SPF50+ and Vitamin D: The Sun-D Trial

A higher-SPF question

Sun-D tested the Australian practice of applying SPF50+ sunscreen during the morning routine on days when the UV index was forecast to reach 3 or higher. The research institute describes it as the first large trial examining SPF50+ use and vitamin D.¹

What changed in the blood tests

The 2025 open-label trial randomized 639 adults aged 18 to 70 who were not routinely using sunscreen or vitamin-D supplements. Of the 628 analysed, 66.1% were female; the median age was 52. The comparison was routine sunscreen versus discretionary use, not sunscreen versus a ban on sun protection.²

Blood 25-hydroxyvitamin D increased by an adjusted average of 1.6 nmol/L in the sunscreen group and 6.8 nmol/L in controls. The between-group effect was −5.2 nmol/L, not a 5.2-point fall within the sunscreen group.²

At the final sample, 45.7% of the sunscreen group versus 36.9% of controls were below the study’s 50 nmol/L deficiency threshold. That is an 8.8-percentage-point difference. Deficiency was an exploratory outcome.²

Skin type and vitamin-D testing

A 2026 published exchange in Australian Prescriber³ discusses the trial’s implications. The response notes limited representation of people with skin of colour and describes vitamin-D testing in regular sunscreen users as a matter of clinical judgment. The trial does not settle a single sun-protection or blood-testing rule for every skin type and location.³

Bring the question to the appointment with specifics: your sunscreen routine, time outdoors, clothing coverage, previous vitamin-D results and any supplements already taken. Ask whether testing or supplementation is appropriate for your situation. A result reported below a study threshold does not tell you which supplement dose to choose.

Keep vitamin D and UV protection in the same plan

In its response to Sun-D, Cancer Council Australia⁴ continued to recommend sun protection and advised people to discuss vitamin-D management with a doctor. It explicitly cautioned against excessive UV exposure even when vitamin D is low.⁴

Its Australian advice at UV index 3 or above combines protective clothing, SPF50 or SPF50+ broad-spectrum water-resistant sunscreen, a broad-brimmed hat, shade and sunglasses. Sunscreen is one part of that arrangement.⁴

Skin, Head to Toe places sunscreen on the short product Shelf in Chapter 5. If you already have a routine, take its details to the vitamin-D conversation rather than replacing it after reading a headline. Agree on any blood test, supplement and follow-up while keeping the purpose of each part clear.

Our earlier sunscreen and vitamin-D overview covers the older lower-SPF studies and now points to this newer trial.