Good news coffee lovers: A recent study published in the International Journal of Dermatology found that caffeine stimulates hair shaft elongation and prolongs the growth cycle by blocking the effects of DHT, the hormone responsible for damaged follicle and hair loss. Not only that, but female hair follicles were found to be more sensitive and responsive to caffeine than male ones. And while we wish we could tell you that your morning cup of coffee habit is playing a role in your thick hair, according to Dr. Robert Dorin, a NYC-based hair restoration specialist, you'd have to drink close to 50 cups a day to see an effect—definitely not recommended. Look for leave-on hair products that contain the ingredient, or switch to a shampoo with caffeine, like Garnier Fructis Fall Fight Shampoo (just make sure to work it into your scalp and leave on for at least two minutes).