Can protein make your beard grow thicker/fuller?

No: It's your genes. About 5% of men, myself included, can't grow a beard or chest hair. Many women prefer this, and guys like us usually don't go bald. Joel kinnaman (failed beard, photo), paul newman, muhammad ali and larry bird are all smooth-faced guys. They don't seem unhappy over it. Your genes are your heritage and for you to enjoy. You're a guy; looking good is 95% about fitness.