It has been within the last 100 years that we have chosen to drastically increase our sun exposure in order to "brown", after tanning became fashionable in the 1920s. The CDC reports that Skin Cancer is the most common form of cancer in the United States. In 1935 approximately one out of 1200 people were diagnosed with malignant melanoma, the most deadly and often fatal form of skin cancer. Today that number has jumped to one out of 67 people in the U.S. Within the next 25 years it is predicted to be one out of 50. Malignant Melanoma is the second most frequently reported cancer in women in their 20s and third only to breast cancer and thyroid cancer for women in their 30s. Malignant melanoma is one of the few forms of cancer actually on the rise while other forms of cancer are starting to show a decline in occurrence. 90% of all melanomas are UV sun exposure related the other 10% might be due to heredity or other genetic abnormalities. In August 2009, tanning beds were classified as carcinogenic to humans. Use of a tanning bed before the age of 30 increases risk of melanoma by 75%. While some malignant melanoma is genetic, the risk of developing malignant melanoma is mainly influenced by sun exposure, particularly sunburns that occur before the age of 10.
We must continually remind ourselves that skin aging is not a process associated with the chronological number of the years we have lived. More correctly, it is not the years that matter nearly as much as the cumulative exposure to sunlight and other environmental factors. As much as 90 to 95% of what we perceive as inevitable aging is sun damage. Most of this damage occurs before the age of 10 and at least 80% before the age of 18. It takes 10, 20, and even 30 years and longer for this damage to show up. It has been proven that skin at 60 years of age could look pretty much the way it did at 20 if it weren't for cumulative sun exposure. It only takes casual exposure over the years to produce visible aging changes.
One of the best and most accepted scientific theories that exists today to explain sun-related aging is referred to as "The Membrane Hypothesis of Aging." Research in this area demonstrates that if the cell membranes can be protected against free-radical destruction, the skin will not appear to age from sun exposure. The cell membrane is a critical barrier that protects and insulates the cells which provide genetic coding, and also maintains the cell's ability to remain active and viable. When skin is exposed to the sun, a complex reaction occurs that sets in motion a chain of events that damages or destroys the membrane, and which translate into skin that shows the visible signs of aging.
As the skin is subjected to these assaults, it loses its ability to reproduce exact copies of healthy cells, prevent the breakdown of collagen and elastin, repair tissue rapidly and prevent the attack of lipids in cell membranes. Finally, the skin gradually breaks down, in general, due to free radical damage. Even minimal sun exposure triggers an intense invasion of free radicals. Consistent release of free radicals has proven to result in the following long-term damage:
Substantial destruction of collagen and elastin (collagen and elastin are the primary components of the skin's support structure).
Skin becomes slack and loses its ability to restore itself to its original shape
Loss of muscle tone
Impairment of the skin's immune function
Lines and wrinkles
Coarse textural changes
Damage to DNA
Weakening and destruction of cells that come in contact with free radicals
Studies have shown that antioxidants can actually "neutralize" free radical activity thus averting free radicals from attacking cell membrane tissue. In order to prevent further damage, full-spectrum sun protection is a must.