FRIDAY, May 8, 2020 (HealthDay News) -- There's been much speculation about whether vitamin D might prevent or help survival with COVID-19, and two new studies appear to underscore the link.
In the first study -- published in the journal Aging Clinical and Experimental Research -- British researchers found that COVID-19 infections and deaths were higher in countries where people had low vitamin D levels, such as Italy and Spain, compared to northern European countries where average vitamin D levels were higher.
The researchers explained that people in southern Europe may have darker pigmentation, which reduces vitamin D synthesis, while people in northern European countries consume more cod liver oil and vitamin D supplements.
The second study appeared in the online journal medRxiv, but has not been peer-reviewed. In it, a team from Northwestern University in Evanston, Ill., analyzed data from 10 countries, including the United States.
Led by postdoctoral researcher Ali Daneshkhah, the study's conclusion was the same: Low vitamin D levels were linked to a hyperactive immune system.
The so-called "sunshine vitamin" bolsters immunity and prevents an overactive immune response, the Northwestern researchers said, adding that their finding could explain several mysteries, including why kids are unlikely to die from COVID-19.
But Dr. Mark Bolland, an associate professor of medicine at the University of Auckland in New Zealand who has investigated the effects of vitamin D on bone health, said neither study proves cause and effect.
"There are numerous examples where low vitamin D levels have been associated with a condition, but raising the levels does not improve it," Bolland said.
He said the papers were both "very speculative" and based on the same fallacy.
"It is far too simplistic to say that because some countries have average lower vitamin D levels, that this is a likely reason for worse COVID statistics," Bolland said.
But William Grant, director of the Sunlight, Nutrition and Health Research Center in San Francisco, had a different take.
To him, the findings add to results from other observational studies that found boosting vitamin D levels might help prevent COVID-19 or make it less severe.
Meanwhile, Dr. Frank Lau, an associate professor of clinical surgery at Louisiana State University, said his research clearly shows that vitamin D can make a difference.
Patients whose levels are low have a weaker immune response to the novel coronavirus, he said. Vitamin D strengthens it, allowing the body to develop antibodies to the virus and prevent it from spreading throughout the body, Lau said.
Clinical trials to see if vitamin D can help infected patients are getting started.
Lau's own trial involves giving vitamin D to patients in the early stages of COVID-19 infection. Meanwhile, a trial in France is investigating whether vitamin D will benefit people with severe infection, he said.
While Lau suspects vitamin D won't help once an infection is severe, he does believe boosting your vitamin D levels may help ward off COVID-19. But there's a more effective way to do it than taking a supplement, he said.
"The easiest way to get your daily dose of vitamin D is just to spend 10 to 15 minutes a day in the sun," Lau said. "It's inexpensive, it's free and you'll get all the vitamin D you'll need."
Vitamin D is also found in such foods as fatty fish, fortified dairy products and cereals, beef liver, cheese and egg yolks.
For more about COVID-19, visit the U.S. Centers for Disease Control and Prevention.
SOURCES: Frank Lau, M.D., associate professor of clinical surgery, Louisiana State University, New Orleans; William Grant, Ph.D., director, Sunlight, Nutrition and Health Research Center, San Francisco; Mark Bolland, M.D., associate professor of medicine, University of Auckland, New Zealand; Aging Clinical and Experimental Research, May 6, 2020; medRxiv, April 30, 2020