A deficiency of vitamin D can lead to weakened bones, teeth, and muscles, as it disrupts calcium absorption. Additionally, a lack of this vitamin has been linked to an increased risk of dementia and colorectal cancer. New research adds another reason to avoid severe vitamin D deficiency: it can significantly worsen the course of respiratory infections.

Vitamin D and Seasonal Infections

It’s no coincidence that respiratory infections such as bronchitis and pneumonia are more common in winter, when sunlight is scarce. This is because lower exposure to ultraviolet light reduces vitamin D levels in the body, which negatively affects the immune system and increases susceptibility to such illnesses.

The Role of Vitamin D in Health

According to researcher Abby Burno from the University of Surrey (UK), vitamin D is essential for physical health. It not only supports healthy bones and muscles but also has antibacterial and antiviral properties that are believed to help lower the risk of respiratory infections that can lead to hospitalization. Despite its importance, many people experience vitamin D deficiency and do not reach the recommended daily intake of 10 micrograms.

Study on the Link Between Vitamin D and Infections

Burno and colleagues from the universities of Surrey, Reading, and Oxford analyzed data from the UK Biobank—a large medical information repository collected from 500,000 volunteers since 2006. In the largest study of its kind to date, 36,258 participants were selected. The results showed that people with severe vitamin D deficiency (less than 15 nmol/L) were 33% more likely to be hospitalized with respiratory infections compared to those with normal vitamin D levels (75 nmol/L and above).

The study also found that for every 10 nmol/L increase in vitamin D levels, the rate of hospitalizations due to respiratory infections dropped by 4%.

Recommendations and At-Risk Groups

Taking vitamin D supplements, especially during the winter months when people spend less time in the sun, is an effective way to boost its levels and reduce the risk of serious respiratory infections. This is particularly important for older adults, who are at higher risk of death from such infections, as well as for members of ethnic minorities in the UK, who are more likely to experience vitamin D deficiency.

Public Health Significance

According to researchers, lower respiratory tract infections—as opposed to upper respiratory tract infections like the common cold and sinusitis—are among the top twenty causes of death in adults aged 50 to 74, and among the top ten for those over 75.

“Our findings, which show a significant association between higher vitamin D levels and fewer hospitalizations, warrant further investigation. They highlight the potential of vitamin D supplementation and consumption of fortified foods to reduce the risk of hospitalization due to respiratory infections in the future, and thus lessen the burden on the healthcare system,” notes study co-author Andrea Darling.

The study was published in the American Journal of Clinical Nutrition.