成人每天4,000-8,000IU.在镁不足下(现代人90%缺乏),D3对癌症和心血管病等不具有保护作用

At the time (in 2007) the recommended level was between 40 to 60 nanograms per milliliter (ng/ml). Since then, the optimal vitamin D level has been raised to 50-70 ng/ml, and when treating cancer or heart disease, as high as 70-100 ng/ml.

Based on this research, it now appears as though most adults need about 8,000 IU's of vitamin D a day in order to get their serum levels above 40 ng/ml. 

http://articles.mercola.com/sites/articles/archive/2011/10/22/carole-baggerly-on-vitamin-d.aspx