Acute respiratory infections are especially dangerous for children, older adults, and those with immune system disorders. The elderly may be more susceptible due in part to immunosenescence, i.e., the immune system's gradual deterioration as a result of ageing.
The process alters the immune organs and cells, as well as immune-related molecules, and "increases susceptibility to various diseases, such as cardiovascular disease, autoimmune disease, and infections".
In a study led by Sichuan University, researchers randomly divided 205 volunteers aged 45 and above into two groups: the control group received no probiotic supplementation, while the intervention group received a daily 300ml of yogurt supplemented with a probiotic strain, Lactobacillus paracasei N1115.
Fewer diagnoses, lower risk
After 12 weeks of treatment, it was found that in the intervention group, the number of people diagnosed with an acute URTI, as well as the number of URTI events, had decreased considerably when compared to the control group.
The study also reported that the risk of URTI in the intervention group was "evaluated as 55% of that in the control group" and that the "change in percentage of CD3+ cells in the intervention group was significantly higher than in the control group".
However, when it came to total albumin, pre-albumin, protein and globulin levels, the differences between the two groups were insignificant.
The researchers hypothesised that the probiotic strain used in the yogurt had helped to reduce the risk of acute URTI in the intervention group by stimulating the natural immune defence of T-cells, thus protecting the intervention group from infection.
They added that "the immune function of yogurt was generated via not only the immunomodulatory pathway of probiotics but also by the improvement in nutritional status from macro- / micro-nutrients".
The study stated that dietary intervention with yogurt containing the probiotic strain Lactobacillus paracasei N1115 could be a way to enhance immune system function and overall health in the middle-aged and elderly, "which could have important clinical, public health, and economic consequences".
However, it concluded that as it was "limited to a blank control trial, a better designed, placebo-controlled trial is needed to clearly clarify the immune effect of the strain N1115 in the future".
Source: Dove Medical Press
"Yogurt supplemented with probiotics can protect the healthy elderly from respiratory infections: A randomized controlled open-label trial"
Authors: Fangfang Pu, et al.