Bulbine natalensis may increase testosterone in rats but has limited human evidence and potential liver toxicity.

“things like Bulbine natalensis, which definitely has support for increasing testosterone but all the studies were in rats, I think there is some evidence in humans but the evidence mainly comes in the form of what we call sponsored research, so companies paying for research, which is different than independent research by people who are not biased in terms of the outcome, and the reason I didn't throw out things like Bulbine natalensis is they seem to have liver toxicity similar to high levels of anabolic exogenous steroids”