The win helped Colorado stay 2 1/2 games ahead of Atlanta in the NL wild-card chase.
Helton's RBI single snapped a 3-3 tie with one out in the bottom of the fifth.
Winner Jorge De La Rosa (16-9) gave up three runs and four hits in five innings with three walks and eight strikeouts.
Closer Huston Street earned his 34th save, despite giving up two hits in the top of the ninth.
Albert Pujols led St. Louis with a three-run third-inning double. Julio Lugo added two hits for the Cardinals, who had clinched the NL Central with a 6-3 victory Saturday.
The losing pitcher was starter Kyle Lohse (6-9).
Copyright 2009 by United Press International.
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