[Effects of nighttime snacking in students on their physiological parameters]

The purpose of the research was a comparative assessment of the level of diet nutrients, characteristics of higher nervous activity, specificity of chronobiological changes of the sleep-wake cycle, the daily dynamics of cortisol level and total antioxidant activity in saliva in students with the presence of night eating compared with students who do not eat at night. The participants were 72 university students aged 17-22 years (59 females and 13 males), a self-administered diet diary for a week was used to acquire dietary pattern and nutrient content. All participants were divided into two groups: group 1--students with food consumption from 06.00 am to 10.00 pm without night meals (n = 34), and group 2--students, whose food consumption include all day period and night snaking from 10.00 pm to 06.00 am (n = 38). High nervous activity parameters were detected according to the Eysenck questionnaire, Spielberg and Taylor anxiety tests, the test "Stress", the three-factor eating questionnaire; chronobiological state was evaluated according to sleep quality, sleep hygiene, daily sleepiness, chronotype. Levels of cortisol and total antioxidant activity were estimated in saliva twice a day: in the morning and in the evening. In both groups, the majority of students (97%) have reduced consumption of vitamins and minerals such as biotin, vitamin D, choline, iodine, cobalt, manganese, sulfur, fluorine and zinc. Deficit of carbohydrates was found in 93% of respondents. The number of students with calcium deficiency was increased in the group 2 compared to the group 1 and reached 27.8% vs 3% (p < 0.05), niacin insufficiency was revealed in 41.7% vs 18.2% (p < 0.05) and proteins insufficiency frequency reached 30.6% vs 0% (p < 0.05). The students from the group 2 had a significantly lower (p < 0.05) intake of vitamins A, B6 and C. In the group 2 it was detected the time shift of food consumption acrophase (15.1 h vs. 13.8 h; p < 0.05), decrease of persons with morning chronotype (5.55% vs 24.24%; p < 0.05), increase of anxiety and daily sleepiness (26 vs 20; p < 0.01, and 10 vs 6; p < 0.03 respectively); decrease of sleep quality (13 vs 15; p < 0.01), increase of evening saliva cortisol level [9.41 (6.96; 13.11) vs 6.51 (5.61; 9.88) ng/ml; p < 0.005) and decrease of saliva total antioxidant activity in the morning [13.00 (9.82; 14.98) vs 16.41 (15.21; 17.51) mg/l; p < 0.001] and in the evening [11.11 (7.85; 12.89)vs 14.32 (13.27; 15.29) mg/l; p < 0.001].