There are no great places to find shelter from this market turmoil.

Stock prices are crumbling around the world, but the usual place for investors to go for safety, bonds, can’t provide as much cover as usual.

Bonds are still doing their job this year as investors’ best friends during a downturn: They’re holding up better than stocks, cushioning the blow for balanced investors. High-quality, investment-grade U.S. bonds have returned 0.9 percent through Wednesday, while the Standard & Poor’s 500 index has lost 7.4 percent on worries about the strength of the global economy.

The problem is that bonds are not doing as good a job as in past downturns, and the outlook for them is dim. Super-low interest rates mean bonds don’t pay investors much for the bonds they hold or are buying now. And those bonds may fall in price in the coming months and years if interest rates increase as the Federal Reserve, as expected, continues to move short-term rates higher.

“It’s just basic math,” says Chris Philips, head of institutional advisory services at Vanguard. “We’re at different levels today, and bonds don’t have as much room to grow on the price side.”

That means it will take longer for most investors — even those with a balanced mix of stocks and bonds — to recoup all their losses from this downturn for stocks.

The diminished expectations for bonds have investors looking for alternatives to protect their portfolios in case stocks keep falling. But financial advisers and mutual-fund providers say investmentgrade bonds, known also as fixed-income investments, are still among the best options available because the alternatives carry risks of their own.

Stock funds that track the S&P 500 have lost 10.1 percent since setting a record high May 21. Bond funds have largely held steady over that time, good enough to trim overall losses for balanced investor’s portfolios.

But unlike in past downturns — when bond funds were offering healthy returns — the protection provided this time has been only modest. The largest bond mutual fund, Vanguard’s Total Bond Market Index fund, has returned 0.8 percent in the nearly eight months since stocks began their tumble.

That same fund returned many times more than that — in a shorter period — the last time stocks had a slide big enough for market watchers to call it a “correction.” The Total Bond Market Index fund returned 5.3 percent in just over five months when the S&P 500 was in the midst of losing 18.6 percent from April 29, 2011 through Oct. 3, 2011.

The professional investors who manage the popular mutual funds that target specific retirement dates are sticking with investment-grade bonds, despite the muted forecasts. Fidelity’s fund built for workers planning to retire in about five years keeps 26 percent of its portfolio in investment-grade bonds, for example. It has only a sliver, 3 percent, in high-yield bonds.

Many strategists say investors just need to get used to lower returns, not only from bonds but also from stocks, after their big gains in recent years.

Research Affiliates, which manages about $160 billion of assets, expects investment-grade U.S. bonds to return 1.2 percent more than inflation over the next decade, on an annualized basis.