Study challenges a common belief about vitamin D and sunlight

Researchers from Newcastle University's Human Nutrition and Exercise Research Centre analyzed vitamin D levels in nearly 300 people living across northern Britain. Their results suggest that a significant number of people could have low vitamin D year-round without realizing it, potentially affecting bone health, overall well-being, and long-term health outcomes.

The study, published in the European Journal of Clinical Nutrition, focused on adults aged 65 and older as well as people from minoritized ethnic backgrounds of all ages. Funding was provided by Better You Ltd, a UK-based health and wellness company that manufactures and sells nutritional supplements.

Vitamin D Deficiency Remains High Throughout the Year

The researchers found that vitamin D insufficiency was common in both groups studied. More than half of the older adults had insufficient vitamin D levels, while the proportion was even higher among participants from minoritized ethnic backgrounds.

Perhaps most notably, vitamin D levels did not improve during the summer months. This finding runs counter to the common assumption that increased exposure to sunlight during summer is enough to bring vitamin D levels back into a healthy range.

Vitamin D is essential for maintaining healthy bones and supporting overall health. Insufficient levels have been associated with a greater risk of conditions including osteoporosis, rickets, and weakened immune function.

Bernard Corfe, Professor of Human Nutrition and Health at Newcastle University and co-leader of the study, said: "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.

"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 message is simple but important. If you are in a higher-risk group, you can't assume that spending more time outdoors in summer will solve the problem.

"We need to be thinking about more consistent, year-round ways to support healthy vitamin D levels."

Researchers Call for Targeted Public Health Measures

Participants were recruited locally through both community outreach and online methods. Each person completed a simple finger-prick blood test, and the samples were analyzed by a specialist laboratory.

The findings also point to a need for more targeted public health strategies. Researchers suggest that clearer guidance, brief vitamin D assessments during GP appointments, and vitamin D supplementation when appropriate could help address the issue.

The study adds important evidence to an area that has received relatively limited attention and offers a better understanding of year-round vitamin D risk among vulnerable populations.

Researchers say the next stage of the project will explore ways to improve vitamin D levels through personalized and culturally appropriate strategies. These may include tailored dietary recommendations and healthcare approaches designed to better meet the needs of different communities.

The study's funder, Better You Ltd, had no role in designing the research, conducting the study, or interpreting the results. All aspects of the research were carried out independently by Newcastle University.