The Most Common Type and Effect of Acute Respiratory Infection
One of the effects of acute respiratory infection is difficulty in breathing. It usually starts with a viral infection in the nose, throat, or lungs. If the condition is left untreated, it can spread throughout the respiratory system. One common type of acute respiratory infection is influenza. People can get vaccinated against flu, but sometimes the vaccine is ineffective because viruses change rapidly, and different strains become dominant each year. So enhancing immunity might be a more practical and effective way to manage flu infections.
The Risk of Acute Respiratory Infection
Acute respiratory infections are dangerous, particularly for older adults and people with weakened immune systems. One of the possible reasons for this risk is immunosenescence, which is the gradual deterioration of the immune system with age. This condition involves changes in the immune organs, cells, and molecules, making people more susceptible to cardiovascular disease, autoimmune disease, and infections.
Health Benefits of Yogurt
Yogurt is fermented milk that contains Streptococcus thermophilus and Lactobacillus bulgaricus. Yogurt has been used for a long time and is known to maintain human health by its excellent nutrition profile. Recent studies have also suggested that supplementation with probiotics can considerably enhance traditional yogurt’s health-promoting effects, such as immunity stimulation. There are certain probiotic lactobacilli that can modify the natural and acquired immune responses and thus protect against respiratory infections. Furthermore, several recent studies have found that probiotics can enhance immunity in elderly humans. A probiotic strain of Lactobacillus Paracasei N1115 (N1115) has been tested to have a strong tolerance to gastric acid and bile acid and can strengthen the intestinal mucosal barrier.
This study evaluated whether yogurt supplemented with N1115 could protect middle-aged and older adults from acute upper respiratory tract infections (URTI).
The Study on Probiotic Supplemented Yogurt for Upper Respiratory Tract Infection
205 volunteers, at least 45 years of age, were randomly divided into two groups. The 103 subjects in the intervention group were asked to consume a 100-milliliter bottle of probiotic N1115-containing yogurt three times each day, preferably during or after meals, for 12 weeks. As with the treatment group, the 102 in the control group retained their regular diet, but the latter had no probiotic supplementation.
The primary outcome was the incidence of acute URTI. The diagnostic criteria for acute URTI were as follows:
- Symptoms of acute rhinitis or acute pharyngitis such as sneezing, nasal congestion, or runny nose that appeared in a short time and with rapidly increasing severity;
- The duration of the above symptoms for at least one day;
- Symptoms that occurred at least seven days after the end of the last acute URTI episode were considered to be new episodes.
Moreover, each infection event was scored using six items:
- Nasal congestion, sneezing, and runny nose
- Conjunctival hyperemia and lacrimation
- Sore throats
- Cough and sputum
- Headache and muscle soreness
Each item was scored as follows: 0 (none), 1 (occurring but did not hinder daily life), or 2 (seriously affecting work, life, and sleep).
Compared to the control group, the number of persons diagnosed with an acute URTI in the intervention group was significantly lower, 30.1% versus (vs) 44.1%; the number of URTI events also significantly decreased in the intervention group, 35.9% vs. 51.0%. The risk of URTI in the intervention group was evaluated as 55% of that in the control group.
The change in the percentage of the cluster of differentiation 3 positive (CD3+) cells in the intervention group was significantly higher than in the control group. This observation is noteworthy because CD3+ cells are involved in recognizing antigens and subsequent activation of immunocompetent thymus (T) lymphocytes to fight these toxic substances. CD3+ cells usually decrease with age, the reason why the elderly are more prone to infections.
Furthermore, no adverse events associated with the consumption of the tested yogurt were reported.
The study suggested that the intake of yogurt with probiotic strain N1115 for 12 weeks may reduce the risk and the frequency of acute upper tract infections in middle-aged and older adults. Enhancing the natural immune defense by T-cells might be one of the essential underlying mechanisms for probiotics to express their anti-infective properties effectively.