Berkshire Hathaway's $1.6 billion stake in UnitedHealth Group is helping to lift the Dow Jones Industrial Average to a new record as investors pile into healthcare sector funds.

Buffett's vote of confidence comes as UnitedHealth faces a challenging year. The stock had fallen nearly 50% through Thursday, weighed down by rising healthcare costs, a Justice Department investigation into Medicare billing practices,

Shares of UnitedHealth Group surged nearly 14% on Friday after billionaire Warren Buffett's Berkshire Hathaway bought 5 million shares of the company, providing a shot in the arm for investors who think the health conglomerate will turn around under its new CEO.