Being in my early 50's I've experienced a significant decrease in my libido over the past several years. Various factors can be attributed to it, age & increased stress, etc. Although a part of me doesn't miss the added distraction of testosterone, I decided to experiment with many different natural enhancers. Most have a general stimulating "edgy" effect which I don't care for. I recently started taking Hydrilla for an occasional food based Calcium and a surprising side effect has been with my libido. More so with erectile dysfunction than enhanced desire. It is considered a nuisance weed, but it is loaded with minerals, so it probably had something my body was lacking. It has a calming (calcium) effect as well.
EC: More information about Hydrilla on Wikipedia: http://en.wikipedia.org/wiki/Hydrilla