It’s summer time, and I’ve been noticing a number of interesting articles floating through the blogosphere claiming that sunscreen could be doing more harm than good for our health in the long term. Claims include that 1) there is no evidence that sunscreen prevents melanoma and 2) that vitamin D deficiency, which can result from a lack of sun exposure, has been at least partially implicated in an increased occurrence of cancer in general.
Sorting through the evidence
There IS, in fact, evidence that sunscreen prevents melanoma, as a simple search on Google scholar led me straight to a number of peer-reviewed studies showing just that. Additionally, sunscreen has been shown time and again in peer-reviewed research to help prevent the other two main types of skin cancers, squamous and basal cell. These skin cancers are generally less deadly than melanoma, are be malignant cancer nonetheless. That being said, it’s worth noting that most deadly melanoma is found in non-sun-exposed areas of the body (source). This fact could cast some doubt on the link between sun exposure and melanoma but doesn’t negate the scientific research on the matter. I’d be skeptical of anything claiming that there’s NO documented connection between sun exposure and melanoma, but there’s certainly more work to be done in investigating this topic. The truth is, we don’t really know if there’s a single cause for melanoma – there probably isn’t. Just like all cancers, melanoma is complicated. But that doesn’t mean that excessive sun exposure isn’t a potential risk factor.
Exposure to UVB rays from the sun is the primary source of vitamin D for humans. We synthesize vitamin D in our skin when we’re exposed to UVB rays, and it plays a vital role in a number of developmental and physiological functions in our bodies. SPF 8 sunscreen, when applied as directed, can block more than 95% of UVB from our skin, preventing this important physiological response, and eventually resulting in a vitamin D deficiency for some (source).
This is where the “more harm than good” part of the argument could ring true in some cases. Vitamin D deficiency is linked to rickets in children and osteoporosis and osteomalacia in adults. It’s also linked to an increased risk for chronic diseases like diabetes, cardiovascular disease, multiple sclerosis, and YES, even some cancers. If we’re applying sunscreen to prevent skin cancer while simultaneously increasing our risk for chronic diseases and other (potentially more deadly) forms of cancer such as colon cancer, could we be doing more harm than good? (source) That seems to be the case, but let’s explore a happy medium.
Before we start jumping to conclusions, emptying our beach bags of all sun protection, and laying out like lizards on rocks, consider that moderate sun exposure is ideal for vitamin D synthesis. Overexposure is still not ideal, nor is it necessary to get all the vitamin D we need to thrive. According to one analysis, 10 to 15 minutes of daily sun exposure between the hours of 10am and 3pm is sufficient for a fair-skinned person to synthesize sufficient vitamin D. After that, it’s time for a little extra protection. The type of protection you use is also an important consideration. (It’s also worth mentioning that A LOT of us don’t get that 10 to 15 minutes every day, so a supplement might be worth considering, especially if you have very dark skin or live at a higher latitude.)
Environmental Factors and Side Effects
An increasing number of experimental studies are showing that sunscreens could have endocrine-disruptive effects, both on the individual applying them and on animals in the environment (source). Humans swimming in natural bodies of water covered in endocrine-disrupting sunscreen are not only exposing marine wildlife to these chemicals, they’re also exposing themselves. Whatever you put on your skin is absorbed into your body and can enter the blood stream, wreaking havoc on regular hormonal function. Chemical sunscreen is not an innocuous substance. The introduction of endocrine disruptors to marine life has been linked to population decline in various species and an increased occurrence of hermaphroditic fish.
It’s also worth noting in this section that those new aerosol sunscreens are not safe to breath in, and it’s basically impossible to avoid when you’re spraying them on. If you prefer a thinner stream of SPF, there are sprays that use a pump instead of an aerosol that are less likely to get into your lungs.
We’ve covered the potential and actual drawbacks of using chemical sunscreens, but as I stated at the beginning of this post, excessive sun exposure could lead to all forms of skin cancer. How can we strike a balance between sun safety, personal safety, and environmental safety?
A good old-fashioned HAT and a light-weight long-sleeved shirt will take you a long way after your first 10 or 15 minutes of unprotected sun exposure. You could also find some shade or bring an umbrella to the beach
Mineral and Natural Sunscreens
There are a number of eco-friendly and human-friendly sunscreens out there that create natural barriers to the sun through minerals and non-chemical alternatives. Here’s a link to the EWG’s (Environmental Working Group) most recent list. Find out if your sunscreen is on that list, and if it’s not, consider a switch.
If you’re feeling creative or curious, you could also consider making your own natural sunscreen at home. A number of natural plant oils on the market have built-in SPF that are just as effective as the chemical stuff. (Just make sure you remember to reapply if you’re going in and out of the water a lot.)
The bottom line here is that all factors should be considered when you’re planning a day at the lake, river, or beach. Bring a hat and find some shade, use a responsible product, but don’t be afraid of the sun. A little bit goes a long way! Have fun out there!