Lecture 7- 24 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 7Water 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        B6

        folate        B12

        Class exercise

Outline of lecture 7Fat 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 CommentsVitamins

    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)

VitaminsOverview      -two things attest to power of vitamins                    absence- eg vitamin A –blindness

                                        vitamin B3-niacin-dementia

                    presence-eg vitamin C prevents scurvy

                                        vitamin E-appears to protect against oxidation

component of atherosclerosis

   

VitaminsOverview-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

   

VitaminsBioavailability  -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

VitaminsPrecursors           -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

VitaminsOrganic 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                  -B12-easily destroyed my microwave

cooking                        -table 10-1

In Summary, p. 326

VitaminsSolubility

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

VitaminsSolubility     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

VitaminsSolubility         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

VitaminsToxicity

      -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 convertedto active form? Significance?

b) why the difference in likelihood of toxicitybetween 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

        B6-meat, fish, poultry, legumes, fortified

cereals

        folate-fortified grains, leafy green vegetables, legumes

        B12-animal products, fortified cereals

B class-roles in metabolism and regulation of metabolismThiamine-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

B6-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

B12-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. 10-13, p. 347

                                                       

file:///E:/Media/Animations/chapter10/Coenzyme_Action/0709.html

E:\Media\Animations\chapter10\Metabolic_Pathways\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 sourceand 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 sourceand function of each of the fat soluble vitamins