A vitamin is an organic compound and a vital nutrient that an organism requires in limited amounts. An organic chemical compound (or related set of compounds) is called a vitamin when the organism cannot synthesize the compound in sufficient quantities, and it must be obtained through the diet; thus, the term “vitamin” is conditional upon the circumstances and the particular organism.

Fat-soluble vitamins are probably the most common vitamins for some people. Unlike water-soluble vitamins, they remain stored in the fat deposits of a body for long periods of time and may accumulate to overdose levels. Note that the only vitamin humans can make is Vitamin D. Vitamin D is made when cholesterol is acted upon by enzymes and sunlight. It should also be noted that the fat-soluble Vitamin K is produced in small quantities in the human intestine by the action of mutually beneficial intestinal bacteria.

Water-soluble vitamins generally function within the cell to help catalyze cellular reactions such as cellular respiration. For your reference, cellular respiration is the process of harvesting energy from the breakdown of food molecules that takes place inside individual cells. Unlike fat-soluble vitamins, excess water-soluble vitamins do not remain stored in the body, but are excreted in urine and feces. Water-soluble vitamins include the eight different types of B complex vitamins and Vitamin C.


Health Benefit
Water-Soluble Vitamins
Vitamin B-1 (Thiamin) Vital for healthy nervous system and nerve transmission

Essential in converting glucose to energy

Disease is beriberi

Symptoms of a deficiency include depression, irritability, attention deficit

Severe deficiency leads to edema,
paralysis, and heart failure

No toxicity has been reported by those taking large doses over prolonged periods of time
Vitamin B-2 (Riboflavin) Essential for metabolizing carbohydrates, fats, and lipids and for the degradation of fatty acids and the synthesis of ATP

Acts as an intermediary in the transfer of electrons in oxidation-reduction reactions

Necessary for the function of vitamins B-6, folic acid, and niacin

Involved in formation of red blood cells and maintenance of body tissues, particularly the skin and eyes

Symptoms are dry, scaly skin on face, oral swelling, and cracking at the corners of the mouth No evidence that high doses have toxic effects
Vitamin B-6 (Pyridoxine) Necessary for immune system function, hormone modulation, gluconeogenesis

Essential in making certain amino acids and turning others into hormones

Involved in metabolizing polyunsaturated fats and proteins

Used to build red blood cells and maintain nerve tissue

Formation of niacin

Not common; symptoms include mouth sores, nausea, nervousness, anemia, convulsions High doses over prolonged periods are very toxic and can cause temporary or permanent nerve damage
Vitamin B-12 (Cobalamin) Works with folic acid to
produce red blood cells


Vitamin C (Ascorbic acid Activates liver-detoxifying systems

Antioxidant to inactivate highly reactive oxygen species; protects against damage to lipids and other molecules

Inhibits formation of carcinogenic compounds

Protects cellular functions

Enhances function of key white blood cells involved in the destruction of bacteria

Protects vitamin E

Integral to maintenance and building of collagen, a protein that holds the body’s cells in place

Vital to bones and teeth, blood vessels, healing of wounds, and iron absorption

Helps metabolize several amino acids and hormones

Scurvy is the deficiency disease Mostly nontoxic; diarrhea is a side-effect

High doses not recommended for those with genetic conditions that cause iron overload

Biotin Key role in metabolizing fats, carbohydrates, and proteins

Part of a number of enzymes in which it functions as a carboxyl carrier

Manufactured in lower digestive tract by bacteria

Not common; symptoms include baldness, a rash around the mouth and nose, and dry, flaky skin No evidence of toxicity at high doses
Choline Helps maintain central nervous system

Precursor to acetylcholine, a neurotransmitter

Involved in production and metabolism of fats and cholesterol

Protects liver from fatty deposits

Increased fatty deposits in liver, memory loss, poor muscle coordination Nontoxic, but excess consumption may result in tension headache
Folic acid (folate, B vitamin Used by body to break down and synthesize amino acids

Helps synthesize nucleic acids, which are needed to build new cells, particularly red blood cells

Involved in a variety of reactions in amino acid and nucleotide metabolism

Recommended for women of childbearing age; helps prevent neural tube birth defects

Leads to anemia similar to that caused by B-12 deficiency

Can exist without anemia with broad signs including generalized weakness, easy fatigability, irritability, and cramps

Can mask B-12 deficiency (which causes neurologic problems) at high doses and interfere with some seizure and cancer drugs
Niacin (sometimes called vitamin B-3) Enables body to use

carbohydrates, fats, and proteins (to provide energy), and amino acids

Influences metabolism of DNA, NAD, NADP

Aids nervous system and digestive tract function and promotes healthy skin

Disease is pellagra, rare in U.S.

Symptoms of deficiency: digestive upsets, insomnia, headaches, fatigue, sore and swollen tongue (disease is much worse)

Symptoms may include itching, skin flushing, and gastrointestinal distress

Time-released capsules have caused impaired liver function, reported jaundice, and liver failure

Toxic in high doses

May produce skin discoloration and dryness, decrease glucose tolerance, produce high uric acid levels, aggravation of peptic ulcers, and symptoms that accompany hepatitis

Pantothenic Acid Necessary for adrenal cortex function

Part of chemistry of coenzyme A, which is vital to metabolism of carbohydrates, fats, and proteins and involved in making fatty acids, cholesterol, acetylcholine, steroid hormones, and nerve regulators

Can result in abdominal distress, vomiting, cramps, burning in heels, fatigue, and insomnia No known toxicity, but research has been inadequate



Fat-soluble vitamins
Vitamin A (and its precursor*, beta-carotene)

*A precursor is converted by the body to the vitamin.

Needed for vision,healthy skin and mucous membranes, bone and tooth growth, immune system health

Vitamin A from animal sources (retinol): fortified milk, cheese, cream, butter, fortified margarine, eggs, liver

Beta-carotene (from plant sources): Leafy, dark green vegetables; dark orange fruits (apricots, cantaloupe) and vegetables (carrots, winter squash, sweet potatoes, pumpkin)

Vitamin D Needed for proper absorption of calcium; stored in bones Egg yolks, liver, fatty fish, fortified milk, fortified margarine. When exposed to sunlight, the skin can make vitamin D.
Vitamin E Antioxidant; protects cell walls Polyunsaturated plant oils (soybean, corn, cottonseed, safflower); leafy green vegetables; wheat germ; whole-grain products; liver; egg yolks; nuts and seeds
Vitamin K Needed for proper blood clotting

Leafy green vegetables and vegetables in the cabbage family; milk; also produced in intestinal tract by bacteria