The sun discharges energy over a spectrum of wavelengths: visible light that we see, infrared radiation that we feel as heat, and ultraviolet (UV) radiation that we neither see nor feel. The stratospheric ozone layer in the earth's atmosphere shields us from most UV radiation. Despite the fact that we never even feel the little bit that breaks through the atmosphere, UV radiation impacts our health.

A recent study from Australia, titled "Vitamin D and Death by Sunshine," explores the effects of UV radiation and finds a little light in all the darkness.

The Message

The hazards of too much sun exposure has become the focus of most public health communications. Solar radiation, in particular UV radiation, penetrates deeply into our skin. It damages collagen fibers, destroys vitamin A, accelerates aging of the skin, and, worst of all, increases our risk of skin cancer. Excessive sun exposure may also cause cataracts and other eye problems as well as diseases aggravated by UV radiation-induced immunosuppression, possibly activating latent viruses.

Certainly sunlight has many benefits, namely its well-known ability to boost the body's vitamin D supply. Vitamin D stimulate calcium absorption from food and thus is essential for maintaining healthy bones and preventing osteoporosis. Additionally, vitamin D is important for muscle function and defense against several diseases, including diabetes.

In an effort to delve deeper into the benefits of vitamin D, researchers in Australia examined how both UV radiation and vitamin D affects our skin cells. In so doing, they discovered surprising results.

Vitamins and Cell Function

Researchers explored the various signaling pathways within cells. These pathways are comprised of molecules that work together to control cell functions, such as cell division or cell death. After the first molecule in a pathway receives a signal, it activates another molecule, which in turn activates another. This process is repeated until the cell function is carried out. The abnormal activation of signaling pathways can lead to cancer, making them a target of developing drugs. These drugs would effectively block cancer cell growth and kill cancer cells

One of the most harmful effects of UV exposure is the irreparable damage to a cell's DNA, which becomes susceptible to oxidative damage. UV exposure also leads to accumulation of p53 protein within the nucleus of skin cells, a well-known tumor suppressor. Known as "the guardian of the genome," p53 protein disrupts the cell cycle allowing time for repair of DNA damage before replication. In abnormal quantities, however, p53 may induce cell death, known as apoptosis, before replication.

Researchers found that applying vitamin D compounds to human skin cells prevented UV-induced cell death and DNA damage.

"Our findings indicate that vitamin D compounds inhibit the DNA damage that leads to both melanoma and non-melanoma skin cancers," said Katie M. Dixon, lead author of the study and professor of physiology at the University of Sydney.

What's Ahead

Further research is necessary to develop these findings into practical applications.

"The active form of vitamin D is calcitriol." said Dixon. "We are currently testing similar vitamin D-like compounds that are less expensive and more stable, with the aim of incorporating one of these agents into a sunscreen or after sun lotion."

A sunscreen or lotion containing vitamin D applied before or after exposure could potentially reduce damage. As for those who have already experienced damage, this research's practical applications may be less hopeful but still beneficial. "Older people are less efficient at producing vitamin D in their skin following sun exposure, under some conditions," writes Dixon. "We anticipate that novel after-sun lotions or sunscreens containing a vitamin D-like compound will help to prevent further skin damage from UV exposure."

Sources: Dixon, KM, Tongkao-On, W, Sequeira, VB, Carter, SE, Song, EJ, Rybchyn, MS, et al. Vitamin D and Death by Sunshine. International Journal of Molecular Science. 2013.

Mead, MN. Benefits of Sunlight: A Bright Spot for Human Health. Environmental Health Perspectives. 2008.