Saw Palmetto is a plant that contains lipid and plant sterols, which are steroid like compounds. The plant is native to Florida and Georgia and it’s used as a remedy for enlarged prostate gland. Saw Palmetto works by inhibiting the enzyme that converts testosterone into dihydro-testosterone (DHT) and also blocks estrogen at its receptors. Studies show that it may not directly influence plasma testosterone levels, but rather reduce the negative effects of hormonal imbalance, such as acne, male pattern baldness and prostate enlargement.
Testosterone is significantly correlated with aggression and competitive behaviour and is directly facilitated by the latter. There are two theories on the role of testosterone in aggression and competition.  The first one is the challenge hypothesis which states that testosterone would increase during puberty thus facilitating reproductive and competitive behaviour which would include aggression.  Thus it is the challenge of competition among males of the species that facilitates aggression and violence.  Studies conducted have found direct correlation between testosterone and dominance especially among the most violent criminals in prison who had the highest testosterone levels.  The same research also found fathers (those outside competitive environments) had the lowest testosterone levels compared to other males. 
I tried the cup of raisins before bed and woke up before dawn with an erection reminiscent of days gone by, that lasted for over an hour. Pretty awesome! Though peeing was a long and drawn out affair.
I just had my T checked as I was not getting them any more, neither was I much interested in sex. The test came back with a paltry 305 @ 46yrs old. Just a year ago my erections used to have a bitter sweet ache to them. After going close to zero carb I lost my power, my head hair, got rosacea, limp erections, and my nitric oxide plummeted. I stopped training as it was painful and although I was eager to exercise my body just didn’t seem up to it. ( come to think of it now after reading all these articles, it would seem that lower elasticity of my arteries(low NO) was the reason.)