chap7 the b complex vitamins

The B Complex Vitamins

Vitamin Defined• An organic substance that occurs in foods in small

amounts and is necessary for normal metabolic functioning of the body

• May be water soluble or fat soluble• Do not contribute directly to the structure of the body,

nor do they supply energy• They regulate metabolism by releasing energy from

fats and carbohydrates• They are involved in amino acid metabolism and also

assist in forming blood, bones and tissues

Division of Vitamin B • Those vitamins that primarily release energy

from carbohydrates and fats namely thiamin, niacin, riboflavin, pantothenic acid and biotin

• Those that catalyze formation of red blood cells namely folic acid and vitamin B12

• The vitamin that is important in protein and amino acid metabolism like Vitamin B6

• The vitaminlike compounds

Thiamine (Vit. B1)

• A member of the B-complex family

• Water Soluble

• Relatively unstable– Destroyed with heat– Destroyed in alkaline environment– Active as thiamine pyrophosphate (TPP)– Or as thiamine tri-phosphate (TT

Absorption and Metabolism

• Easily absorbed from the small intestine

• It is combine with phosphate within mucosal cells of the intestine and transported via the portal vein into the general circulation

• Maybe found in liver, heart, brain and muscle tissue

Function • Important coenzyme in energy

metabolism

• It acts as coenzyme in the production of ribose

• Needed for the metabolism of carbohydrates, proteins and fats

Deficiency• Beri-Beri – affects principally the

cardiovascular, muscular, and nervous system– Wet– Dry– Infantile

• Wernicke’s Syndrome

• Increased sensitivity of the oral mucosa, burning tongue, and loss or diminution of taste

Wet Beriberi

• Edema (accumulation of fluid in tissues spaces) of the legs, cardiac disturbances such as enlarged heart, systolic murmurs and dyspnea (difficulty of breathing) may develop

• The pulse is rapid and irregular, and the neck veins are distented

Dry Beriberi• Edema does not occur

• A condition consisting of paresthesia (prickling or burning) and numbness of the feet and cramps in the legs is present

Infantile Beriberi• Caused by inadequate thiamin in the

breast milk

• Characterized by dyspnea, cyanosis and cardiac failure

Wernicke’s Syndrome

• Severe deficiency of thiamin in the alcoholic individual

• Characterized by confusion, paralysis of eye muscles, and loss of memory

• Peculiar gait and foot and wrist drop are seen in advanced cases

Food Sources

• Cereals, meats, and legumes

• The richest sources are brewer’s yeast, lean pork, liver, beef, dried peas and beans, nuts and whole wheat and enriched cereals and breads

Riboflavin (Vit. B2)

• One of the B-complex vitamins

• Water Soluble

• Relatively stable

• Functions as coenzyme

• Active as flavin mononucleotide (FMN)

• Or flavin adenine dinucleotide (FAD)

Absorption and Metabolism

• It must be phosphorylated (combined with phosphate) in the intestinal tract before it can be absorbed

• Excess riboflavin is excreted in the urine

Function

• Acts as hydrogen carriers

• Assist in the metabolism carbohydrates, protein and fats

• Oxidation of most drugs (called the drug vitamin)

Deficiency • Gastrointestinal disease that causes

vomiting and hypermotility of the gastrointestinal tract

• Angular stomatis

• Glossitis

Sources • Milk, liver, heart, and kidney

• Lean meat

• Cheese

• Eggs

• Leafy green vegetables

Niacin (Vit. B3)

• One of the B-complex nutrients• Water Soluble• Very Stable• Active as nicotinamide adenine

dinucleotide (NAD)• And NAD-phosphate (NADP)• A peculiar vitamin since it can be

synthesized in body (via tryptophane)

Absorption and Metabolism

• Absorbed in the upper part of the small intestine

• It is stored only sparingly in the kidney, heart, brain, and liver and is exreted in the urine

Function• Forms the active portion of the

coenzymes that play an essential role in supplying organ tissues, making its presence necessary for the health of cells

• Acts as catalyst in accepting and releasing hydrogen in cellular respiration, carbohydrate metabolism and fat synthesis

Deficiency• Pellagra – characterized as the disease

causing 4D’s– Dermatitis– Diarrhea– Depression– Death

Symptoms• Weakness

• Persistent fatigability

• Irritability

• Headache

• Depression

• Soreness and inflammation of the tongue (glossitis) and mouth (stomatitis)

Sources • Found in appreciable amounts in liver,

yeast, meat, legumes, peanuts and whole cereals

• Foods that are good sources of tryptophan, such as animal protein and vegetable protein

Pantothenic Acid (Vit. B5)

• Sometimes, erroneously called – Vitamin B5

• So plentiful in grains and vegetables, a deficiency unlikely – except in complete starvation

Function

• Involved in the release of energy from the catabolism of carbohydrates, proteins, and fats

• It initiates the Krebs cycle and releases ATP

• It is the starting substance for the biosynthesis of cholesterol and other sterols, a component of hemoglobin

Deficiency • Fatigue• Sleep disturbances• Headaches• Malaise• Nausea• Abdominal stress• Burning, prickling sensations (paresthesia) of

the hands and feet, cramping of the leg muscles and impaired coordination

Sources • Widely distributed, occuring abundantly

in yeast and in animal tissue such as liver and eggs, whole-grain cereals and legumes

• Other fair sources are milk, fruits, and vegetables such as brocolli,cauliflower, and potatoes

Pyridoxine (Vit. B6)• Water-soluble

• White crystalline compound that is stable to heat and strong acids

Function • Helps make red blood cells

• Helps in amino acid and fatty bacid metabolism

• Aids in normal functioning of nervous tissue

Deficiency • Early deficiency signs

– Weakness– Irritability– Nervousness– Insomnia

• Later deficiency signs– Convulsions– Anemia– Lesions around lips and eyes (red, crusty)

Sources • Liver

• Muscle meats

• Yeast

• Legumes

• Whole grain cereals

• Wheat germ

• Wheat bran

Biotin (Vit. B7)

• Very uneventful.

• Unlikely to have deficiency

• Is blocked by raw egg whites

• Active biological substance

Function• Stimulates the growth of yeast and

bacteria

• Functions as a coenzyme for reactions involving the addition of carbon dioxide in the formation of purines

Deficiency • Dermatitis• Glossitis• Loss of appetite and sleep• Nausea• Muscular pains• Hyperesthesia (increased skin sensitivity• Paresthesia (burning and prickling sensation)• Alopecia

Sources

• The richest sources are liver, kidney, milk, egg yolk and yeast

Folic Acid (Vit. B9)

• Yellow crystalline substance

• Sparingly soluble in water

Function • Essential for the manufacture and

maturation of blood cells

• Necessary for the normal functioning of the hematopoietic system

• Prevent anemia, some birth defects and heart disease

Deficiency

• Disorders of malabsorption associated with infectious disease (tropical diseases) or certain metabolic and endocrine disorders

• Megaloblastic anemia of pregnancy

• Paresthesia

• Angular cheilosis and gingivitis

Sources • Liver• Kidney• Yeast• Dark green leafy vegetables• Asparagus• Brocolli• Soybeans and nuts• Orange juice

Cyanocobalamin (Vit. B12)

• Consist of a cyanide ion and a cobalt ion

• Not a single substance but consist of several closely related compounds having similar activity

• By product of streptomycin

Function

• Plays a biomechanical role in the maintenance of myelin

• Involved in the synthesis of nucleoproteins

Deficiency • Pernicious anemia

– Usual complaints are weakness, numbness and tingling in the extremities

– Patients may have difficulty in walking and coordination of movements

– Vibratory sense may be absent– Patient may have a lemon-yellow complexion

as a result of jaundice caused by red cell destruction, early graying of hair, fast heartbeat, ankle swelling and peripheral neuritis

Sources • Occurs primarily in animal foods, and

liver is the richest source

• Meat

• Eggs

• Milk

• Cheese

• Fish