Vitamins

Vitamins

فيتامين (م 2) / د . صبا ثاني اسنان موصل 17 / 11 / 2015

The Discovery of Vitamins

The Germ Theory of Disease Scurvy: Disease of sailors (Vitamin C deficiency) Beri-Beri: Disease of poor Asians (Thiamin deficiency)

The Discovery of Vitamins

The Germ Theory of Disease Rickets: Disease of poor Northern European children (Vitamin D deficiency) Pellagra: Disease of poor corn eating cultures ( Niacin deficiency)

Polish biochemist Casimir Funk discovered vitamin B1 in 1912 in rice bran. He proposed the complex be named "Vitamin" (vital amines). By the time it was shown that not all vitamins were amines, the word was already ubiquitous.

What are vitamins ?

Vitamins have diverse biological function: Regulate metabolism. Help convert energy in fat, carbohydrate, and protein into ATP. Promote growth and reproduction. Hormone-like functions as regulators of mineral metabolism (vit. D), Regulators of cell and tissu,.e growth and differentiation (some forms of vit. A) Antioxidants (vit. E, C) Eenzyme cofactors (tightly bound to enzyme as a part of prosthetic group, coenzymes
Vitamins are essential for the normal growth and development of a multicellular organism. They are essential for providing good health and are necessary for many life functions.

What does RDA mean? Recommended Dietary Allowances These are suggested levels of essential nutrients considered adequate to meet nutritional needs of healthy individuals.


Classification of Vitamins

2-Fat-soluble vitamins :A, D, E, and KSolubility influences a vitamin’sDigestionAbsorptionTransportationStorageExcretion

What is the difference between fat-soluble and water-soluble vitamins?

Fat-soluble are stored in the liver and fatty tissues. These are not readily excreted from the body. Water-soluble vitamins travel in the blood and are stored in limited amounts. These are readily excreted from the body through urine.

Vitamin Absorption and Storage

All absorption takes place in the small intestine Fat-soluble vitamins Are absorbed in the duodenum Storage: Vitamin A is mainly stored in the liver Vitamins K and E are partially stored in the liver Vitamin D is mainly stored in the fat and muscle tissue Can build up in body to point of toxicity


Water-soluble vitamins Absorbed with water and enter directly into the blood stream Most absorbed in the duodenum and jejunum Most are not stored in the body Excess intake excreted through the urine Important to consume adequate amounts daily Dietary excesses can be harmful

Destruction of Vitamins

Water-soluble vitamins can be destroyed by Exposure to air Exposure to ultraviolet light Water Changes in pH Heat Food preparation techniques Fat-soluble vitamins tend to be more stable

Toxicity with Overconsumption

Vitamin toxicity, hypervitaminosis Rare Results from ingesting excess vitamins and tissue saturation Can damage cells Dietary Reference Intakes include tolerable upper intake limits (UL) for most vitamins to prevent excess


Anti-vitamins (Antinutrient)

What are antioxidants?

Substances that fight off free-radicals in our bodies, or it is a group of compounds that neutralizes free radicals, helping to counteract the oxidation that takes place in cells Includes: Vitamins E, Vitamins C, Carotenoids Free radicals are compounds within our bodies that may lead to chronic disease and/or are involved in cell tissue damage. The antioxidants, stimulate the immune system and interact with hormones to prevent cancers
Oxidative stress occurs when free radicals accumulate faster than the body can neutralize them Contribute to chronic disease and conditions Fruits, vegetables, and whole grains are excellent sources of antioxidants

Free Radicals

Figure 9.3
By-products of the body’s metabolic reactions

Fat soluble vitaminsVitamin A

Sources in diet - Many plants (photoreceptors), also meat, especially liver. Fat soluble, so you can get too much, or too little if absorption is a problem.
Vitamin A - Retinol
Retinol (vitamin A)
Some uses: Vision (11-cis-retinol bound to rhodopsin detects light in our eyes). Regulating gene transcription (retinoic acid receptors on cell nuclei are part of a system for regulating transcription of mRNAs for a number of genes).



What is Vitamin A: retinol
Can be found in animal and plant sources.Biologically active forms – retinoids : retinol, retinal, retinoid acid.Fat-solublealso isolated from various lipids and beta carotene1 beta carotene (plants) = 2 retinols (body)stored in the live requirement level = 1,000 I.U. (international units)sources: fish oils

Cyklohexan ring and isoprenoid chain

What does it do?
Vision Antioxidant Bone growth Reproduction Cell division and differentiation Healthy Skin Regulate Immune System

Vitamin A and vision

Vit. A is necessary to form rhodopsin (in rodes, night vision) and iodopsins (photopsins, in cones – color vision) - visual pigment. Retinaldehyd is a prosthetic group of light-sensitive opsin protein. In the retina, all-trans-retinol is isomerized to 11-cis-retinol → oxidized to 11-cis-retinaldehyd, this reacts with opsin (Lys) → to form the holoprotein rhodopsin. Absorption of light → conformation changes of opsin → photorhodopsin.

Vitamin A and vision

The following is a series of izomerisation→ initiation of nerve impulse.The final step is hydrolysis to release all-trans-retinaldehyde and opsin.Deficiency of vit. A leads to night blindness.

Sources of vitamin A

cod liver oil meat egg milk dairy products cheese
carrot broccoli spinach papaya apricots Sweet potatoes
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Beta-Carotene is precursor of Vitamin A



Polar Bear Liver
One ounce of polar bear liver contains enough vitamin A (retinol) to kill a person!

Vitamin A, Beta-Carotene, and Cancer

Surveys suggest that diets rich in vitamin A and beta-carotene can lower the risk for cancer (especially lung cancer) However, one study was stopped because subjects with increased beta-carotene had a 46% higher risk of dying from lung cancer Another study showed that smokers were more likely to develop lung cancer if they took beta-carotene supplements Beta-carotene supplements are not advisable except in rare situations

Vitamin D

Vitamin D
Calciol, vitamin D2 (cholecalciferol) → precursor of calcitriol, D3 (1,25-dihydroxycalciferol).Regulates with PTH calcium and phosphate level (absorption, reabsorption, excretion).Synthesis in the skin (7-dehydrocholesterol) UV → further transformation in the liver and kidneys .

Vitamin D: Types and Sources

Dietary sources: animal foods, fortified milkHuman Synthesis of Vitamin DSkin: cholesterol + sunlight“Sunshine Vitamin” Liver & Kidney for activation 1,25-di-OH-D3

Vitamin D3: cholecalciferol

Vitamin D found as ergocalciferol (D2) and cholecalciferol (D3) fish appear to use only D3 both activated in plants/animal skin by UV radiation D3 primarily used as precursor for calcium regulation



Synthesis
Non-enzymatic reaction in the skin
Transport to the liver
UV irradiation 270 – 300 nm Photolysis

Vitamin D: Functions

Transported in the blood on a carrier (vitamin-D binding protein, VDBP). The main function is to maintain plasma levels of calcium (essential for neuromuscular activity) and phosphate levels: When blood calcium levels are low, vitamin D (and other hormones): 1- increase Ca absorption in the intestine, 2- decreases the excretion of urinary calcium (stimulates parathyroid hormone-dependent Ca reabsorption in the distal tubule), 3- mobilizing bone mineral, together with parathyroid hormone

Sources of vitamin D

In addition to sunbathing: various fish species (salmon, sardines and mackerel, tuna, catfish, eel), fish oil, cod liver eggs, beef liver, mushrooms. Vit. D is necessary for the prevention of skeletal changes (rickets in growing individuals, osteomalacia in adults).

Vitamin D: Deficiency

Rickets bone deformities in children Osteomalacia weak bones due to low calcium content Vitamin D deficiency Calcium deficiency multiple pregnancies


Elderly woman with dowagers hump, a marked abnormal curving of the spine caused by osteoporosis
Prevention of Osteoporosis
ExerciseDietary Calcium“Rule of 300”300 mg/d from plant sources300 mg/d from each serving of dairy

Vitamin E

Vitamin E: tocopherol

Active form is alpha tocopherol good antioxidant antioxidants used to prevent oxidation of lipids (mainly phospholipids) requirement is tied to selenium deficiency (Se is cofactor in glutathione peroxidase) deficiency in fish = muscular dystrophy, reduced fertility requirement: 50-100 mg/kg sources: alfalfa meal, fish meal, rice bran, wheat middlings, barley grains

Vitamin E

Vitamin E is a famil of a-, b-, g-, d- tocopherols and corresponding tocotrienols izomers. The highest biological activity has a-tokoferol.

What does vitamin E do?

Protects cell membranes and other fat-soluble parts of the body from oxidation May reduce the risk of heart disease May also discourage development of some types of cancer Promotes normal growth and development Promotes normal red blood cell formation Also been known to aid the process of wound healing Vitamin E act as enzyme cofactor Impairment of fertility in men (vitality)

Sources of vitamin E

fortified cereals seeds and seed oils, like sunflower nuts and nut oils, like almonds and hazelnuts green leafy vegetables, broccoli cabbage celery
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Vitamin K

Vitamin K: menadione
Originally identified as a fat-soluble factor required for normal blood clotting menadione is the most active form actually works by activating blood-clotting proteins dietary sources: alfalfa meal, liver meal

Vitamin K1

Vitamin K2
Vitamin K
Vitamin K1 (phylloquinon) – plant originVitamin K2 (menaquinon) – normally produced by bacteria in the large intestineK1 a K2 are used differently in the body K1 – used mainly for blood clothing K2 – important in non-coagulation actions - as in metabolism and bone mineralization, in cell growth, metabolism of blood vessel walls cells. Synthetic derivatives of Vit.K

Vitamin K - function

Cofactor of liver microsomal carboxylase which carboxylates glutamate residues to g-carboxyglutamate during synthesis of prothrombin and coagulation factors VII, IX a X .Carboxylated glutamate chelates Ca2+ ions, permitting the binding of blood clotting proteins to membranes.Forms the binding site for Ca2+ also in other proteins – osteocalcin.

Vitamin K - deficiency

Deficiency is caused by fat malabsorption or by the liver failure. Blood clotting disorders – dangerous in newborns, life-threatening bleeding (hemorrhagic disease of the newborn)Under normal circumstances there is not a shortage, vit. K is abundant in the diet.

Sources of vitamin K

Green leafy vegetables vegetable oil broccoli cereals
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Include Vitamins B complex Vitamin B1 (thiamine) Vitamin B2 (riboflavin) Vitamin B3 or Vitamin P or Vitamin PP (niacin) Vitamin B5 (panthotenic acid) Vitamin B6 (pyridoxine and pyridoxamine) Vitamin B7 or Vitamin H (biotin) Vitamin B9 or Vitamin M and Vitamin B-c (folic acid) Vitamin B12 (cobalamin) Vitamin C
Water soluble vitamins

Vitamin B1 (thiamine)

Thiamin has a central role in energy-yielding metabolism especially for carbohydrate.Active form is thiamine diphosphate (thiamin pyrophosphate, TPP), a coenzyme for three multi-enzyme complex →This complex catalyses oxidative decarboxylation of a-ketoacids → pyruvate dehydrogenase in carbohydrate metabolism, a-ketoglutarate dehydrogenase → cytric acid cycle,Branched-chain keto-acid dehydrogenase .TPP is coenzyme for transketolase – pentose phosphate pathway.

Vitamin B1 - deficiency

Deficiency – leads to loss of appetite. Weakness & Feeling tired Loss of weight Depression. Moderate deficiency - peripheral neuropathy, mental abnormalities, ataxia.Full-blown deficiency - beri-beri – severe muscle weakness, muscle wasting , paresis of the eye muscles, memory loss.Degeneration of the cardiovascular system. .Beri-beri causes long-term consumption of foods rich in carbohydrates but poor in thiamine - husked rice, white flour and refined sugar.

Source of vitamin B1

paddy grains, cerealsmeatyeasthoneynuts fish

Vitamin B2 (riboflavin)

Yellow to orange-yellow natural dye slightly soluble in water. Has a central role in energy-yielding metabolism. Provides the reactive moieties of the coenzymes flavin mononucleotide (FMN) and flavin adenine dinucleotid (FAD). Flavin coenzymes are electron carries in oxidoreduction reaction.

Vitamin B2

FMN → ATP-dependent phosphorylation of riboflavinFAD → further reaction with ATP in which its AMP moiety is transferred to FMN.

B-2 Riboflavin

Important in: energy production carbohydrate, fat, and protein metabolism formation of antibodies and red blood cells cell respiration maintenance of good vision, skin, nails, and hair alleviating eye fatigue

FMN a FAD function

FMN and FAD act as prosthetic groups of many oxidoreduction enzymes, flavoprotein:oxydase of a-amino acids – degradation of amino acidsxantinoxidase – degradation of purinesaldehyde dehydrogenasmitochondrial glycerol-3-phosphate dehydrogenase – transport of reducing unit (H+) from mitochondra to cytosolsuccinate dehydrogenas – citric acid cyclesuccinyl CoA-dehydrogenase – b-oxidation of FANADH-dehydrogenase – part of respiratory chain in mitochondriacoenzymes in hydrogen transfer – formation of reducing forms - FMNH2 a FADH2

Causes of vitamin B2 deficiency

Lack of dietary vitamin B. A result of conditions that affect absorption in the intestine. The body not being able to use the vitamin. An increase in the excretion of the vitamin from the body.

Vitamin B2 – symptoms of deficiency Cracked and red lips. Inflammation of the lining of mouth and tongue. Dry and scaling skin- keratitis, dermatitis and iron-deficiency anemia

Sources of vitamin B2

foods of animal origin (liver, pork and beef, milk, dairy products, fish, eggs) cocoa, nuts, yeast, of smaller quantities in cereals. Warnings: B-2 is nontoxic at supplemental and dietary levels. Light can destroy riboflavin, so purchase milk in opaque containers
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Vitamin B3 - niacin

Active form – nikotinic acid and nikotinamid.NAD a NADP → key components of the metabolic pathways of carbohydrates, lipids, amino acids.Nicotinic acid prevents the release of fatty acids from adipose tissue, decreases lipoproteins VLDL, IDL a LDL.High dose of niacin dilates blood vessels .

B-3 Niacinamide & Niacin

Important in: energy production maintenance of skin and tongue improves circulation maintenance of nervous system health of the digestive track

Niacin

Function: transport of hydrogen ions as NADP, NADPH; electron transport, fatty acid, cholestrol synthesis forms: niacin, nicotinic acid, nicotinamide sources: rice polishings, yeast, rice bran deficiencies: pelagra, dermatitis, anemia , skin lesion, sunburning Can fish convert tryptophan to niacin? requirements: 400 mg/kg

Vitamin B3 - niacin

Absorption: At low concentration by active transport. At high concentration by passive diffusion. Transportation: Both nicotinic acid and nicotinamide bind to plasma proteins for transportation. Biosynthesis: The liver can synthesize Niacin from the essential amino acid tryptophan, but the synthesis is extremely slow and requires vitamin B6 (60 mg of Tryptophan= 1mg of niacin). Bacteria in the gut may also perform the conversion but are inefficient.

Vitamin B3 - deficiency

Pellagra: A serious deficiency of niacin. The main results of pellagra can easily be remembered as "the four D's": diarrhea, dermatitis, dementia, and death. Pelagra is very rare now, except in alcoholics, strict vegetarians, and people in areas of the world with very poor nutrition. Milder deficiencies of niacin can cause dermatitis around the mouth and rashes, fatigue, irritability, poor appetite, indigestion, diarrhea, headache.

Sources of vitamin B3

foods of animal origin yeast sunflower seeds, beans, peas green leafy vegetable broccoli, carrots
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Vitamin B5 – panthotenic acid Part of acetyl-CoA – consists of pantoic acid and b-alaninem.

Vitamin B5 – panthotenic acid Co-enzyme A assists the following reactions: formation of sterols (cholesterol and 7-dehydrocholesterol). formation of fatty acids. formation of keto acids such as pyruvic acid. Other reactions are acylation, acetylation, signal transduction deamination

Sources of vitamin B5

meat, foods of animal origin, yeast, wholemeal bread, broccoli, avocado royal gelly

Vitamin B6

Prekursor of active coenzyme pyridoxalphosphate – PLP.

Vitamin B6

Vitamin B6 is needed for more than 100 enzymes involved in protein metabolism. It is also essential for red blood cell metabolism and hemoglobin formation. The nervous and immune systems need vitamin B6 to function efficiently. It is also needed for the conversion of tryptophan to niacin (vitamin B3). Vitamin B6 also helps maintain blood glucose within a normal range. When caloric intake is low, vitamin B6 helps to convert stored carbohydrate or other nutrients to glucose to maintain normal blood sugar levels.

B-6 Pyridoxine

Important in: Production of red blood cells conversion of tryptophan to niacin (B-3) immunity nervous system functions reducing muscle spasms, cramps, and numbness maintaining proper balance of sodium and phosphorous in the body

Vitamin B6 deficiency

Signs of vitamin B6 deficiency include: Skin: dermatitis (skin inflammation), stomatitis (inflammation of the mucous lining of any of the structures in the mouth), glossitis (inflammation or infection of the tongue ). Neurological abnormalities: Depression, confusion, and convulsions. Vitamin B6 deficiency also can cause anemia. nervousness loss of muscle control, muscle weakness arm and leg cramps water retention

B-6 Deficiency

nervousness loss of muscle control, muscle weakness arm and leg cramps water retention skin lesions

Warnings

High doses of B-6 may be recommended to treat PMS(premenstrual syndrome), carpal tunnel syndrome, and sleep disorders, but continued use of high doses may result in permanent nerve damage. Pregnant women should always consult their doctor before taking this supplement and all others.

Vitamin B6 – narural sources cereals, beans, meat, liver, fish, yeast, nuts and some fruits as banana potatoes. It is also produced by bacterial flora in the colon.


Vitamin B7 - biotin
Prosthetic group of pyruvate carboxylase, acetyl-CoA carboxylase and other ATP-dependent carboxylases.


Biotin – natural source liver meat kidney yeast egg yolk mushrooms milk and diary products.

Vitamin B9(Folic Acid)

Recently shown as very important for pregnant females to avoid birth defects function: synthesis of purines, pyrimidines, nucleic acids (single carbon metabolism), DNA synthesis(cell division) sources: yeast, alfalfa meal, full-fat soybeans deficiencies: anemia, large erythrocytes, pale gills

requirements: 1-4 mg/kg (fish, shrimp)

Vitamin B9 – folic acid Consist of pteroic acid - pteridine + paraaminobenzoic acid (PABA) + glutamic acid

Folic Acid

Recently shown as very important for pregnant females to avoid birth defects function: synthesis of purines, pyrimidines, nucleic acids sources: yeast, alfalfa meal, full-fat soybeans deficiencies: anemia, large erythrocytes, pale gills

requirements: 1-4 mg/kg (fish, shrimp)

Vitamin B9 – folic acid Active metabolit of folic acid is tetrahydrofolate (THF) . THF is coenzym of transferases carrying one carbon units. This reaction participate in nucleotide and nucleic acid synthesis N5,N10-THF carries one carbon units (methylen or methenyl).

Folic acid deficiency

Deficiency results in elevated levels of homocystein. Megaloblastic anemia Deficiency in pregnant women can lead to birth defect Sources of vitamin B9 sources of animal origin milk and milk products yeast greens

Vitamin B-12 (Cyanocobalmine)

Last of 15 vitamins to be identified chemically complex, cobalt nucleus function: coenzyme in metabolic reactions, maturation of erythrocytes deficiency: pernicious anemia, nerve disorders requirement: very low 0.015 mg/kg or not at all

Vitamin B12 - cobalamin

Chemically most complex vitamin Complex of organic compounds atom within the molecule is Co, similar to the heme. In man there are two metabolically active forms: methylkobalamin a adenosylkobalamin.

Vitamin B12 - cobalamin

Cobalamin catalyses two reactionsCytoplasmic methylation of homocystein to methionin.Mitochondrial methylmalonyl-CoA mutase (methylmalonyl-CoA → sukcynyl-CoA) needs deoxy adenosylkobalamin. Functions“single carbon isomerization”synthesis of DNA (folate interaction)nerve fiber sheath synthesis

B-12 Cobalamine

Important in: proper nerve function production of red blood cells metabolizing fats and proteins prevention of anemia DNA reproduction energy production?

B-12 Deficiency

Pernicious anemia nerve damage hypersensitive skin progressive degeneration to death concern among the elderly


Sources of vitamin B12
fish and shellfish, meat (especially liver), poultry, eggs, milk, and milk products

while lacto-ovo vegetarians usually get enough B12 through consuming diary products, vegan will lack B12

Vitamin C

Ascorbic Acid: Vitamin C
Vitamin C is a water-soluble vitamin.function: antioxidant, stress reducer, bone calcification, iron metabolism, tyrosine metabolism, blood clottingVitamin C is a weak acid, called ascorbic acid or its salts “ascorbates”. antioxidant and free radical scavenger → maintain proper immune system. toxicity: toxic at over 150-200 mg/kg requirement: 100 mg/kg varies w/age, metabolism

Ascorbic Acid: Vitamin C

Vitamin C Functions
Antioxidant water soluble free radical scavenger Collagen synthesis connective tissue protein Synthesis of neurotransmitters, thyroxine, etc. Aids in absorption of dietary iron

Deficiency of vitaminC

Fatigue, personality changes, decline in psychomotor performance and motivation. Vitamin C deficiency over 3-5 months results in symptomatic scurvy. Scurvy leads to the formation of liver spots on the skin, spongy gums, and bleeding from all mucous membranes. In advanced scurvy there are open, suppurating wounds and loss of teeth. Severe scurvy may progress to neuritis, jaundice, fever, dyspnea, and death.


Vitamin C as antioxidant

Vitamin C as antioxidant

Vitamin C as pro-oxidant
Ascorbic acid reduces transition metals - Cu2+, to Cu+, and Fe3+ to Fe2+ during conversion from ascorbate to dehydroascorbate. This reaction can generate superoxide and other ROS:Fentonґs reaction:(1) Fe2+ + H2O2 → Fe3+ + OH· + OH−(2) Fe3+ + H2O2 → Fe2+ + OOH· + H+2 Fe2+ + 2 H2O2 → 2 Fe3+ + 2 OH· + 2 OH−2 Fe3+ + ascorbate → 2 Fe2+ + dehydroascorbate