Vitamins: An Overview

1. Vitamins: An Overview

2. Vitamins • Essential organic substances (contain carbon) • Not synthesized • Inadequate synthesis • Yield no energy, but facilitate energy-yielding chemical reactions • If absent from a diet, it will produce deficiency signs and symptoms

3. Body Needs Vitamins for Normal • Function • Growth • Maintenance • Reproduction

4. Two Forms of Vitamins • Precursor/Provitamin • Dietary form inactive • Activated in body • Active form • Dietary form active • Not changed in body

5. Vitamins Often Serve as Coenzymes

6. Vitamin Classification • Fat-soluble vitamins • Dissolve in substances such as ether and benzene but not readily in water • Include vitamins A, D, E, and K • Water-soluble vitamins • Vitamins that dissolve in water • Include B vitamins and vitamin C

7. Vitamin Classification Category determines • Food sources • How handled in body • Best preservation methods

8. Vitamin History • First discovered: fat soluble substance essential for health in 1912-1914 (vitamin A) • B complex: 1915-1916 (water soluble nutrient) • Vitamin C: isolated 1912 • Vitamin D, Vitamin E: 1922 • Last vitamin (B12) discovered in 1948 • Likely all vitamins have been discovered, since people can be maintained on IV solutions fortified with known vitamins

9. Vitamin Facts • Megadose (>10x needs) proved useful in treating certain conditions • Plant and animal foods provide vitamins • Synthesized vitamins work equally well in the body

10. Fat-Soluble Vitamins • Dissolve in organic solvents • Not readily excreted; can cause toxicity • Absorbed along with fat • Deficiency with fat malabsorption • Fat blockers (Orlistat/Xenical) • Mineral oil

11. Fat Soluble Vitamins • Requires protein carrier • Transported like fat in chylomicrons, VLDL, LDL • Stored in body (except Vitamin K) • Fat tissue/liver • Can cause toxicity • Vitamin D and A most likely to be toxic

12. Fat Soluble Vitamin Preservation • Not easily destroyed • Fat addition in cooking vegetables • Fat soluble vitamins leach out • Lost if liquid discarded • Add fat after vegetables drained, just before serving • Baking soda • Used to preserve color of green vegetables • Destroys Vitamin D

13. Water Soluble Vitamins • Found in grains, fruits, vegetables, meat • Low risk of toxicity • Not stored in large amounts • Excess excreted inurine • Need daily intakes • Easily destroyed • Heat – increases enzyme activity • Light – destroys riboflavin • Oxygen: breaks down

14. Water Soluble Vitamins - Preservation • Cooking • Heat – destroys vitamins • Water – leaches out vitamins • Baking soda – destroys thiamin • Conserve vitamins • Store foods covered in refrigerator • Consume soon after purchase (freshest possible) • Minimal cooking/minimal liquid • Freezing preserves vitamin content

15. Vitamin A • Deficiency is most common cause of non-accidental blindness worldwide • Up to 500,000 children in developing nations especially Asia, become blind each year because of Vitamin A deficiency

16. Functions of Vitamin A • Prevents night blindness • Prevents xerophthalmia (dry eye) • Maintains cell health (epithelial cells) • Growth, development, reproduction • Cardiovascular disease prevention • Cancer prevention

17. Night Blindness • Vitamin A is needed for dark vision • Rhodopsin in retina • Light destroys • Constantly reformed • Allows for a chemical process to signal the brain that light is striking the eye • Allows eyes to adjust to dark vision

18. Xeropthalmia • In Vitamin A deficiency, the cells that line the cornea lose their ability to produce mucus • When dirt particles scratch the dry surface of the eye, becomes infected • Leads to blindness • Worldwide public health efforts are fortifying sugar, margarine, MSG, giving large doses of Vitamin A 2x year

19. Macular Degeneration • Leading cause of legal blindness among North American adults over 65 • Changes in the macular area of the eye • Age, smoking, and genetics are risk factors • Macula contains carotenoids lutein and zeaxanthin • High intakes of carotenoids associated with lower risk (but may be fruit and vegetable intake) • Also may reduce risk of cataracts • Multivitamins are adding lutein

20. Cell Health • Vitamin A maintains health of cells that line internal and external surfaces (epithelial cells) • Barriers to bacterial infections • Epithelial cells produce mucus • Without vitamin A, these cells do not produce mucus • Increases infections and decreases immune system

21. Growth • Vitamin A binds to DNA • Assists in protein synthesis • Affects growth, reproductive system, and bone growth

22. Cancer and Cardiovascular Disease • Role in cell development and immune-system • Role as an antioxidant • Lower risk of breast cancer with vitamin A supplements • Megadoses are not recommended • Mixed results in cancer/vitamin A studies • Foods rich in vitamin A and other phytochemicals are advised

23. Prostate Cancer and Carotenoids • One of the most common cancers among North American men • Lycopene (tomatoes, watermelon, other fruits) seems to protect against it, possibly due to antioxidant activity

24. Vitamin A and Your Skin • Topical treatment and oral drug • Accutane (oral) and Retin-A (topical) • Can induce toxicity symptoms • Contraindicated in pregnant women • Use only under supervision of a physician

25. Sources of Vitamin A • Preformed • Liver, fish oils, fortified milk, eggs • Contributes to half of vitamin A intake in North America • Provitamin • Dark leafy green, yellow-orange vegetables/fruits; carrots, spinach and other greens, winter squash, sweet potatoes, broccoli, mangoes, cantaloupe, peaches and apricots • Contributes to half of all the vitamin A intake

26. Vitamin A from the Food Guide Pyramid

27. Deficiency of Vitamin A • Night blindness • Decrease mucus production leading to bacterial invasion in the eye • Irreversible blindness

28. Deficiency of Vitamin A • Follicular hyperkeratosis • Keratin protects the inner layers of skin and maintains moisture • Kertinized cells replaces the normal epithelial cells in the underlying skin layers • Hair follicles become plugged • Bumpy, rough, and dry skin

29. Measuring Vitamin A • International unit (IU)-crude method of measurement • Retinol activity equivalent (RAE) -current, more precise method of measurement 1 ug of retinol = 1 RAE = 3.3 IU =12 ug beta-carotene = 24 ug of other provitamin A

30. RDA for Vitamin A for Adults • 900 mcg REA for men • 700 mcg REA for women • Average intake meets RDA • Daily value used on food and supplement labels is 1000 mcg • Much stored in the liver • Vitamin A supplements are unnecessary • No separate RDA for carotenoids

31. Who is at Risk For Deficiency • Breast fed infants • Preschooler with poor vegetable intake • Urban poor • Elderly • Alcoholics and people with liver disease • Individual with fat malabsorption • HIV, AIDS

32. Toxicity of Vitamin A • Large intake of vitamin A over a long period: supplements, liver, fish oil • Bone/muscle pain, loss of appetite, skin disorders, headache, dry skin, hair loss, increased liver size, vomiting • Possible permanent damage • Discontinue supplement

33. Toxicity of Vitamin A • May produce fetal malformations and spontaneous abortions in pregnant women • May occur with as little as 3 x RDA of preformed vitamin A • Pregnant women and women who may become pregnant should limit to 100% DV • Upper Level for Vitamin A • 3000 ug for adults • Fatal dose -12 g of vitamin A can be fatal

34. Toxicity of Carotenoids • Don’t produce toxic effects because • Rate of conversion to Vitamin A is slow and regulated • Efficiency of absorption decreases as oral intake increases

35. Carotenoids High amounts of carotenoids in the bloodstream • Excessive consumption of carrots/squash/beta-carotene supplements • Skin turns a yellow-orange color

36. Vitamin D • Prohormone • Derived from cholesterol • 90% of needs is synthesized from sun exposure • Insufficient sun exposure makes this a vitamin

37. Sun Exposure to Prevent Vitamin D Deficiency • ~15 minutes 2-3 times a week • Between 8 a.m. and 4 p.m. • Hands, face, arms • Light skin • No sunscreen greater than SPF8

38. Activation of Vitamin D To become the active hormone, Vitamin D must be • Acted on by the liver to produce 25-hydroxyvitamin D • Acted on by the kidney to produce 1,25 dihydroxyvitamin D (active hormone form)

39. Functions of Vitamin D • Regulates blood calcium • Regulates calcium and phosphorus absorption from the intestine • Reduces kidney excretion of calcium • Regulates calcium deposition in bones • Serum calcium involved in nerve transmission and muscle contraction

40. Functions of Vitamin D • Influences cell differentiation • Linked to reduction of breast, colon, and prostate cancer • Controls the growth of the parathyroid gland, aids in immune function, contributes to skin cell development

41. Vitamin D causes Ca + Phos to deposit in the bones Strengthen bones Role in Bone Formation

42. Food Sources of Vitamin D • Fatty fish (salmon, herring) • Fortified milk and yogurt • 10 mcg per quart in US and Canada • Some fortified cereal

43. 5 ug/d (200 IU/day) for adults under age 51 10-15 ug/day (400 - 600 IU/day) for older Americans Light skinned individuals can produce enough vitamin D to meet the AI from casual sun exposure Infants are born with enough vitamin D to last ~9 months of age. The Adequate Intake (AI) for Vitamin D

44. Vitamin D Toxicity • Upper level is 50 mcg/day • Vitamin D can be very toxic especially in children • Regular intake of 5-10x the AI can be toxic • Results from excess supplementation (not from sun exposure or milk consumption)

45. Vitamin D Toxicity • Signs/symptoms: overabsorption of calcium (hypercalcemia) • Signs of high blood calcium: weakness, loss of appetite, diarrhea, vomiting, mental confusion, increased urine output • Calcium deposits in kidneys, heart, and blood vessels • Mental retardation in infants

46. Vitamin D Deficiency At risk • Dark skinned • Lack of sun exposure • Northern climates in wintertime • Breastfed babies

47. Vitamin D Deficiency: Rickets • Is the result of vitamin D deficiency in children • Poor mineralization of bones because of low calcium content • Fortification of milk has greatly reduced rickets in children • Most rickets is associated with fat malabsorption, as in cystic fibrosis

48. Vitamin D Deficiency: Osteomalacia (soft bone) • Is rickets in the adult • Low calcium content in bones due to lack of vitamin D

49. Vitamin E • Group of fat-soluble compounds, tocopherols and tocotrienols • Alpha-tocopherol is the most potent • Fat-soluble antioxidant • Resides mostly in cell membranes

50. Redox Agent • Vitamin E is able to donate electron to oxidizing agent • Protects the cell from attack by free radicals • Protects PUFAs within the cell membrane and plasma lipoproteins • Prevents cell death • Prevents the alteration of cell’s DNA and risk for cancer development