UPDATE 1-U.S. group sues Bayer over vitamin claims

* Center for Science in the Public Interest says filed suit

* Says Bayer made false claims about a vitamin supplement

* Bayer says has not been notified of suit

(Adds comments by Bayer spokesman)

WASHINGTON/FRANKFURT, Oct 1 (Reuters) - A U.S. advocacy group filed a lawsuit against German drugmaker Bayer AG (BAYGn.DE), saying the company made false claims about a vitamin supplement it makes.

The Center for Science in the Public Interest said on Thursday it believed Bayer falsely claimed that the selenium in Men's One A Day multivitamins might reduce the risk of prostate cancer.

The group filed the suit in the Superior Court of California in San Francisco.

A spokesman for Bayer said the company had not yet been notified of the filing. He said the company had based its advertising for the vitamin supplement on the U.S. Food and Drug Administration's claim that selenium could help reduce the risk of certain types of cancer.

The FDA earlier this year changed its stance on selenium and Bayer has been working on altering its packaging and advertising to remove any connection between selenium and a reduced risk of certain types of cancer. Shares of Bayer closed 2.8 percent lower at 46.05 euros. (Reporting by company news desk in Washington and Angelika Gruber in Frankfurt; Writing by Maria Sheahan; Editing by David Holmes)