Supplement analysis backed by scientific evidence · PT

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Limited evidenceJoints & skin

Polypodium Leucotomos

Polypodium leucotomos extract raises the UV dose needed to redden skin and may reduce photodermatosis flares, but trials are small and short and the protection is weak — equivalent to a very low SPF. It is an adjunct to sunscreen, never a replacement.

What the science says

  • Raising the UV erythema threshold Limited evidence

    In a 60-day randomised placebo-controlled study of healthy adults taking 240 mg twice daily, more supplemented subjects showed an increased minimal erythema dose (8 vs 1, p = 0.01) and decreased UV-induced erythema intensity (10 vs 3, p < 0.01), with fewer sunburn episodes. The outcome was counts of responders in a small sample, not a quantified protection factor.

  • Polymorphic light eruption and melasma Limited evidence

    A 2025 systematic review of dermatologic uses found small trials suggesting fewer and milder polymorphic light eruption episodes and modest melasma improvement when added to sunscreen or standard therapy, while rating the evidence base as small, heterogeneous and at risk of bias.

  • Not a sunscreen substitute Limited evidence

    The MED increases observed correspond to a protection factor well under 3 — far below the SPF 30+ recommended for sun protection. No trial has shown reduced skin cancer or photoageing outcomes in humans.

Dosage & safety

Studied dose240 mg once or twice daily is the usual regimen. Photodermatosis studies used 480 mg/day, sometimes as 480 mg taken 2 hours before sun exposure with a further 240 mg at midday. Trials lasted 8 weeks to 6 months.
SafetyGenerally well tolerated in short trials; reported side effects are mild gastrointestinal upset, itching and occasional headache. Safety beyond about 6 months has not been established, and there are no data in pregnancy, breastfeeding or children. No documented drug interactions, but products are unstandardised and content varies between brands. Because it is marketed as an 'oral sunscreen', the main real-world risk is behavioural — people cutting back on sunscreen or extending sun exposure on the strength of it.

Scientific references

Where to buy

Life Extension, Shade Factor™, 120 Vegetarian Capsules

View on iHerb

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