Lecture October 2013 Vitamins in metabolism and regulation Most of this lecture taken from Chapters 7,10,11 of Rolfes et al(Understanding Normal and Clinical Nutrition (Nutrition 2104/2105 text)

Outline of lecture 7 Vitamins Definition of vitamins Overview Bioavailability Precursors Organic nature Solubility Water soluble vitamins Fat soluble vitamins Toxicity Class exercise

Outline of lecture 7 Water Soluble vitamins B vitamins and C Found in what foods

Outline of lecture 7 B class-roles in metabolism and regulation of metabolism Thiamine Riboflavin Niacin Biotin Pantothenic acid B 6 folate B 12 Class exercise

Outline of lecture 7 Fat soluble vitamins Found in what foods Fat soluble vitamins class-roles in metabolism and regulation of metabolism A D E K Class exercise

More detailed comments

More Detailed Comments Vitamins Definition of vitamins-organic essential nutrients required in tiny amounts to perform specific functions that promote growth, reproduction and maintenance of health and life. -vita = life -amine = containing nitrogen (first vitamins discovered contained nitrogen)

Vitamins Overview -two things attest to power of vitamins absence- eg vitamin A –blindness vitamin B 3 -niacin-dementia presence-eg vitamin C prevents scurvy vitamin E-appears to protect against oxidation component of atherosclerosis

Vitamins Overview -differ from carbohydrates, lipids and proteins -single units -do not yield energy when broken down- they assist in energy yielding pathways of carbohydrate, lipid and protein metabolism -daily dietary intake requirements are in the microgram or milligram range as opposed to gram range for energy yielding nutrients

Vitamins Bioavailability -two factors- -amount of vitamin in food -amount absorbed and utilised -efficiency of digestion and time of transit through GI tract -previous nutrient intake and nutrition status -other foods consumed at the same time -method of food preparation-raw, cooked or processed -source of nutrient-synthetic, fortified or naturally occurring

Vitamins Precursors -also called provitamins -provitamins-are metabolised to active form -in measuring a person’s vitamin intake it is important to count the active forms and the potential of the precursors to be converted to active forms

Vitamins Organic nature -this means they can be broken down -eg-excessive heating destroys thiamin -ultraviolet radiation-destroys riboflavin -oxygen- destroys vitamin C -food processing-easily destroys pantothenic acid -B 12 -easily destroyed my microwave cooking -table 10-1

In Summary, p. 326

Vitamins Solubility -affects absorption, transport, storage, and excretion by body

Vitamins Solubility Water soluble vitamins -found in water portions of foods and transported directly by blood -no carriers are required for blood transport -stored in water portion of cells -easy to excrete through kidney

Vitamins Solubility Fat soluble vitamins -found in fat portions of foods and transported first by lymph and then by blood -carriers are required for blood transport -stored in body fat stores -easier to keep stored in fat stores rather than excrete-issue of toxicity

Vitamins Toxicity -water soluble-not likely to reach toxic levels when consumed by supplements -fat soluble-likely to reach toxic levels when consumed by supplements

Class exercise a) are all vitamin pre-cursors equally converted to active form? Significance? b) why the difference in likelihood of toxicity between fat and water soluble vitamins? c) how do you think fat soluble vitamins might be transported in the blood?

Water Soluble vitamins B vitamins and C Found in what foods Thiamine-whole grains Riboflavin-milk products or whole grains Niacin-meat, eggs, fish, poultry, whole grains Biotin-widespread in foods, organ meats, egg yolks, soybeans, fish, whole grains, GI bacteria

Water Soluble vitamins B vitamins and C Found in what foods Pantothenic acid-widespread in foods, organ meats, broccoli, whole grains B 6 -meat, fish, poultry, legumes, fortified cereals folate-fortified grains, leafy green vegetables, legumes B 12 -animal products, fortified cereals

B class-roles in metabolism and regulation of metabolism Thiamine-part of thiamine pyrophosphate (TPP)-a coenzyme-small organic molecule that associates closely with certain enzymes -TPP removes carbon from pyruvate to make acetyl CoA TPP participates in Krebs cycle

B class-roles in metabolism and regulation of metabolism Riboflavin-part of co-enzymes FMN(flavin mononucleotide) and FAD(flavin adenine dinucleotide) (used in energy metabolism) -used in energy metabolism

B class-roles in metabolism and regulation of metabolism Niacin-part of co-enzymes NAD(nicotinamide adenine dinucleotide) and NADP(its phosphate form)-used in energy metabolism Biotin-part of coenzyme used in energy metabolism, fat synthesis, amino acid metabolism and glycogen synthesis Pantothenic acid-part of co-enzyme A-used in energy metabolism

B class-roles in metabolism and regulation of metabolism B 6 -part of coenzymes PLP(pyroxidal phosphate) and PMP(pyridoxamine phosphate) used in amino acid and fatty acid metabolism; helps convert tryptophan to niacin and serotonin folate-part of THF(tetrahydrofolate) and DHF(dihydrofolate) used in DNA synthesis

B class-roles in metabolism and regulation of metabolism B 12 -part of coenzymes methylcobalamin and deoxyadenosylcobalamin used in new cells synthesis(THF metabolism) -reforms folate coenzyme -assists in catabolism of some fatty acids and amino acids -figure 10-13

Fig , p. 347

file:///E:/Media/Animations/chapter10/Coenzyme_ Action/0709.html E:\Media\Animations\chapter10\Metabolic_Pathwa ys\1013.html

B VITAMINS REGULATION OF METABOLISM IS BY DEGREE OF PRESENCE OF CORRECT FORM OF VITAMIN

Vitamin C- found in what foods – -citrus fruits, cabbage type vegetables, dark green vegetables(bell peppers and broccoli), cantaloupe, strawberries, lettuce, tomatoes, potatoes, papaya, mangoes

Vitamin C-functions -collagen synthesis -forms scar tissue(collagen) -forms collagen matrix for bone growth -antioxidant (toxic doses-prooxidant) -thyroxin synthesis -amino acid metabolism(conversion of tryptophan to serotonin and norepinephrine) -helps in absorption of iron

Vitamin C-regulation of metabolism REGULATION OF METABOLISM IS BY DEGREE OF PRESENCE OF CORRECT FORM OF VITAMIN

Class exercise Explain the connections between source and function of each of the water soluble vitamins

Fat soluble vitamins Found in what foods A- retinol-fortified milk, cheese, cream, eggs, liver -Beta-carotene-spinach, dark leafy greens, broccoli, apricots, cantaloupe, carrots, sweet potato D-sunlight, fortified milk, butter, cereals; veal, fish E-polyunsaturated plant oils, leafy green vegetables, liver, yolks K-gi bacteria synthesis, leafy green vegetables, cabbage type vegetables, milk

Fat soluble vitamins class-roles in metabolism and regulation of metabolism A -retinol-protein synthesis -rhodopsin synthesis -not antioxidant(lipids) -Beta-carotene-antioxidant D-regulates bone mineral metabolism, primarily calcium E-antioxidant of lipids(fatty acids) K-activates blood clotting proteins

FAT SOLUBLE VITAMINS REGULATION OF METABOLISM IS BY DEGREE OF PRESENCE OF CORRECT FORM OF VITAMIN

Class exercise Explain the connections between source and function of each of the fat soluble vitamins