GNC Holdings Inc., the parent company of multichannel retailer General Nutrition Centers, cites the strength of it e-commerce channel as one of its leading prospects for growth as it starts trading public shares on the stock market. Its shares were trading at over $17 at mid-day today on the New York Stock Exchange after debuting yesterday at an offering price of $16.

“We believe GNC.com is positioned to continue capturing market share online, which represents one of the fastest-growing channels of distribution in the U.S. nutritional supplements industry,” the retailer says in the S-1 initial public offering statement filed with the Securities and Exchange Commission.

GNC, No. 237 in the Internet Retailer Top 500 Guide, posted a 26% rise in web sales last year to $59.0 million, up from $46.8 million in 2009, the company says in the IPO document. By comparison, total retail sales last year increased 7% to $1.344 billion, up from $1.256 billion in 2009.

GNC’s comparable-store sales—a calculation that includes the retailer’s e-commerce sales in addition to sales from stores open at least a year—were up 5.6% last year. GNC operates 7,200 stores in addition to GNC.com.

GNC says it plans to use the more than $300 million gained in its IPO to pay down debt.

GNC competes directly against Vitamin Shoppe, No. 177 in the Top 500 Guide, which completed its IPO in October 2009.