Let’s talk about vitamin D & immunity- it may be even more important now than ever. There's growing evidence that vitamin D may be relevant to risk of #COVID19 and severity of the disease. Thread from piece by Dr JoAnn Manson of ⁦ @BrighamWomens⁩. https://www.medscape.com/viewarticle/930152

2) “Vitamin D is important to innate immunity and boosts immune function against viral diseases. We also know it has an immune-modulating effect and can lower inflammation, and this may be relevant to the respiratory response and cytokine storm that's been demonstrated.”

3) “There are laboratory (cell-culture) studies of respiratory cells that document some of these effects of vitamin D. There's also evidence that patients with respiratory infections tend to have lower blood levels of 25-hydroxy-vitamin D.”

4) “There's now some evidence from COVID-19 patients as well. In an observational study from three South Asian hospitals, the prevalence of vitamin D deficiency was much higher among those with severe COVID illness compared with those with mild illness.”

5) “In fact, there was about an eightfold higher risk of having severe illness among those who entered with vitamin D deficiency compared with those who had sufficient vitamin D levels.
There's also evidence from a meta-analysis of randomized clinical trials of vitamin D”

6) “...supplementation looking at acute respiratory tract infections (upper and lower). This was published in the British Medical Journal 2 years ago, showing that vitamin D supplementation was associated with a significant reduction in these respiratory tract infections.”

7) “Overall, it was only a 12% reduction, but among the participants who had profound vitamin D deficiency at baseline (such as a blood level of 25-hydroxy-vitamin D of less than 10 ng/mL), there was a 70% lower risk of respiratory infection with vitamin D supplementation.”

8) “So the evidence is becoming quite compelling. It's important that we encourage our patients to be outdoors and physically active, while maintaining social distancing. This will lead to increased synthesis of vitamin D in the skin, just from the incidental sun exposure.”

9) “Diet is also important. Everyone should be reading food labels which list the vitamin D content. Food sources that are higher in vitamin D include fortified dairy products, fortified cereals, fatty fish, and sun-dried mushrooms.”

10) “For patients unable to be outdoors and also have low dietary intake of vitamin D, it's quite reasonable to consider supplement. The recommended dietary allowance is 600-800 IU/daily, but during this period, a supplement containing 1000-2000 IU/daily would be reasonable.”

11) “In the meantime, it's important to encourage measures that will, on a population-wide basis, reduce the risk for vitamin D deficiency.”

Dr JoAnn Manson is a professor of medicine at Harvard Medical School; and chief of the Division of Preventive Medicine @BrighamWomens.