To young children, the sun is a friendly yellow smiley face, with lines around it.

To some of our ancient ancestors, the sun was a powerful god.

To medical researchers, the sun is a dangerous source of cancer-causing radiation.

It’s getting difficult to know just how to regard the sun. Gone are the days when we thought of it strictly in terms of the light and warmth it provides, the seasons it controls, and the crops it helps develop. Rather than just being there, the sun has become something we have to think about and deal with in our lives.

Like most other things, the sun has its positive and negative sides. The more we know about it, the better chance we have to make healthy choices regarding the sun.

What Have You Done For Me Lately?

For a long time, the sun was on every parent’s list of things that were necessary for good health. Sunshine ranked right up there with fresh air, enough sleep and rest, nutritious food, and pure water. “Go outside and play” was secret parent code for “Get some fresh air and sunshine.”

There is a scientific basis for this belief. Without the sun’s rays, our bodies couldn’t produce vitamin D, which is so important for healthy teeth and bones. It only takes 10 to 15 minutes of sun exposure twice a week for the body to meet its daily need for vitamin D, though.

The sun also affects our mood. The warmth of sunlight on skin is pleasant, but there is another, deeper effect. One out of five Americans is thought to suffer from symptoms of “winter depression.” One of the seasonal affective disorders (SAD), it comes back every year at the same time. It is due to the lack of sunlight from shorter days during the period from late fall to early spring.

Researchers have found that the body has two chemical systems that govern mood and are affected by light. Light enters the eye through the retina, then travels to areas of the brain that involve mood.

People who experience winter depression are helped by being exposed every day to very bright artificial light. Some studies show that light treatment, for a period of around two hours, is more effective early in the morning.

Caution: Sun Overhead

These days the message we hear more often regarding the sun is how its rays damage the skin, cause premature aging, and cause skin cancers. There is no such thing as a “healthy” tan, because now we know that a tan is a sign of skin damage.

Sunlight emits radiation, which is composed of infrared rays (heat), visible light, and invisible ultraviolet rays. Ultraviolet radiation is broken down into different wavelengths.

Ultraviolet A (UVA) rays are the tanning rays. They penetrate deeper in the skin than ultraviolet B (UVB) rays. They stimulate cells in the dermis called melanocytes, to make a brown pigment calledmelanin.

Melanin absorbs ultraviolet radiation, so a tan is the body’s attempt to prevent further sun damage. Unfortunately, the protection of a tan is woefully inadequate compared to the power of the sun’s radiation. It just isn’t up to the job.

Ultraviolet B rays are the ones that cause sunburns. They damage the DNA and membranes of cells in the epidermis. This damage adds up over the years, and gets an early start. Children, who spend so much time outdoors (getting all that fresh air), are exposed to about three times more sun than adults. The body tries, but cannot repair all this damage.

A Sunburn For All Seasons

Many people put on sunscreen to protect their skin on a hot, sunny summer day, but that’s not the only time sunscreen is needed. Even on a cloudy day, 70 to 80 percent of ultraviolet rays can pass through clouds. They can go through as much as three feet of water. Even if you can’t feel it happening, you can get a sunburn on a cloudy, hazy, windy, or cool day.

Sometimes you have to go an extra mile to protect your skin.

The great paradox about tanning is how something people do to look good can end up making them look so bad. In the days before we knew better, it was common practice to slather your body with baby oil or some other “quick” tanning oil, and lie for hours in the sun. People used metal reflectors to make sure their face and neck got an even tan. It was work, but that “healthy” dark glow was worth it all.

Ten years or more down the line, a person will likely start to see where all that “healthy” glow leads: deep wrinkles; dry, rough, dull skin; scaly red or brown patches of skin called actinic keratoses (which sometimes progress to squamous cell carcinoma, a skin cancer); white or brown age spots, a sign of melanocytes whose DNA is damaged. (These spots may be related to malignant melanoma, a deadly form of skin cancer.)

Gradually, people are changing their minds about tans, and developing a better attitude about what looking good really means. The large variety of sunscreens–and the volume of their sales–reflects this.

Finally, Cancer

Premature aging is bad enough, but the bottom line on sun damage is skin cancer. Of all cancers that occur, one-third are skin cancers. One out of seven Americans will develop skin cancer during his or her lifetime. Ninety percent of skin cancer is caused by the sun.

The most common form of skin cancer is basal cell carcinoma. It can look like a pale, waxy, pearly bump, or a scaly red patch. It grows slowly, and rarely spreads to other parts of the body. If you find and treat it early, it is not difficult to cure. If you wait too long, it can lead to loss of an ear, nose, or eye.

Squamous cell carcinoma, unlike basal cell, can spread to other organs. It usually grows slowly, but not always. It, too, is almost 100 percent curable if you treat it very early. The signs to watch for include a bleeding, oozing, or open sore, or rough, thick, or scaly patches. It is often found on the lower lip, ears, or other parts of the face.

Malignant melanoma is the least common skin cancer, but also the most dangerous. It begins to grow in a melanocyte, sometimes (but not always) arising in a mole. It can spread quickly to other organs if it is ignored, but if you find and treat it early it can usually be cured.