Naidu K Akhilender
Department of Biochemistry and Nutrition, Central Food Technological Research Institute, Mysore 570 013, India.
Nutr J. 2003 Aug 21;2:7. doi: 10.1186/1475-2891-2-7.
Ascorbic acid is one of the important water soluble vitamins. It is essential for collagen, carnitine and neurotransmitters biosynthesis. Most plants and animals synthesize ascorbic acid for their own requirement. However, apes and humans can not synthesize ascorbic acid due to lack of an enzyme gulonolactone oxidase. Hence, ascorbic acid has to be supplemented mainly through fruits, vegetables and tablets. The current US recommended daily allowance (RDA) for ascorbic acid ranges between 100-120 mg/per day for adults. Many health benefits have been attributed to ascorbic acid such as antioxidant, anti-atherogenic, anti-carcinogenic, immunomodulator and prevents cold etc. However, lately the health benefits of ascorbic acid has been the subject of debate and controversies viz., Danger of mega doses of ascorbic acid? Does ascorbic acid act as a antioxidant or pro-oxidant? Does ascorbic acid cause cancer or may interfere with cancer therapy? However, the Panel on dietary antioxidants and related compounds stated that the in vivo data do not clearly show a relationship between excess ascorbic acid intake and kidney stone formation, pro-oxidant effects, excess iron absorption. A number of clinical and epidemiological studies on anti-carcinogenic effects of ascorbic acid in humans did not show any conclusive beneficial effects on various types of cancer except gastric cancer. Recently, a few derivatives of ascorbic acid were tested on cancer cells, among them ascorbic acid esters showed promising anticancer activity compared to ascorbic acid. Ascorbyl stearate was found to inhibit proliferation of human cancer cells by interfering with cell cycle progression, induced apoptosis by modulation of signal transduction pathways. However, more mechanistic and human in vivo studies are needed to understand and elucidate the molecular mechanism underlying the anti-carcinogenic property of ascorbic acid. Thus, though ascorbic acid was discovered in 17th century, the exact role of this vitamin/nutraceutical in human biology and health is still a mystery in view of many beneficial claims and controversies.
抗坏血酸是重要的水溶性维生素之一。它对胶原蛋白、肉碱和神经递质的生物合成至关重要。大多数植物和动物能自行合成抗坏血酸以满足自身需求。然而，由于缺乏古洛糖酸内酯氧化酶，猿类和人类无法合成抗坏血酸。因此，抗坏血酸主要需通过水果、蔬菜和片剂来补充。美国目前推荐的成年人抗坏血酸每日摄入量为100 - 120毫克/天。抗坏血酸具有许多健康益处，如抗氧化、抗动脉粥样硬化、抗癌、免疫调节以及预防感冒等。然而，最近抗坏血酸的健康益处一直是争论和争议的主题，即：大剂量抗坏血酸有危险吗？抗坏血酸是作为抗氧化剂还是促氧化剂起作用？抗坏血酸会导致癌症还是可能干扰癌症治疗？然而，膳食抗氧化剂及相关化合物小组指出，体内数据并未明确显示抗坏血酸摄入过量与肾结石形成、促氧化作用、铁吸收过多之间存在关联。关于抗坏血酸对人类抗癌作用的一些临床和流行病学研究表明，除了胃癌外，对各种类型的癌症均未显示出任何确凿的有益效果。最近，一些抗坏血酸衍生物在癌细胞上进行了测试，其中抗坏血酸酯与抗坏血酸相比显示出有前景的抗癌活性。硬脂酸抗坏血酸酯被发现可通过干扰细胞周期进程来抑制人类癌细胞的增殖，并通过调节信号转导途径诱导细胞凋亡。然而，需要更多的机制研究和人体体内研究来理解和阐明抗坏血酸抗癌特性背后的分子机制。因此，尽管抗坏血酸在17世纪就已被发现，但鉴于众多有益说法和争议，这种维生素/营养保健品在人类生物学和健康中的确切作用仍是一个谜。
