It’s hard to figure out what to believe. One day, we’re told something is great for us, and the next we’re told that ground breaking new research proves that exact thing to be harmful. Recently, an article was published titled “Is Sunscreen the New Margarine?”, claiming that sunscreen is actually bad for you because it blocks the formation of Vitamin D. What does the science have to say? Let’s find out.
Welcome to the next installment of our Science Explained series. In this video series, we explore scientific myths and misconceptions, and by diving into the primary literature, determine what the body of scientific evidence currently has to say. Today we’ll be exploring whether sunscreen is good or bad for you, and how you can decide whether or not to use it yourself.
Sunscreen is Bad!?
The article, posted on Outside Online, is largely based off the research of Richard Weller and Pelle Lindqvist. Weller is a dermatologist at the University of Edinburgh and Chief Medical Officer of RelaxSol, a sunscreen company that proclaims to provide both sun protection while preserving the health benefits of sun exposure in terms of Vitamin D and nitric oxide synthesis, as based on Weller’s own research. Can you say conflict of interest? Lindqvist is a senior research fellow in obstetrics and gynecology at the Karolinska Institute.
Lindqvist’s paper, titled “Avoidance of sun exposure as a risk factor for major causes of death: a competing risk analysis of the Melanoma in Southern Sweden cohort.”, was published in the Journal of Internal Medicine in 2016.
The researchers conducted a series of questionnaires to 29,518 women between 1990 and 1992 asking about sun exposure, alcohol consumption, smoking, marital status, education level, and parity, meaning the number of births. They asked four questions in particular to assess sun exposure – (i) How often do you sunbathe during the summer time? (ii) Do you sunbathe during the winter, such as on vacations in the mountains? (iii) Do you use tanning beds? (iv) Do you go abroad on vacation to swim and sunbathe?
These women were then followed for 20 years, with the researchers collecting data about their development of diseases and causes of death. Their conclusion?
The longer life expectancy amongst women with active sun exposure habits was related to a decrease in CVD and non-cancer/non-CVD mortality, causing the relative contribution of death due to cancer to increase.
In other words, women with active sun exposure habits were correlated with lower rates of heart disease and non-cancer related causes of death. However, the rates of death secondary to cancer increased, which is explained by the longer life span. If you live long enough, you’re more likely to get cancer.
If you’re confused how they arrived to this conclusion based off their methodology – don’t worry, you’re not the only one. First, we can see that the groups are significantly different in just about every demographic variable measured by the researchers, from education to marital status, parity, smoking, alcohol consumption, age group, disposable income, and most importantly, any comorbidities. While the researchers did attempt to control for these factors, the subgroups are so vastly different that its comparing apples to oranges. Additionally, they did NOT control for several other important confounding factors, such as sun protective measures – did the women use hats or sunscreen? They also didn’t control for several other important factors relevant to their endpoint of heart disease, such as family history of heart disease, dietary factors, exercise, BMI, diabetes, or hypertension, to list a few. Given the drastic differences in each sub-group, it’s safe to assume many of these other factors would also be substantially varied. If any of this confuses you, I recommend you watch my recent video on how to read research articles critically and quickly. Link in the description below.
The author also referenced research conducted by Richard Weller. His study tracked blood pressure in over 300,000 individuals across the U.S., adjusting for age and skin type. Preliminary findings suggest that people from sunnier climates have lower blood pressure. However, it is difficult to assess the validity of the claims or methods without seeing a published and peer-reviewed article. That being said, these results aren’t all that surprising – other published articles have demonstrated an inverse association between sunlight exposure and blood pressure.
The Details Count
The overarching conclusions are already on shaky grounds given the dataset and methods used. But perhaps there is truth to these claims – for that, we’ll need to dig a bit deeper.
A Brief Science of Sunscreen
The author claims that sunscreen blocks all UV radiation and therefore all Vitamin D production. Ask anyone who has gotten sunburned despite using sunscreen and you’ll understand the error in thinking here. The effectiveness of sunscreen is measured in SPF, standing for Sun Protection Factor, which is a measurement of how effectively UVB rays are blocked. This is not a linear scale, but higher numbers correlate to a greater percentage of UVB rays being blocked. An SPF of 15 corresponds to 93% blockage, SPF of 30 corresponds to 97%, and SPF 50 corresponds to 98%.
That being said, the overwhelming majority of people do not apply enough sunscreen. For best results, you should apply 2mg/cm2 of skin, reapplied every two hours. Most people under apply, using only 1/4 to 1/2 of the recommended amount, and are generally not great with reapplication. So what does this mean? In the real world, even with regular use of sunscreen, a great deal of sunlight and radiation is reaching our skin. Studies have also demonstrated that despite sunscreen use, adequate Vitamin D production occurs due to the imperfect nature of sunscreen and lack of perfect skin coverage at all times.
Should I Care About Skin Cancer?
While UVB rays are at the right wavelength to help catalyze vitamin D synthesis, they also cause major damage to our skin, including carcinogenesis, meaning the formation of cancer. The article glosses over the real risks associated with skin cancer. In medical school and plastic surgery residency, I’ve seen some nasty skin cancer cases.
Skin cancer is surprisingly common too. One in five Americans will develop skin cancer by the age of 70. There’s basal cell carcinoma, squamous cell carcinoma, and worst of all, melanoma. Skin cancer can metastasize, require major surgery, radiation, and immunotherapy. It’s not something to be taken lightly.
And sun exposure is the biggest risk factor in developing skin cancer. In fact, Parkin and colleagues found that 86% of melanoma cases can be attributed to UV exposure from the sun.
The real risk of skin cancer should be enough of a deterrent, but if you still need more convincing and you care about your appearance, know that unprotected sun exposure will also cause photoaging, which isn’t a good look.
The Verdict on Sunscreen
I’ve said it before and I’ll say it again. Be very wary when you see media articles summarizing new groundbreaking research that challenges our current understanding. More often than not, these articles, such as “Is Sunscreen the New Margaine?”, overdramatize and oversimplify the research findings without any consideration for the nuances or limitations. It makes sense, the incentives are such that these media outlets want your clicks and attention – their priority isn’t to provide you with truly accurate and unbiased scientific evidence. That being said, what is the actionable advice you can take from this video regarding sun exposure?
First, understand that we must create guidelines based off the current body of research and our understanding of health and disease processes. What we’re looking to balance are the beneficial and detrimental effects of sun exposure, namely Vitamin D production and skin cancer risk, respectively. Is there convincing evidence linking Vitamin D levels to blood pressure and arterial health? Yes! Is there convincing evidence suggesting sunscreen use or sun protection works against this? No! In fact, Scragg et al. found that neither UVA nor UVB exposure significantly lowers blood pressure, despite both increasing vitamin D levels.
For now, best practices are going to base on certain factors, such as your skin color. Melanin, the pigment produced in our skin that protects us from the sun’s radiation, is also responsible for the tan of our skin. If you’re lighter-pigmented, more careful and liberal use of sunscreen will be necessary to avoid sunburn and mitigate an increased risk of skin cancer. If you’re darker-pigmented, you’re less likely to get sunburned and it also takes more time for you to produce Vitamin D. However, sunscreen use is still advised, as darker pigmented individuals do have a higher risk of pigmentary disorders, including melanoma, post inflammatory hyperpigmentation, and scarring.
That translates to daily sun protection, meaning hats or protective clothing in addition to sunscreen, particularly if you’re at high risk for developing skin cancer. Don’t avoid the sun, but at the same time do your best to avoid getting sunburned and avoid using tanning booths.
In short, the research presented as the basis for the argument in this article is not strong enough to warrant any changes to our current understanding of sun exposure, Vitamin D, and how it effects our body. I personally recommend avoiding oxybenzone and parabens in your sunscreen, based on detrimental preliminary findings in animal models, and recommend you stick with zinc oxide or titanium dioxide based sunscreens instead.
During my medical school and plastic surgery training, I became somewhat overzealous in finding the best sunscreen. After going through close to a dozen, I now opt for Australian Gold Tinted and Body Sunscreen, which I’ve been happily using for the past two years. Cost effective, application is easy, and it uses good ingredients.
What is the next controversial piece of science you want me to cover? I’m enjoying making these Research Explained videos and need your help in deciding future topics.