Solar Defense Supplements Probably Don't Work

A great case study in why most supplements are a scam

Photo by James Day on Unsplash

Supplements are an interesting beast. There is the occasional supplement that has demonstrable, proven benefits, although these are almost always for a subsection of the population. Iron supplements for menstruating women who have a heavy flow and fatigue, for example. The supplements that work also tend to have trade-offs - iron supplementation improves fatigue, but makes a lot of people nauseous. That’s just how most real medical treatments work.

The vast majority of supplements, however, are ineffective or unproven. This week, I came across a brilliant example that really encapsulates how problematic most over the counter supplements are - ‘solar defense’ pills. There are dozens of different ones you can find online, but the specific pill I was asked about on Threads was this one. It’s basically a pill that is sold as extra protection against the sun, with the main ingredient being an extract from a species of fern. If you search for the fern - Polypodium leucotomos, or Phlebodium aureum - you’ll find dozens of similar pills with the same claims.

So, I took a look at the literature behind these sun defense pills. It’s very unlikely that a fern supplement will help prevent sunburn, skin cancer, or any of the other issues that the sun causes to your skin.

The Data

The idea that fern pills could help with sunburn and skin protection isn’t particularly new. The first studies looking at whether taking oral fern pills could reduce skin cancer in rats were conducted in the late 90s and early 00s, and found some interesting results. This then spurred a series of clinical trials looking at whether fern supplements could prevent a range of skin disorders, including UV damage from the sun.

Pictured: Cute, but not a human being. Photo by Joshua J. Cotten on Unsplash

The earliest clinical study in humans that I could find was this one, from 2004. The authors took 9 people, and exposed tiny patches of their skin to UV radiation, both with and without taking the fern pills. After 24 hours, the researchers looked at the patches of skin, and graded how damaged they were by UV. The study used a 5-point grading system for skin damage - when people had taken the fern supplements, their skin was on average about 0.75 points less damaged on this scale than when they hadn’t taken the pills.

There are many issues with this trial. It’s tiny, and not randomized. There was no blinding, so the people rating the skin damage knew if their patient had taken the fern supplement or not. This is particularly problematic for this study because it was funded by a company that sells the fern supplements.

Fortunately, this early trial was followed by more research, which given that people are selling the fern extract for more than $2 per pill you’d imagine were all incredibly positive.

Let’s go through the studies I could find.

1. This small unblinded randomized trial comparing 5 people who got the fern pills to 5 who didn’t on a marker of DNA damage after UV exposure. People taking the supplement were slightly less likely to have the marker of DNA damage, but the result was not statistically significant.

2. The largest randomized trial that I could find on the topic. The authors randomized 131 older people with preexisting skin damage to either receive treatment as usual, SPF 100+ sunscreen and advice to use it regularly, or the sunscreen plus oral fern pills. After six months, sunscreen reduced pretty much all markers of skin damage, including actinic keratoses (rough patches on the skin caused by the sun), but there were no statistically or clinically significant differences between people who had sunscreen and those who had sunscreen plus fern pills. Despite the lack of statistical significance, the authors spent a great deal of their discussion noting tiny differences between the fern pill and sunscreen only group, which is perhaps because the paper was industry-funded.

3. A small randomized trial from Brazil that used one of the most confusing designs I’ve ever seen in a study of 50 people. Rather than describe the extensive protocol, which used different forearms of the same people to test different things, I’ll just note that the people taking a placebo pill did better than those taking the fern pill on the main outcome measure of reductions in actinic keratoses in this study.

4. Another small, industry-funded trial from Italy. This trial randomized people to either receive the fern pills or a placebo for the treatment of vitiligo, which is a skin disorder that causes people’s skin to lose colour in large patches. Overall, there wasn’t much difference between the two groups at the end of the study, but the fern pill group did have better results for their head and neck.

5. A third small, industry-funded trial which tested sunscreen against fern pills plus sunscreen for the treatment of melasma, another skin condition which is exacerbated by UV damage. At the end of the trial, there were no statistically or clinically significant differences between the two groups.

6. A randomized trial looking at fern pills for the treatment of eczema in children. The authors found no benefits for their main outcome, which was use of topical steroids, but there was a slight decrease in the use of antihistamines in the last two months of follow-up for children taking fern pills compared to those taking a placebo. This study was also industry-funded.

You may be sensing a theme here. There are a range of industry-funded trials - because there aren’t many people interested in funding expensive clinical trials to test fern extract supplements - most of which find little to no benefit. In fact, only one of the trials I found for these supplements showed a real improvement that could be considered clinically important, which was the study of vitiligo where people saw improvements in their head and neck while taking the pills.

Pictured: Vitiligo. There were no benefits for hands, arms, legs, feet, or other body areas. Photo by Hanen BOUBAHRI on Unsplash

Realistically, however, the data is extremely negative for these pills. It’s possible that they may improve skin pigmentation issues for people with vitiligo, but you’d need a much bigger randomized trial to be sure of that. Given the size of the study, it’s quite likely to be statistical noise rather than a real result.

Meanwhile, the biggest trials of the supplements did not find any benefits for fern extract pills. The authors of these studies did present their findings in very positive lights, which is presumably impacted at least somewhat by the industry funding, but if you look at the actual data there are essentially no proven benefits to taking a fern pill supplement on eczema, sunburn, actinic keratoses, or other markers of skin damage.

Supplements Are A Scam

This is a great example of why I generally say that supplements are a scam (unless specifically prescribed by a medical doctor). There’s some data that suggests that these fern extracts could potentially reduce sun damage. Maybe. There are also a range of small, mostly industry-funded, clinical trials which show that the pills probably don’t do much for common skin conditions that are impacted by the sun. You can’t say anything definitive - the research is, overall, weak - but you could argue that there’s a small potential benefit here that a larger clinical trial might show.

Frankly, I’m skeptical. It’s always possible that spending millions on a clinical trial could prove that fern pills reduce sun damage by a bit, but it’s not very likely given the data so far.

Pictured: Probably not helpful for your skin. Photo by Artur Kulagin on Unsplash

The problem is, none of this uncertainty is reflected in the supplements themselves. If you go to an online store, or a supermarket shelf, you are greeted with a bright shiny bottle that sells itself with promises to help reduce UV damage. Of course, all of them say that they are only meant to be used with sunscreen, for obvious legal reasons, but they also imply that just taking the pills will make you less likely to get sunburned or even cancer.

This is classic for a wide range of supplements. Every once in a while I’ll be in the pharmacy for some reason and just take a look at the claims a few bottles make, and then look them up. Despite looking at dozens of different pills for numerous different applications, I've only ever found one with good evidence to support the implied claims on the packaging.

Crucially, most of these claims are probably entirely legal. In most countries, supplement manufacturers are limited in terms of what direct claims they can make - i.e. they can’t say “this prevents skin cancer” - but they can create misleading impressions very easily. If you buy Sol Defense which uses “specialty ingredients” to “provide an internal sunscreen”, you probably think there’s some evidence that it will work as sunscreen. But the data shows that it doesn’t.

My advice is to avoid solar defense supplements entirely. If you want to avoid sun damage and skin cancer, use sunscreen regularly and stay in shade where possible. You do need some sun for vitamin D, but ideally limit your time under high UV and always wear sunscreen if you’re out in the middle of the day in summer.