Kin 110 Lecture 6 Vitamins Ch 8 1

Kin 110 Lecture 6 Vitamins Ch. 8 1

Learning Objectives • Define vitamin • Classify vitamins as fat-soluble or water-soluble • List the major functions and deficiency symptoms for each fatsoluble vitamin • List three important food sources for each fat-soluble vitamin • Describe toxicity symptoms for excess consumption of certain fatsoluble vitamins • Evaluate the use of vitamin supplements - risk / benefit 2

Vitamins • Vitamin – essential organic (contains carbon) substances needed in small amounts in diet • Required for normal function, growth, maintenance of body structures • Yield no energy, but participate in energy yielding reactions • fat soluble vitamins - ADEK • water soluble vitamins-B vitamins and C • co-enzymes – help enzymes function – B vitamins and vitamin K – Fig. 8 -1 3

Vitamins • To be classified as vitamin – Body unable to synthesize enough – Absence for a defined period of time must produce deficiency (fig 8. 2) – symptoms, if caught in time, are cured when substance is reintroduced to diet • Megadoses of Vitamins – Requires Medical supervision • Toxicity diseases are possible • Many unproven claims continually being made – Niacin - cholesterol lowering – Vit D - treatment of psoriasis • Have they all been found? – People living on intravenous solutions of Protein, Carbohydrates, Fat and all known vitamins and minerals survive, grow, reproduce and fight disease 4

Storage of Vitamins • Fat soluble vitamins A, E and D not readily excreted • Water soluble - lost from body quite rapidly (B 6 and B 12 stored) • In general, limited storage of vitamins – should be consumed daily 5

Vitamin Toxicity • Toxicity theoretical for all vitamins • Fat soluble more frequently observe toxicity (A and D) • E, Niacin, B-6 and C – very large amounts needed to result in toxicity – Only possible from supplements • A and D only 3 -5 times RDA needed on a regular basis for toxicity – Vit A – important to minimize in early pregnancy – Once a day vitamins, less than 2 times daily value – not a risk • Preserving vitamin content - Table 8. 1 6

Fat soluble Vitamins • ADEK – Table 8. 2 • Absorbed along with dietary fat • Travel in bloodstream along with fat to reach body cells • Stored in liver and fatty tissue • 40 -90 % of fat sol. vit. absorbed • Can be reduced further – interference in normal digestion and absorption of fats. – Eg. Mineral oil laxatives 7

Vitamin A • Easy to over dose (toxic) and be deficient – Both cause severe problems • Variety of forms • Retinoids – Preformed vitamin A – – Only found in animal foods • Carotenoids – pro-vitamin A – – plants Yellow-orange pigment in carrots Turned into vitamin A as needed Most potent form is beta-carotene • Both pre and pro – referred to as Vitamin A 8

Functions of Vitamin A • Many roles – not all well understood • Role in vision – best known and most clearly understood – Performs important functions is both light (day) and dark (night) vision – in dim light, one form of A is required to start the chemical process that signals the brain that light is striking the eye. • Without vit A – night blindness • Prolonged deficiency – cells unable to produce mucus for cornea – Dry, dirty, scratched, infected – Xeropthalmia - dry eye • Less-developed nations – children – Blindness. Infection, death 9

Health of Cells • Vitamin A – maintains health of all cells that line internal and external surfaces – Lungs, intestines, stomach, eyes, skin (epithelial cells) – Cells secrete mucus – lubricant – Without A – decrease activity of immune cells, increased infection • Carotenoids play a role in preventing cardiovascular disease • Needed for growth, Development and Reproduction – Synthesis of proteins that stimulate proper growth and development – Resorbing and producing bone 10

Cancer and Vitamin A • Skin, lung, bladder and breast cancer • Adequate intake of vitamin A can lower risk of breast cancer – Megadoses NOT recommended to prevent cancer • Carotenoids – trap energy in free radicals – oxidation can initiate cancer process – Supplements of b-carotene not effective – Variety of fresh fruits and vegetables – Lycopene - tomatoes - may prevent prostate cancer • Acne – topical and internal derivatives – May produce birth defects in pregnant women using treatments – Eg retin-A and accutane 11

Vitamin A in Food • Preformed vitamin A – liver, fish oils, fortified milk and cereal, butter, margarine, eggs • Pro-vitamin – dark green and orange vegetables – Carrots, spinach, winter squash, papaya, apricots, sweet potatoes • RDA – RAE- retinol activity equivalent – 900 mg RAE (males) – 700 mg RAE (females) • Due to difficulty in classifying contributions from preformed and pro-vitamin A sources the labeling has undergone changes recently – Very old - IU, old RA, now RAE • Risk of deficiency – children, poor, alcoholics 12 • Dietary sources table – fig 8. 3

Toxicity of Vitamin A • 3 times the RDA can cause problems if continued for prolonged periods • Early pregnancy (pre-formed) – Fetal malformations, birth defects, spontaneous abortion • Non-pregnant – skin, hair, internal organs and CNS – Permanent damage can occur • Vit A is stored for months – Women in childbearing years – limit to 100% intake -one ounce of liver - 300% • Carotenoids (pro form) not toxic – Rate of conversion is slow – Efficiency of absorption decreases as intake increases 13

Vitamin D • Also considered a hormone – skin cells convert cholesterol like substance into vitamin D using sunlight • effects kidney and bone • 10 -15 minutes of exposure of arms, face and hands; 2 -3 times per week – not effective in winter – must have vitamin intake 14

Functions of Vitamin D • To become active hormone, vitamin D must be activated in liver and kidneys • calcitrol - active form • regulates calcium and bone metabolism along with parathyroid hormone – regulates absorption of calcium and phosphate from intestines – reduces kidney excretion of calcium – regulates deposition of calcium in bones • Immune system and skin development influenced by vitamin D 15

Vitamin D and Bone • Calcium and phosphorus deposition • without vit D bones weaken and bow under pressure – Rickets (children) – fortification of milk – malabsorption of fat (cystic fibrosis) • osteomalacia - adults - soft bones – – – calcium withdrawn from bones inefficient absorption or conservation vit D deficient bones porous and weak - break easily supplement vit D - reduces fractures problem with vitamin D activation or absorption 16

Dietary Sources of D • Fatty fish (sardines, salmon), fortified milk, yogurt and cereals – – under 51 years - 5 mg/day over 51 2 -3 times - 10 -15 mg/day max. 50 mg /day Young, fair skinned 10 -15 min of sun on face and arms 2 -3 times /week • 5 -10 times recommended on regular basis results in toxicity – calcium over absorption - deposition in kidneys and other organs – high blood calcium – Weakness, loss of appetite, diarrhea, vomiting , mental confusion, – sun exposure does not result in toxicity 17

Vitamin E • Fat soluble antioxidant • resides in cell membranes • donates electrons - protection from free radicals • fig 8 -4 • DNA oxidation - cancer, cell death – repair mechanisms for damage • impact on cancer, heart disease very minimal compared to proper diet and exercise – not an alternative to making good overall health choices 18

Deficiency of vitamin E • Few women getting enough vitamin E from food – Supplements not as potent – Smoking destroys vitamin E • Cell membranes break down – red blood cell breakdown in infants – unsaturated fatty acids susceptible to oxidation – hemolysis- breaking of rbc in absence of vit. E • vit E improves vit A absorption • used to metabolize iron in cell, maintain nervous tissue, and insulin function 19

Vitamin E in Foods • plant oils, fortified cereals, fruits and vegetables, eggs, margarine – Sunflower seeds and almonds are an excellent source of vitamin E – vitamin E in plant oils - protects unsaturated fatty acids – Animal foods almost no vitamin E • content of vit E depends on harvesting , processing storage and cooking – easily destroyed by oxygen, metals , light , repeated frying • RNI - 15 mg /day • alpha tocopherol - most active form • megadose therapy - not proven – Upper level is 1000 mg of supplement – toxicity not a problem, except for people on anticoagulants (CVD) or with a vitamin K deficiency - due to 20 increasesd risk of hemorrhage

Vitamin K • Family of compounds known collectively as vitamin K • Found in plant oils, fish oils, and meats – One form is synthesized by bacteria in the intestine (10% of need) • role - vital for blood clotting – synthesis of blood clotting factors • formation of proteins in bone, kidney and muscle – impart calcium binding potential • newborns lack bacteria to produce vitamin K – routine injection at birth • deficiency in adults on prolonged antibiotics or with poor fat absorption 21

Vitamin K in Food • Liver, green leafy vegetables, broccoli, peas and green beans – Also soybean and canola oils • vitamin K not stored well - one day – abundant in diet, deficiency uncommon – resistant to cooking • RDA - 90 -120 mg / day – no risk of toxicity – risk of reduced effectiveness of medications to reduce blood clotting (CVD) 22

Vitamin Supplements • Supplements may be beneficial, and improve health of population – Most unwilling to increase intake of fruits and vegetables • folate (B vitamin) – birth defects – homocystien - risk factor for heart disease – alleviated by adequate folate (and reduction in red meat) • vitamin B 12 - risk over 50 – synthetic more easily absorbed • Eat right and take a multivitamin – Use supplements in consultation with physician – Potential impacts of medications for CVD and cancer 23

Vitamin Supplements • Megadoses of E and B 12 – trials ongoing, may be beneficial – Vit E not very exciting results • Supplements should be taken with or just after meal • no more than 100% of daily values – avoid excess selenium and C • overabsorption of iron – males avoid excess iron – excess zinc - inhibits iron an copper absorption – excess folate - masks B 12 deficiency – avoid other products - PABA, inositol, bee pollen, lecithin 24