Unit Three Nutrition Study Guide: Fluid & Electrolyte Balance, Key Body Functions, and Healthy Tissues

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Micronutrients Overview

Classification of Vitamins

Vitamins are classified based on their solubility, which affects their absorption, transport, and storage in the body.

Water-Soluble Vitamins: Includes the B-complex vitamins and vitamin C. These are absorbed directly into the bloodstream and are not stored in large amounts, so regular intake is necessary.
Fat-Soluble Vitamins: Includes vitamins A, D, E, and K. These are absorbed along with dietary fat and stored in the liver and adipose tissue.
Key Differences: Water-soluble vitamins are found in a variety of foods, are transported freely in blood, and excess amounts are excreted in urine. Fat-soluble vitamins are found in fatty foods, require bile for absorption, and can accumulate to toxic levels if consumed excessively.

Micronutrient Review: For each micronutrient, know its functions, dietary sources, deficiency conditions (with symptoms), and toxicity conditions if significant.

Nutrients Essential to Fluid and Electrolyte Balance

Electrolytes and Fluid Compartments

Electrolytes are minerals that carry an electric charge and are essential for maintaining fluid balance, nerve transmission, and muscle function.

Major Electrolytes: Sodium (Na+), Potassium (K+), Chloride (Cl-), Phosphorus (as phosphate, PO43-).
Intracellular Electrolytes: Mainly potassium and phosphate.
Extracellular Electrolytes: Mainly sodium and chloride.
Charge: Electrolytes can be positively charged (cations, e.g., Na+, K+) or negatively charged (anions, e.g., Cl-, PO43-).

Fluid Compartments

Intracellular Fluid (ICF): Fluid within cells; makes up about two-thirds of body water.
Extracellular Fluid (ECF): Fluid outside cells; includes interstitial fluid (between cells) and plasma (in blood).
Interstitial Fluid: Surrounds tissue cells.
Synovial Fluid: Found in joint cavities, providing lubrication.

Fluid Needs and Water Functions

Calculating Fluid Needs: General guideline: 30-35 mL water per kg body weight per day.
Functions of Water: Solvent, transport medium, temperature regulation, lubrication, and chemical reactions.

Regulation of Body Fluids

Thirst Mechanism: Controlled by the hypothalamus in the brain, which signals thirst in response to increased blood osmolality.
Stages of Dehydration and Heat-Related Illness: Mild, moderate, and severe dehydration; heat exhaustion and heat stroke.

Electrolyte Functions and Blood Pressure

Sodium: Regulates fluid balance, nerve transmission, and muscle contraction.
Potassium Blood Pressure Regulation: Sodium increases blood pressure; potassium helps lower it.

Deficiency and Toxicity Conditions

Sodium Deficiency: Hyponatremia (low blood sodium) – symptoms include headache, confusion, seizures.
Potassium Deficiency: Hypokalemia – symptoms include muscle weakness, cramps, arrhythmias.
Excess Fluid: Can cause cell swelling (if inside cell) or dehydration (if outside cell).

Food Sources and Water Losses

Electrolyte Sources: Sodium – table salt, processed foods; Potassium – fruits (bananas, oranges), vegetables; Chloride – table salt.
Sensible Water Loss: Measurable losses (urine, sweat).
Insensible Water Loss: Non-measurable losses (respiration, evaporation from skin).

Body Fluid Percentage and Factors

Body Fluid Percentage: Adults: 50-70% of body weight is water.
Lower End: Older adults, higher body fat.
Higher End: Infants, lean individuals.

Electrolyte Balance Importance

Importance: Imbalances can disrupt nerve and muscle function, cause arrhythmias, and affect hydration status.

Muscle Contraction and Overhydration

Electrolytes Needed: Sodium, potassium, calcium, and magnesium are essential for muscle contraction.
Overhydration: Can lead to hyponatremia, causing confusion, nausea, and potentially life-threatening complications.

Fluid Conversion and Sports Drinks

Fluid Conversion: 1 cup = 8 fluid ounces.
Sports Drinks: Contain electrolytes and carbohydrates; beneficial for athletes during prolonged, intense exercise.
Replacing Water Loss: For each pound lost during activity, drink about 2 cups (16 fluid ounces) of water.

Nutrients Essential to Key Body Functions

Antioxidants

Antioxidants protect cells from damage caused by free radicals, which are unstable molecules formed during normal metabolism and exposure to toxins.

Oxidation: Loss of electrons from a molecule.
Reduction: Gain of electrons by a molecule.
Antioxidant: A substance that inhibits oxidation and neutralizes free radicals.
Free Radical: An atom or molecule with an unpaired electron; formed during metabolism, pollution, radiation.
Antioxidant Nutrients: Vitamins C, E, beta-carotene, selenium.
Food Sources: Fruits, vegetables, nuts, whole grains.
Deficiency Symptoms: Increased oxidative stress, risk of chronic diseases.
Relation to Cancer: Antioxidants may reduce cancer risk by preventing DNA damage.

Energy Metabolism

Energy metabolism involves the chemical processes that convert food into energy for cellular functions.

Nutrients Involved: B vitamins (thiamin, riboflavin, niacin, pantothenic acid, biotin, B6, folate, B12), minerals (chromium, iodine).
B Vitamins: Act as coenzymes in energy-yielding reactions.
Vitamin B12 Absorption: Requires intrinsic factor produced in the stomach.
Folate: Essential for DNA synthesis and fetal development; prevents neural tube defects.
Minerals: Chromium – enhances insulin action; Iodine – required for thyroid hormone synthesis.
Niacin Synthesis: Can be made from the amino acid tryptophan.
Homocysteine Metabolism: Involves folate, B6, and B12; elevated homocysteine is a risk factor for cardiovascular disease.

Nutrients Essential to Healthy Tissues

Bone Health

Bone health depends on adequate intake of minerals and vitamins, as well as hormonal regulation and physical activity.

Bone Tissue Components: Collagen (protein matrix), minerals (calcium, phosphorus).
Osteoclasts: Cells that break down bone tissue.
Osteoblasts: Cells that build new bone tissue.
Osteoporosis: Condition of reduced bone density; risk factors include age, gender, genetics, low calcium/vitamin D intake.
Bone Growth, Modeling, Remodeling: Growth – increase in size; modeling – shaping; remodeling – renewal.
Bone Growth Timeline: Bones stop growing in late adolescence; peak bone density in early adulthood; decline begins after age 30.
Collagen: Provides structure and flexibility to bone.
Vitamin D Synthesis: Influenced by sunlight exposure, skin pigmentation, age; supplementation may be needed for those with limited sun exposure.
Bone Density Measurement: Dual-energy X-ray absorptiometry (DEXA) is the gold standard.
Parathyroid Hormone (PTH): Increases blood calcium by stimulating bone resorption.
Calcitonin: Lowers blood calcium by inhibiting bone resorption.
Calcium Bioavailability: Influenced by vitamin D, age, dietary factors (phytates, oxalates).

Blood Health

Blood health relies on adequate intake of nutrients involved in red blood cell formation and function.

Key Nutrients: Iron, vitamin B6, vitamin B12, folate, vitamin K.
Heme vs. Non-Heme Iron: Heme iron (animal sources) is more readily absorbed than non-heme iron (plant sources).
Hemochromatosis: Genetic disorder causing iron overload.
Meat Factor: Component in meat that enhances non-heme iron absorption.
Hemoglobin vs. Myoglobin: Hemoglobin carries oxygen in blood; myoglobin stores oxygen in muscle.
Iron Absorption: Enhanced by vitamin C; inhibited by phytates, calcium, polyphenols.
Iron Deficiency Anemia: Diagnosed by low hemoglobin; symptoms include fatigue, weakness, pallor.
Other Anemias: Pernicious anemia (B12 deficiency), microcytic anemia (iron deficiency), megaloblastic/macrocytic anemia (folate or B12 deficiency).
Vitamin K: Produced by gut bacteria; essential for blood clotting.

Table: Types of Anemia and Associated Nutrients

Type of Anemia	Associated Nutrient Deficiency	Key Symptoms
Pernicious Anemia	Vitamin B12	Fatigue, neurological symptoms
Microcytic Anemia	Iron	Small red blood cells, fatigue, pallor
Megaloblastic/Macrocytic Anemia	Folate or Vitamin B12	Large red blood cells, fatigue, weakness

Additional info: For all micronutrients, be familiar with their functions, sources, deficiency and toxicity symptoms, and their role in health and disease prevention.