Yes, there is a real difference in the quality of supplements. Two issues arise in the quality factor. The first is that supplement manufactures are not required to be overseen by an agency such as the FDA. Only the better one voluntarily submit to oversight by an unbiased agency and the cost is expensive. The second is the better supplements are plant-based derived, rather than synthetic laboratory origin.
Two of the better companies are the two we use are Zymogen and Pure. Neither can be purchased in stores. You can purchase these directly by clicking on the Wholescripts box above left for Zymogen, or the Fullscripts box above right for Pure, or several other great companies.