A new study from researchers at Trinity College Dublin has provided fresh insights into why vitamin D deficiency remains common, even in places where it has been widely studied.
The findings show that different people respond differently to sunlight, and this might explain why some groups are more at risk of low vitamin D levels. The study was recently published in the journal Clinical Nutrition.
Vitamin D is an essential nutrient that helps our bodies absorb calcium and supports bone and immune health.
One of the main ways we get vitamin D is through sunlight—specifically, ultraviolet-B (UVB) rays that help our skin produce it. But in northern places like the United Kingdom, where there isn’t much sunlight, vitamin D deficiency is a big problem.
The research team looked at data from 500,000 people in the UK. For each person, they calculated how much UVB sunlight was available in their location. They then looked at how this affected the person’s vitamin D level, along with other personal factors.
Their analysis revealed two major findings. First, the amount of UVB sunlight someone is exposed to is a strong predictor of how much vitamin D they have in their body—even in a cloudy country like the UK.
Second, several personal factors such as age, sex, body mass index (BMI), cholesterol level, and whether or not someone takes vitamin D supplements also affect how much vitamin D their body makes from sunlight. For instance, people who are older or have a higher BMI tend to produce less vitamin D from the same amount of UVB.
Dr. Margaret M. Brennan, the study’s first author, said they hope the research highlights the differences in vitamin D levels across ethnic groups, especially in countries with less sunlight. The team believes this could help health professionals better understand and address vitamin D deficiency.
Professor Lina Zgaga, who led the study, said the results support the idea of moving away from one-size-fits-all vitamin D advice. Instead, she believes the findings should guide more personalized strategies that consider someone’s unique circumstances—like their body size, age, and environment.
Rasha Shraim, a PhD student and co-investigator, added that the research also shows how important natural factors like sunlight are for health. She hopes future public health efforts will include these kinds of environmental influences in their planning and guidelines.
Overall, this study points to a better way of managing vitamin D deficiency. Rather than giving everyone the same advice, public health programs might work better if they tailor vitamin D recommendations to each person’s needs.
If you care about nutrition, please read studies about how Mediterranean diet could protect your brain health, and this plant nutrient could help reduce high blood pressure.
For more information about nutrition, please see recent studies that olive oil may help you live longer, and vitamin D could help lower the risk of autoimmune diseases.
The study is published in Clinical Nutrition.
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