GradedHealth

Sunscreen

Last reviewed October 2026 · Based on 5 studies

Bottom line

Daily broad-spectrum sunscreen slowed skin ageing by 24% over 4.5 years in one large trial, but that is almost the only trial; routine high-SPF use also lowered vitamin D levels in a newer trial.

What it helps with

  • Slows skin ageing — Benefit, evidence grade C (Limited). One large randomised trial plus a systematic review that found only one other small photoageing study; downgraded for single-trial evidence and missing outcome data.
  • Lowers vitamin D levels — Harm, evidence grade C (Limited). One open-label randomised trial of 639 adults; downgraded for measuring a blood level rather than health outcomes, and an earlier review found no significant effect.

What it is

Sunscreen is a lotion or cream applied to the skin to protect it from the sun's ultraviolet light. Sunscreens are recommended as a second-line measure behind protective clothing and shade [1].

What the research says

In the Nambour trial in Australia, 903 adults younger than 55 were followed for 4.5 years. Skin ageing was 24% less in the daily sunscreen group than in the discretionary group, and the daily group showed no detectable increase [2]. A 2021 systematic review found two photoageing studies, both favouring sunscreen, and rated the evidence limited [1]. The Cochrane review of sunscreen and basal or squamous cell skin cancers found only this same trial, with no clear difference after 4.5 years [3]; ten years after the trial ended there were fewer invasive melanomas in the daily sunscreen group [4]. Skin cancer is not graded on this page. A 2025 trial of 639 adults found routine SPF 50+ use for about a year lowered vitamin D levels by 5.2 nmol/L compared with discretionary use [5].

Doses used in studies

The Nambour trial used daily broad-spectrum sunscreen versus discretionary use [2]; the follow-up describes application to the head and arms [4]. The vitamin D trial used SPF 50+ sunscreen on days when the UV index was forecast to reach 3 or higher [5].

Safety and interactions

Sunscreens and their bases sometimes caused side effects affecting skin and eyes [1]. Routine SPF 50+ use lowered vitamin D levels and raised the share of people with vitamin D deficiency from 36.9% to 45.7%; the authors suggest regular users may need vitamin D supplementation [5]. The abstracts we read give no data on upper limits, medicine interactions or pregnancy.

Caveats and open questions

Skin-ageing evidence rests mainly on one trial with some missing outcome data and modest power [2]. It compared daily with discretionary use, and ran in a sunny part of Australia [2]. A 2021 review found no significant vitamin D effect, while the 2025 trial did [1][5].

References

  1. The Preventive Value of Sun Protection.. Curr Probl Dermatol, 2021.
  2. Sunscreen and prevention of skin aging: a randomized trial.. Ann Intern Med, 2013.
  3. Sun protection for preventing basal cell and squamous cell skin cancers.. Cochrane Database Syst Rev, 2016.
  4. Reduced melanoma after regular sunscreen use: randomized trial follow-up.. J Clin Oncol, 2011.
  5. Effect of daily sunscreen application on vitamin D: findings from the open-label randomized controlled Sun-D Trial.. Br J Dermatol, 2025.