Lecture 7a- 12 February 2018 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 lectures 7a,b Vitamins     Definition of vitamins     Overview     Bioavailability     Precursors     Organic nature     Solubility         Water soluble vitamins         Fat soluble vitamins     Toxicity     Class exercise

Outline of lectures 7a,b Water Soluble vitamins     B vitamins and C     Found in what foods    

Outline of lectures 7a,b B class-roles in metabolism and regulation of metabolism         Thiamine         Riboflavin         Niacin         Biotin         Pantothenic acid         B6         folate         B12         Class exercise

Outline of lectures 7a,b 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 B3-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    

-amount of vitamin in food 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                   -B12-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?