Some sunscreen products, notably those containing PABA, may actually break down in the presence of UV exposure and release the harmful oxygen-free radical particles, which theoretically could increase the risk for cancer. The long-term effects are not known. Increased Risk for Other Health Problems. People not only obtain vitamin D from foods but it is also manufactured in the body from a chemical reaction to sunlight. Vigorous sun-protection measures, then, may increase a person's risk for developing vitamin D deficiency.
Vitamin D is important for prevention of rickets, osteoporosis, and some cancers.
It should be noted that one small 2001 study found no higher risk for osteoporosis in elderly people who used SPF 15 sunscreens. Although sunlight is implicated in skin cancers, it also associated with lower risks for breast, prostate, ovarian, and colon cancers. The protection against these cancers appears to be related to vitamin D production but some experts associate a higher risk with the use of sunscreens. The bottom line is that some sunlight is important and even necessary for a healthful and high-quality life. Protective Clothing Wearing sun-protective clothing is extremely important and protects even better than sunscreens.