Big U.S. banks had enough capital to weather a potentially severe economic downturn but some of their risky businesses could hypothetically take a major hit this year, according to results of the Federal Reserve's annual stress test.

The 31 banks that participated showed they could withstand a spike in joblessness and stresses in the commercial real estate market and still have enough capital available to lend.

Their common equity tier 1 (CET1) ratio, a metric that gauges high-quality capital, will dip to 9.9% at its lowest, still far ahead of the 4.5% minimum requirement.