Investigating the effects of Vitamin D on Circadian Rhythms
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Authors
Salma Laraichi
Jhonny Cedillos
Joscelyn Marriott
Issue Date
2026
Type
Language
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Abstract
Circadian rhythms regulate essential physiological processes including sleep-wake cycles, hormone release, and mood, and are influenced by environmental cues such as light exposure, nutrition, and daily habits. Proper circadian rhythm function is critical for overall health, as disrupted rhythms have been associated with numerous conditions including depression, diabetes, and cardiovascular disease. Circadian rhythms can be strengthened by entertainment factors, which provide cues about time of day. The strongest entertainment factor is sunlight, but additional influences such as feeding schedules, physical activity, and nutritional supplements may also contribute. Vitamin D synthesis is stimulated by sunlight, and vitamin D receptors are present in brain regions involved in circadian regulation. Despite this biological connection, limited research has examined the direct relationship between vitamin D supplementation and circadian rhythms. This study evaluated the effect of vitamin D supplementation on circadian rhythm parameters, sleep quality, and mood in healthy young adults. After completing baseline measures of mood, activity, and sleep, forty-five participants received 4000 IU of vitamin D daily for four weeks followed by post-testing. Results demonstrated significant improvements in overall sleep quality, including improved global PSQI scores (p = 0.0046), reduced sleep latency (p = 0.01), and fewer sleep disturbances (p = 0.01). Depression scores showed a trend toward improvement but did not reach statistical significance (p = 0.07). Circadian amplitude increased during winter, suggesting seasonal influences on circadian rhythm strength, while mesor values remained unchanged. In conclusion, vitamin D supplementation appears to improve subjective sleep quality, while circadian rhythm strength and mood outcomes appear to be influenced primarily by seasonal factors. Further data analysis and collection will be done to draw final conclusions.