Key takeaways: But are supplements effective? And if so, what's the best hair supplement for men? Read on to learn what the science says. When it comes to supplements, here are some things to keep in mind: Vitamin or mineral deficiency: Hair loss caused by a vitamin or mineral deficiency (like vitamin B, iron, or zinc) will often improve after taking supplements to correct the deficiency. But, without an actual deficiency, there isn't much science backing up the claim that supplements can help.