Because you need to take it 3 times a day as opposed to once in the morning like most other multi's. Vitamin sources for natural elements are absorbed much faster into the body, so to keep the vitamins in your body the whole day you need to take it in more regularly, like 3 times a day or every 4 hours. When it is not natural elements, you take it in once a day, before your system can even take it in, stomach acid destroy it and you literally just flush it out.
Additionally, when I use optimen I can actually feel the difference in my body, I feel better when I need to do any physical activity, hard to explain. Actually I am shy to admit it but I am very in touch with my body, any slight difference I notice. Like with these I will be more energetic most of the day, yet there is nothing in it that should give you more energy.
The real evidence however is, on the label, look in the () brackets after each vitamin which says where they source the vitamin from ect. You can then google those elements.