Handbook of Vitamin C Research

In: Handbook of Vitamin C Research ISBN: 978-1-60741-874-0Editors: Hubert Kucharski and Julek Zajac©2009 Nova Science Publishers, Inc.Chapter VIIIVitamin C: Daily Requirements, DietarySources and Adverse EffectsJun Yang 1 , Jiaren Liu 2 and John Parry 31 Frito-Lay R&D, Plano, TX, USA2 Department of Anesthesia, Harvard Medical School, Boston, MA, USA3 Agricultural Research Station, Virginia State University, Petersburg, VA, USAAbstractAscorbic acid (vitamin C) is classified as a water-soluble vitamin. It is a powerfulreducing agent and is sensitive to transition metals, light, oxygen, and heat. As a strongantioxidant, ascorbic acid is used as a preservative in the food industry. Humans dependon ascorbic acid for many physiological and biochemical functions such as collagen,carnitine, and neurotransmitter biosynthesis, which is crucial to the maintenance ofbones, teeth, and blood vessels. A deficiency in ascorbic acid can lead to scurvy. Unlikemost plants, animals, and single-cell organisms, humans cannot synthesize their ownsupply of ascorbic acid due to lack of the enzyme responsible for the final step in itsconversion - gulonolactone oxidase. It must be obtained from dietary sources includingfruits, vegetables and supplements. Good dietary sources of vitamin C include citrusfruits, green vegetables, bell peppers, papaya, and tomatoes. However, vitamin C level isreduced in storage and processing. Generally, the US recommended dietary allowance(RDA) for ascorbic acid is from 100 - 120 mg/per day for adults. Ascorbic acid is anantioxidant that can help neutralize free radicals. Many health benefits have beenattributed to ascorbic acid such as protection from viral infections, anti-atherogenesis,anti-carcinogenesis, and immune-modulation. A new study indicates that it has acomplex protective role against toxic compounds formed from oxidized lipids,preventing genetic damage and inflammation. The amount of ascorbic acid to causeoverdose symptoms in humans varies among individuals, and overdose is generallycharacterized by diarrhea and possibly indigestion. Ascorbic acid has been implicatedCorresponding Author