Debunked: the popular stereotype about the link between vitamin D and the sun

Researchers at Newcastle University have found that vitamin D levels in older adults remain low all year round - even during the summer months when sunlight is most abundant. The study has been published in the European Journal of Clinical Nutrition (EJCN).

It is commonly believed that vitamin D deficiency is resolved in summer thanks to the effect of ultraviolet radiation on the skin. This is why medical guidelines often recommend spending more time in the sun rather than taking supplements. The new study challenges this logic as it applies to vulnerable groups.

Scientists from the Newcastle University Centre for Nutrition and Exercise Research analysed vitamin D levels in nearly 300 residents of northern Britain - people over 65 and adults from ethnic minority backgrounds of all ages. Each participant provided a simple finger-prick blood test; the samples were processed by a specialised laboratory.

The results were unexpected: vitamin D insufficiency was widespread in both groups and did not disappear with the onset of summer. More than half of the older participants had insufficient vitamin D levels, and among ethnic minority participants the figure was even higher. Moreover, no significant improvement was recorded during the summer.

"It's striking that vitamin D levels didn't rise even in the summer months, when we would normally expect them to recover. For people living in the north of England, this shows that sunlight may not be enough - especially for older adults and those from ethnic minority backgrounds. The message is simple but important: if you are in an at-risk group, you cannot rely on spending more time outdoors to solve the problem," stressed Bernard Corfe, Professor of Nutrition and Human Health at Newcastle University and one of the study's lead researchers.

The authors call for a rethink of public health approaches: in their view, clearer guidelines are needed, along with brief vitamin D level assessments during GP visits and, where necessary, the prescription of supplements. In the next phase, the researchers plan to explore ways of improving vitamin D levels through personalised dietary and culturally adapted strategies.