* MEMC shares rally after results
* Dean Foods to spin off unit, shares jump
* BoE cuts Britain's growth forecast
* Indexes off: Dow 0.1 pct, S&P 0.2 pct, Nasdaq 0.3 pct
By Rodrigo Campos
NEW YORK, Aug 8 (Reuters) - U.S. stocks dipped on Wednesday following three days of gains on Wall Street as traders awaited more signals about central bank action in support of a stalling global economy.
Growing expectations the European Central Bank could act soon to contain the euro zone's debt crisis and a Federal Reserve seen ready to take stimulus measures have triggered a recent rally in equities, with the S&P 500 up for a fifth week running.
However, the Bank of England gave little indication that it would rush to pour in further stimulus even as it sharply cut its forecast for medium-term economic growth in Britain.
Spanish benchmark 10-year yields briefly rose above 7 percent, underscoring the cautious tone from investors recently disappointed by lack of coordination from European officials in their efforts to reignite the economy.
The market is jittery again as a result of ongoing problems in Europe, according to Kim Forrest, senior equity research analyst, Fort Pitt Capital Group in Pittsburgh.
"Spanish yields are up and I think there's still a lot of nervousness about how Spain gets resolved," she said.
Markets are pricing in the idea that it may take time until Spain asks for a bailout, which would open the door for ECB intervention.
The Dow Jones industrial average dipped 13.93 points, or 0.11 percent, to 13,154.67. The S&P 500 Index shed 2.94 points, or 0.21 percent, to 1,398.41. The Nasdaq Composite dropped 8.38 points, or 0.28 percent, to 3,007.48.
The S&P 500 would have to close above 1,400 with significant volume and have some follow-through to convincingly clear that resistance, according to Art Hogan, managing director of Lazard Capital Markets in New York.
The benchmark closed above 1,400 on Tuesday for the first time since May 2.
Shares of Dean Foods, which is spinning off a unit, jumped 34.5 percent to $16.70 a day after the U.S. dairy company posted a stronger-than-expected quarterly profit.
Shares of MEMC Electronic Materials Inc rallied 34 percent to $2.76 after the silicon wafer maker reported a surprise quarterly profit on an adjusted basis.
Williams Partners shares dropped 4.2 percent to $50.84 after the company announced the offering of 8.5 million common units.