The subject of what lurks inside the human gut had not attracted much in the way of conversation beyond microbiology circles until recently. The commercial success of a number of probiotic products has changed all that, with hundreds of thousands of people now prepared to pay to “top up” the “good bacteria” in their bodies with reinforcements. The claims made for probiotics include a role in helping to treat conditions as varied as Crohn’s disease, irritable bowel syndrome, rheumatoid arthritis, chronic tiredness or teenage acne. Rigorous scientific assessments of the benefits of these competing supplements has been slow in coming, but clear-cut benefits are emerging.

A number of leading researchers in the field, including Professor Glen Gibson, of the University of Reading, outlined yesterday their latest conclusions on a rapidly expanding industry. These are broadly positive and could represent an advance in the prevention of illness. There are “good bacteria” and their relative strength is a significant factor in a person’s health. Almost everyone can be assisted but probiotics are particularly useful for those on antibiotics or over the age of 60. Scientists also believe that they can be employed to lower significantly the chances of patients enduring hospital acquired infections.

That does not, nevertheless, mean that every product which advertises itself as a probiotic is equally valid. While the researchers concluded that well-known names, such as Yakult, Vitality and Actimel, are worthwhile, many of those that are retailed exclusively on the internet or in the more esoteric fringe of the health food shop sector are distinctly dubious. Their estimate is that about half of the 50 products that are marketed as probiotics are pale imitations of probiotics.

The regulation of products sold on the internet is a notoriously complicated question. It is hard to prevent cyberspace becoming the domain of snake oil salesmen. Bodies such as the Food Standards Agency may, therefore, be better advised to publicise the names of those brands that they consider to be correctly labelled and allow consumers to reach the conclusion that anything else is not to be trusted. An important innovation should not be undermined by mis-selling.

There is a far broader public health point here. Reaching a consensus on what substances are unhealthy and how bad they are has proved a contentious business. The argument over how much is too much salt is a classic example. The “traffic light” system of labelling food has encountered difficulties. It might be better to place more weight on highlighting the positive instead of arguing about the negative.