by
Pam Killeen
Sunlight plays an essential role in maintaining bone health and preventing conditions like osteoporosis. While most people recognize the connection between the sun and vitamin D production, the sun’s influence on bone health extends far beyond this vital nutrient. Scientific studies highlight the profound impact sunlight has on bone density and strength. For instance, a study published by Yonsei Medical Journal found that individuals with limited sunlight exposure and low vitamin D levels face an increased risk of osteoporosis and fractures. Additionally, research in the Journal of Bone and Mineral Metabolism revealed that brisk walking combined with sun exposure can increase bone mineral density (BMD) in the elderly with osteopenia.
Here’s a closer look at how sunlight supports our bones:
- Vitamin D Activation
While vitamin D is essential for calcium absorption, it’s the sun’s ultraviolet (UV) rays that trigger the skin to produce this vital nutrient. Once activated by sunlight, vitamin D helps regulate calcium and phosphorus—key elements for maintaining bone density and strength. Without adequate sun exposure, even with sufficient dietary intake of calcium, bones may not fully benefit from the minerals needed to stay strong. - Circadian Rhythm and Bone Remodeling
Sunlight is crucial for regulating our circadian rhythms, which in turn affect bone remodeling. Circadian rhythms help synchronize the body’s repair processes, including bone tissue regeneration. Proper alignment of our internal clock ensures efficient bone formation and repair, reducing the risk of fractures and conditions like osteoporosis. Disrupted circadian rhythms, often linked to excessive artificial light exposure, can hinder this process and impact bone health. - Endorphin Release
Exposure to sunlight stimulates the production of endorphins, the body’s natural “feel-good” hormones. These endorphins can counteract the effects of stress hormones that, when elevated chronically, can impair bone formation and contribute to bone loss. By improving mood and reducing stress, sunlight indirectly supports bone health, helping the body maintain a healthy balance of hormones crucial for bone strength. - Nitric Oxide Production
Sunlight exposure also triggers the release of nitric oxide, a compound that has been shown to improve blood circulation. Efficient circulation is essential for delivering nutrients and oxygen to bone cells, supporting their growth and maintenance. By boosting blood flow, sunlight helps ensure that bones receive the necessary elements to stay strong and healthy. - Melatonin Regulation
Sunlight plays a vital role in regulating melatonin levels, which are important not only for sleep but also for bone health. Melatonin, a hormone that promotes sleep and circadian rhythm, has been shown to support the formation of new bone tissue. By getting sunlight exposure during the day, we ensure that melatonin is produced properly at night, contributing to optimal bone health and repair. - Sunlight and Rickets: A Historical Case Study
Rickets, a condition caused by a deficiency in vitamin D, calcium, or phosphate, results in soft and weak bones—particularly in children. Historically, rickets was especially prevalent among children living in urban, industrialized cities during the 19th and early 20th centuries. These children often lived in overcrowded, smog-filled environments with limited access to direct sunlight. In contrast, children in rural areas, who spent more time outdoors, were far less affected.
A landmark moment came in the early 20th century when scientists, including Sir Edward Mellanby and Harriette Chick, identified a clear link between lack of sunlight and the prevalence of rickets. Mellanby demonstrated that dogs kept indoors developed rickets, while those exposed to sunlight remained healthy. Chick’s research in Vienna during the post-WWI period confirmed that cod liver oil and sunlight were effective treatments for rickets. These discoveries led to public health initiatives encouraging sunbathing and the fortification of foods with vitamin D. However, fortifying foods with synthetic vitamin D is merely a form of duct-taping the issue—the deeper, more biologically sound solution is simply to restore our relationship with natural sunlight by spending more time outdoors. While this historical context reinforces the vital role that sunlight plays in developing strong, healthy bones in growing children, it also serves as a reminder to aging adults that they, too, must embrace the healing power of the sun to preserve bone density and prevent degenerative bone conditions later in life.
The Wisdom of Herodotus: Sunlight and Skull Strength
Ancient wisdom often aligns with modern scientific findings. The Greek historian Herodotus, in his Histories, observed a striking difference in the skeletal strength of Persian and Egyptian soldiers. He noted:
“I saw there a strange thing, of which the people of the country had told me. The bones of those slain on either side in this fight lying scattered separately… the skulls of the Persians are so brittle that if you throw no more than a pebble it will pierce them, but the Egyptian skulls are so strong that a blow of a stone will hardly break them. And this… the Egyptians shave their heads from childhood, and the bone thickens by exposure to the sun. This also is the reason why they do not grow bald… The cause of the Persian skulls being weak is that they shelter their heads through their lives with felt hats.”
Herodotus suggested that habitual sun exposure contributed to the Egyptians’ robust skeletal structure, while the Persians, who kept their heads covered, had more brittle bones. This historical anecdote points to the significant role sunlight may have played in shaping the strength of bones long before modern science confirmed its importance.
The Benefits of Going Hatless: A Nod to History
In light of Herodotus’ observation, there may be value in exposing the head and other parts of the body to sunlight as much as practical, without overdoing it. While it’s important to protect the skin from excessive sun exposure to avoid sunburn or heatstroke, moderate sun exposure can help maintain stronger bones, much like the Egyptians described by Herodotus. The act of going “hatless” occasionally could allow the body to absorb sunlight and gain its benefits for bone health.
Conclusion: The Sun as a Vital Ally for Bone Health
The sun is indispensable for strong bones and the prevention of osteoporosis, primarily through its role in vitamin D production. Yet, as scientific findings show, its benefits go well beyond vitamin D. The sun helps regulate hormones, improve blood flow, and support bone remodeling, making it a powerful, holistic ally in maintaining skeletal health. Historical observations, such as those of Herodotus and early 20th-century rickets researchers, also support the idea that sun exposure has long been linked to stronger bones. By balancing safe sun exposure with modern scientific insights, we can harness the sun’s power to optimize our bone health and overall well-being.
Pam Killeen is a health and sleep coach, author, podcaster and advocate for circadian health, with over three decades of experience in the wellness field. Her career has evolved from focusing on nutrition and natural health strategies to integrating the critical principles of circadian biology into her online practice.
She is the author of three books—The Great Bird Flu Hoax (co-authored with Dr. Joseph Mercola); Addiction: The Hidden Epidemic; and Survival of the Unfittest—which highlight her deep interest in nutrition. Reflecting on her work, she wishes she had included information about circadian practices in her writing and consultations but believes it’s never too late to start. Her website is www.pamkilleen.com.