(Adds analyst comment, updates prices to close)
* TSX ends down 62.43 points, or 0.42 percent, at 14,980.72
* Eight of the TSX's 10 main groups lower
* More advancing issuers than decliners, despite overall slip
By Alastair Sharp
TORONTO, May 13 (Reuters) - Canada's main stock index fell for a third straight session on Wednesday, with heavyweight energy and railway companies among the biggest losers as crude prices slipped and investors worried about economic growth.
The Toronto Stock Exchange's S&P/TSX composite index ended down 62.43 points, or 0.42 percent, at 14,980.72. Eight of the ten main sectors were lower.
"Valuations have been somewhat stretched and we wouldn't be surprised to see a correction somewhere along the way here," said Michael Sprung, president at Sprung Investment Management.
Canadian National Railway Co was the heaviest weight on the index, with the country's biggest railway off 3.2 percent at C$74.11. Canadian Pacific Railway Ltd was not far behind, falling 2.4 percent to C$214.26. The railways are in the index's industrials group, which retreated 1.2 percent.
Sprung said investors had priced the railways assuming economic growth that now appears unsustainable.
Energy stocks fell 0.6 percent, as a rallying U.S. dollar pushed oil prices lower. In the group, Encana Corp fell 2.2 percent to C$16.30 and pipeline company Enbridge Inc lost 0.9 percent to C$61.04.
"Overall, stock markets are struggling here," said Colin Cieszynski, senior market analyst at CMC Markets Canada, citing the latest U.S. data pointing to a struggling recovery in Canada's largest export market.
"U.S. retail sales disappointed, which is still continuing to raise questions about the health of the U.S. economy," he said.
All but the materials and utilities groups gave back early gains. The index's financial sector, home to banks and insurers, was down 0.2 percent, with Sun Life Financial Inc falling 0.9 percent to C$40.63.
The most influential positive movers on the index included Barrick Gold Corp, which led a number of gold miners into positive territory. Barrick rose 2.8 percent to C$15.84, while Goldcorp Inc advanced 2.2 percent to C$23.24.
The overall materials group climbed 0.7 percent.
"In general, materials have not participated with the broader market in the last while. We may be seeing some of the money coming out of other sectors going into materials," Sprung said.
Gold miners were helped by higher gold prices, which rose on the back of a weaker greenback. Gold futures rose 2.2 percent to $1,215 an ounce.
Despite the overall index slip, there were more advancing issues than decliners, at a 1.03-to-1 ratio on the upside.
$1 = $1.20 Canadian Additional reporting by Solarina Ho in Toronto; Editing by Peter Galloway and Matthew Lewis