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Vitamins and mineralsLearning objectives • Understand why V/M are essential to healthy living; • Understand that there are healthy intake levels for V/M and that excesses may be worse than deficiencies; • Know the four fat soluble vitamins and basic roles; • Know the water soluble vitamins we discuss in class and their roles; • Know the roles of the minerals we discuss in class; • Know that processing and storage may affect some vitamins more than others. • What is wrong with “If a little is good, more must be better”?
Fat soluble vitaminsADEK • Dissolve in organic solvents – methanol, gasoline etc.. • Can build up because they are not excreted • Absorbed during fat absorption • Transported in lipoproteins • Vitamin A – carotenoids and retinoids • Vitamin D – cholesterol product • Vitamin E – tocopherols • Vitamin K – menaquinones and phylloquinones
Vitamins • Essential organic substances • Yield no energy, but facilitate energy-yielding chemical reactions • If absent from a diet, it will produce deficiency signs and symptoms • Preservation of vitamins in foods • exposure to light, heat, air, water, and alkaline
Vitamin A • Two general types • Pre-formed • retinoids are found in animal products • Precursors • carotenoids are found in plant products • beta carotene, lutein, lycopene, others • must be converted to retinoids • absorbed and converted by intestinal cells
Absorption of Vitamin A • Requires bile, digestive enzymes, integration into micelles • Dependent on the fat in the diet • olestra • 90% of retinoids can be absorbed • Only ~3% of carotenoids are absorbed • so eat your carrots • Intestinal cells can convert carotenoids to retinoids
Transport in body/storage • Liver stores 90% of vitamin A in the body • polar bear liver • Reserve is adequate for several months • Transported via chylomicrons to the liver • Transported from the liver as retinol via retinol-binding protein to target tissue • Carotenoids can be transported via VLDL
Functions of Vitamin A • Night and color vision • xerophthalmia • Cell health and maintenance • epithelial cell differentiation and division • cells deteriorate without Vit A • follicular hyperkeratosis • Antioxidant • Macular Degeneration • lutein
Sources of Vitamin A • Retinoids - animals • Liver, fish oils, fortified milk, eggs • 50% of vitamin A intake is from these sources • Carotenoids - plants • dark green leafy • yellow orange • the other 50%
Overdose of a Vitamin? • High doses of vitamin A are toxic • HYPERVITAMINOSIS A • 3 – 10x supplements • Teratogenic – birth defects/spontaneous abortion • 3x RDA • Carcinogenic – some feeding trials with smokers • 3 – 10x RDA • Fatal dose – 12 gram
How much do we need? • 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 • 900 REA men 700 REA women • Supplement or no?