Comprehensive University Study Notes: Fat-Soluble Vitamins, Water-Soluble Vitamins, and Minerals

Vitamin A: Preformed Retinoids and Provitamin Carotenoids

• Differences Between Provitamin A and Preformed Vitamin A:
  • Preformed Vitamin A: Consists of retinal and retinoids. These are derived from animal foods and represent the biologically active form of vitamin A used directly by the body.
  • Provitamin A: Consists of carotenoids. These are derived from plant foods and must be converted into retinol by the body before they can be utilized.
• Food Sources of Vitamin A:
  • Preformed Vitamin A Sources: Found in animal-based products such as liver, salmon, fish oils, yogurt, fortified milk, and eggs.
  • Provitamin A Sources: Found in plant-based products such as carrots, kale, and sweet potatoes.

Vitamin D: Synthesis, Metabolism, and Bone Health

• Formation of Vitamin D3 (Cholecalciferol) in the Skin:
  • The process begins with $7\text{-dehydrocholesterol}$ present in the skin.
  • When the skin is exposed to UVB radiation, $7\text{-dehydrocholesterol}$ is transformed into pre-vitamin D3.
  • This is then converted into cholecalciferol, which enters the bloodstream.
  • The cholecalciferol travels to the liver and kidneys.
  • In the liver and kidneys, it is converted into calcitriol, which is the bioactive form utilized by the body.
• The Most Active Form and Its Functions:
  • The most active form of Vitamin D is calcitriol.
  • Functions: It maintains the body's concentration of calcium and phosphorus, which is essential for bone health.

Vitamin E and Vitamin K: Antioxidants and Blood Integrity

• Vitamin E Sources and Functions:
  • Food Sources: Plant oils, wheat germ, avocado, almonds, peanuts, and sunflower seeds.
  • Antioxidant Function: Vitamin E acts as an antioxidant by protecting the cell membrane from oxidative damage.
• Vitamin K: Forms and Sources:
  • Phylloquinones (Vitamin $K_1$): Derived from plant sources; this is the more biologically active form.
  • Menaquinones (Vitamin $K_2$): These can be synthesized by bacteria.
  • Food Sources: Leafy green vegetables are primary sources.
• Vitamin K Deficiency Risks:
  • At-Risk Population: Infants are at the highest risk for vitamin K deficiency.
  • Reasoning: Infants have low initial stores of vitamin K, putting them at a higher risk of bleeding.

Introduction to Water-Soluble Vitamins and Coenzymes

• Vitamins Classified by Metabolic Function:
  • Energy Metabolism: Especially thiamin, riboflavin, niacin, pantothenic acid, and biotin.
  • Amino Acid Metabolism and Red Blood Cell Synthesis (RBCSL): Primarily Vitamin $B_6$ and Vitamin $B_{12}$.
• Defining Coenzymes:
  • A coenzyme is a specific type of cofactor.
  • It functions by joining with inactive enzymes to create active holoenzymes.
  • Coenzymes are essential for performing metabolic reactions.

Thiamin (Vitamin $B_1$) and Riboflavin (Vitamin $B_2$)

• Thiamin (Vitamin $B_1$):
  • Common Food Sources: Whole grains and pork.
  • Coenzyme Form: Thiamine pyrophosphate ($TPP$).
  • Metabolic Involvement: Involved in carbohydrate metabolism, branched-chain amino acid metabolism, and pyruvate processing.
  • Deficiency Conditions: Can lead to Beriberi and Wernicke-Korsakoff syndrome. Physical manifestations include heart failure, gastrointestinal (GI) disease, and eating disorders.
  • Alcoholism and Thiamin: Alcoholics are at high risk for Wernicke-Korsakoff syndrome (cerebral beriberi), which cause damage to brain tissue. This is due to poor dietary intake and impaired intestinal absorption.
• Riboflavin (Vitamin $B_2$):
  • Common Food Sources: Milk, yogurt, and enriched grains.
  • General Functions: Acts as a coenzyme in energy metabolism (specifically $FAD$ donating electrons to the Electron Transport Chain), activates other B vitamins, and serves an antioxidant function in the production of glutathione.
  • Coenzyme Forms: $FMN$ (Flavin mononucleotide) and $FAD$ (Flavin adenine dinucleotide).
  • Deficiency: Known as ariboflavinosis, which affects the mouth, skin, and red blood cells.

Niacin (Vitamin $B_3$), Pantothenic Acid, and Biotin

• Niacin (Vitamin $B_3$):
  • Common Food Sources: Meat and grains. It can also be synthesized from the amino acid tryptophan.
  • Coenzyme Forms: $NAD$ (involved in catabolic pathways) and $NADP$ (involved in anabolic pathways).
  • Deficiency (Pellagra): Characterized by rough skin and the "4 Ds": Diarrhea, Dermatitis, Dementia, and Death.
• Pantothenic Acid (Vitamin $B_5$):
  • Common Food Sources: Beef, chicken, and whole grains.
  • Importance in ATP Formation: It is the primary building block of Coenzyme A ($CoA$) and Acetyl-CoA.
• Biotin (Vitamin $B_7$):
  • Common Food Sources: Eggs, fish, meat, seeds, and nuts.
  • Primary Function: Assists in the production of keratin, which forms the physical foundation of hair, skin, and nails.
  • Causes of Deficiency: Consumption of raw egg whites (due to avidin), certain medications, and extreme dieting.

Vitamin $B_6$, Folate, and Vitamin $B_{12}$

• Vitamin $B_6$ (Pyridoxine Family):
  • The Three Compounds: Pyridoxine, Pyridoxal, and Pyridoxamine.
  • Common Food Sources: Pinto beans, oatmeal, pistachios, and tuna.
  • Main Functions: Amino acid (AA) metabolism, folate metabolism, heme synthesis, neurotransmitter synthesis, and regulation of gene expression.
  • Deficiency and Risk: Deficiency causes seborrheic dermatitis. Those at risk include individuals with high alcohol use or kidney disease.
• Folate (Vitamin $B_9$):
  • Folic Acid: This refers specifically to the synthetic, man-made form of Vitamin $B_9$.
  • Common Food Sources: Leafy greens, legumes, and fortified grains.
  • Mechanisms and Involvement: Acts as folate coenzymes; involved in DNA synthesis and cell division; necessary for the formation of neurotransmitters; helps maintain normal blood pressure and reduces the risk of colon cancer.
• Vitamin $B_{12}$ (Cobalamin):
  • Unique Characteristics: Contains the mineral cobalt and is found naturally only in animal products.
  • Common Food Sources: Meat, fish, dairy products, and fortified cereals.
  • Physiological Process:
    • Absorption: Requires Intrinsic Factor (produced in the stomach) and occurs in the ileum.
    • Transport: Carried through the bloodstream.
    • Storage: Stored in the liver.
    • Excretion: Primarily through bile.
  • Functions: Red blood cell formation, neurological function, and DNA synthesis.
  • Deficiency: Caused by malabsorption, anemia, or dietary deficiency. Conditions include anemia, neurological disorders, and cognitive decline. High-risk groups include older adults, vegetarians, and those with GI disorders.
• Folate and $B_{12}$ Relationship: They are metabolically related because both are required for the conversion of homocysteine to methionine.

Choline and Vitamin C

• Choline:
  • Common Food Sources: Eggs, liver, and soybeans.
  • Target Organs: A choline-free diet most severely affects the liver and brain as choline is essential for their function.
  • Main Functions: Cell membrane structure, neurotransmitter synthesis, and lipid metabolism.
• Vitamin C (Ascorbic Acid):
  • Collagen Synthesis: Essential for the hydroxylation of proline and lysine in collagen, which provides stability and strength to the tissue.
  • Other Functions: Acts as an antioxidant, supports immune function, and enhances the absorption of iron ($Fe$).

Water and Major Minerals: Fluid Balance and Sodium/Potassium

• Body Fluid Compartments:
  • Intracellular Fluid ($\frac{2}{3}$ of body water): Fluid located inside every type of cell, including blood, bone, muscle, and adipose tissue.
  • Extracellular Fluid ($\frac{1}{3}$ of body water): Composed of intravascular fluid (blood and lymph) and interstitial fluid (fluid between cells).
• Hyponatremia: A condition defined by having too little sodium in the blood.
• General Functions of Minerals:
  • Water Balance: Regulated by $Na$, $K$, $Ca$, and $P$.
  • Nerve Impulses: Regulated by $Na$, $K$, and $Ca$.
  • Coenzymes: $Mg$, $Cu$, and $Se$ function as cofactors/coenzymes.
  • Growth and Development: Components of body compounds ($Ca$, $P$).
• Sodium ($Na$):
  • Functions: Essential for glucose and amino acid absorption, required for normal nerve and muscle function, and aids in fluid balance.
  • Excess Sodium Effects: Can lead to hypertension, cardiovascular disease, stroke, and kidney stones.
  • Nephrotic Syndrome: A kidney disorder involving damage to the small blood vessels in the kidneys.
• Potassium ($K$):
  • Location: Primarily found in intracellular fluids.
  • Hypokalemia: Low potassium caused by excessive losses in urine/feces or chronic low intake.
  • Hyperkalemia: High potassium usually due to poor kidney function; can cause irregular heartbeat and cardiac arrest.

Calcium, Phosphorus, and Magnesium

• Calcium Regulation: Regulated via a parathyroid feedback loop during times of low or high blood calcium.
• Phosphorus ($P$):
  • Food Sources: Baked goods, dairy, meats, and cereals.
  • Roles: Essential for bone formation, energy metabolism, DNA/RNA structure, and acid-base regulation.
  • Deficiency Symptoms: Muscle and bone pain.
• Magnesium ($Mg$):
  • Sources: Found in chlorophyll; good sources include leafy greens, seeds, tap water, and dirt.
  • Functions: Stabilizes $ATP$, aids in enzyme function, and promotes muscle relaxation.
  • Deficiency Symptoms: Muscle cramps, irregular heartbeat, weakness, and seizures.
  • Risk Groups: Those with alcoholism, Type 2 diabetes, or GI disorders.

Trace Minerals: Iron, Zinc, Copper, Iodine, and Selenium

• Iron ($Fe$):
  • Heme vs. Non-Heme: Heme iron comes from animal flesh products; non-heme iron comes from plant sources (e.g., broccoli).
  • Absorption Factors: Enhanced by Vitamin C, Vitamin A, and "meat protein factor." Inhibited by gastric acid, fiber, and oxalic acid.
  • Functions: Components of hemoglobin (transports $O_2$ in RBCs) and myoglobin (stores/releases $O_2$ in muscles).
  • Deficiency and Toxicity: Women of childbearing age are at greatest risk for iron deficiency anemia. Children are at high risk for iron toxicity due to lower body mass.
  • Hemochromatosis: A disorder where the body absorbs and stores excessive iron, leading to toxic overload.
• Zinc ($Zn$):
  • Food Sources: Oysters, seafood, meat, and whole grains.
  • Absorption Factors: Enhanced by animal protein. Inhibited by phytates, fiber, tannins, oxalates, high non-heme iron, and calcium ($Ca$). It competes with copper ($Cu$) and iron ($Fe$).
  • Dependency and Deficiency: Important for growth and sexual maturation and immune function. Deficiency causes growth retardation and delayed healing.
• Copper ($Cu$):
  • Food Sources: Red meat, beans, and fortified cereals.
  • Anemia Link: Copper deficiency can lead to iron deficiency anemia because it alters iron status.
• Iodine ($I$):
  • Main Function: Synthesis of thyroid hormones.
  • Prevalence of Deficiency: Soil depletion and inconsistent food supply make it still prevalent.
  • Symptoms: Goiter, lowered metabolism, and neurological issues.
  • Thyroid Hormones: $T_3$ and $T_4$; $T_3$ is the active form.
• Selenium ($Se$):
  • Food Sources: Brazil nuts and seafood.
  • Iodine Link: Selenium is required for the enzyme that converts $T_4$ to the active $T_3$.
  • Deficiency Diseases: Linked to cardiovascular disease and infertility.