Classification of Vitamins

Vitamins are organic molecules or sets of closely related (chemically) molecules that are needed by organisms in small quantities to maintain the proper functioning of their metabolism.

Essential and Non-Essential

The ESSENTIAL VITAMINS are the vitamins that are not produced in the body and thus have to be taken in the diet. The Essential vitamins are: Vitamin A, Vitamin B complex, Vitamin C, and Vitamin E

NON-ESSENTIAL VITAMINS are vitamins that are produced by the constitutive activities of the body. The Non-Essential vitamins are Vitamin D and Vitamin K,

WATER-SOLUBLE VITAMINS

  • Energy production from carbohydrates
  • Nerve signal transmission
  • Muscle contraction
  • Development of myelin sheaths around nerves
    Sources: Whole grains, legumes, nuts, seeds, pork, and fortified cereals. Deficiency can lead to beriberi, a condition affecting the cardiovascular and nervous systems.

Vitamin B1 (Thiamine)

Essential for health, thiamine plays a crucial role in energy metabolism. It helps convert carbohydrates into glucose, which the body uses for energy. The nervous system also relies heavily on thiamine for proper functioning. Key functions include:

Vitamin B2 (Riboflavin)

Riboflavin is critical for cellular growth and energy production. It acts as a coenzyme in numerous metabolic processes and helps convert other B vitamins into their active forms. Notable functions include:

  • Breaking down proteins, fats, and carbohydrates
  • Maintaining healthy skin and vision
  • Supporting antioxidant activity
  • Red blood cell formation
    Sources: Dairy products, lean meats, eggs, green leafy vegetables, and fortified cereals. Deficiency symptoms include sore throat, cracked lips, and inflammation of the tongue.

Vitamin B3 (Niacin)

Niacin is unique among B vitamins as it can be synthesized from tryptophan, though dietary sources are still important. Its primary functions include:

  • DNA repair and cell signaling
  • Converting food into energy
  • Supporting nervous system function
  • Maintaining healthy skin
    Sources: Meat, fish, nuts, seeds, legumes, and enriched grains. Severe deficiency leads to pellagra, characterized by dermatitis, diarrhea, and dementia.

Vitamin B5 (Pantothenic Acid)

Found in virtually all foods, pantothenic acid is crucial for:

  • Breaking down fats and carbohydrates for energy
  • Producing red blood cells
  • Manufacturing sex and stress-related hormones
  • Synthesizing cholesterol
    Sources: Widespread in foods, particularly abundant in whole grains, legumes, eggs, and dairy products. Deficiency is rare due to its widespread availability.

Vitamin B6 (Pyridoxine)

This vitamin is crucial for protein metabolism and cognitive development. Key functions include:

  • Amino acid metabolism
  • Glucose and lipid metabolism
  • Neurotransmitter production
  • Immune system support
  • Red blood cell formation
    Sources: Poultry, fish, potatoes, non-citrus fruits, and fortified cereals. Deficiency can cause anemia, depression, and skin problems.

Vitamin B7 (Biotin)

Though produced by gut bacteria, dietary biotin is still important. Functions include:

  • Glucose regulation
  • Cell growth
  • Fatty acid synthesis
  • Maintenance of healthy hair, skin, and nails
    Sources: Eggs, nuts, seeds, dairy products, and legumes. While deficiency is rare, symptoms include hair loss and skin rashes.

Vitamin B9 (Folate)

Crucial for cell division and DNA synthesis, folate is particularly important during pregnancy. Key roles include:

  • DNA and RNA synthesis
  • Red blood cell formation
  • Prevention of neural tube defects
  • Amino acid metabolism
    Sources: Dark green vegetables, legumes, fortified grains, and citrus fruits. Deficiency can cause anemia and increase birth defect risks.

Vitamin B12 (Cobalamin)

The most complex B vitamin, B12 is essential for:

  • DNA synthesis
  • Red blood cell formation
  • Neurological function
  • Fatty acid metabolism
    Sources: Exclusively found in animal products or fortified foods. Deficiency can cause pernicious anemia and neurological problems.

Vitamin C (Ascorbic Acid)

A powerful antioxidant, Vitamin C serves multiple functions:

  • Collagen synthesis
  • Immune system support
  • Antioxidant protection
  • Iron absorption enhancement
    Sources: Citrus fruits, berries, bell peppers, broccoli, and potatoes. Severe deficiency causes scurvy.

FAT-SOLUBLE VITAMINS

Vitamin A (Retinol)

Essential for vision and immune function, Vitamin A exists in two forms: preformed vitamin A and provitamin A carotenoids. Functions include:

  • Vision maintenance
  • Immune system support
  • Cell growth and differentiation
  • Skin health maintenance
    Sources: Liver, dairy products, eggs, and orange/yellow vegetables (as beta-carotene).

Vitamin D (Calciferol)

Unique among vitamins, Vitamin D functions as a hormone and can be synthesized in the skin. Key functions:

  • Calcium absorption regulation
  • Bone mineralization
  • Immune system modulation
  • Cell differentiation
    Sources: Sunlight exposure, fatty fish, fortified dairy products, and egg yolks. Deficiency is common and can lead to rickets or osteomalacia.

Vitamin E (Tocopherol)

A powerful antioxidant, Vitamin E serves to:

  • Protect cells from free radical damage
  • Support immune function
  • Maintain skin health
  • Aid in blood vessel dilation
    Sources: Vegetable oils, nuts, seeds, green vegetables, and whole grains.

Vitamin K

Exists in two forms: K1 (phylloquinone) and K2 (menaquinone). Essential functions include:

  • Blood clotting
  • Bone metabolism
  • Protein synthesis
  • Calcium regulation
    Sources: K1 from green leafy vegetables; K2 from fermented foods and animal products. Some K2 is produced by gut bacteria.

NON-ESSENTIAL VITAMINS AND SYNTHESIS

While certain vitamins can be synthesized by the body, the amount produced may not be sufficient:

Vitamin D synthesis requires:

  • Adequate sun exposure
  • Healthy kidney and liver function
  • Sufficient cholesterol as a precursor

Vitamin K2 synthesis by gut bacteria depends on:

  • Healthy gut microbiome
  • Proper digestive function
  • Adequate dietary precursors

Niacin synthesis from tryptophan:

  • Requires sufficient dietary tryptophan
  • Is an inefficient process (60:1 conversion ratio)
  • May not meet total needs

This information forms a comprehensive foundation for understanding vitamin classifications, functions, and sources. Each vitamin plays multiple crucial roles in maintaining health, and while some can be synthesized by the body, most must be obtained through diet or supplementation.