Kin 110 Lecture 6

1. Kin 110 Lecture 6 Vitamins Ch. 8

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

3. 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

4. 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

5. Storage of Vitamins • Fat soluble vitamins A, E and D not readily excreted • Water soluble - lost from body quite rapidly (B6 and B12 stored) • In general, limited storage of vitamins • should be consumed daily

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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 • Dietary sources table – fig 8.3

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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 1000mg of supplement • toxicity not a problem, except for people on anticoagulants (CVD) or with a vitamin K deficiency - due to increasesd risk of hemorrhage

21. 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

22. 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)

23. 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 B12 - 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

24. Vitamin Supplements • Megadoses of E and B12 • 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 B12 deficiency • avoid other products - PABA, inositol, bee pollen, lecithin