Vitamins Tasteless organic compounds Required in small amounts

Vitamins Ø Tasteless, organic compounds Ø Required in small amounts Ø Functions • Regulate metabolism • Help convert energy in fat, carbohydrate, and protein into ATP • Promote growth and reproduction Ø Deficiencies can result in potentially serious consequences © 2010 Pearson Education, Inc.

History of Vitamins Ø Disease related to deficiency and foods that help were recognized long before the vitamin was discovered Ø Vitamins became valued for promoting public health Ø 1940 s U. S. government mandated specific vitamins be added to grains and milk to improve health Ø Scientists are now focusing on prevention of disease with vitamin research © 2010 Pearson Education, Inc.

Naming Vitamins Ø Each new vitamin is temporarily named when discovered Ø The naming of vitamins follows the letters of the alphabet, starting with A; we are up to the letter K • A, B, C, D, E, and K - B has many subscripts • F, G, and H were dropped © 2010 Pearson Education, Inc.

Criteria for Vitamins Ø Cannot be synthesized in ample amounts in the body Ø Chronic deficiency is likely to cause physical symptoms Ø Symptoms will disappear once the vitamin level in the body is restored • Deficiency can cause permanent damage Ø 13 compounds meet the above criteria © 2010 Pearson Education, Inc.

Classification of Vitamins Ø Classification is based on solubility • Eight water-soluble: B vitamin complex and vitamin C • Four fat-soluble: vitamins A, D, E, and K Ø Solubility influences a vitamin’s • Digestion • Absorption • Transportation • Storage • Excretion © 2010 Pearson Education, Inc.

Vitamin Structure and Function Ø All vitamins contain carbon, hydrogen, and oxygen • Some vitamins contain nitrogen and sulfur Ø Chemical structure of each vitamin is unique Ø Each vitamin is a singular unit Ø Vitamins are absorbed intact Ø Vitamins perform numerous essential functions © 2010 Pearson Education, Inc.

Vitamin Absorption and Storage Ø All absorption takes place in the small intestine Ø 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 © 2010 Pearson Education, Inc.

Vitamin Absorption and Storage Ø 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 © 2010 Pearson Education, Inc.

Digesting and Absorbing Vitamins Figure 9. 2

Digesting and Absorbing Water-Soluble Vitamins Figure 10. 1

Bioavailability Ø Varies based on • Amount in food • Preparation • Efficiency of digestion and absorption of food • Individual nutritional status • Natural or synthetic Ø Fat-soluble vitamins are generally less bioavailable than water-soluble vitamins Ø Vitamins from animal foods are generally more bioavailable than those in plant foods © 2010 Pearson Education, Inc.

Destruction of Vitamins Ø Water-soluble vitamins can be destroyed by • Exposure to air • Exposure to ultraviolet light • Water • Changes in p. H • Heat • Food preparation techniques Ø Fat-soluble vitamins tend to be more stable © 2010 Pearson Education, Inc.

Toxicity with Overconsumption Ø Vitamin toxicity, AKA hypervitaminosis • Rare • Results from ingesting excess vitamins and tissue saturation • Can damage cells Ø Dietary Reference Intakes include tolerable upper intake limits (UL) for most vitamins to prevent excess © 2010 Pearson Education, Inc.

© 2010 Pearson Education, Inc.

Provitamins and Preformed Vitamins Ø Provitamins • Substances found in foods that are not in a form directly usable by the body • Converted to the active form once absorbed Ø Preformed vitamins • Vitamins found in foods in their active form © 2010 Pearson Education, Inc.

Antioxidants Ø Group of compounds that neutralizes free radicals, helping to counteract the oxidation that takes place in cells • Includes - Vitamins E - Vitamins C - Selenium - Flavonoids - Carotenoids © 2010 Pearson Education, Inc.

Free Radicals Ø By-products of the body’s metabolic reactions Figure 9. 3

Antioxidants Ø These sources also act as antioxidants, stimulate the immune system and interact with hormones to prevent cancers • Phytochemicals - Carotenoids - Flavonoids Ø Get antioxidants and phytochemicals from the diet instead of supplements © 2010 Pearson Education, Inc.

© 2010 Pearson Education, Inc.

Major Functions of Ascorbic Acid Ø Collagen synthesis Ø Tyrosine synthesis and catabolism – epinephrine, norephinephrine, serotonin, dopamine Ø Maturation of glial cells in developing nervous system Ø Iron absorption and storage Ø Bile acid formation/cholesterol degradation Ø Vasodilation and anticlotting (via activation of NO release) Ø Aids in prevention of cancers of oral cavity and pancreas Ø General antioxidant Ø Pro-oxidant (not necessarily good) Ø Common cold? ? ? Ø Immune function? ? ? © 2010 Pearson Education, Inc.

Collagen Synthesis • Collagen is a structural protein in almost all connective tissues, including bone, cartilage, skin, tendons • Composed of a triple helix of helical proteins • Vitamin C is necessary for the helical proteins to crosslink posttranslationally • Indirectly used because Fe 2+ is a cofactor for the enzyme prolyl hydroxylase, and ascorbate is needed to recycle the iron from the Fe 3+ to the Fe 2+ state © 2010 Pearson Education, Inc.

Toxicity (max dose without adverse effects 2 g/day) • GI problems including abdominal pain and diarrhea • Increased risk of kidney stones in susceptible populations • Increased risk of iron toxicity in susceptible populations • Can interfere with clinical lab tests including glucose in urine, fecal occult blood, and urine blood. © 2010 Pearson Education, Inc.

Scurvy © 2010 Pearson Education, Inc.

Vitamin B 1 – Thiamin Found in: meat, legumes, and whole, fortified, or enriched grain products, cereals and breads. Yeast and wheat germ. Exists in a non-phosphorylated form in plant sources, but in a phosphorylated form (thiamin pyrophosphate or TPP) in meats. Absorption: • Intestinal phosphatases hydrolyze the phosphates prior to absorption. • Can be absorbed either actively, or move through membrane passively depending on concentration of vitamin present. • Transport into blood is energy dependent and requires sodium co-transport. Inhibited by ethanol. © 2010 Pearson Education, Inc.

Functions: • As a coenzyme in energy transformation reactions • Synthesis of pentose sugars and NADPH as a coenzyme • Maintenance of membrane and nerve conduction (not as a coenzyme) p. 276 a

Riboflavin (B 2) Found In: milk and milk products, eggs, meat and legumes Freed by HCl in stomach, absorbed by a saturable, energy requiring carrier in the duodenum. Phosphorylated to form FMN, enters portal system. Transported by a variety of proteins. Tissues take it up via carrier mediated processes – not brain!

Functions: • Electron transport chain (see below) or as intermediate electron carriers • In succinate dehydrogenase • In fatty acyl dehydrogenase (beta oxidation) • In metabolism of drugs or toxins • As a coenzyme for: xanthine oxidase, aldehyde oxidase, pyridoxine phosphate oxidase, glutathione reductase • Synthesis of folate • Monoamine oxidase metabolism – neurotransmitters • Prevention of cataracts • Treatment of migraine headaches

Deficiency • Ariboflavinosis • Cheliosis, angular stomatitis, magenta tongue, seborrheic dermatitis, vascularization of the cornea • Normochromic normocytic anemia • Preeclampsia

Niacin (B 3); nicotinamide, nicotinic acid Sources: • Fish (tuna and halibut), beef, chicken, turkey, pork (nicotinamide). • Enriched cereals and breads, whole grains, seeds, and legumes (bound to carbs as niacytin; bound to peptides as nyacinogen). • Coffee and tea!!! • Synthesized in liver from tryptophan

Breakdown and Excretion: • Degraded by glucohydrolase into nicotinamide and ADP-ribose • Released nicotinamide is oxidized in the liver into a variety of products; excreted in urine Deficiency: Pellagra (4 D’s) • Dermatitis • Dementia • Diarrhea • Death

Toxicity (> 35 mg/day): • Used to treat high cholesterol but often results in several unpleasant side effects including; • Flushing • Heartburn, nausea, vomiting • Liver injury, jaundice, hepatitis, liver failure • Hyperuricemia and gout • Glucose intolerance

Pantothenic Acid (pantothenate; B 5) Sources: virtually all foods; high in meats, egg yolk, potatoes, mushrooms, legumes and whole grain cereals, royal jelly from bees Found in both free and bound forms – 85% occurs bound as a part of coenzyme A (Co. A) Absorption: Co. A is hydrolysed to pantothenate; passive absorption in the jejunum, but at low concentrations shares a multivitamin transporter with biotin and lipoic acid. Fig. 9 -20, p. 292

Functions: • A part of coenzyme A • Acetylates sugars, proteins, fatty acid metabolites • Oxidative decarboxylation of pyruvate • Synthesis of cholesterol, bile salts, ketones, fatty acids, steroid hormones • A part of 4’-phosphopantetheine • Prosthetic group for acyl carrier protein (ACP) in fatty acid synthesis • Wound healing • Cholesterol metabolism; pantethine Excretion – primarily urine Toxicity – rare; tingling hands and feet Nutrient and Drug Interactions: • Oral contraceptives containing both estrogen and progesterone

Biotin (B 7) Sources: liver, soybeans, egg yolk, cereals, legumes, nuts; found combined to lysine (biocytin) or other proteins; intestinal bacteria can synthesize biotin Fig. 9 -22, p. 295

Absorption: • Protein portion digested off by peptidases or biotinidase • 100% absorption in the jejunum and ileum • Passive diffusion into enterocytes; carrier mediated into plasma; cotransport with sodium into tissues • Stored in small quantities in muscle, liver, and brain

Deficiency: rare • Lethargy, depression, hallucinations, muscle pain, parathesia, anorexia, nausea, alopecia, dermatitis • May occur during pregnancy • May occur with excessive consumption of alcohol • Is known as a teratogen in mammals

Folic Acid (folacin; folate; pteropolyglutamate) Glu Glu Glu Fig. 9 -30, p. 301

Sources: mushrooms, green leafy vegies, legumes, citrus fruits, and liver; raw foods have more than cooked Absorption: brush border enzymes cut off the glutamates (requires Zinc; inhibited by alcohol, legumes, lentils, cabbage and oranges); transporter is p. H and sodium dependent; mostly in jejunum; efficiency estimated to be about 50%

Dementia Colon cancer Neural tube defects

Cobalamin (B 12) Sources: all naturally occurring B 12 is made by microorganisms; we get ours from animals that have B 12 from microorganisms Meat, meat products, poultry, fish, shellfish, and eggs (yolk), milk and milk products, tobacco!!!!! Fig. 9 -35, p. 311

Deficiency; megaloblastic, macrocytic anemia; symptoms include: pallor, fatigue, sortness of breath, palpitations, insomnia, tingling and numbness in extremities, abnormal gait, loss of concentration, memory loss, and possibly dementia. Anemia can be corrected with large doses of folate, but the neuropathies cannot. Associated with risk factors for coronary heart disease via homocysteine production Most deficiencies associated with: • malabsorption (long term vegetarians; vegetarian children and infants; changes in intrinsic factor production; • GI diseases such as sprue; • prolonged use of H blockers and proton pump inhibitors Excretion: not extensively degraded prior to excretion; almost all excreted in bile Toxicity: none known

Vitamin B 6 (pyridoxine, pyridoxal, pyridoxamine and their phosphate derivatives) Sources: Pyridoxine in plant sources; pyridoxal phaophate and pyridoxamine phosphate primarily in animal products Overall found in meats, whole-grain products, vegies, bananas, and nuts, also fortified cereals; processing influences availability Fig. 9 -38, p. 316

Absorption: dephosphorylation by alkaline phosphatase in the brush border; absorption in the jejunum by passive diffusion; overall efficiency about 75% Dephosphorylated forms move into blood and taken up by the liver where it is converted by pyridoxal phosphate. This requires riboflavin. Pyridoxial phosphate is bound to albumin for circulation in the systemic blood Tissues only take up unphosphorylated forms (alkaline phosphatase in plasma), they are then rephosphorylated intracellularly.

Functions: Coenzyme (>100 reactions) most in amino acid metabolism • Transamination • Decarboxylation Initial step in glycogen metabolism • Glycogen phosphorylase Fig. 9 -40, p. 317

Deficiency: relatively rare Symptoms include: sleepiness, fatigue, cheilosis, glossitis, stamatitis, and neurological problems; alteration of magensium and calcium metabolism; impairs niacin synthesis; inhibits homocysteine metabolism Toxicity: sensory and peripheral neuropathy (100 mg/day); High doses used for hyperhomocysteinemia, carpal tunnel syndrome, premenstrual syndrome, depression, muscular fatigue, and autism.