大多数微量元素在几年前还不为人们所知道,但现在有证据表明,起码有25种与健康有某种关系。大约14种是必不可少的。有些则因其有害作用而受到重视。二十世纪初发现维生素时,人们誉为营养学的一个惊人的突破。新的维生素一个接一个地发现,已有的维生素又不断有新的功能。最后能从不同来源的食物得到不同的维生素,订出每日需要量(Recomme-nded Daily Allowances),并描述、诊断和治疗很多维生素缺乏的疾病。然而,人们很快就知道某些维生 Most trace elements are unknown to people a few years ago, but there is now evidence that at least 25 of them have some relationship to health. About 14 kinds are essential. Some are valued for their detrimental effects. When the discovery of vitamins in the early twentieth century, people called an amazing breakthrough in nutrition. New vitamins one by one found that existing vitamins continue to have new features. Finally, you can get different vitamins from foods of different origins, set up Recommen-nded Daily Allowances, and describe, diagnose and treat many vitamin-deficient diseases. However, people soon know some subsistence