Micronutrients: Fat-Soluble Vitamins, Water-Soluble Vitamins, Major and Trace Minerals

Fat-Soluble Vitamins

Overview of Fat-Soluble Vitamins

• Fat-soluble vitamins include vitamins A, D, E, and K. They are absorbed with dietary fat and stored in the body's fatty tissue and liver.

• They are generally more stable than water-soluble vitamins but can be destroyed by heat, light, and oxidation.

• Excess intake can lead to toxicity due to storage in the body.

Classification and Characteristics of Vitamins

• Vitamins are organic compounds required in small amounts for normal metabolism.

• They are classified by solubility: fat-soluble (A, D, E, K) and water-soluble (B vitamins, C).

Antioxidants and Free Radicals

• Antioxidants are substances that neutralize free radicals, preventing cellular damage.

• Vitamins A (as beta-carotene), C, and E act as antioxidants.

• Free radicals are unstable molecules that can damage cells, contributing to aging and diseases.

• Antioxidants from foods are generally more beneficial than supplements.

Bioavailability, Absorption, and Storage

• Fat-soluble vitamins require bile and dietary fat for absorption.

• They are transported via chylomicrons in the lymphatic system and stored in the liver and adipose tissue.

• Bioavailability can be affected by food preparation, presence of other nutrients, and individual health status.

Vitamin A

• Types: Retinoids (animal sources), carotenoids (plant sources).

• Functions: Vision, immune function, reproduction, cellular communication.

• Food sources: Liver, dairy, carrots, sweet potatoes, leafy greens.

• Deficiency: Night blindness, xerophthalmia, increased infection risk.

• Toxicity: Liver damage, birth defects.

• At-risk groups: People with fat malabsorption, low dietary intake.

Vitamin D

• Types: D2 (ergocalciferol, plant), D3 (cholecalciferol, animal/sunlight).

• Synthesis: Produced in skin via UVB exposure; influenced by latitude, skin color, sunscreen use.

• Functions: Calcium and phosphorus homeostasis, bone health.

• Food sources: Fatty fish, fortified milk, egg yolks.

• Deficiency: Rickets (children), osteomalacia (adults).

• Toxicity: Hypercalcemia, kidney stones.

• At-risk groups: Elderly, limited sun exposure, dark skin, fat malabsorption.

• Regulation of blood calcium: Vitamin D increases intestinal absorption of calcium.

Vitamin E

• Functions: Antioxidant, protects cell membranes.

• Food sources: Vegetable oils, nuts, seeds, green leafy vegetables.

• Deficiency: Rare, but can cause nerve and muscle damage.

• Toxicity: Can interfere with vitamin K and blood clotting.

• At-risk groups: People with fat malabsorption disorders.

Vitamin K

• Types: K1 (phylloquinone, plants), K2 (menaquinone, bacteria/animal foods).

• Functions: Blood clotting, bone metabolism.

• Food sources: Green leafy vegetables, broccoli, Brussels sprouts.

• Deficiency: Bleeding disorders.

• Toxicity: Rare, but can interfere with anticoagulant medications.

• At-risk groups: Newborns, people with fat malabsorption.

Dietary Supplements

• Supplements can help individuals with specific deficiencies or increased needs.

• Not essential for everyone; whole foods are preferred sources.

• Regulation: In the U.S., supplements are regulated as foods, not drugs.

• Some populations (e.g., pregnant women, elderly, vegans) may benefit from supplements.

Water-Soluble Vitamins

Overview of Water-Soluble Vitamins

• Include B vitamins (thiamin, riboflavin, niacin, pantothenic acid, biotin, B6, folate, B12) and vitamin C.

• Absorbed directly into the bloodstream; not stored in large amounts (except B12).

• Excess is excreted in urine; toxicity is rare but possible with supplements.

Bioavailability and Factors Affecting Vitamin Content

• Bioavailability can be reduced by heat, light, and oxidation during food processing and storage.

• Individuals with poor diets, malabsorption, or increased needs are at higher risk for deficiencies.

Thiamin (Vitamin B1)

• Functions: Energy metabolism, nerve function.

• Food sources: Whole grains, pork, legumes, seeds.

• Deficiency: Beriberi (muscle weakness, nerve damage), Wernicke-Korsakoff syndrome (neurological disorder, often in alcoholism).

Riboflavin (Vitamin B2)

• Functions: Energy production, antioxidant function.

• Food sources: Dairy, eggs, green vegetables, enriched grains.

• Deficiency: Ariboflavinosis (sore throat, mouth inflammation).

• Destroyed easily by light (e.g., milk in clear bottles).

Niacin (Vitamin B3)

• Functions: Energy metabolism, DNA repair.

• Food sources: Meat, fish, poultry, whole grains.

• Deficiency: Pellagra (dermatitis, diarrhea, dementia, death).

• Toxicity: Flushing, liver damage (from supplements).

• Pharmacological use: High doses used to lower cholesterol.

Pantothenic Acid

• Functions: Synthesis of coenzyme A, energy metabolism.

• Food sources: Widespread in foods (meats, whole grains, vegetables).

Biotin

• Functions: Coenzyme in metabolism of fats, carbohydrates, and amino acids.

• Food sources: Eggs, nuts, whole grains.

• Deficiency: Rare, but can occur with high intake of raw egg whites (contain avidin, which binds biotin and reduces absorption).

• Toxicity: Rare.

Vitamin B6 (Pyridoxine)

• Functions: Amino acid metabolism, neurotransmitter synthesis, hemoglobin formation.

• Food sources: Meat, fish, potatoes, bananas.

• Deficiency: Anemia, depression, confusion.

• Toxicity: Nerve damage (from supplements).

Folate and Folic Acid

• Functions: DNA synthesis, cell division, amino acid metabolism.

• Food sources: Leafy greens, legumes, fortified grains.

• Deficiency: Neural tube defects in infants, macrocytic anemia.

• Toxicity: Can mask B12 deficiency.

• Folate: Natural form in foods; Folic acid: Synthetic form in supplements/fortified foods.

• Homocysteine: Amino acid linked to heart disease; folate helps reduce its levels.

Vitamin B12 (Cobalamin)

• Functions: Nerve function, red blood cell formation, DNA synthesis.

• Food sources: Animal products (meat, dairy, eggs).

• Deficiency: Macrocytic anemia, neurological issues.

• Intrinsic factor: Protein needed for B12 absorption in the stomach.

• At-risk groups: Vegans, elderly, people with absorption disorders.

Vitamin C (Ascorbic Acid)

• Functions: Antioxidant, collagen synthesis, immune function, enhances iron absorption.

• Food sources: Citrus fruits, strawberries, peppers, broccoli.

• Deficiency: Scurvy (bleeding gums, poor wound healing).

• Toxicity: Gastrointestinal upset (from supplements).

• Supplements: Limited evidence for preventing the common cold.

Diet, Lifestyle, and Cancer Risk

• Healthy diet (rich in fruits, vegetables, whole grains) and lifestyle (physical activity, avoiding tobacco/alcohol) can reduce cancer risk.

Major Minerals

Overview of Major Minerals

• Major minerals are required in amounts >100 mg/day and include sodium, potassium, calcium, phosphorus, magnesium, chloride, and sulfur.

• Solubility, stability, and toxicity can be affected by heat, light, and oxidation.

Bioavailability of Minerals

• Bioavailability is influenced by other dietary components (e.g., phytates, oxalates, fiber), stomach acidity, and mineral-mineral interactions.

Absorption, Transport, and Storage

• Minerals are absorbed in the small intestine, transported in blood, and stored in various tissues.

Sodium

• Functions: Fluid balance, nerve transmission, muscle contraction.

• Food sources: Processed foods, table salt.

• Deficiency: Rare; symptoms include muscle cramps, confusion.

• Toxicity: Hypertension, increased heart disease risk.

• DASH Diet: Emphasizes sodium reduction and increased potassium, calcium, magnesium.

Potassium

• Functions: Fluid balance, nerve transmission, muscle contraction.

• Food sources: Fruits, vegetables, dairy, legumes.

• Deficiency: Can cause muscle weakness, arrhythmias; mild deficiencies are common.

Calcium

• Functions: Bone and teeth structure, muscle contraction, nerve signaling.

• Food sources: Dairy, leafy greens, fortified foods.

• Bioavailability: Enhanced by vitamin D; reduced by oxalates, phytates.

• Deficiency: Osteoporosis, muscle spasms.

• Toxicity: Kidney stones, impaired absorption of other minerals.

• Supplement tips: Divide doses, take with meals, avoid excess.

• Blood calcium is tightly regulated by hormones (parathyroid hormone, vitamin D).

Phosphorus

• Functions: Bone structure, energy metabolism (ATP), cell membranes.

• Food sources: Meat, dairy, nuts, legumes.

• Deficiency: Rare, but can contribute to bone loss.

Magnesium

• Functions: Enzyme function, muscle and nerve function, bone health.

• Food sources: Nuts, whole grains, leafy greens.

• Deficiency: Uncommon, but possible with poor intake or certain conditions.

Sulfate/Sulfur

• Functions: Component of amino acids, vitamins, and other compounds.

• Food sources: Protein-rich foods.

Chloride

• Functions: Fluid balance, stomach acid production.

• Food sources: Table salt, processed foods.

Minerals and Bone Health

• Calcium, phosphorus, and magnesium are critical for bone structure.

• Osteoporosis risk factors: Age, gender, genetics, low calcium/vitamin D, inactivity.

• Treatment: Adequate nutrition, weight-bearing exercise, medications if needed.

Trace Minerals

Overview of Trace Minerals

• Needed in small amounts (<100 mg/day); include iron, copper, zinc, selenium, fluoride, chromium, iodine, molybdenum, manganese.

• Bioavailability affected by dietary factors, stomach acidity, and food processing.

Soil Content and Food Processing

• Trace mineral content in foods depends on soil composition and processing methods.

Iron

• Types: Heme iron (animal foods, better absorbed), nonheme iron (plant foods).

• Functions: Oxygen transport (hemoglobin), energy metabolism.

• Food sources: Red meat, beans, fortified cereals.

• Absorption: Enhanced by vitamin C, inhibited by phytates, calcium.

• Regulation: Hepcidin (hormone) controls absorption; ferritin stores iron.

• Deficiency: Iron-deficiency anemia (fatigue, weakness).

• Toxicity: Hemochromatosis (genetic disorder causing iron overload).

• At-risk groups: Women of childbearing age, infants, vegetarians.

Copper

• Functions: Iron metabolism, antioxidant enzymes.

• Food sources: Shellfish, nuts, seeds, whole grains.

• Deficiency: Anemia, immune dysfunction.

• Toxicity: Liver damage.

• Genetic diseases: Wilson's disease (copper accumulation), Menkes disease (copper deficiency).

Zinc

• Functions: Immune function, wound healing, DNA synthesis.

• Food sources: Meat, seafood, dairy, whole grains.

• Deficiency: Growth retardation, impaired immunity.

• Toxicity: Nausea, immune suppression.

• Supplements: May reduce duration of common cold, but evidence is mixed.

Selenium

• Functions: Antioxidant (part of glutathione peroxidase), thyroid hormone metabolism.

• Food sources: Brazil nuts, seafood, grains.

• Deficiency: Keshan disease (heart disorder), possible increased cancer risk (prostate cancer).

• Toxicity: Selenosis (hair loss, nerve damage).

Fluoride

• Functions: Tooth and bone health.

• Food sources: Fluoridated water, tea, seafood.

• Deficiency: Increased dental caries.

• Toxicity: Fluorosis (mottled teeth).

• No strong evidence linking fluoride to cancer or ADHD.

Chromium

• Functions: Enhances insulin action, glucose metabolism.

• Food sources: Whole grains, meats, vegetables.

• May benefit individuals with impaired glucose tolerance (diabetes).

Iodine

• Functions: Thyroid hormone synthesis.

• Food sources: Iodized salt, seafood, dairy.

• Deficiency: Goiter, hypothyroidism, cretinism (in infants).

• Goitrogens: Substances in some foods (e.g., cabbage, soy) that interfere with iodine utilization.

Molybdenum and Manganese

• Both are trace minerals required for enzyme function.

• Food sources: Widespread in foods.

Nutrient-Deficiency Anemias

• Anemia: Condition with reduced oxygen-carrying capacity of blood.

• Macrocytic anemia: Large, immature red blood cells (due to folate or B12 deficiency).

• Microcytic anemia: Small, pale red blood cells (due to iron deficiency).

• Treatment: Address underlying nutrient deficiency (iron, folate, B12).

Table: Comparison of Fat-Soluble and Water-Soluble Vitamins

Property	Fat-Soluble Vitamins	Water-Soluble Vitamins
Absorption	With dietary fat, lymphatic system	Directly into blood
Transport	Chylomicrons, lipoproteins	Free or protein-bound in plasma
Storage	Liver, adipose tissue	Minimal storage (except B12)
Excretion	Not readily excreted	Excreted in urine
Toxicity	Possible with excess intake	Rare, but possible with supplements
Examples	A, D, E, K	B vitamins, C