In a paper published in the British Medical Journal this month, 21 experts from the U.K., Ireland and the U.S. conclude that while vitamin D is “essential for good health” (especially for bones and muscles) and may bolster the immune system, it can also be dangerous in high doses.

“Many people have low blood levels of vitamin D, especially in winter or if confined indoors, because summer sunshine is the main source of vitamin D for most people,” the authors write. “Taking a daily supplement … and eating foods that provide vitamin D is particularly important for those self-isolating with limited exposure to sunlight.” Foods high in vitamin D include fatty fish (such as salmon and tuna), portobello mushrooms, fortified milk and yogurt and eggs. 

But high doses of the vitamin — which the authors refer to as “mega doses” can be extremely dangerous.

The paper comes on the heels of a study suggesting that vitamin D deficiency may be linked to higher rates of mortality with COVID-19. But the report warns individuals not to simply start taking those mega doses. “The continued spread of the novel SARS-CoV-2 virus, and the disease COVID-19 that is caused by SARS-CoV-2, has led to calls for widespread high-dose vitamin D supplementation,” the authors write. “These calls are without support from pertinent studies in humans at this time, but rather based on speculations about presumed mechanisms.”

31 PHOTOS

States reopen, relax guidelines to prevent coronavirus spread

See Gallery

NEW YORK, NEW YORK – MAY 06: An employee wearing a mask cleans the inside of the restaurant, Blue Stripes Cacao Shop as it prepares to reopen for takeaway and delivery orders after being closed for over a month amid the coronavirus pandemic on May 6, 2020 in New York City. Governor Andrew Cuomo made the announcement that all bars and restaurants must close by on March 16th unless it was takeout or delivery. COVID-19 has spread to most countries around the world, claiming over 263,000 lives with over 3.8 million cases. (Photo by Alexi Rosenfeld/Getty Images)

NEW YORK, NEW YORK – MAY 06: An employee wearing a mask cleans the inside of the restaurant, Blue Stripes Cacao Shop as it prepares to reopen for takeaway and delivery orders after being closed for over a month amid the coronavirus pandemic on May 6, 2020 in New York City. Governor Andrew Cuomo made the announcement that all bars and restaurants must close by on March 16th unless it was takeout or delivery. COVID-19 has spread to most countries around the world, claiming over 263,000 lives with over 3.8 million cases. (Photo by Alexi Rosenfeld/Getty Images)

THOUSAND OAKS, CA – MAY 06: A Cadillac Dealership displays a sign stating its reopened during the Coronavirus Pandemic on May 06, 2020 in Thousand Oaks, California. The coronavirus pandemic worldwide has claimed over 263,000 lives and infected over 3.7 million people. (Photo by Josh Lefkowitz/Getty Images)

HOUSTON, May 5, 2020 — Customers shop at a shopping mall in Frisco, on the outskirts of Dallas, Texas, the United States, May 5, 2020. After closed for several weeks due to the outbreak of COVID-19 pandemic, the shopping mall reopened with shortened business hours on Tuesday. (Photo by Dan Tian/Xinhua via Getty) (Xinhua/ via Getty Images)

HOUSTON, May 5, 2020 — Cars are parked in front of a shopping mall in Frisco, on the outskirts of Dallas, Texas, the United States, May 5, 2020. After closed for several weeks due to the outbreak of COVID-19 pandemic, the shopping mall reopened with shortened business hours on Tuesday. (Photo by Dan Tian/Xinhua via Getty) (Xinhua/ via Getty Images)

Dawson Padilla (L), owner of a protein shakes store, works behind the bar on May 5, 2020 in Stillwater, Oklahoma. – In the face of intimidation against employees and the threat of an armed attack by local residents wielding their individual liberties, the mayor of Stillwater had to give in: he gave up imposing the wearing of masks on customers in shops. This demand was included in a 21-page document that was supposed to accompany the gradual reopening of restaurants and shops from 1 May, as authorized by the state of Oklahoma. “About three and a half hours after the law came into effect” of the text, “we started receiving calls from stores claiming that employees were being threatened and insulted, and threatened with physical violence,” said Norman McNickle, the city’s director of services. (Photo by Johannes EISELE / AFP) (Photo by JOHANNES EISELE/AFP via Getty Images)

A worker of the Aspen Cafe wears a mask as she makes coffee on May 5, 2020 in Stillwater, Oklahoma. – In the face of intimidation against employees and the threat of an armed attack by local residents wielding their individual liberties, the mayor of Stillwater had to give in: he gave up imposing the wearing of masks on customers in shops. This demand was included in a 21-page document that was supposed to accompany the gradual reopening of restaurants and shops from 1 May, as authorized by the state of Oklahoma. “About three and a half hours after the law came into effect” of the text, “we started receiving calls from stores claiming that employees were being threatened and insulted, and threatened with physical violence,” said Norman McNickle, the city’s director of services. (Photo by Johannes EISELE / AFP) (Photo by JOHANNES EISELE/AFP via Getty Images)

Kelly Lyda, owner of the Aspen Cafe, stands in his Cafe on May 5, 2020 in Stillwater, Oklahoma. – In the face of intimidation against employees and the threat of an armed attack by local residents wielding their individual liberties, the mayor of Stillwater had to give in: he gave up imposing the wearing of masks on customers in shops. This demand was included in a 21-page document that was supposed to accompany the gradual reopening of restaurants and shops from 1 May, as authorized by the state of Oklahoma. “About three and a half hours after the law came into effect” of the text, “we started receiving calls from stores claiming that employees were being threatened and insulted, and threatened with physical violence,” said Norman McNickle, the city’s director of services. (Photo by Johannes EISELE / AFP) (Photo by JOHANNES EISELE/AFP via Getty Images)

Computer specialist Toby Angel drinks his coffee on May 5, 2020 in Stillwater, Oklahoma. – In the face of intimidation against employees and the threat of an armed attack by local residents wielding their individual liberties, the mayor of Stillwater had to give in: he gave up imposing the wearing of masks on customers in shops. This demand was included in a 21-page document that was supposed to accompany the gradual reopening of restaurants and shops from 1 May, as authorized by the state of Oklahoma. “About three and a half hours after the law came into effect” of the text, “we started receiving calls from stores claiming that employees were being threatened and insulted, and threatened with physical violence,” said Norman McNickle, the city’s director of services. (Photo by Johannes EISELE / AFP) (Photo by JOHANNES EISELE/AFP via Getty Images)

WESTPORT, CONNECTICUT – MAY 05: A cafe along a shopping street in the affluent community remains mostly empty of pedestrians and open stores on May 05, 2020 in Westport, Connecticut. A growing number of states have begun reopening parts of the economy amid demonstrations like the one yesterday that targeted the Connecticut state capital and the governor’s mansion in Hartford. (Photo by Spencer Platt/Getty Images)

WESTPORT, CONNECTICUT – MAY 05: A cafe along a shopping street in the affluent community remains mostly empty of pedestrians and open stores on May 05, 2020 in Westport, Connecticut. A growing number of states have begun reopening parts of the economy amid demonstrations like the one yesterday that targeted the Connecticut state capital and the governor’s mansion in Hartford. (Photo by Spencer Platt/Getty Images)

LAGUNA HILLS, CA – MAY 05: Customers maintain safety protocols at The BarberHood in Laguna Hills, CA, on Tuesday, May 5, 2020. The shop is one of the first to re-open and defy the state”u2019s stay-at-home order during the COVID-19 (coronavirus) lockdown. (Photo by Paul Bersebach/MediaNews Group/Orange County Register via Getty Images)

SAN CLEMENTE, CA – MAY 05: Visitors walk on the beach south of the pier in San Clemente, CA on Tuesday, May 5, 2020. The city opened its beaches for daily active use after coordinating with Gov. Gavin Newsom”u2019s office to maintain social distancing during the COVID-19 (coronavirus) lockdown. (Photo by Paul Bersebach/MediaNews Group/Orange County Register via Getty Images)

SAN CLEMENTE, CA – MAY 05: Surfers were back on the waves at T Street in San Clemente, CA on Tuesday, May 5, 2020. The city opened its beaches for daily active use after coordinating with Gov. Gavin Newsom”u2019s office to maintain social distancing during the COVID-19 (coronavirus) lockdown. (Photo by Paul Bersebach/MediaNews Group/Orange County Register via Getty Images)

KENMORE, WA – MAY 05: Lynette Fisher-Charles and her dog Gracie, a two-year-old springer spaniel, go for a hike in Saint Edward State Park on May 5, 2020 in Kenmore, Washington. The first phase to reopen the state begins today easing some restrictions including opening some parks, that were put in place during Governor Jay Inslees Stay Home, Stay Healthy order last March to help reduce the spread of COVID-19. Kenmore, WA is located northeast of Seattle. (Photo by Karen Ducey/Getty Images)

KENMORE, WA – MAY 05: Daryl Kline, a park ranger at Saint Edward State Park removes a sign saying the park is closed on May 5, 2020 in Kenmore, Washington. The first phase to reopen the state begins today easing some restrictions that were put in place during Governor Jay Inslees Stay Home, Stay Healthy order last March to help reduce the spread of COVID-19. Kenmore, WA is located northeast of Seattle. (Photo by Karen Ducey/Getty Images)

LAGUNA BEACH, CA – MAY 05: Lifeguards keep a lookout at Laguna Beach, CA after officials reopened access to the sand on Tuesday, May 5, 2020. The beach has been closed since March 23, 2020 due to the COVID-19 (coronavirus) outbreak. City parks along the beach are still closed and people cannot sit or linger on the sand. (Photo by Paul Bersebach/MediaNews Group/Orange County Register via Getty Images)

NEW YORK, May 4, 2020 — Photo taken on May 4, 2020 shows Times Square in New York, the United States.
Amid the ongoing COVID-19 pandemic, New York Governnor Andrew Cuomo on Monday outlined additional guidelines regarding when regions can reopen.
According to the Governor’s Press Office, the state will monitor four core factors to determine if a region can reopen: number of new infections, health care capacity, diagnostic testing capacity and contact tracing capacity. (Photo by Wang Ying/Xinhua via Getty) (Xinhua/Wang Ying via Getty Images)

NEW YORK, May 4, 2020 — A worker cleans a cafe’s signboard at Times Square in New York, the United States, May 4, 2020.
Amid the ongoing COVID-19 pandemic, New York Governnor Andrew Cuomo on Monday outlined additional guidelines regarding when regions can reopen.
According to the Governor’s Press Office, the state will monitor four core factors to determine if a region can reopen: number of new infections, health care capacity, diagnostic testing capacity and contact tracing capacity. (Photo by Wang Ying/Xinhua via Getty) (Xinhua/Wang Ying via Getty Images)

ASBURY PARK, NJ – MAY 4: People walk near the closed boardwalk due to the outbreak of COVID-19 in the state on May 4, 2020 in the Jersey Shore in New Jersey. Some towns at Jersey Shore expect the reopening of beaches soon. (Photo by Eduardo MunozAlvarez/VIEWpress/Corbis via Getty Images)

NORTH ANDOVER, MA – MAY 4: Although all golf courses in Massachusetts are still ordered to stay closed by governor Charlie Baker, workers at the North Andover Country Club in North Andover, MA work on the grass on May 4, 2020, getting the course ready for when they eventually are allowed to re-open. (Photo by Jim Davis/The Boston Globe via Getty Images)

LOS ANGELES, CA – MAY 04: Gov. Gavin Newsom announced select retail businesses will be allowed to reopen starting Friday in California during the coronavirus pandemic on Monday, May 4, 2020 in Los Angeles, CA. (Jason Armond / Los Angeles Times via Getty Images)

SANFORD, UNITED STATES – MAY 04, 2020: Customers enjoy a meal at Racks Billiards Sports Bar and Grill on the first day that retail stores and restaurants in all Florida counties except Palm Beach, Broward, and Miami Dade were permitted to reopen as COVID-19 restrictions are eased. Under phase one of the plan to reopen the state, stores and restaurants are limited to 25 percent of their indoor capacity.- PHOTOGRAPH BY Paul Hennessy / Echoes Wire/ Barcroft Studios / Future Publishing (Photo credit should read Paul Hennessy / Echoes Wire/Barcroft Media via Getty Images)

SANFORD, UNITED STATES – MAY 04, 2020: A customer leaves a Books-A-Million store on the first day that retail stores and restaurants in all Florida counties except Palm Beach, Broward, and Miami Dade were permitted to reopen as COVID-19 restrictions are eased. Under phase one of the plan to reopen the state, stores and restaurants are limited to 25 percent of their indoor capacity.- PHOTOGRAPH BY Paul Hennessy / Echoes Wire/ Barcroft Studios / Future Publishing (Photo credit should read Paul Hennessy / Echoes Wire/Barcroft Media via Getty Images)

BOZEMAN, MT – MAY 04: Sales staff wear masks at the reopened Schnee’s Boots, Shoes and Outdoors on Main Street on May 4, 2020 in Bozeman, Montana. Wyoming health officials today reported that the state’s confirmed coronavirus cases grew by nine to a total of 444. (Photo by William Campbell/Getty Images)

BOZEMAN, MT – MAY 04: Signs for restaurants and stores announce their reopenings on Main Street on May 4, 2020 in Bozeman, Montana. Wyoming health officials today reported that the state’s confirmed coronavirus cases grew by nine to a total of 444. (Photo by William Campbell/Getty Images)

JENSEN BEACH, FLORIDA – MAY 04: Cole Hunter carries Harper Hunter, 1, as Holly Hunter,4, follows along as they arrive at the beach on May 04, 2020 in Jensen Beach, Florida. Restaurants, retailers, as well as beaches and some state parks reopened today with caveats, as the state continues to ease restrictions put in place to contain COVID-19. The counties of Palm Beach, Broward and Miami Dade continue to maintain restrictions. (Photo by Joe Raedle/Getty Images)

JACKSONVILLE BEACH, FLORIDA – MAY 04: People are seen dining outside at Cruisers Grill as the state of Florida enters phase one of the plan to reopen the state on May 04, 2020 in Jacksonville Beach, Florida. Restaurants, retailers, beaches and some state parks reopen today with caveats, as the state continues to ease restrictions put in place to contain the coronavirus (COVID-19). (Photo by Sam Greenwood/Getty Images)

JACKSONVILLE BEACH, FLORIDA – MAY 04: People are seen at a department store as the state of Florida enters phase one of the plan to reopen the state on May 04, 2020 in Jacksonville Beach, Florida. Restaurants, retailers, beaches and some state parks reopen today with caveats, as the state continues to ease restrictions put in place to contain the coronavirus (COVID-19). (Photo by Sam Greenwood/Getty Images)

SAINT AUGUSTINE, FLORIDA – MAY 04: A mask is seen on the statue of Henry M. Flagler as the state of Florida enters phase one of the plan to reopen the state on May 04, 2020 in Saint Augustine, Florida. Restaurants, retailers, beaches and some state parks reopen today with caveats, as the state continues to ease restrictions put in place to contain the coronavirus (COVID-19). (Photo by Sam Greenwood/Getty Images)

A man works on power lines in Los Angeles, California on May 4, 2020, amid the coronavirus pandemic. – California governor Gavin Newsom earlier today announced the gradual reopening of the state later this week as dismal US employment figures are expected with the release of figures Friday May 8 for April’s US jobs report, as 30 million Americans filed for unemployment in the last six weeks. (Photo by Frederic J. BROWN / AFP) (Photo by FREDERIC J. BROWN/AFP via Getty Images)

HIDE CAPTION

SHOW CAPTION

The authors note that inundating the body with vitamin D can cause toxicity, and emphasize that there is no proof that doing so prevents the coronavirus. “There is no strong scientific evidence to show that very high intakes (i.e., mega supplements) of vitamin D will be beneficial in preventing or treating COVID-19,” the report reads. “There are evidenced health risks with excessive vitamin D intakes especially for those with other health issues such as a reduced kidney function.”

Amesh D. Adalja, an infectious disease expert and senior scholar at the Johns Hopkins University Center for Health Security, says that vitamin D deficiency is prevalent in the U.S., especially among black people, but agrees that taking large doses of it blindly can be dangerous. “Vitamin D is a medication, it’s a drug, so it can have side effects,” Adalja tells Yahoo Life. “When you have acute intoxication you can get a lot of different problems including confusion, vomiting — all kinds of things can happen.”

Vitamin D toxicity — officially referred to by the Mayo Clinic as hypervitaminosis D — is rare, but can cause “a buildup of calcium in your blood (hypercalcemia), which can cause nausea and vomiting, weakness and frequent urination.” The condition can prove most dangerous for those with liver or kidney problems, which Adalja says may lead to a “lower threshold for overdose.”

In an earlier interview on the topic with Yahoo Life, medical contributor Dr. Kavita Patel said it’s important to be aware of the potential dangers, but adds that overdosing on vitamin D is extremely uncommon. “It’s pretty low-risk, especially if you have normal kidney function,” says Patel. “Vitamin D is not the best for everyone, but if you have normal kidney function then your body should be able to process and clear it through the urine.”

The Mayo Clinic notes that “taking 60,000 international units (IU) of vitamin D a day for several months” has been shown to cause toxicity. But in the U.S., current recommendations are just a fraction of that. The National Institutes of Health’s Office of Dietary Supplements recommends 600 IUs a day of vitamin D for most people, 400 IUs for those under 2 and 800 IUs for those over 70. The BMJ authors write that high doses — up to 10,000 IUs/day — of the nutrient are being recommended online, but the authors “strongly caution against doses higher than the upper limit 4,000 IUs/day.”

And although a major a link between COVID-19 and vitamin D has not been drawn, there is still research that suggests taking the supplement may help with immune function. One large meta-analysis published by Harvard University in 2017, for example, found that taking vitamin D may help prevent serious respiratory infections, such as influenza, especially in those who are deficient in the vitamin.

Dr. Karl Z. Nadolsky Jr., an endocrinologist and clinical assistant professor of medicine at Michigan State University, says that he recommends it for some patients. “I often tell people who seem to be at risk (northern hemispheres, not much sunlight, risk of potential bone disease, etc.) to take 1,000 international units,” Nadolsky tells Yahoo Life. “This BMJ article cites many appropriate guidances for that and emphasizes to avoid overdosing via keeping under 4,000 international units daily. Doses higher than 1,000 international units should not be necessary for most people with normal absorption.”

Adalja says that those who feel unsure how to proceed should talk to their doctor about getting their vitamin D levels tested. “You want to avoid vitamin D deficiency but you don’t want to overdose on vitamin D,” says Adalja. He adds, like the BMJ authors, that on top of supplements and vitamin D-rich foods, sunlight can be extremely beneficial. “Sunlight is important because it helps synthesize the active form of vitamin D in your body,” says Adalja. “So sun exposure does help with keeping your vitamin D levels higher.”

7 PHOTOS

Foods high in vitamin D

See Gallery

Tuna

(Photo by Tomohiro Ohsumi/Getty Images)

Salmon

(Photo by David McGlynn via Getty Images)

Soy milk

(Photo via Getty Images)

Orange juice

(Photo by Francesco Dibartolo via Getty Images)

Cheese

(Photo via Getty Images)

Egg yolk

(Photo via Getty Images)

Beef liver

(Photo by Naotaka Tamura via Getty Images)

HIDE CAPTION

SHOW CAPTION

More from Yahoo News:

Symptoms of COVID-related inflammatory syndrome in kids are ‘not subtle’ — here’s what to look for

Struggling with the day-to-day? How daily affirmations can help you during an unprecedented time

If you hate jogging, here are other ways to get your heart pumping outdoors

Read More

Leave a Reply

Your email address will not be published. Required fields are marked *