First it was Jamie Lee Curtis flogging Activia yoghurt, and its, uh, ability to restore digestive regularity.

Now New Zealand brewer Tui has shattered one of the great myths of the sexes, with a billboard that reads, "Chicks never fart. Yeah, right.”

A survey of almost 600 women was carried out by Anchor's low-fat probiotic yoghurt brand Symbio, which is promoting a 14-day programme to reduce digestive problems.

The company says the programme - run through www.abetteryou.co.nz - has already registered 10,000 people.

The study of digestive health has found that 45 per cent of women experienced gas at least two to three times a week, but only 12 per cent of women are likely to tell their friends they're experiencing some sort of discomfort, even though three-quarters feel embarrassment when it strikes during social situations.

Sue McCarty, chief executive of the Auckland-based Via finishing school, said it was a "complete myth women don't pass wind."

For those suffering, her advice was: Better out than in. She said women here had less to be concerned about. "We're in New Zealand, remember. Lots more things are acceptable here than in other cultures."