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  • 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 methodologydon'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 measuresdid 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 claimsfor 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 asIs 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.

It's hard to figure out what to believe.