It seems Warren Buffett has healthcare on his mind as he approaches retirement. The 94-year-old investor's Berkshire Hathaway scooped up just over 5 million shares of UnitedHealth stock last quarter, securing a stake in the health insurer worth $1.6 billion at the end of June. The new holding was revealed in the conglomerate's quarterly portfolio update, known as a 13F, on Thursday. Business Insider tells the innovative stories you want to know Business Insider tells the innovative stories you want to know ...