Fat-Soluble Vitamins

2 Vitamins: Essential Dietary Components Essential organic substances –Water-soluble: Vitamin B complex and C –Fat-soluble: Vitamins A, D, E and K Absorption of vitamins Malabsorption of vitamins Transport of vitamins Storage of vitamins in the body Vitamin Toxicity

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Vitamin A in Foods 4

5 Vitamin A Needs RDA –Men 900 micrograms –Women 700 micrograms Daily Value –Approximately 1,000 micrograms

6 Functions of Vitamin A (Retinoids) Growth and Development Cell Differentiation Vision –rhodopsin Immune Function –Maintenance of the epithelium Use of vitamin A analogs in Dermatology

7 Vitamin A Diseases Rare in North America, but major problem in developing countries Deficiencies –Night blindness –Xerophthalmia (irreversible blindness) –Follicular hyperkeratosis Toxicities –Hypervitaminosis A –Upper Limit: 3000 micrograms/d –Acute and chronic toxicity

8 Vitamin D “Conditional” vitamin or a prohormone Vitamin D 2 in Foods: –Fatty fish, cod liver oil, fortified dairy products and some fortified breakfast cereals Vitamin D 3 is formed in skin from cholesterol: –Sunlight changes 7-dehydrocholesterol to cholecalciferol –Travels to liver and then kidneys, where converted to bioactive form (calcitriol) Requirement: sunlight 2-3 times/week for 10-15min –Several factors influence this

9 Vitamin D Needs RDA –Under age 70: 15 µg –Over 70: 20 µg Breastfed infants: 10 µg Daily Value: 10 µg

10 Functions of Vitamin D Calcitriol is the active form Calcium and Phosphorus Homeostasis –Aids in increasing absorption of Ca & P –Aids in releasing Ca & P from bone, if blood levels are low Bone Health Immune Function Chronic diseases (see Perspective from the Field)

11 Vitamin D Diseases Deficiencies –Children: rickets –Adults: osteomalacia Toxicities –Does not occur from sunlight or dietary sources –Can occur with supplementation –Upper Limit: 100 µg –Calcium deposits in soft tissues

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13 Vitamin E 8 compounds –4 tocopherols –4 tocotrienols Dietary sources: –Plant oils (e.g., canola), wheat germ, avocado, almonds, peanuts and sunflower seeds

Vitamin E in Foods 14

15 Vitamin E Needs RDA –15 mg of alpha-tocopherol –Based on hemolysis prevention –Adults consume approximately 2/3 the RDA Daily Value –30 IU (approximately 20 mg)

16 Vitamin E Functions Antioxidant –Stops lipid peroxidation (chain reactions) caused by free radicals –Works with vitamin C

17 Vitamin E Diseases Deficiency –Hemolytic anemia -- rare in healthy people –Pre-term infants and smokers are most susceptible –Immune function impairment and neurological changes Toxicity –Can interfere with Vitamin K and cause hemorrhaging –Upper Limit: 1000mg natural sources (1100 IU from synthetic sources)

18 Vitamin K Menaquinones –Synthesized by bacteria in colon (10%) –From fish oils and meats Phylloquinones –From plants: green leafy vegetables, broccoli, peas, and green beans –Most biologically active

Vitamin K in Foods 19

20 Vitamin K Needs AI –Women 90 micrograms daily –Men 120 micrograms daily Daily Value –80 micrograms

21 Vitamin K Functions & Diseases Functions –Synthesis of blood clotting factors –Bone metabolism Deficiency is rare –Newborns; long-term antibiotic use; fat malabsorption Toxicity –No UL

22 Dietary Supplements: Healthful or Harmful? Dietary Supplement Health and Education Act of 1994 (DSHEA) Definition: –A vitamin, a mineral, an amino acid, an herb, a botanical, a plant extract, or a combination of any of the above Quality, purity, and consistency are not closely monitored by FDA

23 Supplementation Is Not a Substitute for a Poor Diet Some individuals may benefit Things to look for: –No more than 100% Daily Value –USP certification –Diet and supplement shouldn’t exceed ULs –Check for superfluous ingredients