The Supplement Database is an ever-growing resource providing objective information to allow you to decide on which product best fits your needs.
The conclusion on these three ingredients falls in line with what we've previously found; there is very little evidence backing up their claim of increasing testosterone levels for the vast majority of people.
There is a good reason caffeine and beta-alanine are the two most popular ingredients found in preworkout supplements. There is plenty of research on both ingredients, and the research is overwhelmingly positive on their ability to improve workout performance. The same is not true for tyrosine. Verdict: caffeine and beta-alanine...