The Water Soluble Vitamins B Vitamins and Vitamin C Chapter 10 Dr Alisha Rovner Fall 2013 NTDT 200 The Vitamins An Overview Vitamins differ from energy yielding nutrients Structure Individual units not linked together like glucose or amino acids Function No energy yielded Food contents amount measured in mircrograms g or milligrams mg not grams Similarities to energy yielding nutrients Vital to life organic available from foods The Vitamins An Overview Bioavailability Quantity provided by food Amount absorbed and used by body Factors influencing bioavailability Efficiency of digestion Nutrition status Method of food preparation Source of nutrient Other foods consumed at same time The Vitamins An Overview Precursors some vitamins available from foods in inactive forms In body precursor is converted to active form in body When measuring person s vitamin intake need to count 1 amount of active vitamin and 2 amount from precursors The Vitamins An Overview Organic nature Can be destroyed and unable to function Must be handled with care during storage and in cooking Ways to minimize nutrient losses Minimizing Nutrient Losses The Vitamins An Overview Solubility Affects absorption transport and excretion Water soluble Move directly into blood Most travel freely Fat soluble Enter lymph and then blood Require transport proteins Dose Levels and Effect Toxicity More is NOT necessarily better Excessive intakes can be DANGEROUS Levels higher than UL The B Vitamins Vitamins do NOT provide the body with fuel for energy Coenzymes Assist enzymes with release of energy Without coenzyme an enzyme cannot function The B Vitamins DRIs Recommended Dietary Allowance RDA Thiamin Riboflavin Niacin Vitamin B6 Folate Vitamin B12 Vitamin C Adequate Intake AI Biotin Pantothenic acid Choline Tolerable Upper Limit UL Niacin Vitamin B6 Folate Choline Vitamin C The B Vitamins Thiamin B1 Part of coenzyme thiamin pyrophosphate TPP which assists in energy metabolism Conversion of pyruvate to acetyl CoA TCA cycle Occupies site on membranes of nerve cells important for nerve activity and muscle activity The B Vitamins Thiamin RDA Men 1 2 mg day women 1 1 mg day Deficiency Malnourished and alcoholics at risk Beriberi Dry nervous system Wet cardiovascular system Toxicity No adverse effects no UL The B Vitamins Thiamin Food sources Pork richest source Enriched grains typically make greatest contribution to day s intake Prolonged cooking destroys thiamin leaches into water when boiling or blanching foods Cooking methods that conserve thiamin include steaming and microwaving Thiamin in Selected Foods The B Vitamins Riboflavin B2 Serves as coenzyme in energy metabolism Flavin mononucleotide FMN Flavin adenine dinucleotide FAD RDA Men 1 3 mg day Women 1 1 mg day Deficiency Inflammation of membranes Toxicity No UL The B Vitamins Riboflavin Food sources Milk and milk products Whole grain or enriched bread and cereal Vegans and others who don t consume milk must rely on other sources Destruction of riboflavin Ultraviolet light milk not sold in clear containers Irradiation Not destroyed by cooking Riboflavin in Selected Foods The B Vitamins Niacin Two chemical structures Nicotinic acid Nicotinamide major form of niacin in blood Part of coenzymes Nicotinamide adenine dinucleotide NAD and NADP its phosphate form used in energy metabolism Unique among B vitamins because the body can make it from the amino acid tryptophan The B Vitamins Niacin RDA stated in niacin equivalents NE Body manufacturers niacin from tryptophan after protein synthesis needs have been met 1 NE 1 mg niacin or 60 mg tryptophan Men 16 mg NE day Women 14 mg NE day Deficiency Pellagra Symptoms 4 D s Diarrhea Dermatitis Dementia and eventually Death Niacin Deficiency Symptom The Dermatitis of Pellagra The B Vitamins Niacin Toxicity Naturally occurring no harm Supplements or drugs Niacin flush doses 3 4x RDA Potential health benefits of large doses of nicotinic acid LDL HDL adiponectin Food sources Protein rich foods meat fish poultry pb Less vulnerable to food preparation losses Niacin in Selected Foods The B Vitamins Biotin Coenzyme that carries activated carbon dioxide Critical in TCA cycle Delivers carbon to pyruvate to form oxaloacetate Gluconeogenesis and fatty acid synthesis Breakdown of fatty acids and amino acids The B Vitamins Biotin Needed in very small amounts No RDA AI Adults 30 g day Deficiencies rare Toxicity no UL Food sources Widespread in food Produced by GI bacteria The B Vitamins Pantothenic Acid Part of chemical structure of coenzyme A Involved in 100 different steps in the synthesis of lipids neurotransmitters steroid hormones and hemoglobin No RDA AI Adults 5 mg day Deficiency rare Toxicity none reported Food sources widespread in food Easily destroyed by food processing The B Vitamins B6 Three forms pyridoxal pyridoxine and pyridoxamine Conversion to coenzyme PLP Amino acid metabolism Urea metabolism Conversion of tryptophan to niacin or serotonin Synthesis of heme nucleic acids lecithin Unlike other water soluble vitamins it s stored exclusively in muscle tissue The B Vitamins B6 RDA Adults 19 50 years 1 3 mg day Deficiency Symptoms scaly dermatitis anemia Alcohol causes destruction of B6 isoniazid tuberculosis drug acts as antagonist Toxicity UL Adults 100 mg day Irreversible nerve degeneration Food sources meats fish poultry fortified cereals Vitamin B6 in Selected Foods The B Vitamins Folate Known as folacin or folic acid Primary coenzyme form THF tetrahydrofolate Transfers single carbon compounds during metabolism Convert vitamin B12 to coenzyme form Synthesize DNA Regenerate methionine from homocysteine The B Vitamins Folate RDA 400 ug day adults UL 1000 ug day Deficiency Impairs cell division and protein synthesis Anemia of folate deficiency characterized by large immature blood cells Neural tube defects NTD s malformations of brain spinal cord or both Toxicity Masks B12 deficiency Normal Blood Cells Blood Cells in Macrocytic Anemia Compared The B Vitamins Folate Prevention of neural tube defects Supplement use important1 month before conception through 1st trimester FDA mandated fortification of grain products Research suggests may prevent other congenital birth defects cleft lip and palate Safety concerns with fortification Mask a vitamin B12 deficiency Decreasing Prevalence of NTDs since Folate Fortification The B Vitamins Folate Heart disease Folate breaks down homocysteine Without folate homocysteine accumulates which enhances
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