Should you avoid retinyl palmitate in sunscreens?

Does retinyl palmitate in sunscreens increase skin cancer? This is a myth heavily promoted by clean beauty organizations like the Environmental Working Group (EWG), especially in their annual sun protection guide.

Recently, this was included as the first point in a video by toxicologist Dr Yvonne Burkart: “You’ve Been Lied About Sunscreen: A Toxicologist Reveals 6 Things You Should Know About Sunscreen”.

This is Part 1 of the response to the video by Dr. Yvonne Burkart, myself and toxicologist and cosmetic safety tester Mohammed Kanadil (@MoSkinLab on YouTube and Instagram, he also has the new Substack). We also reviewed two doctors with extensive experience in our field (Dr. Norbert Kaminski and Dr. Lyle Burgoon), so this is a peer review!

The video is here, keep scrolling for the article version…

Retinyl palmitate: what is the evidence?

Retinyl palmitate is a form (from which) of vitamin A. It has been used in skin care products for decades, including sun creams. Some people say it can increase skin cancer, including Dr. Yvonne Burkart:

YB: “Some [sunscreen] ingredients can actually promote skin cancer. This one is really shocking because that is the exact opposite of what sunscreen is supposed to do. Retinyl palmitate is a synthetic form of vitamin A that is often added to sunscreens for its so-called anti-aging benefits. You’ll see it often promoted as helping to reduce wrinkles or improve your skin’s texture.

But here is the most shocking thing. When exposed to the sun, retinyl palmitate becomes very unstable, breaking down into free radicals, which are very active. These free radicals damage DNA and lipids, as well as proteins, accelerate skin aging and can even increase the risk of tumor formation over time.

In fact, research shows that retinyl palmitate when applied to the skin and exposed to sunlight produces reactive oxygen species or ROS and lipid peroxides, two well-established drivers of oxidative stress and photocarcinogenesis, which is the formation of cancer due to sunlight. “

Based on these statements, and the phrase “when applied to the skin”, you would expect the study to find early signs of skin cancer in humans, or at least in human skin. You would be wrong – the evidence is actually very weak. There are three main types he refers to:

In vitro testing: In test tube studies, retinyl palmitate breaks down with UV exposure to form reactive oxygen species. This can damage cellular structures such as DNA, leading to oxidative stress, which is one of the ways skin cancer can develop.

Cell studies: Cells in petri dishes exposed to UV changed significantly when retinyl palmitate was added.

Animal studies: Dr Yvonne Burkart highlights some animal research:

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These results seem very concerning, but it is important to note that these studies are very old, so they have been publicly known for a long time. If retinyl palmitate was still found in sunscreens, it’s possible that safety inspectors would consider the potential danger raised by this study, and decide that it is safe. Of course it is!

Why is retinyl palmitate safe?

For example, the European Union’s Scientific Committee for Consumer Safety reviewed this data in 2016. This is a panel of highly experienced scientists (mainly toxicologists) who assess EU product safety. Their safety assessment (much more detailed and rigorous than a typical peer-reviewed paper) analyzed the most relevant studies including this NTP study, and reveals the reasons they don’t think retinyl palmitate is a problem in sunscreens:

The in vitro test does not reflect the human skin surface

Depending on what else is around, retinyl palmitate can increase oxidative stress, or reduce it (antioxidant).

For in vitro (test tube) testing, retinyl palmitate is usually alone. On the other hand, the skin is a complex mixture of substances, including many antioxidants. In this case, retinyl palmitate may behave in a very different way, and reduce overall oxidative stress.

Human and hairless mouse skin are very different

The NTP study used hairless mice, which are very different from us humans. They are used purposefully because they are very sensitive to UV, so they start to grow quickly and get clear results in a short time. However, this means that their skin has many differences that do not translate:

• Mice are generally nocturnal, so their skin has not evolved from any sun exposure unlike ours.
• Hairless mice are even more vulnerable to light, because fur usually protects the mouse’s skin to some degree.
• The specific type of mouse used was an albino, which lacks protective melanin.

On the other hand, human skin is very sensitive to the sun. So for us, retinoids can actually work the other way around and protect.

Real-world data suggest that retinoids are protective

Dermatologists have used retinoids for about 50 years (most of the evidence shows that retinol and tretinoin also work), and they are actually used prevent skin cancer. Dermatology patients are examined by dermatologists a lot, so if skin cancer was a serious problem, we should have seen more symptoms by now.

Another factor in the NTP mouse study

The NTP rat study had some strange results that could not be explained by retinyl palmitate being problematic. More UV resulted in smaller tumors, but cream outside retinyl palmitate also caused more tumors.

This can be explained by another ingredient in the cream base, dipropyl adipate. This appears to cause increased UV sensitivity in hairless mice, but it has also been tested on human skin, and this did not occur.

The decision

For these reasons, the SCCS concluded that retinyl palmitate is safe in sunscreens for both 2016 and 2022. The 2022 report also recommended limiting retinol in skin care, because it may add little to the large amounts of vitamin A we get from food and bones. So it’s not like they are vigilant!

Secondary sources such as reviews have problems: authors may be biased, they may leave out studies, many review authors are not qualified experts and do not understand the topic (sometimes they are paper grinders). For product safety, the best sources are often official reports such as SCCS safety assessments. When someone points to individual studies as evidence but leaves out these official reports, it’s a huge red flag.

References

National Toxicology Program. Photocarcinogenesis studies of retinoic acid and retinyl palmitate [CAS Nos. 302-79-4 (All-trans-retinoic acid) and 79-81-2 (All-trans-retinyl palmitate)] in SKH-1 mice (Simulated Sunlight and Subject Performance Study). Natl Toxicol Program Tech Rep Ser. 2012;(568):1-352.

Tolleson WH, Cherng SH, Xia Q, et al. Photodecomposition and phototoxicity of natural retinoids. Int J Environ Res Public Health. 2005;2(1):147-155. doi:10.3390/ijerph2005010147

Mei N, Xia Q, Chen L, Moore MM, Fu PP, Chen T. Photomutagenicity of retinyl palmitate by ultraviolet a irradiation in mouse lymphoma cells. Toxicol Sci. 2005;88(1):142-149. doi:10.1093/toxsci/kfi291

Scientific Committee on Consumer Products. Opinion on Vitamin A (Retinol, Retinyl Acetate, Retinyl Palmitate). October 6, 2016.

Scientific Committee on Consumer Safety. Review of Scientific Opinion (SCCS/1576/16) on Vitamin A (Retinol, Retinyl Acetate, Retinyl Palmitate). October 24, 2022.