The advert wrongly implied that Danone's popular Actimel product could help prevent children from catching bacterial infections, said the UK Advertising Standards Authority (ASA), upholding complaints from five viewers.
Its ruling is another example of the fine line food and drink firms must tread when making claims about their products, particularly as functional food trends move further into the mainstream.
Danone's advert showed a mother telling her child to stop licking the window of a bus, because it was dirty. The ad moved to another scene showing how probiotic bacteria in Actimel plugged holes in the consumer's gut, enabling it to repel bad bacteria.
The ASA said these images, coupled with claims such as "Actimel helps to support their natural defences", could mislead consumers. The authority did accept Actimel had a proven probiotic effect, however.
Both Danone and the Broadcast Advertising Clearance Centre actively opposed the complaints to the ASA.
The dispute shows how interpretation and inference may continue to cause uncertainty for food firms looking to make health claims on their products, despite new EU health claims legislation designed to tighten up the practice.
Consumer wariness of health claims in both the EU and US remains a major barrier to growth in functional food markets, research group Datamonitor reported recently.
Danone said independent medical experts supported the claim that Actimel in children "tops up their natural good bacteria making life harder for the bad bacteria".
Sales of Actimel have soared in the UK over the last five years as consumer awareness of probiotic products has grown. It is now established as one of Danone's 'blockbuster brands' and was named the fastest growing food brand in the UK in 2004, by AC Nielsen.
Some scientists have recently expressed skepticism about the perceived health benefits in some probiotic products.
But their rising popularity appears to have continued unabated for now. In dairy, probiotic yoghurt drinks have continued to spearhead strong growth in the UK yoghurt sector, a recent report from Mintel said.