Can't blame private equity for sniffing around the vitamin retail industry, shares of the sector's main players have been crushed as people take to finding deals for nutritional supplements online. 

GNC (GNC) shares spiked as much as 11% on Friday morning after a report citing Dealreporter surfaced that private equity firm KKR has been in contact with Chinese pharmaceutical company Sinopharm and Chinese investment firm Fosun regarding GNC.

In February, GNC reported a $433 million fourth-quarter loss after the company closed all its U.S. stores to overhaul its pricing strategy. Same-store sales plunged 12% in domestic company-owned stores, and fell 6% in domestic franchise locations. Adjusted earnings per share was 7 cents, far off Wall Street's estimate of 36 cents a share.

Shares of GNC have lost more than 70% over the past 52 weeks.

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GNC rival Vitamin Shoppe hasn't been immune to fierce industry headwinds, either.

Vitamin Shoppe's fourth quarter earnings came in at 36 cents a share, badly missing forecasts for 40 cents a share. Same-store sales fell 2.2%, and the company warned that more challenging times are ahead.

"Our top line growth is not yet where we want it to be as fourth quarter comparable sales were disappointing, but generally in line with our expectations," said Colin Watts, CEO of Vitamin Shoppe (VSI) . "Although the external environment was more difficult than we planned coming into 2016, we made significant progress in rolling out initiatives tied to our reinvention strategy."

Vitamin Shoppe's stock has crashed 28% over the past year. 

But, the outlook for the sector isn't exactly dire. And based on now even lower valuations, the private equity guys could make a case that the time is right to pounce on nutritional supplement sellers. 

The U.S. vitamin and dietary supplement market was expected to grow by 5% in 2016 to sales of $27.6 billion, according to research from Euromonitor. The growth continued even though doubt over product safety and efficacy continued to be raised.

"Due to high healthcare costs and an increased emphasis on preventative care, consumers are willing to spend on vitamins and dietary supplements in addition to their regular foods to maintain their health," Euromonitor said in a September report.

An ageing American population and increasing consumer engagement with health and wellness should also help the industry longer term. The market is expected to generate revenues of $37.16 billion by 2024, according to Grand View Research.

There could even be a brighter future ahead for GNC in particular, Hamish Kumar from Integer Investments points out. The company has improved its strategy by overhauling its loyalty program and sharpening its prices, which consumers could start to appreciate over time.

GNC also launched on Amazon (AMZN) on Jan. 12, with sales looking "exceptional so far," Kumar said. Management is also looking at enhancing its e-commerce presence.

A boost from KKR could be just the medicine GNC -- and the beat up industry -- needs.

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