The life-giving rays of the sun are an invaluable blessing and provide a number of healthful benefits. Sunlight has the ability to kill microorganisms and prevent growth of mildew and mold. Sunshine can lift the human spirit and help fight off depression, especially during the short days of winter. For hospital patients recovering from surgery, sunlight appears to be therapeutic. Patients in rooms receiving a lot of natural light took less pain medication throughout their hospital stay than patients in darker rooms.

Fifteen minutes of bright sunlight containing UVB (ultraviolet B) rays on the arms and face two to three times per week is usually sufficient for the body to manufacture enough vitamin D to meet one's needs. However, during the winter months when the sun's rays are of insufficient strength, people living in northern states are unable to manufacture sufficient vitamin D.

Persons with dark skin need twice as much sunlight exposure as a fair-skinned person, since skin pigmentation reduces vitamin D production. In addition, the use of sunscreen also reduces vitamin D production. Sunblock with a SPF (Sun Protection Factor) of 15 or greater can block out most of the UVB rays.

It is important to have a good dietary source of vitamin D, especially during the winter months. Many breakfast cereals, some dairy products and orange juices, and some soy and rice beverages are fortified with vitamin D. One could get excessive levels of vitamin D [over 2000 IU (International Units) a day] from taking vitamin supplements.

For adults up to age 50 years, 200 IU of vitamin D is required daily. The elderly need two to three times more since their vitamin D metabolism is impaired. By age 70, vitamin D production is only about 30 percent of what it was at age 25. The elderly at highest risk of vitamin D deficiency include those homebound or institutionalized and those living in the northern third of the country who have a low vitamin D intake.

A deficiency of vitamin D can increase the risk of bone fractures since vitamin D is needed for efficient calcium absorption and bone formation. The sunshine vitamin is also involved with a diverse range of body processes beyond maintaining healthy bones. Vitamin D promotes better muscle function; stronger muscles are better able to support the body and reduce the risk of falls in the elderly. Vitamin D is known to inhibit the growth of breast, colon, and prostate cancer cells. Adequate vitamin D can also lower blood pressure in adults.

Adequate sunlight provides many benefits. However, excessive sun exposure can accelerate aging, and give us freckles, sunspots, wrinkles, and skin cancer.

Winston Craig is professor of nutrition at Andrews University.

Sunlight can provide many health benefits.

Sunlight is too weak during winter for vitamin D synthesis.