increase resistance to infection
Moderate UV light, not enough to redden the skin, increases the number of white blood cells in the blood stream. UV helps the body metabolize cholesterol by turning it into Vitamin D, and reduction of cholesterol in the bloodstream results from this process, increasing the oxygen carrying capacity of the blood. Oxygen helps white blood cells do their work by contributing to the process by which they destroy invading organisms. Over time, this can boost immunity and promote healing.

supply vitamin D
Cholesterol turns to vitamin D - a vitamin needed for proper bone formation - when UV light strikes the skin. Without vitamin D, bones do not become calcified and bend easily, which can lead to rickets in children, and in adult cases to bone diseases such as osteoporosis and osetomalacia. A study published in the March 1998 New England Journal of Medicine showed that more than half of all Americans may be vitamin D deficient, and 37% of those with proper levels of vitamin D in their diets were still deficient upon testing.

lower blood pressure, cholesterol and prevent heart disease
Studies show that blood pressure can drop an average of 6 - 20 mm HG systolic and 8 - 40 mm HG diastolic after a single UV treatment. In addition, UV helps the body metabolize cholesterol by turning it into Vitamin D, and reduction of cholesterol in the bloodstream results from this process, increasing the oxygen carrying capacity of the blood. After a single UV treatment, there can be up to a 13% decrease in the blood cholesterol. As these are the two major contributors to a high risk of heart disease, UV exposure may lower risk of heart disease as well.

increase resistance to colds
Exposure to UV light increases the number of white blood cells in the human blood. One type of these white blood cells is called a neutrophil. Neutrophils eat and destroy foreign material in the blood, like germs, bacteria and fungus. After exposure to UV, neutrophils are stimulated to eat germs more rapidly. Studies have shown a correlation between the temperature and days of sunshine and the frequency of colds.

prevent some cancers
UV exposure increases the use of oxygen in the tissues, and many types of cancer cells do not like oxygen.