A new evaluation by Nutrimedia, a project that scientifically analyses the veracity of messages concerning nutrition, has found that the consumption of probiotics may help prevent the onset of colds and, therefore, that this message may be true. The studies evaluated show that taking probiotics, either in the form of foods containing these “good bacteria” (mainly yoghurts and other dairy products) or as food supplements, may reduce the number of colds and their duration among the general population.

The common cold is the most common disease. Each person suffers an average of more than two colds a year and children even more. To prevent getting cold, in addition to trying to minimize contact with infected people or handwashing, some news items spread the message that the consumption of probiotics may contribute to preventing the disease among the general population, which the new Nutrimedia study shows may be true.

When analysing the number of persons affected by at least one cold or similar infection, it was noted that there were fewer among those who took probiotics than among those who did not (34 compared to 44 colds per 100 people). In addition, the duration of the process was reduced by 1.2 days on average among those who took probiotics. However, in both cases the certainty of this evidence is low and will require contrasting with future studies.

Nutrimedia is a project of the Scientific Communication Observatory of Pompeu Fabra University and the Iberoamerican Cochrane Center that evaluates the degree of certainty of scientific evidence on food and health. This evaluation of probiotics to prevent colds is based on a recent Cochrane review, which also shows that these microorganisms likely help reduce the number of children taking antibiotics to treat colds and other acute upper respiratory infections.

Probiotics are defined as live microorganisms that, when taken in adequate amounts, may provide health benefits. Although the mechanisms of these beneficial health effects are not well understood, there is limited evidence that probiotics are useful in treating infectious diarrhoea, preventing antibiotic-associated diarrhoea, and treating vaginal infections in pregnancy.

The adverse effects of probiotics have been studied in 8 of the 23 clinical trials analysed in the review, which include a total of 2,456 participants. These adverse effects were scarce and mild; for the most part, gastrointestinal symptoms, such as vomiting, gases (flatulence), diarrhoea, and intestinal pain.

Proposals to improve the methodology of studies on the effects of probiotics on colds

Studies on the effects of probiotics on colds and other similar infections offer results with a low degree of certainty for the main benefits and risks analysed, as shown by the evaluation. This is mainly because the participants in the clinical trials could know which treatment they were receiving and some trials suffered methodological shortcomings. In addition, the size of some trials was very small and the data for some of the benefits analysed come from only one or two studies. “Larger, better-designed studies are needed to better estimate the beneficial and potential detrimental effects of the use of probiotics”, the Nutrimedia review concludes. “Likewise, these studies should not have links with the companies that manufacture the probiotics analysed”.

Further information:

You can read the full review and download the PDF of the technical report here.

Nutrimedia (www.upf.edu/web/nutrimedia) is a project of the Science Communication Observatory of Pompeu Fabra University (OCC-UPF) and the Iberoamerican Cochrane Center (CCIb), with the collaboration of the Spanish Foundation for Science and Technology of the Spanish Ministry of Science and Innovation, which scientifically evaluates the degree of truthfulness of some messages about food and health (news, advertisements, myths and questions from the public). The results of the evaluations, which are published on the project website, are intended to provide scientific data and criteria to help citizens make informed decisions concerning nutrition. The OCC-UPF is a special research centre for the study of the transfer of scientific and technological knowledge to society. The CCIb is one of the international centres of Cochrane, a global organization whose systematic reviews have helped to transform decision-making on health interventions.