I started buying this over a year ago. It's really helped with my immune system and a bit with energy. I have fibromyalgia and get colds easily. When I take this daily, I notice a slight improvement in energy (and you'll take any improvement when you have fibromyalgia) plus I avoid or get mild colds. When I forget to take it, I notice a slight drop in energy. I just waded through a 5-day cold since I was out of this. Just placed an order for 2 bottles.