Several studies published in the last month have found a possible connection between getting enough vitamin D and experiencing less severe COVID-19 outcomes. But doctors warn that there isn’t enough evidence to know for sure.
The most recent, published last week in PLOS One, found that of 235 patients who had contracted COVID-19, the people with sufficient vitamin D levels were less likely to experience dangerous complications like unconsciousness, low blood oxygen and death. The findings suggest that “vitamin D sufficiency had improved the immune function in these patients,” the study’s authors write.
It’s in line with findings from another study published in the Journal of the American Medical Association in early September. That study, of 489 patients who were tested for COVID-19, found that the people with vitamin D deficiencies were 1.77 times more likely to test positive for the virus than people with significant levels of the vitamin.
So, what does this mean?
The authors of both studies say that more research is needed to prove any definitive link between vitamin D levels and COVID outcomes.
“Like all things COVID, we need more evidence, we need more studies,” Dr. Dina Kulik, a pediatrician based in Toronto, told HuffPost Canada.
Vitamin D slows down inflammation, and given that COVID causes inflammation of the blood vessels, “it could make sense that low vitamin D could be associated with more severe covid outcome,” Kulik said.
Low vitamin D levels have been linked to many different ailments, she pointed out, but most of them remain unproven.
We should all be getting enough vitamin D, COVID or not
“Many, many, many children and adults are vitamin D deficient in Canada,” Kulik said. “It’s somewhat ubiquitous.” That can be bad for our bones, teeth and muscles, among other things.
To get more, it’s a good idea to eat foods that are rich in the vitamin. A lot of fish have high vitamin D levels, including salmon, herring and tuna. You’ll also find it in egg yolks and mushrooms. And many foods are fortified with extra vitamin D, including lots of milk and milk alternatives, orange juice, yogurt, breakfast cereals and tofu. Next time you’re buying any of those foods, take a look at the nutritional information to see how much vitamin D you’re getting.
If you’re not eating those foods, “we do recommend giving a vitamin D supplement each day, particularly in the winter,” Kulik said.
Health Canada recommends that most adults should be getting about 600 IUs (international units) of Vitamin D per day, and should take no more than 4,000 IUs a day. (The IU rate will be listed on the bottle — many supplements are sold in increments of 1,000 IU pills.) Children under one year old should be getting about 400 IUs a day, and adults over 70 should get about 800.
But that doesn’t mean you should take too much of it!
If vitamin D is so good for you, the more you take, the healthier you’ll be. Right?
Actually, not at all.
Up to about 1,000 IUs a day is fine for most adults, Kulik said. “I would not be giving anybody more 2000 IUs a day, unless they were counselled by their physician to do so.”
Taking too much vitamin D can elevate your blood levels, which can lead to symptoms like fatigue, forgetfulness, nausea, vomiting, and slurred speech.
And while some vitamin D is good your bones, taking too much can actually lead to more fragile bones, Kulik said. A 2010 study found that very high vitamin D doses in older women lead to more falls and fractures.
And it’s also possible that in the same way, taking too much could stop being helpful against inflammation and actually trigger it, Kulik said.
“We never want to be super-supplementing anything,” she said. “It’s never helpful.”
There’s no “silver bullet” against COVID-19
Vitamin D is good for our bodies, in limited amounts, and making sure we get enough could lead to us being healthier generally. But it’s important to keep it in perspective: we don’t know for that it’s actually effective in reducing COVID risks.
It’s also worth looking at these studies — and any scientific studies, really — with a critical eye. One of the co-authors of the PLOS One study, Dr. Michael Holick, has touted vitamin D as preventing against almost everything, and has been criticized for accepting money from pharmaceutical companies selling supplements.
It would also be dangerous for people to think relying on supplements meant they didn’t have to take the precautions that experts know for sure are effective, like wearing a mask and regularly washing your hands.
“Getting enough vitamin D will absolutely benefit you in many ways that we know for sure,” Kulik said. “If there’s a bonus of COVID protection, that’d be great.”