18 May 2023
For the month of May on my blog and socials, it’s going to be all cultivating good sun protection and anti-aging skincare habits! This post is a critical look at oral sunscreens; and the evidence behind them.
The risks of unprotected UV exposure to the skin may be well known to many; but finding a convenient way to ensure consistent and long lasting sun protection has always been tricky. Topical sunscreens need to be reapplied every 2-3 hours; and if you don’t apply enough, your SPF and PA protection will be less than expected.
A new approach has emerged in the last 2 decades to overcome these inconveniences of using sunscreens. Enter oral sunscreens- pills that claim to shield your skin from the sun. The sunscreen pills are essentially nutritional supplements; and because the term “oral sunscreen” is not regulated, the active ingredients vary in type, quality and concentrations across oral sunscreens differ widely.
For this blogpost, I’ll be focusing on one of the more common ingredients in such “oral sunscreens”- Polypodium leucotomos.If you’re already consuming them or thinking about trying oral sunsceens, here’s what you need to know.
Polypodium leucotomos is a fern of the Polypodiaceae family, native to Central and South America. It has been used in indigenous medicine in these regions for treating inflammatory skin conditions such as psoriasis and eczema1. The extract obtained from the leaves of the Polypodium leucotomos, is commonly found in supplements and is known by its commercial name, Fernblock®. Polypodium leucotomos extract, as Fernblock, is widely available in many countries including Singapore; and it is also heavily marketed as an “oral sunscreen”.
The chemical composition of Polypodium leucotomos extract (Fernblock) consists of:
• Phenolic compounds (benzoates and cinnamates) e.g. caffeic and ferulic acids2
• Biological acid molecules (quinic, shikimic, glucuronic, and malic acids)3
The high phenolic content is the basis of the antioxidant activity and photoprotective effects of Polypodium leucotomos extract (Fernblock)4. Ferulic and caffeic acids are the most potent antioxidants present in Polypodium leucotomos extract (Fernblock). Caffeic acid inhibits peroxide and nitric oxide formation induced by UV rays; and ferulic acid absorbs UV photons5. These effects reduce the formation of reactive oxygen species6 and have been shown to reduce sunburn after sun exposure7.
Based on studies (mostly in vitro human and animal studies); Polypodium leucotomos extract (Fernblock) has shown to offer protection against the following effects induced by UV exposure:
• DNA damage8,9
The histoloigical findings on these cells and tissues showed that the administration of Polypodium leucotomos extract (Fernblock) reduced tissue damage; with lesser angiogenesis, photocarcinogenesis, and solar elastosis8-12. Polypodium leucotomos extract (Fernblock) also improved cell membrane integrity and elastin levels8-12.
But what do the clinical trials and human studies show?
One of the important studies that illustrated the photoprotective benefits of Polypodium leucotomos extract (Fernblock) was a clinical trial in 200413. Subjects in this study were exposed to varying doses of artificial UV radiation, before and after administration of Polypodium leucotomos extract.The study showed that patients treated with Polypodium leucotomos extract developed less redness (one of the signs of sunburn)13. Biopsies obtained also corresponded with less cellular damage at the 24 and 72 hour marks in the group that hadPolypodium leucotomos extract13. Significant to note in this study is the omission of sunscreen use in the subjects meaning that these photoprotective benefits could be attributed to Polypodium leucotomos extract.
However, there were only 9 subjects in this trial; and long term endpoints were not assessed. Nonetheless, this small study supports the observation that oral Polypodium leucotomos extract reduced photodamage at cellular and clinical levels13.
Another trial of 22 subjects with fairer skin (Fitzpatrick I-III) by Kohli et al also illustrated the photoprotective effects of Polypodium leucotomos extract14. This study did not include subjects with darker skin; and this would have been significant as Asians have darker skin than Caucasians.
Melasma is a type of hyperpigmentation that is common in Singapore and the rest of Asia. It is influenced by exposure to UV, genetic factors and hormonal influences. Melasma has been covered in great detail in this post Hyperpigmentation Disorders: Causes, Types, Treatments. It is a complex disorder; and current standards of treatments still leave the patient with incomplete clearance and recurrences.
The role of Polypodium leucotomos extract in improving melasma has been studied in Singapore by a team of doctors from the National Skin Center15. This was a randomised controlled trial over 12 weeks involving 40 subjects. All participants used hydroquinoine and SPF 45 sunscreen; with the subjects consuming Polypodium leucotomos extract twice a day; and the controls consuming a placebo.The results showed that both groups had significant improvements in their melasma scores (mMASI); with the group that received Polypodium leucotomos extract showing greater reduction in their melasma scores15. This study concluded that Polypodium leucotomos extract is a useful adjunctive for treatment of melasma15.
However, another randomised, placebo controlled trial in the US on 40 Hispanic patients with melasma does not lend support to the use of Polypodium leucotomos extract as an adjunct to treatment of melasma16. Similar to the study conducted in Singapore, all subjects were also given sunscreen and hydroquinone, however, the dose of Polypodium leucotomos extract given to the subjects was half of the dose used in the Singapore study. The results of this study in the US showed that both the subjects and controls had reduced melanin index at the end of the study; with no significant intergroup difference in their results16. The authors concluded that these findings do not support the use of Polypodium leucotomos extract as an adjunct to topical sunscreen in the treatment of melasma in Hispanic women16
If exposure to UV rays accelerate signs of aging, can Polypodium leucotomos extract (Fernblock) reduce or delay these signs? The symptoms of photoaging such as wrinkles, dark spots, and sagging appear much later in response to UVA exposure; so it can be difficult to assess these in a study.
One study that looked at DNA modifications induced by UVA rays found that subjects that had taken Polypodium leucotomos extract had less DNA changes induced by UVA radiation, as compared to the controls that did not take Polypodium leucotomos extract17. This study, a randomised, investigator-blinded, controlled trial, of 10 participants irradiated with UVA did not assess longer term outcomes or clinical findings.
Based on the studies and trials on oral sunscreens/ Polypodium leucotomos extract (Fernblock); we can see that the results are ambiguous, with some studies showing benefits as well as a lack thereof. These studies are also limited by small power; with differing doses of oral sunscreens/ Polypodium leucotomos extract and protocols used. Without standardisation, comparisons between studies are not valid.
Importantly, these studies also did not mention whether sunscreen was applied adequately; as we know that the amount of sunscreen applied affects the final UV protection. So whether oral sunscreens/ Polypodium leucotomos extract truly provides additional protection above sunscreen cannot be assessed.
As more studies emerge, I will continue to update this blogpost on oral sunscreens/ Polypodium leucotomos extracts. That said, we can conclude that:
1. “Oral sunscreens” or “sunscreen supplements” are not truly sunscreens– in that they do not function as true sunscreen filters that absorb or reflect UV rays. Instead, Polypodium leucotomos extract and “oral sunscreens” are essentially nutritional supplements rich in antioxidants that mitigate the downstream effects of UV exposure.
2. “Oral sunscreens” may offer photoprotective benefits. However, these have not shown to be superior to, or serve as a replacement for topical sunscreen. They are at best, a supplement or adjunct to good sunscreen habits. It is best to use oral sunscreen pills in conjunction with topical sunscreen.
3. “Oral sunscreens” may benefit some groups of patients, not all. Those who suffer from melasma, are at risk of sunburn or use inadequate sunscreen may benefit from consuming oral sunscreens/ Polypodium leucotomos extracts.
But what if, one still decides to consume oral sunscreens/ Polypodium leucotomos extract, what are the risks? It is a relatively safe supplement to consume, with low risk of harm. Several studies have adverse drug reactions are very rare with oral sunscreens/ Polypodium leucotomos extract13, 18, 19 .
If oral sunscreens/ Polypodium leucotomos extract are nutritional supplements, are there foods that we can consume to protect our skin against UV rays? There are common food that you can include in your diet to improve your photoprotection- stay tuned for a follow up blogpost on this! Meanwhile, please remember to use sunscreen diligently 🙂
1. Fernblock (Polypodium leucotomos Extract): Molecular Mechanisms and Pleiotropic Effects in Light-Related Skin Conditions, Photoaging and Skin Cancers, a Review. Parrado et al. Int J Mol Sci. 2016 Jun 29;17(7):1026.
2. Phenolic components and antioxidant activity of Fernblock, an aqueous extract of the aerial parts of the fern Polypodium leucotomos. Garcia et al. Methods Find Exp Clin Pharmacol . 2006 Apr;28(3):157-60.
3. Polypodium leucotomos extract: antioxidant activity and disposition. Gombau et al. Toxicol In Vitro. 2006 Jun;20(4):464-71.
4. Inhibition of ultraviolet-induced formation of reactive oxygen species, lipid peroxidation, erythema and skin photosensitization by polypodium leucotomos. González and Pathak. Photodermatol Photoimmunol Photomed . 1996 Apr;12(2):45-56.
5. Fernblock, a nutriceutical with photoprotective properties and potential preventive agent for skin photoaging and photoinduced skin cancers. Gonzalez et al. Int J Mol Sci. 2011;12(12):8466-75.
6. Dermatologic Applications of Polypodium leucotomos: A Literature Review. Segers et al. J Clin Aesthet Dermatol. 2021 Feb; 14(2): 50–60.
7. In vitro and in vivo evaluation of caffeic and ferulic acids as topical photoprotective agents. Saija et al. Int J Pharm . 2000 Apr 10;199(1):39-47.
8. Oral Polypodium leucotomos decreases UV-induced Cox-2 expression, inflammation, and enhances DNA repair in Xpc +/− mice. Zattra et al. Am. J. Pathol. 2009;175:1952–1961.
9. Decrease of ultraviolet A light-induced “common deletion” in healthy volunteers after oral Polypodium leucotomos extract supplement in a randomized clinical trial. Villa et al. J. Am. Acad. Dermatol. 2010;62:511–513.
10. A Polypodium leucotomos extract inhibits solar-simulated radiation-induced TNF-alpha and iNOS expression, transcriptional activation and apoptosis. Janczyk et al. Exp. Dermatol. 2007;16:823–829.
11. Polypodium leucotomos extract inhibits glutathione oxidation and prevents Langerhans cell depletion induced by UVB/UVA radiation in a hairless rat model. Mulero et al. Exp. Dermatol. 2008;17:653–658.
12. Polypodium leucotomos inhibits ultraviolet B radiation-induced immunosuppression. Photodermatol. Photoimmunol. Siscovick et al. Photomed. 2008;24:134–141.
13. Oral Polypodium leucotomos extract decreases ultraviolet-induced damage of human skin. Middelkamp-Hup et al. J Am Acad Dermatol. 2004 Dec;51(6):910-8.
14. The impact of oral Polypodium leucotomos extract on ultraviolet B response: A human clinical study. Kohli et al. J Am Acad Dermatol. 2017;77(1):33–41.e1.
15. Double-blind, Placebo-controlled Trial to Evaluate the Effectiveness of Polypodium Leucotomos Extract in the Treatment of Melasma in Asian Skin. Goh et al. J Clin Aesthet Dermatol. 2018 Mar; 11(3): 14–19.
16. A randomized, double-blinded, placebo-controlled trial of oral Polypodium leucotomos extract as an adjunct to sunscreen in the treatment of melasma. Ahmed et al. JAMA Dermatol. 2013;149(8):981–983.
17. Polypodium leucotomos extract supplement in a randomized clinical trial. Villa et al. J Am Acad Dermatol. 2010 Mar;62(3):511-3.
18. Oral administration of a hydrophilic extract of Polypodium leucotomos for the prevention of polymorphic light eruption. Tanew et al. J Am Acad Dermatol. 2012;66:58–62.
19. Photoprotective activity of oral Polypodium leucotomos extract in 25 patients with idiopathic photodermatoses. Caccialanza et al. Photodermatol Photoimmunol Photomed. 2007;23:46–47.