- Recent studies suggest that a deficiency in a specific vitamin may increase the risk of severe flu infections.
- Experts indicate that vitamin D, in particular, might reduce the chances of serious complications from respiratory infections.
- Medical professionals believe that many individuals could gain from taking vitamin D supplements.
Flu cases remain high across the nation, mainly due to the contagious subclade K variant. Although there are various natural methods to enhance your immune system, new findings highlight a supplement that could mitigate severe flu reactions: vitamin D.
This conclusion stems from recent research published in The American Journal of Clinical Nutrition. The study examined health data from 36,258 participants in the UK Biobank, a long-term biomedical research database.
Researchers found that individuals with a severe vitamin D deficiency (defined as less than 15 nmol/L) were 33% more likely to be hospitalized for respiratory infections than those with vitamin D levels of 75 nmol/L or above. Moreover, for every 10 nmol/L increase in vitamin D, the hospitalization rate for respiratory infections decreased by 4%.
Considering that 18% of Americans have suboptimal vitamin D levels, this finding warrants attention.
Experts involved in the discussion include Amesh A. Adalja, M.D., from Johns Hopkins; Thomas Russo, M.D., from the University at Buffalo; Jessica Cording, R.D., C.D.N.; and William Schaffner, M.D., from Vanderbilt University.
This study is not the first to associate low vitamin D levels with an increased risk of respiratory infections, which prompts consideration regarding personal vitamin D levels.
Why might vitamin D reduce the risk of severe respiratory infection?
The study did not delve deeply into this issue, but medical professionals are not surprised by the results. “Vitamin D supports optimal immune function,” explains Amesh A. Adalja, M.D..
Vitamin D is known to improve both innate immunity—the body’s initial defense against germs—and adaptive immunity, which learns to combat specific pathogens after exposure, according to Thomas Russo, M.D.. He emphasizes that adequate vitamin D is crucial for a proper immune response, noting that even moderate deficiencies may hinder immune functions.
However, two key points are worth noting about this study: first, it’s observational, meaning researchers identified a correlation between low vitamin D and an increased infection risk; second, the focus was on those with severe deficiencies.
“The existing research on vitamin D supplementation is somewhat mixed,” says William Schaffner, M.D.. “It seems that the more severe the vitamin D deficiency, the less optimal your immune system functions.”
How much vitamin D is recommended?
The recommended daily allowance of vitamin D varies with age and life stage. However, most adults are advised to take 600 international units (IU) daily, as per the National Institutes of Health (NIH). For those aged 70 and above, the recommendation rises to 800 IU.
What are the signs of a vitamin D deficiency?
Vitamin D deficiency is particularly prevalent among lactose intolerant individuals, vegans, or those with limited sunlight exposure, according to the NIH. Symptoms can be subtle or difficult to identify, but commonly associated signs include:
- Fatigue
- Brain fog
- Low mood
- Frequent illnesses
- Bone fractures (primarily in severe cases)
How can you enhance your vitamin D intake?
Sun exposure is the primary source of vitamin D, but it can also be obtained through food. Significant dietary sources include:
- Cod liver oil
- Trout
- Salmon
- Mushrooms
- Fortified milk
- Fortified cereal
Additionally, supplements can be a viable option, as noted by Dr. Russo.
Should you take vitamin D supplements for immune health?
It varies. Consulting with a healthcare provider before starting any supplements is crucial, according to Dr. Schaffner. A blood test is typically recommended to evaluate vitamin D levels, as advised by Dr. Adalja.
This is important because vitamin D is a fat-soluble vitamin that can accumulate in the body, leading to potential issues from excess. “Avoid taking excessive amounts as it could cause complications related to high calcium levels,” warns Dr. Russo.
At the same time, many individuals, particularly in temperate regions, might not have optimal vitamin D levels. Dr. Adalja suggests that if you fall into this category, “daily vitamin D supplementation is generally a good approach.” Just remember to consult with a healthcare provider first.
For flu prevention, Dr. Russo reminds that measures like vaccination, staying away from sick individuals, and wearing masks in crowded indoor spaces remain effective. “A vitamin D supplement can be an additional help,” he states, “but it should not be the sole strategy.”
Dr. Schaffner, however, stops short of recommending universal vitamin D supplements for immune health, suggesting blood tests for those particularly interested. “Your healthcare provider can help determine if supplementation is appropriate for you based on your levels,” he advises.
