I was wondering the same thing. I started on Supreme Greens about four months ago, and at first I felt terrific, it gave me great energy. I was only taking half the recommended amount. Then I started taking the full amount (3 capsules twice a day) and now I am feeling tired and irritable, and don\'t know if there is a connection. So I\'m going to go to two pills twice a day instead of three and see if that makes a difference. I have friends who started taking it and say they like it. I don\'t know of any studies outside of the Dr.\'s who concocted this, although I don\'t see how it could hurt a person, I hate vegetables, so I thought it would help me as I had been feeling really tired before I started taking them. Maybe I\'ll change to one capsule three times a day. You can see I\'m undecided. I was even thinking of quitting them altogether for a while to see what would happen. I have a relative who is 91 years old and never took a vitamin or supplement in his life. He is a retired Navy doctor, and acts and looks and has the energy of a forty year old, so go figure. Maybe it\'s all in our minds, I don\'t know. Hope this helps. Feel free to write if you wish.