Sun Exposure and Protection – Shedding a light on the benefits and risks

For this episode, we will take a closer look at a recent opinion piece in The Atlantic titled “Against Sunscreen Absolutism.” This article has gained quite a bit of attention, so I wanted to shed some light on the data behind the risks and benefits of sunlight, and ultimately, take this as an opportunity to explore how to critically evaluate literature/data to help make an informed decision.

“Only a Sith deals in absolutes”

You should be cautious when heeding advice based on broad generalizations. Our bodies are incredibly complex and unique, thus advice that applies to one person, may not be the best for others. Plenty of research seeks to evaluate population-based data (that is, data about the general public) but will often make firmer conclusions about specific subgroups (i.e. Patients with vitamin D deficiency, or patients with heart disease, or people over the age of 60, etc).

Knowing this, we can all likely agree that “absolutism” is likely not a great thing. Like (almost all) things, moderation is key, and there is likely more nuance to the advice. In the article, the author reviews a recent update to sun exposure guidelines put forth by the Australian Skin and Skin Cancer Research Center, noting that sun exposure can be a good thing for us. They argue that vitamin D supplementation is ineffective and that sunlight is needed to reap the benefits of vitamin D. So, let’s explore this a bit further.

The Good

I am in favor of consistently re-analyzing current evidence, exploring the nuance of current research, and applying it to our lives. Notably, this article suggests that some level of sun exposure may be beneficial, in ways that extend beyond simple supplementation of vitamin D. This makes sense, as we know that light can help regulate circadian rhythm, activate melanin, release endorphins, and modulate the immune system(1), so this is not a revolutionary opinion. 

Now, not experiencing the full benefits of a particular action via isolated supplementation isn’t a new concept. We see this with other things as well. For example, we have evidence that fish oil can help (mildly) reduce heart disease risks, but often find that eating the fish, getting these nutrients from your diet rather than supplementation alone, is generally more effective or associated with better outcomes. This concept represents one of the first things to keep in mind when critically evaluating research – biases, particularly confounding bias.

While we do our best to limit bias in scientific research, not everything can be completely accounted for. When we see beneficial effects from dietary fish oil, are we really noticing effect from eating fish alone? Perhaps we are noticing a correlation as many people who get plenty of fish in their diet are more cautious about their diet and health overall, eating a wider variety of foods (fish, veggies, fruits, etc.) compared to those who don’t eat any fish at all.

Similarly, it can be hard to judge the efficacy of sunlight exposure in this regard. Are we seeing benefits of sun exposure alone? Or are those who get more sun exposure also getting more activity/steps in their day and that’s what brings them outside? Sometimes we cannot account for all of these variables, so we make our best judgments.

The Bad

Unfortunately, the article itself makes (or emphasizes) a few broader absolutes itself, quoting an editorial by saying “People should stop taking vitamin D supplements to prevent major diseases or extend life.”(2)

Personally, and professionally, I take issue with this statement. While it comes from an editorial in response to the VITAL trial, it’s worth diving into the data a bit further, rather than taking this at face value. In fact, Dr. Robert Fakheri has critically analyzed the data for us in “To D or not to D.”(3) which brings me to our second suggestion in evaluating literature, check for significance in results and the baseline study characteristics, selection bias.

When claiming that Vitamin D supplementation offers essentially no benefits, it’s important to note that the average participant in the trial was NOT deficient in vitamin D at baseline. Would we really expect to see much improvement in vitamin D related variables in taking a non-deficient person and making them slightly less non-deficient?

That said, there were some benefits noted, anyway. There were benefits in those with low bone density (which agrees with prior research suggesting a positive role for Vitamin D supplementation in those with osteopenia and/or osteoporosis). Additionally, supplementation DID seem to offer a significantly protective benefit in autoimmune disease, as well (4).

So, what is the takeaway message?

Ultimately, more research is needed to help fully evaluate these questions and offer more concrete answers, but there are several takeaways from the Australian Skin and Skin Cancer Research Center that we can use to make broader recommendations (5).

The American Academy of Dermatology does still note that there is no ‘safe’ level of UV exposure, and this is ultimately true. Any UV radiation has the risk of damaging skin cells, altering DNA, and increasing cancer risk. However, there is a dose-dependent response to UV exposure, meaning ‘sub-erythemal’ or non-sunburning exposure to the skin leads to less damage than exposure that does result in a sunburn. 

Fortunately, it seems we can get the benefits of vitamin D synthesis from this ‘sub-erythemal’ exposure, as well. While it depends on the UV index, research suggests that just 6 minutes in the Miami sun can be equivalent to 1,000 IU of vitamin D (a common over-the-counter supplement dose)(6).

Because of these variabilities, the Australian Skin and Skin Cancer Research Center offers a very personalized approach to sun exposure based on geographic location and month (i.e. UV exposure) and skin type. For those of you looking for the most evidence-based recommendation, their appendix (cited below) offers a nice flow chart to identify your personal recommendation(5).

Simplified, 5-30 minutes of sun exposure, less for lighter skin and at higher UV-indexes is likely enough to achieve the benefits we need from sunlight exposure. More exposure beyond this should be combatted with sufficient sunscreen and skin protection. Additionally, if you have a family history of melanomas, take immunosuppressive medications, or have many moles, you should err on the side of caution and opt for more sun protection.

Do not be discouraged if you need to supplement vitamin D through dietary means or supplementation. There is evidence that this still leads to improvement and is a rather safe and cost-effective measure. That said, if you have any specific concerns about your own risks, do not hesitate to speak to your primary care physician to address these questions.

Bonus – Sunscreen tips

It’s important to note that if you are spending more than 2 hours outside, you should be re-applying your sun protection as it will fade in efficacy over time.

Sunscreen comes in two main forms: physical and chemical. Physical forms (generally zinc oxide or titanium oxide) create a physical barrier that blocks the sun. Chemical forms will result in a chemical reaction that absorbs and blocks the UV light. While both are effective, particularly for those of us with sensitive skin, physical sunblock is often less irritating and better tolerated.

Lastly, while there are forms of sunscreen that are combined with bug repellant chemicals, the American Academy of Dermatology actually recommend utilizing two separate products, as the bug repellant does not need to be reapplied as often and should be used less frequently.

Stay active, stay healthy, and look forward to a bright future ahead.

Sources and Further Readings:

1. Juzeniene A, Moan J. Beneficial effects of UV radiation other than via vitamin D production. Dermatoendocrinol. 2012 Apr 1;4(2):109–17. 

2. Jacobsen R. Against Sunscreen Absolutism. The Atlantic [Internet]. 2024 May 10 [cited 2024 May 22]; Available from: https://www.theatlantic.com/magazine/archive/2024/06/sun-exposure-health-benefits/678205/

3. Fakheri RJ. Vitamin D Supplementation: To D or Not to D? Mayo Clin Proc. 2024 Apr 1;99(4):529–33. 

4. Hahn J, Cook NR, Alexander EK, Friedman S, Walter J, Bubes V, et al. Vitamin D and marine omega 3 fatty acid supplementation and incident autoimmune disease: VITAL randomized controlled trial. BMJ. 2022 Jan 26;376:e066452. 

5. Neale RE, Whiteman DC, Beedle V, Ebeling P, Francis D, Girgis C, et al. Position statement: balancing the harms and benefits of sun exposure [Internet]. Brisbane, QLD, Australia: The University of Queensland; 2023 Jul [cited 2024 May 22] p. V1.11. Report No.: V1.11. Available from: https://espace.library.uq.edu.au/view/UQ:17c76bd

6. Craig A. Elmets MD. How Much Sunlight Is Equivalent to Vitamin D Supplementation? NEJM J Watch [Internet]. 2010 Jun 4 [cited 2024 May 22];2010. Available from: https://www.jwatch.org/JD201006040000002/2010/06/04/how-much-sunlight-equivalent-vitamin-d