My experience, Fo ti (He shou Wu) has worked quite well for darkening hair, and reducing grey hair. I'm a 50 something male, had about 20 to 25 percent grey, mainly on top and on the sides. I reduced it to about 5 to 10 percent in a few weeks. I purchased some of the prepared root from a vendor on Ebay in China. Here's what worked for me. The root is quite leather like and dark when you get it. I would take 5 or 6 pieces of the root and brew my cup of coffee into it and let it soak overnite. Drink the coffee the next day. I do that 2 or 3 times a day. When the root softens up enough, I put it in the coffee grinder and break it down as much as possible, and then drink that in with my coffee the next few days. Been doing this for a few weeks, and have noticed quite a difference, my brown hair has darkened and I notice alot of new hair growth that is dark. I plan on continuing it for about a month on and then a month off, month on, month off. It's a somewhat gradual process, I would give it a month or 2 for results. I didn't experience any negative side effects.