A new study from Newcastle University is challenging the assumption that warm summer months provide enough natural vitamin D for everyone. Researchers found that older adults and people from minoritized ethnic backgrounds in northern Britain continue to have dangerously low levels even during peak sunshine season.
The research examined nearly 300 people across the North of England and discovered that vitamin D insufficiency remained stubbornly consistent year-round. More than half of adults aged 65 and older tested insufficient, with even higher rates among participants from minoritized communities. Critically, those levels did not improve when summer arrived.
"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," said Bernard Corfe, a professor of human nutrition at Newcastle University and co-leader of the study. "For people living in places like the North of England, this shows that sunlight alone may not be enough, particularly for older adults and those from minoritized ethnic backgrounds."
The findings, published in the European Journal of Clinical Nutrition, suggest that vulnerable populations cannot rely on seasonal exposure to boost their vitamin D naturally. This matters because the nutrient is essential for bone health, immune function, and overall well-being. Low levels have been linked to osteoporosis, rickets, and weakened immunity.
Participants underwent simple finger-prick blood tests, with samples analyzed by specialist laboratories. Recruitment occurred through both community outreach and online methods across northern Britain.
The study raises questions about current public health guidance that may underestimate vitamin D risk in specific populations. Researchers are calling for more targeted interventions, including routine vitamin D screening during GP appointments, clearer guidance tailored to at-risk groups, and supplementation when necessary.
Newcastle University plans to continue the research by exploring personalized and culturally appropriate strategies to improve vitamin D levels. These could include tailored dietary recommendations and healthcare approaches designed for different communities.
The work was funded by Better You Ltd, a UK health and wellness company, though the funder had no involvement in study design, execution, or interpretation.
Author Jessica Williams: "The research demolishes a comfortable myth that's kept many people dangerously deficient for years."
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