Agricultural commodities such as corn, wheat and soybeans plunged Tuesday as a surge in oil prices sent traders scurrying for the safety of precious metals and government bonds.

With oil futures surging 7% in New York trading to $98, riskier assets took a beating. Stocks dropped almost 2%, while the price of copper slid almost 3% and some of the food commodities dropped more than 4%.

The turn is noteworthy because these prices have generally been rising sharply for the past six months, since the Federal Reserve said it would support the U.S. economy by buying government bonds.

Meanwhile, gold rose to within a few dollars of $1,400, while silver edged toward $33, its high since 1980. The yield on the 10-year Treasury note dropped to 3.48%.

Of course, a one-day reversal in the commodities rally won’t spell relief for those getting pinched by rising food prices.

Even after the selloff Tuesday, the price of the near-month corn future is up 62% over the past year, driven by robust global food demand, rising ethanol use and surging prices of other, competing commodities. Organizations such as the World Bank have been warning of a food crisis in poor countries as rising prices shove millions into poverty.

At the same time, central bankers around the world have been eager to talk a big game about tamping down inflation, without showing any inclination to actually do anything. China, for instance, has repeatedly raised bank reserve rates — a step widely seen as ineffective in controlling speculation in an economy where real interest rates, adjusted for inflation, are negative.

Negative real rates are often associated with bubbles of various sorts, as those who enjoyed the housing bubble in this country will recall.

So there’s no particular reason to expect food prices to keep falling even if a more acute crisis does develop in the Middle East.

But if nothing else, Tuesday’s action shows that even in a world of scarce resources and central bank support for asset prices, there is no trade that goes only one way for long.

Also on Fortune.com:

• How Egypt spells oil price spike
• Here comes $4 gasoline
• Food spike puts 44 million in poverty