Shares of Herbalife Ltd soared Monday after the Los Angeles health supplement maker said that its largest shareholder had made a bid to take the company private.

Whitney & Co.’s $38-per-share offer values the company at $2.7 billion, and is 15 percent more than the closing price of Herbalife shares on Feb. 2, when news first broke of the offer. Connecticut-based Whitney has a 27 percent stake in the company, which sells its products via a global independent distributor network.

Herbalife shares closed up $7.02, or 21 percent, to $40.12 on the New York Stock Exchange. Investors may have been listening to A.G. Edwards & Sons Inc. analyst Andrew Speller, who in a note to clients said Whitney was taking advantage of the significant drop in Herbalife’s stock price after the company lowered its 2007 outlook a month ago.

Speller urged Herbalife’s board to reject the offer, arguing that the company should be valued in the mid-40s.