[surferjoe2007]

Probably ok but 18 is a little early.  Sometimes a little puberty can go as far as 23.  Fenugreek is even more likely to be ok.  Other herbs, especially PM and PC, are more likely to cause trouble.  Still probably ok because puberty is mostly over, but it's safer to not use too much PM or PC.  You can still do nutritional stuff at any age.

Spearmint can decrease testosterone, though the studies used 10,000 mg a day to make tea.  And even then it only decreases it a little.  I don't think the other herbs decrease testosterone.