Herbalife Ltd. has retained financial and legal advisers to help it review an acquisition proposal by private equity firm Whitney V LP the first acknowledgment the offer is being taken seriously, despite criticism it is too low.

The Los Angeles nutritional supplement company, which created a special board committee to review the proposal, has hired Goldman Sachs as its financial adviser and two Los Angeles law firms to serve as legal advisers: Gibson, Dunn & Crutcher LLP will advise the company; Munger, Tolles & Olson LP will advise the special board committee.

The company received the offer Feb. 2 from Whitney, which owns about 27 percent of Herbalife's outstanding stock. Whitney, whose managing director Peter Castleman is the chairman of Herbalife, offered to buy Herbalife for $38 per share in cash, or a 15 percent premium to the share's closing price the day of the offer. Some industry analysts consider a fairer valuation of the company to be more than $40 a share.

Herbalife shares on Wednesday fell $1.31, or 3 percent, to close at $38.49 on the New York Stock Exchange.