Dannon has vowed to fight the class action filed in a Californian court accusing it of making unsubstantiated gut and digestive health claims. The US arm of French food giant Danone stated it "strongly disagreed" with the allegations and "proudly" stood by the nutrition claims it makes on its probiotic spoonable (Activia and Activia Lite) and drinkable (DanActive) yoghurts products, and the science that backs them up.

The action, mounted by two law firms — Stoia Geller Rudman & Robbins and Mager & Goldstein — accuses Dannon of spending more than $100 million advertising claims about its probiotic yoghurt products repudiated by a clinical trial it sponsored. The class action seeks reimbursement for all probiotic Dannon purchases by US consumers and calls on Dannon to mount a corrective advertising campaign.

In response Dannon stated: "The filed complaint does not contain any support for the broad generalisations made in the lawsuit. The one publication cited in the lawsuit does not disprove Dannon's scientific substantiation for its proven product benefits. Indeed, the report cited in the lawsuit, published by the American Academy of Microbiology, does not even reference any Dannon products."

The court action claims the Danone-funded study called "Probiotic Microbes: The Scientific Basis" demonstrated consuming probiotics has no tangible health benefits.

Dannon added: "All of Dannon's claims for Activia and DanActive are completely supported by peer-reviewed science and are in accordance with all laws and regulations. Dannon's advertising has always been and will continue to be absolutely truthful, and Dannon will vigorously challenge this lawsuit."

Although only launched in 2006 (Activia) and 2007 (DanActive) Dannon's probiotic division expects to account for 40 per cent of Dannon's yoghurt sales in 2008 as American consumers warm to the purported benefits of probiotic bacteria.

Industry will be concerned that the legal action and extensive media coverage could damage a sector that has been slow to lift off but is now finally booming with many other companies launching probiotics yoghurts, drinks and other products. It is estimated the market is worth more than $400 million, with Activia and DanActive, along with Danone-owned Stonyfield Farm probiotic yoghurts, accounting for 80 per cent of that figure.