Summer Sunlight Doesn't Fix Vitamin D Deficiency in Older or Minoritized Ethnicity Adults, Study Finds
Just get outside and get some sun is one of the most repeated pieces of vitamin D advice out there, and for a lot of people it holds up reasonably well once summer arrives. A new study out of Newcastle University found it does not hold up for everyone equally, and I wanted to look closely at who it leaves behind before repeating the advice myself.
- A new Newcastle University study found more than half of older adults and nearly three quarters of adults from minoritized ethnic backgrounds had insufficient vitamin D year round.
- Unlike the general population, these groups did not see meaningful improvement in vitamin D levels during summer months.
- Aging skin and higher melanin content both reduce how efficiently skin makes vitamin D from sunlight, which helps explain the pattern.
- The study was done in Northern Britain, a higher latitude than most of the US, so treat the exact numbers as specific to that population.
Sunlight on skin. For the two groups in this study, this does noticeably less than it does for everyone else.
Unsplash
Illustrative. Not a participant in this study.
For these two groups specifically, they stayed roughly flat all year.
What the study actually found
Researchers screened nearly 300 adults in Northern Britain as part of a larger clinical trial, focusing on two groups, adults 65 and older, and adults from minoritized ethnic backgrounds. They found vitamin D insufficiency or deficiency in 54.8% of the older adults and 72.1% of the minoritized ethnicity adults. The part that broke from the usual pattern is that these rates barely moved across the seasons. For most people, vitamin D levels rise in summer and fall in winter. For these two groups specifically, they stayed roughly flat all year.
Adults 65 and older
Insufficient or deficient, and the rate barely moved across the seasons.
Adults from minoritized ethnic backgrounds
Nearly three quarters, also roughly flat all year.
Screening data from nearly 300 adults in Northern Britain, a higher latitude than most of the United States. Observational screening from within a larger trial, not a randomised supplementation test.
Why the seasonal boost doesn't show up
Two things are likely working against these groups at once. Skin becomes less efficient at producing vitamin D from sunlight as it ages, and higher melanin content also reduces how much vitamin D the skin can synthesize from a given amount of sun exposure. Put those together and summer sun simply does not deliver the same boost it gives everyone else.
Honest caveat
This is one study, screening data from about 300 people in one region of Northern Britain, which sits at a much higher latitude than most of the United States. The exact percentages should not be assumed to apply directly to an American audience, and this is observational screening data from a clinical trial rather than a randomized supplementation trial, so it shows a pattern rather than testing a fix. No contradicting research turned up in my search, and the finding lines up with well established biology around aging skin and melanin, but it has not yet been independently repeated in a second study.
What this means for you
If you are over 65 or have more melanin in your skin, this is a real reason to treat vitamin D as a year round habit rather than something you only think about in winter. Getting your levels checked and talking to a doctor about supplementation, regardless of season, is a reasonable and low risk step worth considering for these two groups specifically.
Primary sources
- Circannual prevalence of vitamin D insufficiency in older and minoritized ethnic adults in Northern Britain, European Journal of Clinical Nutrition, 2026. Screening outcomes from clinical trial ISRCTN13778806.
- ScienceDaily, Study challenges a common belief about vitamin D and sunlight, June 2026. Secondary reporting corroborating the same figures.
Common questions
Does summer sun exposure fix low vitamin D for everyone?
Not for everyone. This study found older adults and adults from minoritized ethnic backgrounds stayed insufficient across seasons, unlike the general population pattern.
Why would summer sun not help these groups as much?
Aging skin and higher melanin content both reduce how efficiently skin produces vitamin D from sunlight, which likely explains why the usual seasonal boost does not show up.
Do these findings apply directly to someone living in the United States?
Not exactly. This study was done in Northern Britain, a higher latitude than most of the US, so the specific percentages should be treated as specific to that population rather than a national number.
Stay Curious.
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