Vitamins: Their sources and functions

The word vitamin is derived from the Latin word ‘vita’ meaning life.  A vitamin is a vital nutrient required for the survival of organisms. But the interesting aspect is that vitamins are not produced by the body. If at all some of the vitamins are produced, it is only in limited quantity and is not at all sufficient to meet the requirement of body. Fortunately, vitamins are present in many food substances. The body absorbs the required vitamins from the food intake.  For body, vitamin is an essential factor like, water, carbohydrates, proteins and fats. 

vitamin 2

What is a vitamin?

Vitamin is basically an organic compound.  A chemical compound, with carbon being an essential ingredient in the molecule is called an organic compound.  But all compounds with molecules that contain carbon are not considered organic. Certain compounds of carbon like oxides of carbon, cyanides, carbides and carbonates are classified under inorganic group.  

What are the classifications of vitamins?

There are many kinds of vitamins. But 13 only come under universally accepted category of vitamins.  These are vitamin A, B, C, D, E and K. Vitamins are broadly classified under two categories;  water- soluble and fat-soluble. Vitamins A, D, E and K are fat soluble. There are 9 vitamins under water-soluble category; vitamin C and other 8 members that belong to B family of vitamins. 

vitamin 3       vitamin 4

Deficiency of vitamin results in disorders or diseases like reduced digestive power, weakening of eye sight, tiredness, beri-beri, rickets, weakening of bones etc. 

What are the roles and major sources of vitamins? 



Role of the vitamin

Food Source

Disorders/diseases caused because of lack of the vitamin

Vitamin A

Promotion of eye sight, control of digestive system

Liver, cod liver oil, broccoli, butter , carrot, spinach, pumpkin, collard greens, cheeses, egg, apricot,  milk

Night-blindness,  keratomalacia

Vitamin B1 –(Thiamine)

Helps body in processing carbohydrates and certain proteins

Yeast, pork, cereal grains, kale, cauliflower, sunflower seeds, oranges, liver, brown rice, whole grain rye, potatoes, eggs.


Beriberi, Wernicke-Korsakoffsyndrome

Vitamin B2


Converts food into energy, formation of  red blood cells.


Asparagus, okra, chard,  bananas, eggs, fish, persimmons, yogurt, meat, cottage cheese, milk, green beans


Vitamin B3


Supports digestion, converts food into energy; helps formation of cholesterol.

Liver, beef, fish (tuna, salmon), milk, eggs, avocados, dates, kidney, chicken, tomatoes, brewer's yeast, leafy vegetables, broccoli, carrots,  nuts, whole grains, mushrooms.



Vitamin B5

(Pantothenic acid)

Formation of blood cells, maintains healthy digestive track.

Meats, avocados, royal jelly, whole grains (milling may remove it), broccoli, fish ovaries.



Vitamin B6


Supports nervous system. Breaks down proteins and stored sugar.

Meats, bananas, vegetables, whole grains and nuts.

Anemia, peripheral neuropathy

Vitamin B7


Converts food int glucose, produces amino acids and fatty acids

Egg yolk, some vegetables, liver.

Dermatitis, enteritis

Vitamin B9

(Folic acid)

Formation of red blood cells, help work iron in body.


Leafy vegetables, some fortified grain products, legumes, sunflower seeds, liver, baker's yeast, certain  fruits

Pregnancy deficiency linked to birth defects

Vitamin B12


Helps cell division, formation of red blood cells.

Fish, shellfish, milk, dairy products, soy products, meat, poultry, eggs, fortified cereals, fortified nutritional yeast

Megaloblastic anemia

Vitamin C

(Ascorbic acid)

Supports a healthy immune system,  helps make collagen

Fruits like kakadu and camu, vegetables, liver

Megaloblastic anemia

Vitamin D

Maintains bone health, helps  processing  calcium, important for immune system function, may protect from cancer

Exposure of skin to ultraviolet B light from the sun or artificial sources, eggs, fatty fish, beef liver, and mushrooms

Rickets, osteomalacia

Vitamin E

Functions as antioxidant, protects cells from damage.

Kiwi fruit, eggs,  almonds, avocado, milk, nuts, wheat germ,  leafy green vegetables, unheated vegetable oils, and wholegrains

Deficiency is uncommon. May cause mild hemolytic anemia in newborns

Vitamin K

Helps blood clot, maintains bone health.

Leafy green vegetables, kiwi fruit, avocado.

Bleeding diathesis

Elizabeth Paul



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