Vitamin D Deficiency Increases Risk Of COVID, Colds And More

Do you always seem to come down with the sniffles? Or do you get COVID-19 again and again even when your loved ones don’t?

The reason for that may be your body’s levels of vitamin D (or lack thereof).

Vitamin D is crucial to many systems in our body, ranging from bone development to, yes, immune function. We can get it through food, sunlight and supplements, but food and sunlight, generally, don’t provide enough of it (more on that below).

“We know that vitamin D is playing a critical role in controlling both adaptive and innate immunity,” said Dr. Michael Holick, a professor of medicine, pharmacology, physiology & biophysics and molecular medicine at Boston University Chobanian & Avedisian School of Medicine.

“It is one of the major regulators of your immune system,” Holick added.

Diane Stadler, the director of the graduate programs in human nutrition at the school of medicine at Oregon Health & Science University, agreed. “There is a lot of evidence that is becoming readily available to associate vitamin D deficiency, so low vitamin D blood concentrations, with an increased risk of developing respiratory diseases [and] having different types of bacterial infections,” said Stadler.

The vitamin D deficiency itself doesn’t cause the illnesses you come down with, Stadler added. Instead, the sicknesses are due to the role vitamin D plays in our body’s immune response, she said.

“Vitamin D acts in a few different ways to enhance the immune response, and if you don’t have sufficient amounts of vitamin D, your immune system isn’t going to act as effectively in combating those traditional bacterial, viral infections that we seem to be more exposed to, especially in the winter months,” Stadler said.

Without enough vitamin D, your body can’t react as efficiently to fight off threats like colds and COVID-19. In his research at Boston University, Holick found that people who had low vitamin D levels had a higher risk of death and complications from COVID-19. Other research of his also found that people who are vitamin D deficient have a 54% higher risk of catching COVID-19.

Further protecting you from pesky winter illnesses, having sufficient vitamin D is good for your fall and winter vaccines like the COVID shot, flu shot and pneumococcal vaccine, according to Stadler.

“One of the things that vitamin D can really help with is improving the response to vaccinations,” Stadler said.

Your body better responds to vaccination when you have good vitamin D status.

“It helps to kind of prime, or make our bodies ready to have the appropriate response if we are getting vaccinated,” Stadler said.

“Vitamin D deficiency continues to be a worldwide health problem. It’s estimated upwards of 60% of the world’s population is vitamin D deficient or insufficient,” Holick said.

Our hunter-gatherer ancestors were outside much more than modern society allows, which allowed them to soak in sunlight (and, in turn, vitamin D) through their skin, Holick noted.

Vitamin D levels are measured via blood test, but it generally isn’t a test that’s ordered by primary care doctors, unless there is a reason to do so. Years ago, physicians may have been more likely to add a vitamin D panel to routine blood tests orders, but now “because vitamin D insufficiency or deficiency is so prevalent, there’s almost an assumption that people are going to have relatively low vitamin D concentrations … it’s almost like they don’t do the test, they just recommend vitamin D supplementation,” according to Stadler.

Vitamin D levels are measured in nanogram per milliliter (ng/mL), but the definitions of what exactly constitutes vitamin D deficiency vs. insufficiency vs. healthy levels vary, depending on the source. Stadler said deficiency is broadly defined as 15 ng/mL and below and insufficiency is 30 ng/mL and below.

Levels at 30 or above are, generally, recognized as a good range, but both experts think folks should aim for a little higher. (Stadler said values above 50 are ideal, and Holick likes folks to be in the 40 to 60 range, if not a little higher.)

Talk to your doctor to see where your vitamin D levels should be. People with certain kidney issues or other health problems may not be suitable candidates for vitamin D supplementation; chat with your physician before starting vitamin D or any new supplements.

Many daily multivitamins contain vitamin D, so check the ingredients and see how many units are already included and chat with your doctor about any potential additional supplementation.

It’s common for PCPs to recommend between 1,000 to 2,000 IUs per day of vitamin D3, Stadler said. Holick thinks adults should be on a higher amount than this, though.

“Typically, I recommend adults should be on minimum 2,000 units per day — and most I recommend 5,000 units a day because you want to get your blood level, in my opinion, of [vitamin D] between 40 and 60 ng/mL, [but] up to 100 is perfectly safe,” said Holick.

Once you get the go-ahead from your doctor, you can buy vitamin D supplements online or in stores like CVS and Walgreens. You’ll likely find vitamin D3 and vitamin D2 on the shelves, but vitamin D3 is more readily available and tends to be more recommended. Holick said vitamin D2 is perfectly acceptable, too, and is often preferred by vegans.

While it’s better to get some nutrients directly from food, that isn’t easy or potentially even possible with vitamin D. Oily fish, milk and orange juice are all good for increasing vitamin D levels, but can’t do so to the level necessary, said Holick. The same goes for the sun, which also carries a risk of skin cancer with too much exposure.

Holick said he recommends vitamin D supplementation to all of his patients, friends and family.

“You cannot get enough from your diet. You aren’t able to get enough from sunlight, unless you’re a … hunter-gatherer, so vitamin D supplementation is essential,” Holick said.

Older adults and people with darker skin are at higher risk of vitamin D deficiency, Stadler added. But, once again, it’s advisable for most people to take a supplement.

“Vitamin D insufficiency and deficiency is a public health concern,” said Stadler. “We need to be very aware of it, and it’s something that we can do something about very efficiently and inexpensively.”