Vitamins: An Overview

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

Body Needs Vitamins for Normal Function Growth Maintenance Reproduction

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

Vitamins Often Serve as Coenzymes

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Sources of Vitamin A Preformed Provitamin 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

Vitamin A from the Food Guide Pyramid

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

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

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

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

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

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

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

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

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

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

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

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)

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

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

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

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

The Adequate Intake (AI) for Vitamin D 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.

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)

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

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

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

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

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

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

Vitamin E, An Antioxidant

The More The Better? Vitamin E is only one of many antioxidants It is likely that the combination of antioxidants is more effective Best to diversify antioxidant intake with a balanced and varied diet Megadose of one antioxidant may interfere with the action of another

Vitamin E and Cardiovascular Disease Epidemiological studies suggest higher intakes of Vitamin E are associated with lower risk of CHD Clinical trial results have been mixed American Heart Association states it is premature to recommend vitamin E supplements to the general population FDA has denied permission for supplement mfr’s to claim that Vitamin E prevents heart disease and cancer

Other Functions of Vitamin E Protects the double bonds in saturated fat Helps vitamin A absorption Role in iron metabolism Inhibits LDL oxidation Maintenance of nervous tissue and immune function

Food Sources of Vitamin E Plant oils: salad dressings, mayonnaise Fortified cereals, oatmeal Wheat germ Asparagus, tomatoes, green leafy vegetables

Food Sources of Vitamin E Peanuts Margarine Nuts and seeds (sunflower seeds) Actual amount is dependent on harvesting, processing, storage and cooking

Food Sources of Vitamin E

Vitamin E: Easily Damaged Oxygen Metals Light High heat Deep fat frying

RDA for Vitamin E 15 mg/day alpha-tocopherol for women and men (=22 IU of natural source or 33 IU of synthetic form) Average intake meets RDA 1 mg d--tocopherol = 0.45 IU (synthetic source) 1 mg d--tocopherol = 0.67 IU (natural sources)

Deficiency of Vitamin E Hemolytic anemia Hemolysis occurs in preterm infants because they did not receive enough vitamin E from their mothers Preemie formulas and supplements compensate for increased needs

Deficiency of Vitamin E: Who’s At Risk? Smokers are especially at risk (smoking destroys vitamin E in the lungs) However even megadoses may not prevent damage Adults on very low fat diets Fat malabsorption

Toxicity of Vitamin E Supplements up to 800 IU probably harmless Upper Level is 1,000 mg/day of any form of supplementary alpha-tocopherol Upper Level is 1500 IU (natural sources) or 1100 IU (synthetic forms) Inhibits vitamin K metabolism especially in conjunction with anticoagulants Possible hemorrhage

Vitamin K (“Koagulation”) Family of compounds found in plants, plant oils, fish oils, and meats Synthesized by the bacteria in the colon and are absorbed (10% of needs)

Role of Vitamin K Role in the coagulation process Contributes to the synthesis of several blood-clotting factors Helps form proteins present in bone, muscle, and kidneys Imparts calcium-binding potential Poor intake linked to increase in hip fractures

Vitamin K in Newborns Newborn’s intestinal tract lacks bacteria to allow blood to clot effectively Vitamin K is routinely given by injection shortly after birth to bridge the gap May also occur in adults with chronic malabsorption

Drugs and Vitamin K Anticoagulant Antibiotics Lessens vitamin K reactivation Lessens blood clotting process Monitor vitamin K intake Antibiotics Destroy intestinal bacteria Inhibit vitamin K synthesis and absorption Potential for excessive bleeding

Food Sources of Vitamin K Liver Green leafy vegetables Broccoli Peas Green beans Soybeans/canola oil Resistant to cooking losses Limited vitamin K stored in the body

Adequate Intake for Vitamin K 90 ug/day for women 120 ug/day for men Amount met by most Excess vitamins A and E interferes with vitamin K Newborns are injected with vitamin K (breast milk is a poor source) Toxicity unlikely; readily excreted

Next: Water Soluble Vitamins