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 is now 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.
But what does the science have to say?
Let's find out.
Dr. Jubbal, MedSchoolInsiders.com.
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.
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 children they had.
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.
Now 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 variables, 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,
which is heart disease. These other factors include 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 the methods without seeing a
published and peer-reviewed article.
That being said, these results aren’t all that surprising, as other published articles
have demonstrated an inverse association between sunlight exposure and blood pressure.
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.
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.
Now 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.
And 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. And like any cancer, it can be quite serious.
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.
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.
Now, 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
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 melasma,
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.
Given my higher risk of skin cancer,
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.
They're cost effective, application is easy, and it uses good ingredients.
I’ve placed links to these items in the description below.
If you decide to purchase them through those links, we receive a small kickback at no additional
cost to you.
What is the next controversial piece of science you want me to cover?
I’m enjoying making these Science Explained videos and need your help in deciding future
topics.
Let me know with a comment down below.
If you enjoyed the video, let me know with a thumbs up, and if you weren’t a fan, I
don’t mind if you leave a thumbs down.
Thank you for watching.
Much love to you all.
And I will see you guys, in that next one.