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U.S. stock market dips, led by health care stocks

Recent stock market volatility is "healthy"

Health care companies are leading stocks broadly lower in early trading on Wall Street as the market gives back some of its big gain from the day before. 

Drug distributor companies were especially hard hit morning Tuesday, after news broke that Amazon was seeking to expand its medical supplies business and that Walgreens Boots Alliance wants to buy the rest of AmerisourceBergen. It already owns a 26 percent stake in the company, which is one of the largest prescription drug distributors in the U.S. and also distributes products to hospitals and other health systems. 

Patterson Companies (PDCO) slumped 10 percent, and Cardinal Health (CAH) lost 4 percent. The drop came after the Wall Street Journal reported that Amazon was looking to distribute a variety of medial items. 

The S&P 500 fell 10 points, or 0.4 percent, to 2,645 as of 10 a.m. Eastern time. The Dow Jones industrial average lost 114 points, or 0.5 percent, to 24,486. The Nasdaq composite slid 18 points, or 0.3 percent, to 6,963. The Russell 2000 index of smaller-company stocks declined 8 points, or 0.5 percent, to 1,483.

Athletic gear maker Under Armour (UA) rose 17 percent after reporting better-than-expected sales, as shoe and accessory revenue picked up.