A new memo from U.S. health regulators is raising questions about a recent decision to authorize the first fruit-flavored e-cigarettes for adult smokers. The Food and Drug Administration document posted online this week shows that adding flavors like mango and blueberry didn't help smokers quit when compared with older, tobacco-flavored vapes. The memo provides the first detailed look at how the FDA made its decision to approve the e-cigarettes from a small California vaping company. The decision marked a first for the agency and has been heavily criticized by health groups and lawmakers.