American colonists used a very different recipe for root beer than we know today from brands such as A&W and Barq's. As some of its key ingredients have been deemed unsafe to consume by the Food and Drug Administration, selling authentic root beer is off-limits to the general public for this reason.

Although brewers' mixes differed, commercial root beers usually featured the sassafras tree or the sarsaparilla vine to give their root beer its distinctive taste. However, that all changed in 1976 when the FDA revealed that the safrole inside these two plants could cause cancer, outlawing food products that utilized safrole, sassafras, and sarsaparilla.

The unconventional study involved feeding rats some 32-odd bottles of root beer daily, and after consuming this amount of the product, the rats consequently showed signs of liver cancer. At the very least, the U.S. isn't alone in its vendetta against sassafras, as AllRecipes reports that the European Commission on Health also banished the ingredient for the same reason.

Interestingly enough, McGill University reports that modern studies have not been able to verify safrole as carcinogenic. Despite all the counter-evidence or the questionable notion that the average person would consume 32 bottles a day, the FDA's regulation is unlikely to be overruled, so sassafras and sarsaparilla will remain forbidden from commercial root beer.