Ronkonkoma-based supplement and vitamin maker NBTY Inc. announced Monday it had acquired Balance Bar Co. for $78 million from private equity firm Brynwood Partners.

NBTY will finance the purchase with a revolving line of credit, according to an SEC filing from the company. Balance Bar, based in upstate Valhalla, makes and distributes nutritional energy bars.

"Balance Bar is a good strategic fit within our existing portfolio of sports nutritional bars . . . and that was the reason why we made the acquisition," said Andrea Staub, a spokeswoman for NBTY.

Nutrition bars that NBTY currently makes include Pure Protein, Good 'n Natural Bars and Met-Rx. In October, NBTY opened a new facility in Amityville to make sports and nutritional bars. The 66,000-square-foot plant can produce one million bars a day and was built with $750,000 in state aid.

NBTY has plans to expand Balance Bar's distribution in the coming months so its products will be available in more stores, Staub said.

Nutritional bars have become increasingly popular with consumers since companies began expanding flavor varieties in 2005, said Caitlin Moldvay, a senior analyst with market research group IBISWorld. The industry was also largely unaffected by the recession because of its low prices.

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In recent years, concerns about obesity and the convenience of an on-the-go snack have driven growth for nutrition bars, Moldvay added.

NBTY is owned by private equity firm The Carlyle Group. The company was publicly traded until it was bought for $3.8 billion and taken private in 2010; it employs about 2,600 people on Long Island.

Balance Bar was founded in 1992 and was owned by Kraft Foods Inc. when Brynwood Partners bought the company in 2009.