iron is absorbed

Ferittin and Hemosiderin

these (in the liver, bone marrow and other organs) store iron, if there is a surplus; inadequate dietary iron intake will first affect the body's ________ levels then the _______________ levels

Transferrin

- the body's iron carrying protein which is produced by the liver
- carries the iron to tissues throughout the body; combines with ferittin to transport iron to where new red blood cells are made

hepcidin

- hormone central to regulation of iron balance
- secreted by the liver in response to elevated blood iron,
- reduces iron's absorption from the intestine and its release from storage

roles of iron

- cofactor to enzymes (two ionic states, ferrous and ferric)
- part of electron transport chain
- make up hemoglobin and myoglobin (oxygen-carrying proteins in blood and muscle, respectively)

bioavailability of iron

- Iron status of the individual
- Iron food source (animal or plant food source)
- Presence/absence of dietary factors

heme iron

- found in animal products such as meat and fish (part of hemoglobin and myoglobin)
- higher absorption

non-heme iron

- found in plant and animal sources
- lower absorption

iron absorption enhancing factors

- MFP or "meat" factor
- found in Meat, Fish, and Poultry
- promotes heme iron and non-heme iron absorption (prevents - non-heme iron Fe3+ binding to inhibiting factors)
Vitamin C
- also promotes non-heme iron absorption
- converts non-heme iron Fe3+ to heme iron Fe2+ and forms a - - Fe2+-vitamin C complex

iron absorption inhibiting factors

- Phytates (found in grains, beans etc)
- Fibres (found in fruits, vegetables, grains etc)
- Oxalates (found in spinach, beets etc)
- Soybean protein
- Calcium (found in dairy etc)
- Ethylenediaminetetraacetic acid EDTA (food additives)
- Polyphenols (coffee, tea, red wine)

iron needs

- Average diet provides about 6-7 mg in 1000 kcalories
- Men usually do not have problem reaching RDA of 8 mg
- Women receive about 12-13 mg/day but need 18 mg during childbearing years
- Premenopausal women need to select iron-rich foods at every meal
- RDA
variability (ferric vs ferrous) taken into account
men < women < pregnancy

iron sources

-clams
- beef steak
- navy beans
- black beans
- enchriched cereal
- spinach
- swiss chard
- beef liver

consume too little iron

- Iron deficiency anemia is the most common nutrient deficiency in the world
- High risk people include
- infants and young children
- preadolescent girls
- premenopausal women
- pregnant women
- vegan diets

Zinc Roles

-assists in production of (heme) hemoglobin
-interacts with platelets in blood clotting
-important cofactor for many enzymes (e.g. pancreatic enzymes)
- affects immune and thyroid function
-involved in insulin synthesis, storage, and release
- transforms vitamin A to visual pigment

zinic is similar to iron

body handling and storage
needs relatively small
absorption influenced by a number of factors

zinc status

if body needs zinc, metallothionein releases to albumin and transferrin for transport to the pancreas, if the body does not need zinc it is excreted

zinc sources

- oysters
- beef steaks
- shrimp
- enriched cereal
- pork chop
- yogurt

zinc enhancing factors

dietary protein (animal-based more so than plant-based)

zinc inhibiting factors

phytates (found for example in beans, nuts and grains)

copper role:

- Serves as constituent of enzymes
- Key factor in hemoglobin synthesis
- Helps cells use iron
- Required in reactions related to respiration and energy metabolism
- Controls damage from free radicals by being part of superoxide dismutase (_______-dependent antioxidant enzyme)

copper include

organ meats
legumes
whole grains
seafood
nuts and seeds

folate and B12

- Both play a role in protein metabolism and DNA synthesis
- Both involved in RBC production in the bone marrow
- deficiencies in either/both will result in large RBC with insufficient hemoglobin (megaloblastic anemia)

Vitamin K family of compounds are called?

quinones

phylloquinone (vitamin K1)

diet: leafy green vegetables, cabbage, vegetable oil

menaquinone (vitamin K2)

bacteria in large intestine

anatomy of bone

trabecular (spongy)
~20%
cortical (compact)
~80%
very dense

structure and support

- physical support for organs and body segments
- protection for organs
- attachment sites for muscles

metabolic proccesses

- storage reservoir for many minerals
- produced by red blood cells

bone remodelling

1. Resorption - surface of bones is broken down
- Osteoclasts - cells that erode the surface of bones
2. Formation - of new bone
- Osteoblasts - cells that produce the collagen-containing component of bone

bone density

- peak bone density is reached before the age of 30
- remodelling maintains bone density during early adulthood
- bone density begins to decrease after age 40 because bone resorption exceeds new bone formation

bone health

- Dual-energy X-ray absorptiometry (DXA) measures bone density
- non-invasive low radiation scan
compare against a reference (healthy 30 year old adult of same sex and race)

calcium

- Body's most abundant mineral
- Adequate intake early in life helps growth of skeleton and prevents bone disease later
- 99 percent stored in bones and teeth
- Integral part of bone structure
- Serves as calcium bank, supplying body fluids when blood calcium levels drop
- Osteoporosis can result if amount withdrawn exceeds amount deposited

calcium role

- bone structure (99%)
- muscle contraction
- blood clotting
- nerve impulse
- hormone secretion
- metabolism

calcium recommendations

- Needs are dependent on age, sex, pregnancy and lactation
- Calcium recommendations high during adolescence (1300 mg/day)
- Lower for adults over age 19
- Raised again for women over 50 and all adults over 70
- Risk of kidney stone formation with high supplemental doses

calcium homeostasis

- Keep blood calcium levels within a very narrow range
- protect at all costs
- Dietary deficiency does not change blood calcium
- reduces bone calcium

osteoclasts

When calcium consumption and/or absorption are low, these erode the bone and release calcium

osteoblasts

When calcium consumption and/or absorption are high, these build bone and take up calcium

falling blood Ca++

parathyroid hormone (PTH)
vitamin D
Net result is to raise blood calcium

raising blood Ca++

calcitonin
Net result is to lower blood calcium

Calcium bioavailbility

Decreased
- needs are low
- phytates and oxalates
- other minerals (Fe, Zn, Mg, P) result in competitive inhibition

increased
- needs are high (e.g. pregnancy and lactation)
- vitamin D

calcium and osteoporosis

•High peak bone mass
-Best protection against bone loss and fracture later in life
-Achieved by adequate _______ intake during growing years
•Bone ______ losses can result in fractures under normal, everyday stresses
•Osteoporosis is a disease characterized by low bone mass and deterioration of bone tissue, which can lead to increased risk of fracture.

calcium food sources

- milk and milk products
- Daily consumption of low-fat or fat-free milk products recommended
- Cheddar Cheese
- Fortified foods offering large amounts
- Juices, cereals, and some mineral waters
- Broccoli, kale, and other vegetables
- sardines
- milk
- broccili
- tofu
- waffle
- turnip greens

vitamin D

- Increases calcium uptake from digestion
- Without ________, our bodies cannot effectively absorb calcium, which is essential to good bone health.

- hormone which doesn't always have to come from the diet (synthesized from cholesterol-based compound with help of sunlight)

- Fat soluble vitamin (stored in fat)

- RDA assumes no access to sunlight
- used for bone growth (maintain blood levels of calcium and phosphorus)

factors that limit vitamin D

- geographic location (e.g. Alaska vs California)
- season (summer vs winter)
- time of day (afternoon vs evening)
- air pollution
- clothing
- sunscreen
- age

Vitamin D sun:

- Natural exposure to sunlight necessary to maintain adequate vitamin D levels
- Sufficient synthesis with five to ten minutes of sun exposure few times a week
- Darker skin needs more time
- Sunscreens with SPF >8 retard vitamin D synthesis
- Low levels are common at end of winter months and in northern latitudes

vitamin D sources

- Few animal foods provide significant source
- Eggs, liver, butter, some fatty fish
- Fortified milk, margarine, and cereals
- Fortified infant formulas
- Milk fortification best guarantee for meeting vitamin D needs of children

phosphorus

- Animal protein is the best source
- Milk and cheese are also rich sources
- Diets that provide adequate energy and protein also supply adequate _____________

magnesium role

- bone structure (50-60%)
- catalyst in energy metabolism (ATP synthesis)
- synthesis of protein, fats and nucleic acids
- membrane transport
- inhibits muscle contraction enabling muscle to relax
- prevents abnormal blood clotting

magnesium sources

- spinach
- bran cereal
- oysters
- black beans
- yogurt
- soy milk

flouride role

strengthen bones and teeth: majority of our body's stores (about 99%) are found in our bones and teeth

flouride source

- drinking water (0.09-0.14 mg/L naturally occurring)
- dental products such as fluoride toothpaste (directly absorbed in the mouth)
- processed soft drinks and juices made with fluorinated water

vitamin C

aids in the production of collagen (the foundation that bone mineralization is built on)

Vitamin K (especially K2)

- is a essential for synthesizing osteocalcin (osteocalcin is an important protein which is secreted by osteoblasts, the body's bone-building cells and plays role in bone formation)

- activation of blood clotting proteins
- synthesis of bone building proteins