Vitamins are organic compounds that are essential for the normal growth and functioning of the body.

They are required in small amounts and play vital roles in various biochemical processes. Since the body
either cannot synthesize most vitamins or produces them in insufficient quantities, they must be obtained
through diet or supplements.
Sir Frederick Gowland Hopkins's experiment, which he conducted around 1910, demonstrated the
importance of "accessory substances" (later called vitamins) for growth. He found that when young rats
were fed only pure nutrients, their growth stopped, but adding a small amount of milk to their diet
allowed them to grow again. This led to the discovery that certain substances, present in natural foods.

1. The Experiment and Discovery:

Hopkins's experiment involved feeding young rats a synthetic diet consisting of pure proteins, fats,
carbohydrates, and minerals. He observed that these rats ceased to grow even though they were getting
all the known essential nutrients.

When Hopkins added milk to the rats' diet, they began to grow again, indicating that the milk contained
an essential substance not present in the synthetic diet.
Casimir Funk, a Polish biochemist, is widely credited with the discovery and naming of vitamins in 1912.
He coined the term "vitamine" to describe essential dietary factors that prevent deficiency diseases like
beriberi.

2. Casimir Funk and the Discovery of Vitamins

In 1912, Casimir Funk conducted a series of experiments while working at the Lister Institute in
London. He was studying a disease called beriberi, which caused symptoms like weakness, paralysis,
and heart problems.

The Experiment and Discovery:

 Funk observed that people who consumed polished (white) rice often developed beriberi, while
those who ate unpolished (brown) rice did not.
 He hypothesized that the outer layer (Husk) of rice contained a vital substance that prevented
the disease.
 He extracted a substance from the rice bran that cured beriberi in pigeons.
 He named this substance a “vitamine” — from “vital amine (NH2)” — because he believed it
was a type of amine compound essential for life.

1. Fat-Soluble Vitamins

These dissolve in fat and are stored in the body’s fatty tissue and liver. They are absorbed along with
dietary fat.

Examples:

Vitamin A (Retinol)
  Function:
Supports vision (especially night vision), immune system, skin health, cell growth, and
reproduction.
 Sources:
o Animal: Liver, eggs, butter, milk.
o Plant: Carrots, sweet potatoes, spinach, mangoes.
 Deficiency:
Causes night blindness, dry eyes , poor immunity, and growth retardation.

 Vitamin D (Calciferol).

Vitamin D – Summary

 Function:
Helps in calcium and phosphorus absorption, essential for strong bones and teeth.
 Sources:
Sunlight (main source), fortified milk, egg yolk, fish liver oils, fatty fish (salmon, sardines).
 Deficiency:
Causes rickets in children (soft, weak bones) and osteomalacia in adults (bone pain, muscle
weakness).

Vitamin E (Tocopherol) – Summary

 Function:
Acts as an antioxidant, protects cell membranes from damage, supports immune function.
 Sources:
Vegetable oils (sunflower, wheat germ), nuts, seeds, green leafy vegetables.
 Deficiency:
Rare, but may cause nerve and muscle damage, weakness, and impaired vision or coordination.

 Vitamin K (Phylloquinone K1 and Menaquinone K2)

Vitamin K – Summary

 Function:
Essential for blood clotting and bone metabolism.
 Sources:
Green leafy vegetables (spinach, kale), broccoli, cabbage, liver, and produced by gut bacteria.
 Deficiency:
Causes delayed blood clotting, excessive bleeding, and in severe cases, hemorrhage.

Key features:

 Stored in the body

 Excess intake to cause toxicity
 Require fat for absorption
2. Water-Soluble Vitamins

These dissolve in water and are not stored in the body in significant amounts; excess is usually excreted
in urine.

Examples:

Vitamin C (Ascorbic acid)

Functions of Vitamin C:

1. Antioxidant Activity:
2. Collagen Synthesis:
3. Enhances Iron Absorption:.
4. Immune System Support:
5. Wound Healing:
6. Supports Enzymatic Reactions:

Deficiency of Vitamin C:

 Scurvy: Characterized by bleeding gums, joint pain, and poor wound healing.

 Vitamin B-complex group, which includes:

o B1 (Thiamine)
o B2 (Riboflavin)
o B3 (Niacin)
o B5 (Pantothenic acid)
o B6 (Pyridoxine)
o B7 (Biotin)
o B9 (Folic acid)
o B12 (Cobalamin)

Water-Soluble Vitamins, Sources, and Functions:

Vitamin Sources Functions

Helps convert food into energy, supports

Vitamin B1 (Thiamine) Whole grains, nuts, pork, beans
nerve function

Milk, eggs, green vegetables, Supports energy production and healthy

Vitamin B2 (Riboflavin)
whole grains skin

Meat, poultry, fish, whole grains, Helps digestion and keeps skin and nerves
Vitamin B3 (Niacin)
peanuts healthy
 Vitamin Sources Functions

Vitamin B5 (Pantothenic Needed to make hormones and energy

Meat, eggs, broccoli, whole grains
acid) from food

Bananas, potatoes, chicken, Helps brain development and immune

Vitamin B6 (Pyridoxine)
fortified cereals function

Vitamin B7 (Biotin) Eggs, nuts, soybeans, whole grains Supports healthy hair, skin, and nails

Vitamin B9 (Folate/Folic Leafy greens, oranges, beans, Important for making DNA and
Acid) fortified foods preventing birth defects

Vitamin B12 Meat, fish, dairy, eggs, fortified Needed for red blood cells and nerve
(Cobalamin) cereals function

Vitamin C (Ascorbic Citrus fruits, strawberries, Boosts immunity, helps absorb iron, and
acid) tomatoes, broccoli heals wounds

Composed by Sana Ullah

Lecturer of Plant Pathology.
LUAWMS