After a series of cloudy days, just a few hours of bright light is enough for many people to describe a surge of energy, improved mood and greater motivation to act. This effect is real, but its essence is primarily neurobiological and psychophysiological. We cannot automatically interpret it as evidence of sufficient vitamin D3 levels.
Light entering the eye activates special cells that are sensitive to brightness. These cells then send a signal to the centre of the brain that controls our internal biological clock and influences our sleep-wake cycle and daily energy levels. Our internal biological clock synchronises with daylight, reducing the production of melatonin (the sleep hormone) and adjusting serotonin (the good mood hormone) levels. According to a study published in The Lancet Psychiatry¹, exposure to daylight is associated with a lower incidence of depressive symptoms and a more stable circadian rhythm.
Based on the mechanisms described above and the studies cited, I conclude that this is an immediate neuroregulatory effect of light, not a rapid change in vitamin D3 stores.
Vitamin D is traditionally referred to as a vitamin, but from a biological point of view, it is a prohormone. When UVB radiation from the sun hits our skin, vitamin D3 begins to form from a substance naturally present in the skin. However, it is not yet active. It is first processed in the liver and then in the kidneys, where it is converted into its active form. Only this final form then functions in the body as a hormone that binds to specific receptors in cells and influences their activity.
According to a study published in The New England Journal of Medicine², the vitamin D3 receptor is present in many tissues, including immune cells, the pancreas, muscles and the brain. This means that its action is not only targeted at regulating calcium and phosphorus, but also interferes with many other processes in the body. It influences gene expression related to immune response, inflammation, cell differentiation and metabolic balance.
I believe that understanding the hormonal nature of vitamin D3 changes the way we should think about its deficiency. It is not a minor nutritional deficit, but a disruption of a complex regulatory network³.
Increased light intensity has a direct effect on the autonomic nervous system. Daylight promotes parasympathetic activity and reduces stress hormone levels. According to a study published in the journal Psychoneuroendocrinology⁴, greater exposure to natural light is associated with reduced cortisol levels and improved subjective well-being.
At the same time, serotonergic activity increases. Light intensity therefore directly shapes our psyche through neurochemical mechanisms. However, it is important to emphasise that vitamin D3 synthesis in the skin is a gradual process and depends on several factors, including latitude, season, skin pigmentation and age. A few hours of exposure to the spring sun does not automatically mean optimised vitamin levels in the serum.
According to a study published in The American Journal of Clinical Nutrition⁵, a significant proportion of the European population has suboptimal levels of vitamin D3, especially during the winter and spring months. This deficiency can manifest itself in fatigue, weakened immunity, mood disorders or impaired muscle function.
The sun is a natural source, but in our geographical conditions, it is not intense enough to ensure adequate synthesis for most of the year. Therefore, I consider vitamin D3 supplementation to be a rational and preventive measure, especially during periods of low UVB exposure.
When we talk about vitamin D3 as a hormone, we inevitably come to the topic of hormonal balance. The endocrine system functions as an interconnected network. Changes in one part can affect other regulatory axes.
Plant adaptogens and micronutrients play a supportive role in this context. Moringa oleifera contains bioactive substances with antioxidant potential. Peruvian maca is traditionally associated with supporting vitality and hormonal balance. Vitex agnus-castus is still being researched in the field of menstrual cycle and prolactin regulation. Zinc contributes to the proper functioning of the immune system and to maintaining normal testosterone levels in the blood. Vitamins B1 and E play a role in energy metabolism and protecting cells from oxidative stress.
Hormone Balance+ represents a comprehensive approach to supporting the body’s regulatory mechanisms. It is not a substitute for vitamin D3, but rather a supplement to a comprehensive approach to hormonal stability and metabolic balance.
The sun has an immediate psychological effect and long-term biological significance. A photon hitting the retina or skin triggers a cascade of reactions leading to neurochemical and hormonal changes. This process is fascinating and precisely regulated.
Feeling better on a sunny day is natural. However, assuming that this means our vitamin D3 status is resolved is not scientifically justified. A responsible approach involves understanding the mechanisms, objectively measuring vitamin D3 levels and, if necessary, systematic supplementation. Light shapes our bodies and minds. But hormonal balance requires more than just a clear sky.
Ing. Mária Zajičková, PhD.
organic chemist, science populariser
Explanatory notes:
Circadian rhythm – internal biological clock regulating sleep, wakefulness and hormonal processes.
Prohormone – a substance that is converted into an active hormone in the body.
Parasympathetic nervous system – part of the autonomic nervous system that promotes relaxation and regeneration.
Adaptogens – plant substances that promote the body’s resistance to stress and maintain hormonal balance.
