Immune System COVID | City of Hope

Does vitamin D help protect against COVID-19?

Until vaccines for the coronavirus are widely available, many people quite naturally look for other ways to protect themselves from infection. For starters, the oft-repeated basic prevention practices that have kept many safe continue to hold true: appropriately worn face masks, physical distance between people, frequent hand-washing, and avoidance of crowded or poorly ventilated indoor spaces.
 
Those seeking more protection may have taken note of the occasional headline-touting studies that associate low levels of vitamin D with severe illness from coronavirus. They may wonder, will a vitamin D supplement help keep away COVID-19 infection or mitigate symptoms?
 
Unfortunately, the jury is still out on that question.
 
“The data are inconsistent from studies that look at the relationship between vitamin D levels and COVID-19 infection risk and outcomes,” said Ping Wang, M.D., professor and chair of the Department of Diabetes, Endocrinology & Metabolism at City of Hope. “Right now, we don’t know because some studies show associations between them, but others couldn’t verify that connection.”
 
Ping H. Wang, M.D.

Ping Wang, M.D.

“We know even less about whether taking vitamin D can improve outcomes with COVID because there are no large, well-designed studies to answer that question.”

 
Vitamin D is both a nutrient and a hormone. It is perhaps best known for its role in helping the body absorb calcium, making healthy vitamin D levels important for bone health. It’s found in a number of natural sources:
 
  • The body generates vitamin D when skin is exposed to direct sunlight.
  • Fatty fish is a rich source of the nutrient.
  • Smaller amounts can be found in cheese, egg yolks and mushrooms.
  • Store-bought milk is typically fortified with vitamin D.
The nutrient also seems to have a role in metabolic processes, muscle function and communication in the nervous system. Inquiry into vitamin D’s influence on COVID-19 infection derives from strong signs that the nutrient does indeed seem to modulate the immune system as well:
 
  • Certain immune cells have receptors where molecules of vitamin D can connect to them.
  • Low levels of the vitamin seem to increase risk for conditions in which the immune system attacks the body itself.
  • Low levels similarly may be linked to infections such as the flu.
However, the larger question of how exactly vitamin D modulates the immune response is an active area of investigation. And before you reach for the pill bottle, it’s important to know that there is such a thing as getting too much of a good thing when it comes to vitamin D.
 
“People shouldn’t take more vitamin D beyond the daily recommendations,” Wang said. “An excess can lead to high levels of calcium in the blood, which has been associated with problems such as hypertension, the formation of kidney stones and changes in mental status.”
 
The Institute of Medicine has placed the recommended dietary allowance, or RDA, for vitamin D at 600 international units (IU) per day for young adults and 800 IU per day for adults older than 70 — although some experts say those recommendations are too low.
 
“If you have questions about it, don’t take vitamin D by yourself. Consult your physician,” Wang said.
 
So, for those curious about the benefits of vitamin D supplements in the era of the COVID-19 pandemic, the story of Goldilocks might be a good guide: Not too much. Not too little. Shoot for “just right.”