Kin 110 Lecture 6 Vitamins Ch. 8

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

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

Vitamins To be classified as vitamin Megadoses of Vitamins 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

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

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

Fat soluble Vitamins ADEK Absorbed along with dietary fat 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

Vitamin A Easy to over dose (toxic) and be deficient Variety of forms 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

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

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

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

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

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

Vitamin D Also considered a hormone effects kidney and bone 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

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

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

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

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

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

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

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

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)

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

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