The effect of milk fermented by yogurt cultures plus Lactobacillus casei DN-114001 on the immune response of subjects under academic examination stress

Summary Background A suppressed immune response has been documented in students under examination stress. Aims The current study aimed to evaluate the effect of milk fermented with yogurt cultures plus Lactobacillus casei DN-114001 (Actimel^®) on the immune system of subjects under academic examination stress. Methods University students were allocated to one of two groups, receiving during 6 weeks (3 weeks prior to, as well as the 3-week duration of the examination period) either: a) a glass of semi-skimmed milk each day (control group, n=63) or b) two 100mL portions per day of fermented milk (treatment group, n=73). Anxiety and immunological measurements were monitored at baseline (Phase 0) and study end (Phase 1). Results The results were expressed as the differences between the data obtained from Phase 0 and Phase 1. This was calculated by subtracting Phase 1 results from the Phase 0 and it is denominated Treatment effect. Mean (± SE) anxiety increased significantly (P<0.05) over the 6-week study in all students, from 40.74±2.50 to 61.19±2.64 (in percentiles). There was no significant treatment effect since this increase was similar in the control and the treatment groups (21.65±5.09 vs 19.14±3.67, respectively). However, there was a significant treatment effect (P<0.05) on the mean change in absolute number of lymphocytes during the 6-week study, which decreased in the control group (–0.04±0.12 cells x 103/mm³) and increased in the treatment group (0.37±0.11 cells x 103/mm³). There was also a significant treatment effect (P<0.05) on the change in absolute numbers of CD56 cells during the 6-week study. Mean absolute CD56 cells significantly decreased (P<0.05) in the control group (–51.97±21.33 cells/mm³),while remaining similar in the treatment group (17.29±17.27 cells/mm³). During the study, mean serum cortisol increased 4.30±0.98 µg/dL in the control group, and 1.75±1.05 µg/dL in the treatment group and no significant differences were found between both values (P=0.062). Conclusions Milk fermented with yogurt cultures plus Lactobacillus casei DN-114001 was able to modulate the number of lymphocytes and CD56 cells in subjects under academic examination stress.