Vitamins Overview • Support nutritional health • Vitamins differ from macronutrients • Structure • Vitamins are individual unlinked molecules • Function • No energy yielded, necessary in enzyme rxn’s • Amount needed • Measured in micrograms not grams • Similar to macronutrients- vital to life, organic
Vitamins Overview • Bioavailability • NOT just quantity provided by food • Amount absorbed and used by body • Factors influencing bioavailability • Efficiency of digestion, transit time • Nutrition status, current stores • Method of food preparation • Source of nutrient- fortified vs. natural • Other foods consumed at same time
Vitamins Overview • Precursors, aka Provitamins • Can be converted to active form in body • Ex: beta carotene to Vitamin A • Organic nature • Can be destroyed during storage and in cooking • Heat • UV • Oxygen • Soaking / Dilution
Vitamins Overview • Solubility • Affects absorption, transport, and excretion • Water-soluble vitamins • Move directly into blood • Most travel freely • Fat-soluble vitamins • Enter lymph and then blood • Require transport proteins
Vitamins Overview • Consumption frequency of B vitamins & C • Uptake relative to vitamin stores • Toxicity • More is not necessarily better • Excessive intakes • Risks with levels higher than UL • See “In Summary” for overview section
Better Better Better More More More As you progress in the direction of more, the effect gets better and better, with no end in sight (real life is seldom, if ever, like this). As you progress in the direction of more, the effect reaches a maximum and then a plateau, becoming no better with higher doses. As you progress in the direction of more, the effect reaches an optimum at some intermediate dose and then declines, showing that more is better up to a point and then harmful. That too much can be as harmful as too little represents the situation with most nutrients.
How it is with Vitamins Better More
The B Vitamins – As Individuals • Vitamins do not directly provide the body with fuel for energy • Coenzymes • Assist enzymes with release of energy • Without coenzyme, an enzyme cannot function • B vitamins form integral part of coenzymes • Deficiencies disrupt metabolism
Enzyme Active site Compounds CD A B Active site Enzyme Without coenzymes, compounds A, B, and CD don’t respond to their enzymes.
Enzyme Coenzyme Vitamin B CD A Vitamin Coenzyme Enzyme With the coenzymes in place, compounds are attracted to their sites on the enzymes . . .
Enzyme CD B A Enzyme . . . and the reactions proceed instantaneously. The coenzymes often donate or accept electrons, atoms, or groups of atoms.
Enzyme C D A B New products Enzyme The reactions are completed with either the formation of a new product, AB, or the breaking apart of a compound into two new products, C and D, and the release of energy.
Thiamin B1 • Part of coenzyme thiamin pyrophosphate (TPP) • Energy metabolism • In conversion of pyruvate to acetyl CoA • TCA cycle conversion of acetyl CoA to succinylCoA • Nerve activity and muscle activity
Thiamin B1 • Deficiency- malnourished / alcoholics • EtOH impairs absorption, displaces food, causes urinary loss • Beriberi- refined, unenriched rice • Dry – nervous system, muscle weakness • Wet – CVS damage, overworked blood vessels and kidneys retaining salt and water • No toxicity- excess wasted in urine • No adverse effects • No UL
Thiamin B1 • Food sources: pork, soy milk, enriched grain foods • Prolonged cooking destroys thiamin • Leaches into water when boiling or blanching foods • Cooking methods that conserve thiamin • Steam • Microwave
The B Vitamin Riboflavin B2 • Serves as coenzyme in energy metabolism • Flavin mononucleotide (FMN) • Flavin adenine dinucleotide (FAD) • Recommendations • Deficiency • Inflammation of membranes • Toxicity • No UL
FAD FADH2 FADH2 carries the hydrogens to the electron transport chain. At the end of the electron transport chain, the hydrogens are accepted by oxygen, creating water, and FADH2 becomes FAD again. For every FADH2 that passes through the electron transport chain, 2 ATP are generated. During the TCA cycle, compounds release hydrogens, and the riboflavin coenzyme FAD picks up two of them. As it accepts two hydrogens, FAD becomes FADH2.
Riboflavin B2 • Deficiency- usually accompanies other deficiencies • Inflammation of membranes of eyes, mouth, skin, GI tract • No toxicity- excess wasted in urine • No adverse effects • No UL
Riboflavin B2 • Food sources • Liver, clams, eggs, mushrooms • Milk and milk products • Enriched grain foods • Destruction of riboflavin • Ultraviolet light • Irradiation • Not destroyed by cooking
The B Vitamin Niacin B3 • Has two chemical structures • Nicotinic acid • Nicotinamide • Major form of niacin in blood • Two coenzyme forms – metabolic reactions • Nicotinamide adenine dinucleotide (NAD) • Carries hydrogens and their electrons • NADP (the phosphate form)
Niacin B3 • Recommendations • Body can manufacture from tryptophan • Only occurs after protein synthesis needs have been met. • RDA is stated in niacin equivalents • 60 tryptophan make 1 niacin • Deficiency • Pellagra • Diarrhea, dermatitis, dementia, death • Noted in low-protein, corn-based diet
Niacin B3 • Recommendations • Adequate intake (AI) • Prescription megadose to lower LDL, raise HDL and adiponectin • Toxicity with some diagnoses • No UL for general population • Large dose (3-4x RDA) causes “niacin flush”
Niacin B3 • Food sources • Chicken breast, canned tuna, liver, ground beef, peanut butter, enriched grain foods • Less vulnerable to food preparation losses • Mg per serving refer to pre-formed niacin not equivalents
The B Vitamin Biotin • Coenzyme that carries activated carbon dioxide • Critical in TCA cycle • Delivers carbon to pyruvate to form oxaloacetate • Participates in gluconeogenesis and fatty acid synthesis • Participates in breakdown of fatty acids and amino acids
Biotin • Food sources: liver, egg yolks, soy, fish, also produced by GI tract bacteria • Deficiency: depression, lethargy, numbness in extremities, red, scaly facial rash • No toxicity
The B Vitamin Pantothenic Acid • Deficiency • Rare- involves general failure of all body’s sysems • No toxicity • No UL • Food sources- chicken, beef, potatoes, oats, tomatoes, liver