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On 25th January 2005, the Daily Mail (1) reported that individuals may soon be able to take a pill to protect themselves from the harmful rays of the sun. The administration of Polypodium leucotomos (PL), an extract derived from a Central American fern, was reported to result in substantial decreases in skin reddening, burning of cells and damage that could lead to cancer.
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The newspaper article was based on a study of nine healthy individuals exposed to artificial ultraviolet radiation before and after ingestion of oral PL. The pill was found to exert effective systemic protection.
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The newspaper article accurately reported the results from this preliminary study and included comments from an expert highlighting that such research is at a very early stage.
Evaluation of the evidence base for the photoprotective effect of oral Polypodium leucotomos (PL) extract
Where does the evidence come from?
Middelkamp-Hup and colleagues, based in Boston, Massachusetts and Malaga, Spain, conducted the study. Funding was provided by Industrial Farmaceutica Cantabria, a Spanish pharmaceutical company.
What were the authors' objectives?
The authors investigated the photoprotective effect of orally administered PL against acute UV-induced damage to human skin using a solar simulator.
What was the nature of the evidence?
Nine healthy individuals participated in this observational study.
What interventions were examined in the research?
Participants were subjected to ultraviolet radiation exposure alone and subsequently to ultraviolet radiation exposure preceded by two doses of PL. Dose was calculated according to body weight (7.5mg/kg) and administered orally. Clinical evaluation of erythema response and histological examination of skin biopsies were carried out.
What were the findings?
The authors noted less acute erythema reactions in participants following administration of PL. Differences were detected whether exposure was sustained 30 minutes, 1 hour, 1 hour 30 minutes or 2 hours after administration of the drug.
The authors further highlighted the lower number of sunburn cells per millimetre of epidermis in treated skin (16.3) compared with untreated skin (22.4). Similarly, the amount of cyclobutane pyrimidine dimer (CPD) cells were also lower in treated skin: 43.7 cells/mm versus 74.7 cells/mm. Epidermal proliferation was observed at a higher rate in untreated skin, with 38.85% Ki-67 positive epidermal cells measured compared with 25.94% in treated skin. Finally, administration of PL was associated with reduced numbers of tryptase-positive mast cells in the papillary dermis: 126.4 cells/mm2 versus 173.76 cells/mm2.
What were the authors' conclusions?
The authors concluded that oral PL is an effective systemic chemophotoprotective agent, leading to significant decreases in UV-induced erythema, sunburn cell formation, DNA damage, epidermal hyperproliferation, and dermal mast cell infiltration.
How reliable are the conclusions?
This observational study reported a clear research question. Clinical endpoints were measured unblinded by at least two investigators; histologic parameters were predominantly quantified under blinded conditions. However, in view of the small sample size and short-term nature of the study, generalisability to a larger population over a longer period is unwarranted at this stage. The authors' conclusions need to be substantiated by further research using a more rigorous study design.
Systematic reviews
Information staff at CRD searched for systematic reviews relevant to this topic. Systematic reviews are valuable sources of evidence as they locate, appraise and synthesize all available evidence on a particular topic.
There were no related systematic reviews identified on the Cochrane Database of Systematic Reviews (CDSR) or on the Database of Abstracts of Reviews of Effects (DARE).
References and resources
1. The pill that can prevent sunburn. Daily Mail, 25 January 2005 p.50.
Consumer information
NHS Direct Online Health Encyclopaedia - Sunburn