Even a sunny summer may not fix your vitamin D if you’re in a high-risk group

The standard advice for vitamin D is simple: get outside more in summer and your levels will take care of themselves. A 2026 Newcastle University study of nearly 300 people across northern Britain found that advice quietly fails for two specific groups — older adults and people from minoritized ethnic backgrounds — even during the sunniest months of the year.

What the study measured

Researchers from Newcastle University’s Human Nutrition and Exercise Research Centre tracked vitamin D levels via simple finger-prick blood tests in adults aged 65 and older, and in people from minoritized ethnic backgrounds of all ages, across multiple points in the year. More than half of the older adults had insufficient vitamin D, and the proportion was even higher among participants from minoritized ethnic backgrounds.

Summer sunshine didn’t move the needle

The most notable finding was what didn’t happen: vitamin D levels did not meaningfully improve during summer months in either group, contradicting the common assumption that increased sunlight exposure during warmer seasons is enough to restore healthy levels. For groups already at elevated risk — due to skin pigmentation reducing UVB-driven synthesis, reduced sun exposure, or aging skin’s reduced capacity to produce vitamin D — the seasonal "top-up" that works for much of the population simply doesn’t happen at the same scale.

"What’s striking about these findings is that vitamin D levels didn’t improve, even in the summer months when we would usually expect them to recover." — Prof. Bernard Corfe, Newcastle University

Why this matters beyond a single supplement recommendation

Vitamin D is essential for bone health, and insufficient levels are linked to a greater risk of osteoporosis, weakened immune function, and other downstream issues — the same territory covered by osteopenia and bone-density research. The practical implication isn’t "everyone needs a supplement" — it’s that people in these specific higher-risk groups can’t assume more time outdoors in summer is solving the problem, and need a blood test rather than an assumption to actually know where they stand.

The takeaway

If you’re over 65, or from an ethnic background associated with higher melanin/lower cutaneous vitamin D synthesis, this is a case for measuring rather than assuming — year-round, not just checking in winter. Consistent, evidence-based supplementation (rather than relying on seasonal sunlight) is likely to matter more for these groups than for the general population.

Vitamin D is one of the markers Misi flags automatically from any uploaded lab PDF, specifically because — as this study shows — season and self-reported sun exposure are unreliable proxies for your actual blood level.