Do nutritional supplements really work?

I ask this question because everyone involved with marketing a nutritional product says their products work.  Exactly what does that mean?  Do they provide the benefits that the customer is looking for with their health?  Or is the company only interested in promoting itself thru distributors and really not interersted in helping people get results?   Do you have to take tons of it to get results? (Many companies have gone to the wayside because of this).  Since there are so many nutritional supplement companies out there, which one makes for a good opportunity to represent?   Is price the best indicator that a product is superior over the competition?

   Consider this:  How much science does the company really promote when talking about its products?

                         How much research can they provide proving that their products work?

                         Are there any clinical trials, double-blind placebo tests performed to state their case?

                         Who endorses their product?  Professional organizations, research organizations etc..

   The problem I feel with these nutritional companies is a lack of information promoted by the company itself as well as its distributors knowing themselves what the company has.  Simply getting people to take your product and NOT getting any health results  isn't going to build you a sustainable business.  As others have said "if the product works, price is not an option".  (I agree).  You don't need to be a registered dietician to explain your products, but you do need to know everything about the company, and its mission!  

   I welcome your thoughts!