Day/Night and Summer/Winter Changes in Serum Total Antioxidant Capacity

Area of Science:

• Biochemistry
• Human Physiology
• Chronobiology

Background:

• Biological molecule levels can be influenced by seasonal and circadian rhythms.
• Total Antioxidant Capacity (TAC) is a key indicator of a system's antioxidant status.
• Previous research has yielded inconclusive findings regarding diurnal and seasonal variations in TAC.

Purpose of the Study:

• To investigate seasonal variations (summer vs. winter) in TAC concentrations.
• To examine diurnal variations (day/night) in TAC concentrations.

Main Methods:

• Study involved 98 healthy subjects in summer and 64 in winter.
• Blood samples were collected at 09:00, 12:00, and 00:00 hours.
• TAC was quantified using the ABTS radical cation assay, with results reported in mmol/L trolox equivalents.

Main Results:

• Significantly higher TAC levels were recorded in summer compared to winter across all time points.
• In summer, TAC was highest at 09:00, followed by 12:00, and then 00:00 (1.34±0.26 vs 0.83±0.19 vs 0.75±0.18 mmol/L).
• In winter, TAC was also highest at 09:00, followed by 12:00 and 00:00 (1.24±0.16 vs 0.73±0.10 vs 0.67±0.13 mmol/L), with no significant difference between 12:00 and 00:00.

Conclusions:

• Seasonal variations significantly affect serum TAC concentrations.
• Circadian variations, particularly the difference between morning and night, are evident in TAC levels.
• Failure to account for seasonal and circadian changes may introduce methodological bias in related research.