MEC has worked with the French dairy and beverage company company since October 2006. It pitched against Havas Media-owned MPG.
Danone, which owns brands including Actimel, Activia and Shape as well as Evian, and V Energy Drink, is reviewing its media arrangements in 19 other European countries.
Recently the ASA banned an Actimel ad on the grounds that there was insufficient evidence to support claims that it improves children's health.
Last month the company agreed to reimburse consumers for Activia and DanActive yoghurt purchases in order to settle a class-action lawsuit that accused it of overstating health benefits in ads.
The company spent £25m on media last year according to figures from The Nielsen Company. WPP owned MEC has held the account since October 2006. The agency also holds local market accounts in Hungary, Romania and Turkey.