Sunlight has long been considered an important natural factor for human health, especially in supporting hormonal balance through vitamin D. Some studies and experts believe that vitamin D not only helps maintain bone health but also participates in the regulation of many hormones in the body.
According to Dr. Narendra K. Shetty - Health Care Director at the Kshemavana Yoga and Natural Therapy Center, Bangalore (India), sunlight plays an important role in controlling hormones, including thyroid hormones, testosterone and estrogen. He said that in human skin there is a vitamin D3 precursor, 7-dehydrocholesterol, which when exposed to ultraviolet B (UVB) rays will convert into vitamin D3. Therefore, safe sun exposure is necessary to maintain health and endocrine balance.
Vitamin D has a wide impact on many biological functions. Vitamin D deficiency not only affects bones but also affects the immune system, energy levels, sleep cycle, mood and hair loss. Many hormones in the body also need vitamin D to function normally, so deficiency can lead to many different disorders.
In the thyroid gland, some studies published in the journal Frontiers in Immunology in 2026 show that vitamin D can support immune response regulation, thereby contributing to improving thyroid function. Meanwhile, in men, the form of vitamin D in the body (25-hydroxyvitamin D) is believed to be related to the activity of enzymes involved in the production of testosterone. Some studies also recorded vitamin D receptors appearing in the testicles and semen system, suggesting that vitamin D may play a role in male reproduction.
For women, vitamin D contributes to regulating estrogen and progesterone, affecting menstrual cycle, fertility and pregnancy. Pregnant women with vitamin D deficiency may face the risk of complications such as gestational diabetes, pre-eclampsia and low birth weight babies. In addition, in people with polycystic ovary syndrome (PCOS), vitamin D deficiency can increase insulin resistance and birth hormone disorders.
Not only related to reproductive hormones, sunlight also stimulates the production of serotonin, a neurotransmitter that helps regulate mood. Low serotonin levels can be associated with seasonal mood disorders (SAD), often encountered when natural light is lacking for a long time.
However, experts recommend that sun exposure should be done reasonably to avoid the harmful effects of ultraviolet rays such as premature skin aging and increased risk of skin cancer. On average, about 15 minutes of sun exposure in the morning, performed several times a week, is considered an appropriate level to support the body to synthesize vitamin D and contribute to maintaining hormonal balance.
