Many people in England who are at greater risk of vitamin D deficiency may not achieve adequate vitamin D levels simply by spending more time outdoors in summer, according to new research from Newcastle University. The findings challenge the common assumption that seasonal sunlight naturally restores vitamin D stores.

Scientists from the University's Human Nutrition and Exercise Research Centre measured vitamin D levels in nearly 300 residents of northern Britain. Their analysis revealed that many participants remained vitamin D deficient or insufficient throughout the year, raising concerns about bone health, immune function, and overall well-being.

The study, published in the European Journal of Clinical Nutrition, included adults aged 65 and older as well as participants from minoritized ethnic communities of all ages. The research was funded by Better You Ltd, a UK company producing nutritional supplements, although the company had no involvement in the study design, data collection, or interpretation of the results.

Deficiency Persists Even in Summer

Researchers found that vitamin D insufficiency affected more than half of the older participants, while the prevalence was even higher among people from minoritized ethnic backgrounds.

One of the most significant findings was that vitamin D levels showed little or no improvement during the summer months, despite increased exposure to sunlight. This contradicts the widespread belief that summer sun alone is sufficient to restore healthy vitamin D status.

Vitamin D plays an essential role in maintaining healthy bones and supports many other bodily functions. Long-term deficiency has been linked to osteoporosis, rickets, weakened immunity, and other health problems.

Professor Bernard Corfe, Professor of Human Nutrition and Health at Newcastle University and co-leader of the research, said the findings were unexpected because vitamin D levels normally rise during summer.

He noted that in northern regions such as the North of England, sunlight may not provide enough vitamin D for vulnerable groups, particularly older adults and people from minoritized ethnic backgrounds.

According to Professor Corfe, individuals at increased risk should not assume that spending more time outdoors during summer will solve the problem. Instead, year-round approaches to maintaining adequate vitamin D levels should be considered.

Need for Better Public Health Strategies

Participants were recruited through community outreach and online advertising. Each volunteer provided a finger-prick blood sample, which was analyzed in a specialist laboratory.

The researchers believe the findings highlight the need for more targeted public health measures. They suggest clearer advice on vitamin D, routine assessments during GP visits, and appropriate supplementation for people at higher risk.

The study also provides valuable new evidence about year-round vitamin D deficiency among vulnerable populations, an area that has received relatively little attention.

The next phase of the research will investigate personalized and culturally appropriate strategies for improving vitamin D status, including tailored dietary guidance and healthcare interventions designed to meet the needs of different communities.

The researchers emphasized that the study was conducted independently and that the funding organization had no influence over any stage of the research.