Are there any supplements I can take to naturally increase my testosterone levels?
Maca is your best bet. Grown in Peru, this plant contains compounds called sterols that may block the body's production of estrogen while boosting testosterone levels. Try mixing three to six tablespoons of whole maca root powder into a drink daily (extracts and capsules are not as effective). Stick with it for at least four weeks — some guys report that it makes them hornier as well as stronger.
Zinc is another good option. Several studies have shown that taking 50 mg of zinc citrate per day increases testosterone. In general, though, your training will have the biggest impact on your "T" levels, so keep doing heavy, compound exercises and be careful not to over-train. The more testosterone in your system, the stronger you'll get.