NUTR.2060 Lecture 12: Chapter 12
20 Mar 2017
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Document Summary
Vitamins: essential organic substances needed in small amounts. Fat-soluble: vitamins a,d, e and k: absorption and excretion of vitamins. Fat-soluble vitamins require dietary fat to be absorbed (40-90%) and not easily excreted: malabsorption syndromes. Water-soluble vitamins absorbed by active transport independently from other nutrients (90-100%) and excess easily excreted in urine: transport of vitamins in blood. No special mechanism for transport of water soluble vitamins: storage of vitamins in the body. Only fat-soluble vitamins and b12 are stored easily. Either in adipose tissue or liver: vitamin toxicity. Most fat-soluble vitamins can be toxic if stored in liver: severe health issues; death. A couple of water-soluble vitamins can be toxic but don"t cause severe health issues. 3 active forms of vitamin a in the body: retinol, retinal and retinoic acid. Only retinol is in foods: liver, sh oils, forti ed dairy products and egg yolks. Provitamins (inactive): some can be converted to vitamin a (others behave as phytochemicals)
