Plain language summary
Upper respiratory tract infections (URTIs) significantly impact the quality of life in susceptible individuals and account for considerable economic costs in days of work lost and medical visits. Previous studies have shown that URTIs may be reduced by the consumption of yeast beta-glucans through their affect on the immune system. This randomised double-blind placebo controlled study aimed to investigate whether the incidence and severity of the common cold could be altered by consumption of yeast (1,3)-(1,6)-beta-glucan. 291 subjects susceptible to URTI’s were randomly assigned to placebo or (1,3)-(1,6)-beta-glucan for 16-weeks. There were no statistically significant differences on overall symptom severity or duration of URTIs with beta-glucans at 16 weeks. Feelings of joy were significantly reduced with placebo. Further analysis showed that the beta-glucan group did experience reduced severity of symptoms in the first 7 days of contracting the URTI. Interesting to note was a significant reduction in blood pressure with beta-glucans, which was even more pronounced in subjects with clinically high blood pressure. Nutrition practitioners working with individuals suffering from chronic URTIs may wish to consider beta-glucans for their ability to reduce symptom severity in the first week of infection and increase feelings of wellbeing.
Abstract
OBJECTIVES Each year, adults suffer about two to four upper respiratory tract infections (URTIs), mostly in winter. The aim of the study was to evaluate the effects of brewers' yeast (1,3)-(1,6)-beta-glucan on incidence and severity of upper respiratory tract infections (URTIs). METHODS Generally healthy men and women (n = 299) reporting at least three URTIs during the previous year were randomized to receive either a placebo or 900 mg of yeast beta-glucan daily for 16 weeks during winter. In cases of acute URTI, the severity of URTI symptoms was assessed via the WURSS-21 questionnaire and the Jackson scale, and a clinical confirmation was implemented by the investigator. RESULTS Overall, 70 subjects under placebo and 71 subjects under yeast beta-glucan experienced at least one clinically confirmed URTI episode. The global severity using WURSS-21 had been quite similar between the study groups (p = 0.5267), whereas during the first days of URTIs the severity was less pronounced in the yeast beta-glucan group. On the episode level, the severity of physical symptoms was significantly lower for all investigated time intervals up to 7 days under yeast beta-glucan (WURSS (Q2-11) (days 1-2: p = 0.0465, days 1-3: p = 0.0323, days 1-4: p = 0.0248, days 1-7: p = 0.0278), also confirmed for the Jackson scale). The reduction of severity was accompanied by a significant increase in the joy subscore of the Perceived Stress Questionnaire (PSQ20) (p = 0.0148). In addition, there was a reduction of systolic (p = 0.0458) and diastolic (p = 0.1439) blood pressure. CONCLUSION Subjects supplementing with yeast beta-glucan benefit by a reduced severity of physical URTI symptoms during the first week of an episode, even though the incidence and global severity of common colds could not be altered in comparison to placebo. Furthermore, accompanying benefits in terms of blood pressure and mood were identified. Altogether, yeast beta-glucan supports the immune function.
Methodological quality
Jadad score
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4
Allocation concealment
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No
