(Reuters) - Kroger Co , the biggest U.S. supermarket operator, raised its full-year profit forecast and reported a better-than-expected 9 percent increase in quarterly profit on Thursday, helped by the acquisition of Harris Teeter Supermarkets Inc. But shares of Kroger, which also owns the Ralphs, Smith's and Food 4 Less grocery chains as well as online vitamin and supplements seller Vitacost.com, dropped about 1 percent after it announced only a modest rise in a key sales forecast. Shares recovered most of those losses, and Kroger was down 0.2 percent to $51.76 at 1:25 p.m. EDT. Kroger completed the $2.5 billion acquisition of North Carolina-based Harris Teeter on Jan. 29, adding more than 200 supermarkets, mostly in the southeastern United States. It closed its $280 million acquisition of Vitacost.com on Aug. 18. Kroger raised its adjusted earnings forecast for the year ending Jan. 31, 2015, to a range of $3.22 to $3.28 per share from the previous $3.19 to $3.27. Analysts on average were expecting full-year profit of $3.28 per share before the announcement, according to Thomson Reuters I/B/E/S. Kroger raised its forecast for an increase in same-store sales, excluding fuel, to between 3.5 to 4.25 percent from an earlier estimate of a 3-4 percent rise. This applies to supermarkets open without expansion or relocation for five quarters. "We are optimistic as we look forward to the remainder of the year, but keep in mind that we had a very strong fourth quarter last year to compare to," Kroger Chief Financial Officer Mike Schlotman said on a conference call with analysts. When pressed on why that sales outlook appeared to imply a slowdown in the back half of the year, an executive attributed Kroger's conservatism to those results and added that he did not expect significant changes to inflation, the economy or customer behavior. Kroger, whose rivals include Wal-Mart Stores Inc , Safeway Inc and Whole Foods Market Inc , is seen as one of the top performers in the hyper-competitive U.S. supermarket industry. As of Wednesday's close, Kroger shares were up more than 31 percent this year, outperforming the S&P 500 Food Retail Index <.SPLRCRETF>, which has risen just over 1 percent. Net income attributable to Kroger rose to $347 million, or 70 cents per share, in the second quarter ended Aug. 16 from $317 million, or 60 cents per share, in the same period a year earlier. Total sales rose 12 percent to $25.3 billion. Analysts on average had expected a profit of 69 cents per share and sales of $24.92 billion. Same-store sales, excluding fuel, were up 4.8 percent, higher than the 4.2 percent increase analysts polled by Consensus Metrix had expected. (Reporting by Siddharth Cavale in Bangalore and Lisa Baertlein in Los Angeles; Editing by Kirti Pandey, Paul Simao and David Gregorio)