While the stock market has largely treaded water so far this year, healthcare shares have scored solid gains.

The S&P 500 Health Care Index has generated a total return of 4.5 percent year-to-date, compared with 1 percent for the Standard & Poor's 500 Index as a whole. The Health Care Index has returned 27.6 percent during the last year, compared with 20.9 percent for the S&P 500.

The winners include old-line defensive stocks such as Merck, UnitedHealth Group and Johnson & Johnson, The Wall Street Journal reports. They also include new-fangled growth stocks, such as Biogen Idec, Gilead Sciences and Celgene.

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"The healthcare industry is going through a fundamental change," Eddie Yoon, a portfolio manager at Fidelity Investments, tells The Journal. "There are ways to get offensive and defensive within the sector. It fits both categories."

The rise of biotech shares coincides with the industry's growing importance in medical treatment.

Pharmaceutical companies now make up 47 percent of the healthcare industry, down from 55 percent five years ago, Jeffrey Rubin, director of research at Birinyi Associates, told The Journal.

And biotech companies account for 23 percent of the S&P 500 Health Care Index, up from 10 percent five years ago.

"When healthcare outperforms in panic-driven bear markets, that's not a huge surprise," says Doug Ramsey, chief investment officer at Leuthold Weeden Capital Management. "But when a defensive sector outperforms significantly in a roaring bull market, there's something more going on there.

"Healthcare stocks are still cheap on a relative basis in a market that is no longer cheap," he adds.

Susan Aluise of InvestorPlace lists three stocks that she thinks will benefit from Obamacare: Molina Healthcare, a managed care company; Magellan Health Services, another managed care company; and Cerner, a health information services company.

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