Advertising authorities in the UK received a complaint about an advertisement for the Yakult probiotic drink, headlined 'Why friendly bacteria works for a girl'.
The accompanying text claimed: "During your period, you're more prone to an upset tummy. Did you know that friendly bacteria could help?".
Yakult UK said the symptoms of 'menstrual syndrome' were well documented and showed that many women experienced diarrhoea and constipation. It said consumption of the drink resulted in an increase in faecal moisture content in healthy individuals and showed beneficial effects on patients with chronic constipation.
The firm also sent a letter from an academic physician, acting as a consultant, who asserted that there was a reasonable body of evidence to show that a substantial number of normal life variations could give rise to a change in the balance of intestinal bacteria and that these could be associated with disturbances in gut function such as constipation, bloating and abdominal discomfort.
He admitted that although there is no absolute proof available for the association, these temporary problems are difficult to study in clinical trials.
But experts advising the UK's ,a href="http://www.asa.org.uk"target="_blank">Advertising Standards Authority said the evidence submitted did not prove the symptoms related to menstrual syndrome in healthy women were caused by, or contributed to, variations in gut bacteria, or that the product successfully treated menstrual syndrome in healthy women.
It was also concerned that the advertisers had not sent evidence to explain the cause of menstrual syndrome, or studies to prove that the product had successfully treated menstrual syndrome in otherwise healthy women.
It has advised Yakult not to repeat the claim unless it gains substantiation to prove it.
According to the consulting doctor, Yakult is undertaking serious studies in this area. The firm was unavailable to comment.