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July 9 (Reuters) - Stifel Nicolaus downgraded Coca-Cola Enterprises Inc (CCE.N: Quote, Profile, Research) to "hold" from "buy", and lowered its estimates for the beverage bottler, citing the recent spike in corn prices and increased sales of vitaminwater at convenience stores.

The brokerage said vitaminwater is cannibalizing Coca-Cola and other fizzy single-serve soft drinks in convenience stores.

The weakening North American economy has been cutting into sales volume of the world's largest bottler of Coca-Cola Co (KO.N: Quote, Profile, Research) beverages, especially in higher-margin 20-ounce bottles, which are sold in convenience stores.

Stifel also lowered earnings estimates for Pepsi Bottling Group Inc (PBG.N: Quote, Profile, Research).

The brokerage said both Coca-Cola Enterprises and Pepsi Bottling are being hit by higher corn prices, increases in estimated PET costs and deteriorating demand for non-alcoholic beverages sold by both companies.

High-fructose corn syrup is a key beverage ingredient, while PET is used in plastic bottles. Last month, floods in the U.S. Midwest destroyed millions of acres of corn, sending prices to record highs.

The brokerage lowered its 2009 earnings estimate for Coca-Cola Enterprises to $1.26 from $1.46, and Pepsi Bottling to $2.37 from $2.53.

Shares of Coca-Cola Enterprises were down about 3 percent at $16.55 in early morning trade on the New York Stock Exchange, while Pepsi Bottling was flat at $27.88 on the NYSE. (Reporting by Eric Yep in Bangalore; Editing by Bernard Orr)