Semen makes women happy.
I picked up this interesting news from on ScienceBlogs.com yesterday. The original research was published in the Archives of Sexual Behavior and is available online .
I can't claim to understand all the details, but apparently, you absorb it through your vaginal walls, and it stops you getting depressed.
If you would like to explore this in more detail, please contact me directly.
 Gordon G. Gallup Jr., Rebecca L. Burch, Steven M. Platek (2002). Does semen have antidepressant properties? Archives of Sexual Behavior, 31 (3), 289-293 DOI: 10.1023/A:1015257004839