What is the best possible way to verify claims a manufacturer makes about a supplement's safety and effectiveness?

The best possible way to verify claims a manufactures makes about a supplement's safety and effectiveness would be to go to the manufactures website and look at the reviews, research the studies behind their product and ask around. Since supplements are usually regulated by the FDA, manufacturers are basically given the "honor system" to provide accurate information to consumers. Doing your own research will help immensely. If you ever see something on a supplement(s) that says, "This statement has not been verified by the Food and Drug Administration", I would take it at my own risk.

Africa has 54 countries

Dialect is probably part of the answer