Notes on Chapter 8 - Water Soluble Vitamins

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University of Florida
Food Science and Human Nutrition
HUN 2201

Water—Soluble vitamins – Ch 8 • Vitamins: organic compounds essential in the diet in small amounts to promote and regulate processes necessary for growth, reproduction, and maintenance of health • Water-soluble include B vitamins and vitamin C • Fat-soluble include A, D, E, and K • Vitamins in our diet o 13 of them o Natural food sources of vitamins  Grains: B vitamins  Leafy greens: folate, vitamin A, vitamin E, vitamin K  Fish: B vitamins  Citrus: C  Milk: riboflavin, A and D  Oils: vitamin E  Cooking, storage, and processing can affect vitamin content o Fortified foods  Degree of fortification depends on food supply, needs of population, and public health policies  Enriched: food that had nutrients added to restore those lost in processes to a level equal or higher than originally present  Much fortification today is not government mandated, but commercially discretionary  This can cause toxicities, however! o Dietary supplements  Increase nutrient intake, enhance athletic performance, promote weight loss, alleviate existing symptoms and conditions, extend life, prevent chronic disease  Do not provide all the benefits of a diet containing a wide variety of foods • No phytochemicals  Avg intake of vitamin C, thiamin, riboflavin, and niacin from food exceed recommendation, but calcium is below, which is exactly what supplements are generally lacking • Absorption, storage, and excretion of vitamins o 40-90% of vitamins absorbed in small intestine o Bioavailability refers to how readily a nutrient is absorbed and utilized by the body  Key factor: water or fat soluble  Fat soluble depend on simple diffusion and bind to lipoproteins or chylomicrons for transport  Water soluble may depend on energy transport systems or bound to specific molecules to be absorbed • Bound to blood proteins to be absorbed by cells • Availability of transport protein affects amount of vitamin delivered to cells  Some vitamins absorbed in inactive provitamin/vitamin precursor • Must be converted to active form once inside body o Storage and excretion  With exception of B12, water soluble are easily excreted in urine  Takes more than a few days to develop deficiency symptoms, takes much longer for fat-soluble to develop since they are stored in liver and fatty tissues • What vitamins do o Promote and regulate activities  A: vision, growth, development  K: blood clotting and bone health  B6: amino acid production and protein metabolism  Folate and B12 work together to ensure normal cell division  All B vitamins act as coenzymes  Vitamins C and E function together as antioxidants  Do NOT provide energy, though coenzymes help power reactions involving metabolism of energy yielding nutrients • Meeting vitamin needs o Recommended vitamin intakes  Made by DRIs  RDAs and AIs amount to prevent deficiency and promote health o Vitamins on food labels  Required to list amount of vitamins a and C as daily values  Vitamin content can be lost due to exposure to light or oxygen, preparation, or cooking • Thiamin o B1, beriberi during deficiency o May be destroyed due to heat, oxygen, and low acid conditions o Enzymes in fish degrade thiamin during food storage and preparation and GI passage, affecting bioavailability if food hasn’t yet been cooked o Other anti-thiamin factors not inactivated by cooking include: coffee, tea, blueberries, cabbage • How thiamin functions in the body o Thiamin pyrophosphate is active form and coenzyme for reactions in which a carbon is lost o Essential for production of ATP from glucose o Needed for metabolism of sugar and other amino acids, synthesis of ACH, and production of ribose • Thiamin deficiency o Beriberi: fatigue, lethargy, cardiovascular problems o Depression and weakness: due to inability to use glucose, which inhibits ability to form ACH from pyruvate…affects nervous system  Tingly, poor coordination  Alcohol also affects it  Wernicke-Korsakoff syndrome: mental confusion, psychosis, memory disturbances, coma • Recommended Thiamin Intake o RDA is 1.2 mg/day and 1.1 mg/day o Pork and sunflower seeds are good sources o Requirement increased during pregnancy • Thiamin toxicity and supplements o UL has not been established, since increasing thiamin intake does not increase ability to produce ATP • Riboflavin o Riboflavin in the diet  Milk is the best source  Liver, red meat, poultry, fish, whole and enriched grain products, greens  Destroyed by exposure to light o Riboflavin function  Forms active coenzymes FAD and FMN  FAD functions in citric acid cycle and is important in breakdown of fatty acids  Both FAD and FMN function as electron carriers in the ETC, so riboflavin is critical in providing energy from carbs, fat, and protein, and involved in converting other vitamins into their active forms o Riboflavin deficiency  Ariboflavinosis: tissues heal poorly, symptoms may appear after 2 months and include greasy skin, confusion, inflammation of face  Often occurs with deficiency of other B vitamins o Recommended intake:  1.3 mg/men, 1.1 mg for women  additional is recommended during pregnancy and lactation o Toxicity and supplements  no data to establish a UL  large doses excreted, causing bright yellow urine  does not provide energy, despite supplement claims o Niacin  Pellagra: causes physical and mental deterioration  Good sources include meat, fish, legumes, peanuts, mushrooms  Large source in American diet comes from enriched flours  Can be synthesized in the body from amino acid tryptophan • High protein diet including milk and eggs, which are poor sources of niacin but good sources of tryptophan, niacin needs can be met if tryptophan needs are met first • Food tables only list amount of niacin in food, not contained in tryptophan  Association between niacin deficiency and limited diet based on corn due to low tryptophan content of corn and fact that niacin in corn is attached to other molecules and therefore not well absorbed o How niacin functions in the body  ATP production  2 forms: nicotinic acid and nicotinamide • 2 active enzymes are NAD and NADP • NAD functions in glycolysis and citric acid cycle, converting ADP to ATP • NADP is electron carrier in reactions that synthesize fatty acids and cholesterol o Niacin deficiency  Damage throughout the body  Fatigue, decreased appetite, indigestion, then 3 Ds • Dermatitis, diarrhea, dementia • GI and mental symptoms  Recommended niacin intake • RDA expressed as NE, niacin equivalents • One NE is 1 mg niacin or 60 mg tryptophan • Protein is assumed to be 1% tryptophan..urinary excretion of niacin metabolites estimates RDA • RDA is 16 and 14 mg • Needs increased during pregnancy and lactation  Niacin toxicity and supplements • UL is set at 35 mg/day • Symptoms including flushing, tingling, high blood sugr, liver function abnormalities • High doses can be used to treat elevated blood cholesterol, doses of 50mg or above o nicotinic acid, though this is higher than the upper amount o Biotin  In the diet • Good sources include liver, egg yolks, yogurt, and nuts. • Fruit and meat are poor sources • Raw egg whites should be avoided because avidin binds biotin and prevents absorption o How biotin functions in the body  Coenzyme for group of enzymes that add acid group COOH to molecules, makes 4 carbon molecule in citric acid cycle and gluconeogenesis  Also important in synthesis of fatty acids and some amino acids o Deficiency  Uncommon, but has been observed in people who have malabsorption or protein energy malnutrition, receiving TPN, taking anticonvulsants, or consuming raw egg whites  Symptoms include thinning hair, skin rash, lethargy, hallucinations, etc o Recommended intake  Difficult to determine because some is produced by bacteria in GI tract and absorbed into blood, but AI of 30 ug/day has been established  No additional amount recommended for pregnancy, but AI increased during lactation to account for amount secreted in milk  No toxicity established o Pantothenic Acid  In meat, eggs, whole grains, and legumes  Damage by heat or low/high acid conditions o Function in body  Part of coenzyme A needed for breakdown of carbs, fatty acids, amino acids, midofication of proteins, synthesis of neurotransmitters, steroid hormones, and hemoglobin  Needed for activity of acyl carrier protein, for synthesis of cholesterol and fatty acids o Pantothenic acid deficiency  Rare in humans, but can result in multiple b vitamin deficiency from malnutrition or alcoholism o RDA:  None, but AI of 5 mg/day, increased for pregnant and lactating women o Toxicity  Relatively nontoxic, no UI • Vitamin B6 o Important for amino acid and protein metabolism o In both animal and plant foods o Organ meats and whole grains o Bananas, broccoli, spinach, soybeans o Destroyed by exposure to heat and light, easily lost in processing o NOT added back in enrichment of grain products, but fortified breakfast cereals • Function in body o Aka pyridoxine, comprises pyridoxal, pyridoxine, and pyridoxamine which can all be converted into active coenzyme form, pyridoxal phosphate which is needed for activity of over 100 enzymes involved in metabolism of carb, fat, and protein o Coenzyme for transamination reactions that synthesize nonessential amino acids, deamination reactions needed, and synthesis of neurotransmitters from amino acids o Pyridoxal phosphate is also coenzyme needed to synthesize hemoglobin, cysteine from methionine, forms white blood cells, converts tryptophan to niacin, metabolizes glycogen, and synthesizes lipids on myelin coating of nerves • B6 deficiency o Abdominal distress, convulsions, depression, headaches, confusion, numbness o May be related to role in neurotransmitter synthesis and myeline formation o Anemia may occur due to impaired hemoglobin synthesis o Since B6 is needed for amino acid metabolism, deficiency may b hastened by a diet low in B6 but high in protein o Can be affected by alcohol and oral contraceptives o Alcohol decreases formation of active coenzyme pyridoxal phosphate, makes it more susceptible to breakdown • How B6 status is related to cardiovascular disease o Through role in breakdown of amino acid homocysteine, an intermediate in methionine metabolism…cannot be converted to cysteine, so levels rise • Recommended intake o RDA: 1.3 mg/day, RDA increased in older adults, pregnant women,
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