BI-304: Chapter 6 Vitamins

Vitamin A

Forms:

• Preformed (active form): retinol, retinaldehyde, retinoic acid
  → Found in animal sources

• Provitamin A carotenoids: beta-carotene, alpha-carotene, cryptoxanthin
  → Found in plant sources, converted into retinol in the body

Functions:

• Vision: formation of visual pigment “rhodopsin”

• Growth & Development: bones and teeth

• Epithelial maintenance: skin, hair, mucosal lining

• Immunity: strengthens body defenses against infection

Toxicity: from supplements (teratogenic, toxic in high doses)
Excess carotenoids: cause yellow-orange skin, not toxic

Sources:

• Retinol (animal): beef liver, milk, cheese, egg yolk

Vitamin B₁

Thiamin

Function:

• Coenzyme in energy metabolism

• Promotes normal appetite

• Supports nervous system function

Sources (most → least):

• Pork

• Whole grain & enriched breads/cereals

• Liver

• Wheat germ

• Nuts, dried peas, beans

Vitamin B₂

Riboflavin

Function:

• Coenzyme in energy metabolism

• Converts tryptophan → niacin

• Converts homocysteine → methionine

• Aids in cell growth and energy production

Sources (most → least):

• Milk and dairy

• Liver

• Eggs

• Meat

• Spinach

• Whole/enriched breads & cereals

Vitamin B₃

Niacin

Function:

• Coenzyme in energy metabolism (NAD, NADP formation)

• Supports redox reactions

Vitamin B₅

Pantothenic Acid

Function:

• Component of Coenzyme A for energy metabolism

• Synthesizes fatty acids, cholesterol, and hormones

Vitamin B₆ 

Pyridoxine, Pyridoxal, Pyridoxamine

Function:

• Coenzyme in protein metabolism

• Amino acid synthesis & breakdown

• Neurotransmitter synthesis

• Converts tryptophan → niacin

Vitamin B₉

Folate

Types:

• Natural folate: leafy greens, legumes, seeds, liver, OJ

• Synthetic folic acid: supplements/fortified foods (2x more bioavailable)

Function:

• Coenzyme in DNA synthesis & cell division

• Supports rapidly dividing cells

• Prevents macrocytic anemia

• Neural tube development in fetuses

Vitamin B₁₂

Cobalamin

Function:

• Coenzyme in new cell synthesis

• Activates folate

• Maintains myelin sheath of nerve cells

• Helps metabolize fatty acids & amino acids

• Coenzyme in homocysteine metabolism

Sources:

• Animal foods: meat, fish, eggs, dairy

• Fortified foods: cereals, plant milks

• Stored in liver

Vitamin C

Ascorbic Acid

Functions:

• Collagen synthesis (skin, blood vessels, connective tissue)

• Antioxidant (protects from oxidative damage)

• Immune system support

Sources:

• Citrus fruits, strawberries, bell peppers, broccoli, tomatoes

Vitamin D

Forms:

• D3 (cholecalciferol): animal sources & synthesized in skin

• D2 (ergocalciferol): plant sources

Function:

• Promotes calcium absorption in intestines

• Supports bone mineralization

• Aids cell growth, immune, and neuromuscular function

Sources (best → least):

1. Sunlight exposure

2. Fatty fish & cod liver oil

3. Egg yolks & beef liver

4. Fortified foods (milk, cereal, orange juice)

Vitamin E

Active form: Alpha-tocopherol

Function:

• Fat-soluble antioxidant

• Protects PUFAs and cell membranes

• Prevents RBC hemolysis

• Protects vitamin A from oxidation

Sources:

• Vegetable oils (sunflower, canola, olive)

• Nuts, seeds, wheat germ

• Whole grains, dark leafy greens, fortified cereals

Vitamin K

Types:

• K1 (phylloquinone): plants

• K2 (menaquinone): animal sources; synthesized by gut bacteria

Functions:

• Blood clotting: coenzyme for prothrombin

• Bone health: activates proteins for bone formation

Sources:

• K1 (plants): Brussels sprouts, broccoli, spinach, lettuce, asparagus

• K2 (animals): liver, meat, eggs, dairy

Avoiding Vitamin Deficiencies

Vegans no

Commonly consumed vitamins

B₁₂

Commonly Under consumed Vitamin

A

C

E

D

Choline

Vitamin A deficiency

• Night Blindness (zerophthalmia)

• Impaired vision, dry eyes, skin issues

Vitamin D Deficiency

• Rickets in Children Osteomalacia in Adults

• Weak, soft bones

Vitamin C Deficiency

Scurvy

Bleeding gums, poor wound healing, fatigue

Vitamin E Deficiency

• Hemolytic

• Anemia Breakdown of red blood cells, neuropathy

Vitamin K Deficiency

Hemorrhagic disease Impaired blood clotting

Vitamin B₁ Deficiency

• Beri-Beri / Wernicke-Korsakoff

• Muscle weakness Nerve damage

Vitamin B₂ Deficiency

• Ariboflavinosis

• Cracked lips, sore throats, glossitits

Vitamin B₃ Deficiency

• Pallegra

• Dermatitis, dementia, diarrhea, death

Vitamin B₅ Deficiency

• Burning feet syndrome

• Fatigue, numbness, tinging

Vitamin B₆ Deficiency

• Microcytic anemia

• Dermatitis, depression, confusion

Vitamin B₉ Deficiency 

• Megaloblastic Anemia / Neural Tube Defects

• Enlarged RBC’s, fatigue

Vitamin B₁₂ Deficiency

• Pernicious anemia

• Neruological damage