- Vitamin D is a nutrient that plays an important role in maintaining the body’s health beyond bone health.
- Despite vitamin D’s importance, past research indicates that up to 1 billion people worldwide are vitamin D-deficient.
- A new study found a potential link between vitamin D deficiency and a higher rate of hospitalization for respiratory tract infections.
Vitamin D is a nutrient that plays an important role in maintaining the body’s health. While everyone knows vitamin D helps build strong bones, it also supports the immune system, muscle function, metabolic health, and brain health.
Despite vitamin D’s importance, past research shows that
“While vitamin D’s role in bone health is well-established, recent research shows that vitamin D deficiency has implications for an extensive range of health outcomes beyond bone health, including muscle function, cardiovascular disease, cancer, and immune function,” Abi Bournot, MSc, ANutr, PhD research fellow in the BBSRC Food Biosystems Doctoral Training Partnership at the University of Surrey in the U.K., told Medical News Today.
Adding to this list is a new study recently published in The American Journal of Clinical Nutrition, for which Bournot is the lead author, that found a potential link between vitamin D deficiency and a higher rate of hospitalization for respiratory tract infections.
For this study, researchers analyzed Health data from more than 36,000 participants between the ages of 40-69 in the U.K. Biobank.
Participants had their vitamin D levels measured via blood samples and were categorized by their levels. At the lowest end were participants with a vitamin D level of 15 nmol/L or less, which is well within the
Scientists then examined how vitamin D levels impacted participants’ risk of being hospitalized for a respiratory tract infection, such as bronchitis and pneumonia.
“We decided to look at the potential link between vitamin D and respiratory infections because there’s growing evidence that vitamin D plays an important role in our immune system,” Bournot said. “Because respiratory infections remain a major threat to public health globally, understanding whether vitamin D could be a modifiable risk factor for these infections could have important public health implications.”
At the study’s conclusion, researchers found that study participants with severe vitamin D deficiency had a 33% higher risk of being hospitalized for a respiratory tract infection, when compared to those vitamin D levels of 75 nmol/L or higher.
Additionally, scientists discovered that for every 10 nmol/L a participant’s vitamin D level increased, their respiratory tract infection hospitalization rate lowered by 4%.
“Because severe vitamin D deficiency is common in many populations, this association highlights the importance of raising public Health awareness about maintaining adequate vitamin D levels and its potential role in supporting immune function,” Bournot explained. “It also points to the need for further research, particularly randomized controlled trials, to see whether supplements could reduce the risk of hospital admissions for respiratory infections.”
Who should take vitamin D supplements?“Supplementation of the vitamin, especially in the winter months when our exposure to sunlight is limited, is an effective way of increasing vitamin D and potentially reducing the risk of serious respiratory tract infections. This is particularly important for older people who are at higher risk of such infections, and ethnic minority communities in the U.K., who are at a higher risk of vitamin D deficiency.”
— Abi Bournot, MSc, ANutr,
MNT spoke with Fady Youssef, MD, a board certified pulmonologist, internist, and critical care specialist at MemorialCare Long Beach Medical Center in Long Beach, CA, about this study.
Youssef commented that when he saw the results, they fit with what we already know — low vitamin D has been linked to a range of conditions, including bone disease, muscle weakness, cardiovascular disease, and impaired immune function.
“Seeing it associated with serious respiratory infections requiring hospitalization adds another important piece to that picture,” he continued.
“This study shows an association, not cause and effect. That said, vitamin D is known to play a role in immune regulation, and low levels may impair the body’s ability to fight infections or lead to an exaggerated inflammatory response in the lungs.”
— Fady Youssef, MD
“The next (research) step is establishing whether this relationship is causal and better defining the biological mechanisms involved — specifically whether improving vitamin D levels can reduce the risk of severe respiratory infections,” Youssef added.
MNT also spoke with Monique Richard, MS, RDN, LDN, a registered dietitian nutritionist and owner of Nutrition-In-Sight, for her top tips on how readers can make sure their vitamin D levels are healthy.
Richard encouraged readers to prioritize assessing what their vitamin D status is as well as the ways in which to address it accordingly, with their registered dietitian nutritionist (RDN) and healthcare team.
“Know your risk for deficiency,” she detailed. “People with limited sun exposure — especially in winter living in the northern half of the U.S. — darker skin and certain ethnicities, older adults, those with specific chronic conditions, and those with malabsorption disorders are at higher risk of low vitamin D.”
Richard said that consuming a variety of foods rich in Vitamin D, in addition to a balanced dietary pattern rich in vitamins and minerals, will help safeguard the risk of infections or possibly shorten recovery time. Food sources of Vitamin D include:
- Fatty fish (salmon, sardines, mackerel)
- Cod liver oil
- Egg yolks
- UV-exposed mushrooms
- Fortified foods (meaning vitamin D has been added to them)
- Milk and dairy
- Plant milks
- Orange juice
- Breakfast cereals and oatmeal
And if needed, Richard said to consider vitamin D supplements when appropriate, and work with a clinician to optimize dose and monitor levels.
“Remember that immune health is a holistic approach,” she explained. “Vitamin D is one part of a broader approach and an essential part of a cascade of nutrients that build a healthy, robust foundation for health and disease prevention. Quality sleep, balanced nutrition, stress management, and physical activity all contribute to resilient immunity and recovery.”
“The takeaway isn’t that vitamin D prevents infections — it’s that deficiency is a risk factor we can identify and address,” Richard added. “That’s where nutrition science and clinical care intersect.”
