Vitamin D deficiency increases mortality among critically ill patients

Patients admitted to the intensive care unit often lack vitamin D, resulting in more complications, prolonged ICU stay, and increased mortality compared with patients who have adequate vitamin D levels in their blood. This was demonstrated in an Iranian study from three hospitals. The study is published in BMJ Nutrition. Many older people and individuals with chronic diseases generally lack vitamin D, which is a problem.

The new Iranian study was carried out at seven intensive care units in three hospitals. For 24 hours after patients were admitted to ICU, blood levels of vitamin D were measured. The patients’ condition was assessed using a severity-of-disease classification system called APACHE 11 and another score called SOFA (Sequential Organ Failure Assessment). The researchers also looked at nutritional risk factors in critically ill patients (mNUTRIC).
The study included 236 patients. As it turned out, 163 of the patients (= 69.1%) had blood levels of vitamin D below 20 ng/ml (or 50 nmol/L), which is below the official threshold value. Also, the patients with low vitamin D levels had a higher APACHE, SOFA, and mNUTRIC score, indicating that they had more complications. Patients with sufficient vitamin D levels in their blood (higher than 30 ng/ml or 75 nmol/L), on the other hand, had fewer complications and spent fewer days in the ICU.
The scientists concluded that critically ill patients who are vitamin D-deficient have a greater risk of developing serious complications and dying because of this within a period of 28 days. Supplementation with vitamin D may help reduce these complications and improve the clinical outcome in ICU patients.

Why is it so problematic when critically ill patients lack vitamin D?

Vitamin D is considered a steroid hormone and regulates different genes in the cells of the body. Blood levels of vitamin D in healthy people depend on factors such as sun exposure, age, body fat percentage, and the amount of melanin in skin. People with dark skin have a slower vitamin D synthesis than people with lighter skin.
Critically ill patients often lack vitamin D because they get too little sunshine, spend too much time indoors, and tend to be overweight. Also, many are older and have dysfunctions in their liver and kidneys, which are vital organs for converting vitamin D into its active form.
It is commonly known that lack of vitamin D is linked to complicated infections, prolonged hospital stays, acute kidney failure, blood poisoning (sepsis), and increased mortality. This is because vitamin D is of key importance to a variety of immune cells, including dendrite cells and macrophages in the innate immune defense and T cells B cells and antibodies in the adaptive immune defense. Vitamin D also regulates inflammatory processes and prevents them from becoming unhinged. This is a vital function because complicated respiratory infections caused by influenza and COVID-19 are a result of ARDS (acute respiratory distress syndrome), which is characterized by hyperinflammation and comes with an increased risk of organ failure and death.
Blood poisoning is often accompanied by similar mechanisms, which is a result of derailed inflammatory processes and dysfunctional epithelial cells. Another problem is chronic low-grade inflammation, which accompanies most chronic diseases and contributes to oxidative stress and increased vulnerability to comorbidities.
There has been some uncertainty about blood levels of vitamin D in critically ill patients admitted to the intensive care unit with regards to disease severity and duration. This is what the new study tried to clarify, and it appears that vitamin D plays a critical role in how the patients feel and also affects their survival rate.

• The official recommendations for daily intake of vitamin D are around 5-20 micrograms. Older people and vulnerable population groups are advised to take the highest dose.
• These recommendations primarily address bone health but not immune health and many other vitamin D-dependent functions.
• Vitamin D supplements with up to 100 micrograms of vitamin D (or more) are available. This corresponds with the safe daily upper intake level for children aged 11 years and older and adults.
• The need for vitamin D varies from person to person. It is advisable to strive to have a blood level of 75 nmol/L or higher throughout life.

Reference:

Fatemeh Sistanian et al. Low plasma vitamin D is associated with increased 28-day mortality and worse clinical outcomes in critically ill patients. BMC Nutrition. 2024

Justyna Nowak et al. Could vitamin D concentration be a marker of a long hospital stay in older adult patients? Frontiers in Nutrition. 2023

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