Athletes who engage in prolonged, strenuous or rapid changes in their exercise routine are at an increased risk of upper respiratory infections (URIs)
Previous studies have demonstrated that exercise training sessions can decrease salivary sIgA, which is one of the body’s first line of defenses against pathogens entering the oral cavity.
Decreased salivary sIgA is an indication of temporary immune depression and related to an increased risk of URIs.
Chlorella pyrenoidosa (chlorella) is a freshwater microalgae that is used as a supplement in Japan.
Chlorella is a rich source of vitamins, minerals, amino acids, polysaccharides and glycoproteins that likely work in concert to support immune function.
Previous human studies have shown that chlorella increases sIgA concentration and secretion rate and maintains sIgA levels throughout intense athletic training.
In a randomised controlled trial published by Chidley and Davison in 2017, researchers evaluated the effects of chlorella on immune responses to a 2-day intensified training programme.
A total of 34 healthy and physically active adults (27 male and 7 female) were randomised to take 6 g per day of chlorella (Sun Chlorella A tablets from Sun Chlorella Corporation, Kyoto, Japan) or a placebo for 6 weeks: from 4 weeks before until 2 weeks after 2-days of intensified exercise training.
Chlorella significantly increased sIgA secretion rate by week 4 and resting sIgA concentration by week 5.
In response to intensified training, sIgA concentrations did not significantly change in either the chlorella or the placebo group, but sIgA secretion rate was increased during some periods of training in the chlorella but not in the placebo group.
There were no differences between groups in the number of URIs in the 2 weeks following training (31% of subjects in each group reported URIs) and no differences in the duration or severity of URI symptoms.
The authors of this study conclude that daily supplementation with chlorella increases salivary sIgA concentration and secretion rate at rest, but a longer duration of supplementation may be required to observe clinical protection against URIs.