FILE - In this July 17, 2014 file photo, Senate Consumer Protection, Product Safety and Insurance subcommittee chair Sen. Claire McCaskill, D-Mo., questions witnesses during a hearing on Capitol Hill in Washington. McCaskill is pushing some of the country’s largest retailers and online companies to drop dubious dietary supplements and vitamins, especially those promising seniors protection from memory loss, dementia and other age-related mental problems. (AP Photo/Lauren Victoria Burke, File)WASHINGTON (AP) — A high-ranking Senate Democrat is probing retailers and online companies about sales of dubious dietary supplements, especially those promising seniors protection from memory loss, dementia and other age-related problems.