In a double-blind study on 60 test subjects over 12 weeks the herbal yeast group achieved an average improvement of 64% in comparison with the improvement in the placebo group of 10%. The following parameters were measured: concentration, fatigue, reaction, nervous tension, physical and mental efficiency, resistance and vitality.
Dörling E., Bio-Strath and increased efficiency, a double-blind study with Bio-Strath Food Supplement on 60 test subjects, SWISS PHARMA 1981; 11: 27–3
In a trial with 24 school pupils, it was demonstrated that taking an herbal yeast product for three months resulted in improved performances (better marks) and fewer absences.
Neukomm M., Increasing powers of concentration, a school trial with 24 secondary school pupils, 1968
