Probiotics VS Colds

According to the National Institute of Allergy and Infectious Diseases, 1 billion common colds occur annually in the United States. The socioeconomic cost of these noninfluenza viral respiratory tract infections is high, with direct and indirect costs of $40 billion per year.

While many patients take OTCs for symptomatic management of colds, others use supplements such as high-dose vitamin C, zinc, and Echinacea. Recently, probiotics have also been studied to assess their potential efficacy in combating respiratory diseases, including the common cold. Although their mechanism of action is unknown, probiotics might influence immune responses by stimulating antibody production and improving phagocytic activity of leukocytes.

It May Help Prevent and Reduce Cold and Flu Symptoms

Healthy bacteria like L. acidophilus can boost the immune system and thus help reduce the risk of viral infections. 

In fact, some studies have suggested that probiotics may prevent and improve symptoms of the common cold (Source,  Source).

A few of these studies examined how effectively L. acidophilus treated colds in children. 

In one study in 326 children, six months of daily L. acidophilus probiotics reduced fever by 53%, coughing by 41%, antibiotic use by 68% and days absent from school by 32% (link). 

The same study found that combining L. acidophilus with another probiotic was even more effective (link).

A similar study on L. acidophilus and another probiotic also found similar positive results for reducing cold symptoms in children (link).

Meta-analysis

In a recent meta-analysis, the effect of probiotics, specifically Lactobacillus and Bifidobacterium strains, on the duration of respiratory infections was evaluated. Twenty trials were included in the meta-analysis: 10 trials on the use of probiotics in children aged 12 months to 12 years, and 10 in adults. One-half of the trials were conducted in western Europe and the remainder in various countries, including two in the United States. The duration of probiotic treatment ranged from 3 weeks to 7 months, with most trials lasting 3 months.

For inclusion into the meta-analysis, the Lactobacillus and Bifidobacterium strains could be administered at any dose; dosage forms included tablets, capsules, and liquids. Lactobacillus strains were studied in 15 trials, 7 of which evaluated the fermented milk drink Actimel, also known as DanActive in the United States. Lactobacillus strains were administered with Bifidobacterium strains in five trials. Using the Cochrane Risk of Bias tool, researchers determined that 12 studies had low risk of bias and that no trials had a high risk.

Participants receiving a probiotic preparation were reported to have had shorter illness episodes than those taking a placebo, with a half-day to 1-day mean difference in illness duration. Absenteeism was calculated by dividing the number of days absent from day care, school, or work by the number of participants with at least one illness episode.

Twelve trials reported on absenteeism due to respiratory infections or common infectious diseases, of which 11 could be pooled in a meta-analysis. The results suggested fewer days absent compared with days absent among participants taking a placebo.