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Can supplements really help fight COVID-19? Here’s what we know and don’t know

Consumers take time resorting to vitamins and herbs to try to protect themselves from disease. This pandemic is no different, especially with the headlines screaming “This supplement can save you from the coronavirus”.

It also helps to have celebrity enthusiasts. When President Donald Trump was diagnosed with COVID-19, his arsenal of pills included vitamin D and zinc. And in an Instagram chat with actress Jennifer Garner in September, infectious disease expert Anthony Fauci promoted vitamins C and D as ways they can generally boost the immune system. "If you have vitamin D deficiency," he noted, "that has an impact on your susceptibility to infection. I wouldn't mind recommending, and I do, taking vitamin D supplements."

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But it is unclear whether over-the-counter supplements can prevent or even treat COVID-19. Since the disease is so young, researchers haven’t had much time for the kind of big experiments that provide the best answers. Instead, scientists relied primarily on new data from old data. Some studies have looked at the results of patients who usually take certain supplements and found some promising advice. But so far there is little data of the kind of scientifically rigorous experiments that give doctors confidence when they recommend supplements.

This is what we know today about three supplements that receive a lot of attention on COVID-19.

Vitamin D

What is: Called “the vitamin of the sun” because the body produces it naturally in the presence of ultraviolet light, vitamin D is one of the most studied supplements (SN: 27/01/19). Some foods, including fish and fortified dairy products, also have a high vitamin content.

Why it can help: Vitamin D is a hormone block that helps strengthen the immune system.

How it works for other infections: In 2017, the British Medical Journal published a meta-analysis that suggested a daily vitamin D supplement could help prevent respiratory infections, especially in people with vitamin deficiencies.

But one keyword here is deficient. That risk is highest during dark winters in high latitudes and among people with more skin color (melanin, a higher pigment on darker skin, inhibits vitamin D production).

“If you have enough vitamin D in your body, the evidence doesn’t add up to say that giving it more will make a real difference,” says Susan Lanham-New, head of the Department of Nutritional Sciences at the University of Surrey in England. .

And taking too much can create new health problems, stressing certain internal organs and causing a dangerously high calcium buildup in the blood. The recommended daily allowance for adults is 600 to 800 international units per day, and the upper limit is considered to be 4,000 IU per day.

What we know about vitamin D and COVID-19: Few studies have directly analyzed whether vitamin D makes a difference in COVID.

In May, at BMJ Nutrition, Prevention & Health, Lanham-New and colleagues published a summary of existing evidence and concluded that there is only enough to recommend vitamin D to help prevent COVID-19 for people with disabilities. That work made inferences about how vitamin D works against other respiratory tract infections and immune health.

More than a dozen studies now test vitamin D directly for its prevention and treatment, including a large one led by JoAnn Manson, a leading vitamin D expert. An epidemiologist and preventive medicine physician at Harvard Medical School and Brigham & Women's Boston Hospital. That study will look at whether vitamin D can affect the course of a COVID-19 infection. The trial aims to recruit 2,700 people across the United States with newly diagnosed infections, along with their close family contacts.

The goal is to determine whether newly diagnosed people who receive high doses of vitamin D (3,200 IU per day) are less likely than people who receive a placebo to experience severe symptoms and need hospitalization. “The biological likelihood of obtaining a benefit in COVID is compelling,” she says, given the theoretical ability of the nutrient to prevent the severe inflammatory reaction that can follow coronavirus infection. "However, the evidence is not conclusive at this time."


What is: Zinc, a mineral found in cells throughout the body, is found naturally in certain meats, beans and oysters.

Why it can help: It plays several supporting roles in the immune system, which is why zinc tablets are always hot sellers in the cold and flu season. Zinc also aids in cell division and growth.

How it works for other infections: Studies on the use of zinc for colds, which are often caused by coronavirus, suggest that using a supplement right after the onset of symptoms can make them go away faster. That said, a clinical trial conducted by researchers in Finland and the United Kingdom, published in January at BMJ Open found no value for zinc tablets for the treatment of colds. Some researchers have theorized that inconsistencies in cold data may be explained by varying amounts of zinc released in different tablets.

What we know about zinc and COVID-19: The mineral is promising enough to have been added to some initial studies on hydroxychloroquine, a drug tested in the early pandemic. (Studies have since shown that hydroxychloroquine cannot prevent or treat COVID-19 (SN: 8/2/20).)

In July, researchers at the University of Aachen in Germany wrote in Frontiers of Immunology that current evidence "strongly suggests great benefits of zinc supplementation" based on the observation of similar infections, including SARS, another disease caused by a coronavirus. For example, studies suggest that administering zinc reduces the risk of death from pneumonia infection. Researchers cite evidence that zinc can help prevent the virus from entering the body and help slow virus replication when it does.

Another review – also based on indirect evidence – published Aug. 1 in Advances in Integrative Medicine also concluded that zinc could be helpful in people with disabilities.

In September, researchers at Hospital Del Marin Barcelona reported that among 249 patients studied, those who survived COVID had higher plasma zinc levels (an average of 63.1 mcg / dl) than those who died (43 mcg / dl). ).

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However, the jury is still out, says Suma Thomas, a cardiologist at the Cleveland Clinic Foundation, who in June led a team that reviewed tests for popular supplements in the Cleveland Clinic Journal of Medicine. Given what is already known, zinc could decrease the duration of infection, but not the severity of symptoms, he said, especially among people with disabilities. About a dozen studies are now looking at zinc for the treatment of COVID, often with other medications or supplements.

Thomas and colleagues are comparing the severity of symptoms and future hospitalization in patients with COVID-19 who take zinc with and without high doses of vitamin C with whom they receive regular care without the supplement. Results are expected soon, she says.

Vitamin C

What is: Also called L-ascorbic acid, vitamin C has a long list of functions in the body. It is found naturally in fruits and vegetables, especially citrus fruits, peppers and tomatoes.

Why it can help: It is a potent antioxidant that is important for a healthy immune system and for preventing inflammation.

How it works for other infections: Thomas warns that data on vitamin C is often contradictory. A review by Chinese researchers, published in February in the Journal of Medical Virology, looked at what is already known about vitamin C and other supplements that may play a role in COVID-19 treatment. Among other encouraging signs, studies in humans find a lower incidence of pneumonia among people taking vitamin C, "suggesting that vitamin C may prevent susceptibility to lower respiratory tract infections under certain conditions."

But to prevent colds, a Cochrane review conducted in 2013 in 29 studies did not support the idea that vitamin C supplements could help the general population. However, the authors wrote, given that vitamin C is cheap and safe, "it may be worthwhile for patients with colds to try it individually if therapeutic vitamin C is beneficial."

What we know about vitamin C and COVID-19: About a dozen studies are underway or planned to examine whether vitamin C added to coronavirus treatment helps symptoms or survival, including Thomas' study at the Cleveland Clinic.

In a review published online in July in Nutrition, researchers at KU Leuven in Belgium concluded that the vitamin can help prevent infection and reduce the dangerous inflammatory reaction that can cause severe symptoms, based on what is known about how the nutrient works in the body. . .

Melissa Badowski, a pharmacist specializing in viral infections at the University of Illinois at the College of Pharmacy of Chicago and colleague Sarah Michienzi has published an extensive look at all the supplements that may be helpful in the coronavirus epidemic. There is still not enough evidence to see if they are useful, the couple concluded in July in Drugs in Context. “It’s not very clear if it’s going to benefit patients,” Badowski says.

And while supplements are generally safe, he adds that nothing is risk-free. She says the best way to prevent infection is to follow the advice of epidemiologists and public health experts: "Wash your hands, wear a mask, stay six feet away."

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