But two other researchers whose work is used the by the tanning industry to bolster its claims said they don't advocate using tanning salons to reduce cancer. In its information packet, the Smart Tan Network quotes one, Dr. Michael Holick, chief of endocrinology, nutrition and diabetes at Boston University, as advocating exposure to sunlight to prevent disease. One reason is that, although sunlight activates the vitamin D that may reduce the growth of cancer cells, the body only produces as much activated vitamin D as it can use, Holick said. Therefore, increased exposure to sunlight does not increase the amount of activated vitamin D the body will produce. Levy said that's what the tanning industry is advocating, and that's why he supports the use of sun index guides in newspaper weather reports.
Dermatologists argue, however, that the best way to be sun smart is to avoid tanning.