Nutrition CH 9

Fluids and electrolytes

Approximately what percentage of the human body is water?

50–70%.

Why is water called the universal solvent?

It dissolves many substances, allowing nutrient transport, waste removal, and metabolic reactions.

Major functions of water? (6)

• Universal solvent

• Nutrient transport

• Waste removal

• Temperature regulation

• Lubrication/cushioning

• Medium for chemical reactions

How does water transport nutrients and wastes?

Blood and lymph are water-based; nutrients dissolve in water and wastes are carried to kidneys for excretion.

What is metabolic water?

Water produced during nutrient metabolism.

How does water regulate body temperature?

Sweat evaporates from skin and removes heat.

How much heat is lost when 1 L of sweat evaporates?

A: ~600 kcal.

Give examples of water acting as a lubricant/cushion.

• Saliva

• Mucus

• Tears

• Synovial joint fluid

• Cerebrospinal fluid

• Amniotic fluid

AI for total water — adult females?

2.7 L/day (11 cups).

AI for total water — adult males?

3.7 L/day (15 cups).

Major sources of body water?

• Beverages

• Foods

• Metabolic water

Major routes of water loss?

• Urine

• Skin/perspiration

• Lungs

• Feces

Largest source of water output?

Urine

Average urinary water loss per day?

~1–2 L/day.

What body systems monitor fluid balance?

Kidneys, blood vessels, and brain receptors.

Main hormones controlling fluid balance?

• ADH

• Aldosterone

• Angiotensin

Function of ADH?

Tells kidneys to retain water when blood solute concentration is high.

Function of aldosterone?

Tells kidneys to retain sodium and water when blood volume is low.

What triggers thirst?

Increased blood solute concentration or decreased blood volume.

Good food sources of water?

• Fruits

• Vegetables

• Milk

• Soups

• Beverages

Many fruits and vegetables contain about how much water?

>80% water.

Many meats contain approximately how much water?

At least 50% water.

Clear/pale yellow urine indicates what?

Good hydration

Dark yellow, strong-smelling urine suggests what?

Poor hydration/dehydration

What is dehydration?

Inadequate water intake replacing body water losses.

Early symptoms of dehydration (1–2% loss)?

• Thirst

• Reduced appetite

• Hemoconcentration

Symptoms of ~4% water loss?

• Fatigue

• Dizziness

• Headache

• CNS issues

Effects of ~10% body water loss?

Reduced heat tolerance and weakness.

Severe dehydration can ultimately lead to?

• Kidney failure

• Coma

• Death

Dehydration contributes to which conditions?

• Heat exhaustion

• Heat stroke

• Kidney stones

When isn't thirst always reliable?

During illness, exercise, and in infants/children, thirst can lag behind fluid needs.

How much fluid should athletes replace per pound lost during exercise?

2–3 cups per pound lost.

What is water intoxication (hyponatremia)?

Excess water dilutes blood sodium to dangerously low levels

Consequences of hyponatremia?

• Brain swelling

• Nerve problems

• Fluid in lungs

• Potentially fatal

What are electrolytes?

Charged ions that conduct electrical current.

Four important electrolyte minerals?

• Sodium

• Potassium

• Chloride

• Phosphate

Main extracellular electrolytes?

Sodium & chloride.

Main intracellular electrolytes?

Potassium & phosphate

What is osmosis?

Movement of water from lower solute concentration → higher solute concentration.

Define isotonic.

Equal solute

Define hypotonic

Lower solute concetration

Define hypertonic

higher solute concentration

How do electrolytes regulate fluid balance?

Ion concentrations determine water movement between fluid compartments.

Electrolytes are essential for what nervous system function?

Nerve impulse transmission

What is depolarization?

Temporary disruption of cell membrane charge during nerve signaling.

What is repolarization?

Return of nerve cell to resting electrical state.

What is an action potential?

Electrical signal transmitted along nerve cells

Normal extracellular pH?

7.4

What is acidosis?

Excess acid accumulation.

Acidosis symptoms?

Disorientation and fatigue.

Causes of acidosis?

• Diabetes

• Starvation

• Diarrhea

• Emphysema

What is alkalosis?

Excessive loss of acid.

Alkalosis symptoms?

• Agitation

• Dizziness

Causes of alkalosis?

• Vomiting

• Diuretic use

• Altitude sickness

• Pneumonia

What systems help maintain acid–base balance?

• Buffers/proteins

• Respiratory system

• Kidneys/electrolytes

Sodium functions?

• Fluid balance

• Nerve transmission

• Nutrient absorption

• Flavor/preservation

Major sodium food sources?

• Packaged foods

• Processed foods

• Fast food

• Soups

• Cheese

• Cold cuts

Lower-sodium foods?

• Fruits

• Vegetables

• Whole grains

• Unprocessed foods

Sodium recommendation (CDRR)?

A: ≤2300 mg/day.

Potassium functions?

• Water balance

• Nerve transmission

• Lowers blood pressure

Potassium AI — males?

3400 mg/day.

Potassium AI — females?

2600 mg/day.

Potassium-rich foods?

• Fruits

• Vegetables

• Beans

• Whole grains

• Milk

• Meats

What is hypokalemia?

Low blood potassium.

Causes of hypokalemia?

• Vomiting

• Diarrhea

• Laxative abuse

• Diuretics

• Eating disorders

Symptoms of hypokalemia?

• Muscle cramps

• Confusion

• Constipation

• Irregular heartbeat

Chloride functions?

• Acid–base balance

• Component of stomach acid

• Immune function

• Nerve function

Chloride UL?

3600 mg/day

What is hypertension?

Chronically elevated blood pressure

Why is hypertension called the “silent disorder”?

Often has no symptoms.

Health consequences of hypertension?

• Cardiovascular disease

• Stroke

• Kidney disease

• Vision problems

• Brain decline

• Sudden death

Top contributors to hypertension

1. Obesity

2. Physical inactivity

3. Excess alcohol

4. High sodium intake

What does DASH stand for?

Dietary Approaches to Stop Hypertension.

DASH diet characteristics? (high in and low in)

High in:

• Fruits

• Vegetables

• Low-fat dairy

• Calcium

• Potassium

• Magnesium

Low in:

• Sodium

• Saturated fat

Lifestyle changes that lower blood pressure?

• Lose excess weight

• Follow DASH diet

• Exercise regularly

• Reduce sodium

• Increase potassium

• Limit alcohol

Recommended exercise for lowering blood pressure?

90–150 min/week aerobic activity

Optimal sodium goal for BP reduction

A: <1500 mg/day.

Recommended potassium intake for BP improvement

3500–5000 mg/day from foods.

Alcohol recommendations for BP management

Men: ≤2 drinks/day
Women: ≤1 drink/day

What is a solution?

A liquid mixture made of a solvent and one or more solutes.

What is a solvent?

The larger component of a solution; dissolves other substances.

What is a solute?

The smaller component dissolved in the solvent.

What is concentration?

The amount of solute dissolved or mixed into a solvent.

Why is water an ideal solvent in the body?

it dissolves nutrients, wastes, and ions, allowing transport and chemical reactions.

What is intracellular fluid (ICF)?

Fluid inside cells; makes up about 63% of body fluid.

What is extracellular fluid (ECF)?

Fluid outside cells.

Two locations of extracellular fluid?

1. Plasma/lymph (fluid portion of blood)

2. Interstitial fluid (between cells)

What is an ion?

An atom or molecule with a positive or negative electrical charge

What are electrolytes?

Charged ions that conduct electrical current in body fluids.

Why are electrolytes important?

They regulate:

• fluid balance

• acid–base balance

• nerve impulse transmission