It is obvious that people with darker skin (for example African-Americans and Asians) have a lower risk of skin cancer than fair skinned people (for examples those of European lineage). That is because they incur less ultraviolet-induced DNA damage for the same amount of sun exposure. So, people assume that having a tan will also protect them against sun damage. This is a common rationale people give me for going to a tanning salon to obtain a “base tan”. I have always argued that more of a bad thing does not make a good thing, and that a dark tan only has an SPF of 4. At that level you can blister off your base tan in one morning by the pool if you don’t wear sunscreen, so I recommend wearing sunscreen from the get go (SPF of 30 or higher) and just tan slowly.
Now there is even better evidence against getting a “base tan”. In a recent study published in Pigment Cell Melanoma Research by Miyamura et al, the investigators looked at the protection from a tan caused by tanning beds (UVA) and the tan caused by the wavelength that dominates natural sunlight (UVB), and compared that to untanned skin. First they tanned people with either UVA or UVB, then then they exposed the tanned skin to a combination of UVA and UVB in a ratio that mimics natural sunlight. The people who had a tan from UVA suffered just as much DNA damage as people whose skin had no “base tan”. The people who had a tan from UVB were modestly protected, but to obtain their tan they already had extensive DNA damage.
Summary: Do not go to tanning beds. Do not use natural sunlight to tan. If you want a tan for cosmetic reasons, use a self-tanner. When outside, wear sunscreen and hope for the best!
