Probiotics proved better than placebo at reducing cold symptoms, clinical trial suggests

By Adi Menayang

- Last updated on GMT

Getty Images / Jay Zynism
Getty Images / Jay Zynism

Related tags Probiotic Common cold Placebo Upper respiratory tract infection Yogurt

Chinese researchers linked probiotic supplementation to fewer incidence of flu-like symptoms in new study, building the science backing probiotics’ benefits to the upper respiratory tract.

Study participants supplemented with a probiotic blend delivered in a yogurt drink had fewer incidence of flu-like symptoms in a 12-week study period compared to participants given a placebo, according to a study​ published in Synthetic and Systems Biotechnology​.

The researchers, affiliated with several universities in Beijing as well as Indiana State University, investigated the effects of probiotic supplementation who have contracted the common cold four or more times in the past year.

“Numerous studies have illustrated the effects of the intestinal microflora on the functioning immune response, therefore, it seems reasonable that changing the microflora with probiotics could potentially modulate the immune response and, in fact, improve the immune status of individuals,”​ they wrote.

Probiotic versus placebo

The investigational yogurt drink contained probiotics from Denmark-based global supplier Chr. Hansen​. In addition to starter strains Lactobacillus bulgaricus, Streptococcus thermophiles, ​and Lactobacillus paracasei, ​the drink also contained Chr. Hansen’s branded probiotic strains Lactobacillus casei​ 431 and Lactobacillus fermentum ​PCC.

Meanwhile, the placebo drink only contained two of the starter strains (Lactobacillus bulgaricus ​and Streptococcus thermophiles​) without the two branded strains included in the probiotic drink.

The double-blind, randomized, placebo-controlled trial was conducted in a single center. The 134 study participants were selected if they have had the common cold or influenza-like respiratory illness at least four times in the previous year.

They were randomly allocated to either a probiotic versus placebo group, with 67 participants in each. All participants had their blood and fecal samples collected at the beginning and end of the 12-week trial.

During the study period, each participant received 150 ml per day of either placebo or probiotic drink, to be taken after lunch for a total of 12 weeks. To measure compliance and the participant’s health and wellness, the researchers used a daily questionnaire.


By the end of the study, 11 participants from the placebo group had influenza-like illness with body temperature higher than 38 degrees Celsius and at least one of the upper respiratory infection symptoms (like cough, nasal congestion, headache, etc.).

Meanwhile, only three from the investigational group reported these symptoms.

Additionally, the average days of the symptoms was statistically less among the probiotics group compared to the placebo.

“The findings of our study indicate that the combination of probiotics (Lactobacillus paracasei, Lactobacillus casei 431 and Lactobacillus fermentum PCC) could reduce the incidence of the upper respiratory infection,”​ they wrote.

Analysis of blood serum suggested that the benefit may come from increased level of the cytokine IFN-Y, linked to a human’s immune support, that followed probiotic supplementation.

“Though there is good evidence that probiotics stimulate the immune system, additional in vivo studies are needed to confirm that probiotic-mediated immune stimulation can promote prolonged resistance to various infections and diseases in humans,”​ they added.

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Source:Synthetic and Systems Biotechnology
Published online ahead of print,
Prospective study of probiotic supplementation results in immune stimulation and improvement of upper respiratory infection rate
Authors: Hong Zhang, et al.

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