Nutrition Study Guide: Body Fluids, Electrolytes, Vitamins, and Bone Health

How do age and gender affect body fluid percentage?

Younger people generally have more body water. Males typically have a higher percentage than females due to greater lean mass.

What are the functions of body fluid?

Transports nutrients and wastes, regulates temperature, lubricates joints, and supports chemical reactions.

What happens when electrolyte concentration is higher outside the cell?

Water moves out of the cell by osmosis, causing it to shrink.

What happens when fluid outside the cell is less concentrated?

Water moves into the cell, causing it to swell and possibly burst.

Why do we sweat?

To cool the body through evaporation and maintain normal body temperature.

How does the body regulate temperature?

Sweating and skin blood vessel dilation release heat; constriction helps conserve heat.

How does the body lose fluid?

Urine, feces, sweat, and water lost through breathing.

What is the body's fluid command center?

The hypothalamus, which helps regulate thirst and body temperature.

Which mineral triggers muscle contraction?

Calcium (Ca²⁺).

What is sensible water loss?

Measurable fluid loss, mainly through urine and feces.

What is insensible water loss?

Unnoticed fluid loss through skin evaporation and exhaled air.

What is the primary cause of hyponatremia?

Excess water relative to sodium, often from overhydration or sodium loss.

What conditions contribute to dehydration?

Heavy sweating, vomiting, diarrhea, fever, inadequate fluid intake, and excessive urination.

How can you reduce dietary sodium?

Limit processed foods, read labels, choose low-sodium products, and reduce added salt.

What foods provide potassium?

Potatoes, bananas, beans, leafy greens, tomatoes, dairy, fruits, and vegetables.

What is the main dietary source of chloride?

Sodium chloride (table salt), especially from processed and packaged foods.

Where is phosphorus stored, and what foods provide it?

Mostly in bones and teeth. Sources include dairy, meat, fish, eggs, beans, and nuts.

How many milliliters are in a cup, and how many cups are in a liter?

About 240 mL per US cup; 1 liter is about 4.2 cups.

Who has a higher body-fluid percentage: lean or overweight individuals, and why?

Lean individuals, because muscle contains more water than fat tissue.

What are examples of low-sodium foods?

Fresh fruits and vegetables, plain grains, fresh unprocessed meats, and unsalted nuts.

What are intracellular, interstitial, and intravascular fluids?

Intracellular: inside cells. Interstitial: between cells. Intravascular: within blood vessels.

Which electrolytes enable nerve responses, and what are their charges?

Sodium (Na⁺): positive; potassium (K⁺): positive; calcium (Ca²⁺): positive; chloride (Cl⁻): negative.

How should fluids be replaced during exercise in the heat?

Drink regularly, avoid excessive fluid intake, and replace electrolytes during prolonged heavy sweating. Needs vary by individual.

What is the primary role of B vitamins?

They act mainly as coenzymes that help enzymes release energy from nutrients and support metabolism.

How does a coenzyme function? Give examples.

A coenzyme helps an enzyme perform a chemical reaction. Examples include NAD, FAD, and coenzyme forms of B vitamins.

Wernicke-Korsakoff syndrome is associated with decreased absorption or deficiency of which B vitamin?

Thiamin (vitamin B1).

What are the best food sources of thiamin?

Whole and enriched grains, pork, legumes, seeds, and nuts.

Which B vitamin is destroyed by light?

Riboflavin (vitamin B2).

What is vitamin B6 important for?

Transamination, amino acid metabolism, and neurotransmitter synthesis.

Pellagra results from a deficiency of which vitamin?

Niacin (vitamin B3).

What is vitamin B12's role, deficiency symptoms, and food sources?

Supports DNA synthesis, red blood cells, and nerve function. Deficiency can cause megaloblastic anemia and neurological problems. Sources: meat, fish, eggs, dairy, and fortified foods.

What are good sources of folate in the American diet?

Fortified grains and cereals, leafy green vegetables, beans, and citrus fruits.

High blood homocysteine may indicate increased risk of what?

Cardiovascular disease. Elevated levels can be associated with low folate, B6, or B12.

Overconsumption of which food can cause biotin deficiency?

Raw egg whites, because avidin binds biotin and reduces its absorption.

Iodine is essential for producing which hormones?

Thyroid hormones T3 (triiodothyronine) and T4 (thyroxine).

Chromium helps insulin move what into cells?

Glucose.

What are oxidation and reduction?

Oxidation is loss of electrons; reduction is gain of electrons.

How can free radicals damage cells?

They can damage cell membranes, proteins, and DNA by reacting with them.

How are we exposed to free radicals?

They form naturally during metabolism and can arise from smoke, pollution, UV radiation, and other environmental exposures.

How do antioxidant systems reduce free-radical damage?

They neutralize free radicals or limit their formation, helping protect cells from oxidative damage.

Which vitamins act as antioxidants, and what is their role?

Vitamins E, C, and A (including beta-carotene) help protect cells against oxidative damage.

What are good food sources of vitamins A, C, and E?

A: liver and dairy; C: citrus, peppers, and berries; E: vegetable oils, nuts, and seeds.

What foods provide beta-carotene, a provitamin A carotenoid?

Orange and dark-green vegetables, such as carrots, sweet potatoes, pumpkin, spinach, and kale.

What are good sources of preformed vitamin A?

Animal foods such as liver, fish liver oils, eggs, and dairy products.

What is the difference between compact and trabecular bone? How do hormone levels affect them?

Compact bone is dense and forms the outer layer; trabecular bone is porous and found inside bones. Estrogen loss increases bone resorption, especially in trabecular bone.

Describe bone growth, modeling, and remodeling.

Growth increases bone size. Modeling changes bone shape as formation and resorption occur on different surfaces. Remodeling replaces old or damaged bone with new bone.

What is the difference between osteoclasts and osteoblasts?

Osteoclasts break down bone; osteoblasts build new bone.

How does bone remodeling help maintain blood calcium levels?

Bone resorption releases calcium into the blood; bone formation stores calcium in bone.

What are hydroxyapatite crystals made of?

Calcium and phosphorus, primarily as calcium phosphate.

Where is magnesium stored, and what are good food sources?

Much of the body's magnesium is stored in bones. Sources include nuts, seeds, whole grains, legumes, and leafy greens.

At what age does bone resorption begin to outpace bone formation?

Often around age 30-40, although timing varies; bone loss accelerates after menopause in women.

What do T-scores indicate for bone density?

Normal: −1.0 or higher. Osteopenia: below −1.0 but above −2.5. Osteoporosis: −2.5 or lower.

How much calcium can the body absorb at one time?

Absorption is most efficient in doses of about 500 mg or less at a time.

How bioavailable is calcium from plant foods, and how do oxalates affect absorption?

Bioavailability varies. Oxalates bind calcium and reduce absorption; spinach is high in oxalates, while kale is lower.

When blood calcium falls, which hormone is released and what does it do?

Parathyroid hormone (PTH) is released. It promotes activation of vitamin D, increasing intestinal calcium absorption.

What is the difference between hemoglobin and myoglobin?

Hemoglobin transports oxygen in red blood cells; myoglobin stores oxygen in muscle.

Low folate or B12 can cause what type of anemia, and why?

Megaloblastic anemia. Impaired DNA synthesis prevents normal red blood cell maturation, producing abnormally large cells.

Vitamin D is known as which vitamin?

The sunshine vitamin, because the skin can produce it with UVB exposure.

Vitamin D toxicity is usually caused by what?

Excessive vitamin D supplements, not ordinary sun exposure or typical food intake.

What can insufficient vitamin D intake in adulthood cause?

Osteomalacia, or softening of bones in adults.

What can vitamin D deficiency in childhood cause?

Rickets, which causes poor bone mineralization and skeletal deformities.

What is vitamin K's role in blood function, and what are its food sources?

It supports blood clotting. Sources include leafy greens, broccoli, and vegetable oils. Gut bacteria also produce some vitamin K.

Which vitamins are fat-soluble?

Vitamins A, D, E, and K.

How do meat factor and vitamin C enhance iron absorption?

Meat factor (the meat/fish/poultry effect) enhances nonheme iron absorption. Vitamin C converts iron to a more absorbable form and improves absorption.

Which vitamin may reduce the duration of colds?

Vitamin C may modestly shorten cold duration when taken regularly, but it does not reliably prevent colds.

What is the difference between heme and nonheme iron?

Heme iron comes from animal foods and is generally absorbed more efficiently. Nonheme iron occurs in plant and animal foods and is less readily absorbed.