"When consumers see or hear an advertisement, whether it’s on the Internet, radio or television, or anywhere else, federal law says that ad must be truthful, not misleading, and, when appropriate, backed by scientific evidence. The Federal Trade Commission enforces these truth-in-advertising laws, and it applies the same standards no matter where an ad appears – in newspapers and magazines, online, in the mail, or on billboards or buses."

and:

"Statements that are literally true may be deceptive if they leave a misleading impression".

Unfortunately, the first step the FTC takes if they even get around to it is to direct the advertiser to remove such statements. No fines are levied if the advertiser complies with this request.