Could A Portable Ultraviolet Device Prevent Age-Related Bone and Muscle Loss?

Osteoporosis (the loss of bone density) and sarcopenia (the decline in muscle mass) are both debilitating diseases of ageing that greatly impact the daily life of the sufferer. While there are drugs and lifestyle interventions that can help, neither of these conditions can be cured.

One possible cause of osteoporosis and sarcopenia is deficiency of vitamin D, which is obtained through food and produced when the skin is exposed to sunlight. Vitamin D deficiency has become common in many parts of the world, especially among older people whose digestive systems are less able to absorb nutrients.

A research team in Japan is now looking to develop a device that could provide a stable supply of vitamin D to patients – using ultraviolet light.

The research team, consisting of Prof. Yoshihiro Nishida, Dr. Kazuya Makida, and colleagues at the Nagoya University Graduate School of Medicine, has been working to establish a method of supplying vitamin D in a safe and stable manner at low cost. “Unlike sunlight, LED-based UV irradiation could be a consistent and stable source of vitamin D,” says Dr. Makida.

In a previous study, the team had revealed that narrow-range UV irradiation using LEDs – which is an energy efficient light source — increased serum vitamin D levels in animal models with vitamin D deficiency and thereby prevented their bone weakness. However, due to its wavelength and intensity, the UV-LED irradiation could have harmful effects on the human body.

In the new study, the team first conducted experiments to determine the minimal intensity and the minimal dose of UV-LED irradiation that would supply sufficient vitamin D with few side effects. The minimal intensity was found to be 0.16 mW/cm² and the minimal dose 1,000 J/m².

Next, senescence-accelerated mice (mice bred with accelerated aging effects) were irradiated by UV-LEDs set to these levels: the serum vitamin D levels, bone density, and muscle mass and strength were all observed to increase compared to those of mice that were not irradiated.

The researchers also verified that the UV-LED irradiation did not damage the skin of the mice. Therefore, they concluded, irradiation with narrow-range UV-LED light with minimal intensity and dose can safely and adequately supply vitamin D to aged mice, thereby preventing osteosarcopenia.

The team is now developing a small portable UV-LED irradiation device.

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