Can Vitamins Protect Your Lungs Against Respiratory Illnesses?

Vitamins and minerals are nutrients that perform hundreds of important functions in the human body. They help our immune system fight infection, heal our skin after a cut, and strengthen our muscles and bones — to name just a few examples. Luckily, most people get the vitamins they  need from natural sources like food and sunlight. 

Many of us reach for multivitamins in the winter months to help prevent infections. But what’s the evidence for this? As the weather gets colder, with both the flu and COVID-19 to worry about, here’s the science on whether vitamins and supplements can protect against respiratory illnesses.

How do our bodies get vitamins?

Vitamins are considered essential micronutrients — substances required in very small amounts to power essential bodily functions. Each type of vitamin is unique. They come from different sources and perform specific functions to keep us healthy. 

Some vitamins come from the foods we eat. Examples of these are vitamins A, B, C, E, and K. Of these, vitamins A, D, E, and K can all be stored in the body. That means that your body keeps a surplus of these vitamins for times when it’s running low. Vitamins B and C can’t be stored, so you need a little bit of these in your diet every day. 

Vitamin D isn’t really a vitamin at all — it functions more like a hormone. Our bodies can actually make it when our skin is exposed to sunlight, which is why it’s often called the “sunshine vitamin.” 

Are vitamins important for the immune system? 

The idea that vitamins boost the immune system is not entirely accurate. Some vitamins play a key role in immune system function: Vitamin A, vitamin D, and to a lesser extent, vitamin C, E, and some B vitamins (B6, B12, and folate), have all been scientifically linked to the body’s ability to fight infection. 

In people who are malnourished with very low vitamin levels, increasing those low levels with vitamin supplements can protect against certain diseases. 

Can vitamins help to repair the lungs?

Not really. But vitamins A, D, and E are involved in how the lungs defend themselves to prevent infection. Much of the scientific research into vitamins and the immune system has focused on the link between these three vitamins and the body’s ability to fend off lung infections.    

In one of the latest studies to support this link, researchers looked at the food diaries of more than 6,000 people. They found that people who had diets rich in vitamin A and E, or who took vitamin A or E supplements, were less likely to have self-reported respiratory illnesses. People who took vitamin D supplements also reported fewer respiratory illnesses, but just eating a diet rich in vitamin D didn’t seem to do the trick.

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It’s worth noting that this was an observational study, meaning that it confirms a link between vitamins and respiratory illnesses, but it can’t prove that consuming more vitamin D will decrease the risk of respiratory infections.

So it’s unclear if healthy people with normal levels of vitamin A, D, and E will benefit from supplements.   

Does vitamin D protect against the flu?

Because vitamin D levels are affected by direct sunlight, it’s possible that there’s a link between low vitamin D levels in the winter months and the seasonality of the flu. But more research is needed to clarify this question.

Here’s what we can say for sure:

• Vitamin D plays a role in the body’s defense against all infections — including the flu.  

• There may be a link between low vitamin D levels and the risk of infectious illnesses.

• On average, 42% of people in the U.S. have low vitamin D levels. Vitamin D deficiency is even more common in people with darker skin because the melanin in their skin decreases the absorption of sunlight. As many as 82% of Black people and 69% of Latinos have low vitamin D levels. Low vitamin D levels are also found in around 57% of people who are hospitalized and 60% of people in care homes because they tend to spend less time outdoors.

• People with low vitamin D levels should take supplements to normalize their vitamin D levels.

• There is no research (yet) that supports taking vitamin D supplements to prevent infection if your vitamin D levels are within the normal range. 

Can vitamins or supplements protect against COVID-19?

Given the link between vitamin D and other respiratory infections, there has naturally been interest in whether vitamin D can help prevent COVID-19. 

Here’s the current evidence on the connection between vitamin D levels, vitamin D supplements, and COVID-19: 

• Low vitamin D levels have been linked to a higher risk of testing positive for COVID-19 in a study of 500 people in Chicago, but this hasn’t been shown consistently across all studies. In fact, a study of 350,000 people in the U.K. found that there was no connection between vitamin D levels and either risk of getting COVID-19 or of dying from it. 

• There is no convincing evidence yet that vitamin D supplements improve outcomes in COVID-19, although larger trials are ongoing.  

For now, the recommendation is that people with low vitamin D levels should take supplements to keep their vitamin D levels within normal limits. Anyone at high risk for deficient vitamin D should get their levels checked, especially people who: 

• Have darker skin

• Spend a lot of time indoors, for example in care homes or hospitals

• Frequently cover most of their skin with clothing or sunscreen

• Have other medical conditions such as obesity, osteoporosis, Crohn’s disease, or celiac disease 

• Take certain medications that lower vitamin D levels, for example epilepsy medications 

Are there other supplements that can protect against COVID-19?

In addition to vitamins, some micronutrients are known to be essential building blocks of a functioning immune system. These are:

• Selenium

• Zinc

• Copper

• Iron 

Selenium and zinc have received a fair bit of attention for their role in the immune system’s fight against viruses. This makes them particularly interesting in the context of respiratory viral illnesses — including COVID-19. There’s no hard evidence yet to say that taking zinc or selenium supplements protects someone from COVID-19. And it’s important to know that both selenium and zinc can be dangerous if you take too much. 

At the end of the day, the best way to protect yourself against COVID-19 is to get the vaccine, and follow public health recommendations from the CDC. 

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Written by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. An experienced and dedicated pulmonologist and hospitalist, she spent a decade practicing and teaching clinical medicine at academic hospitals throughout London before transitioning to a career in health education and health technology.

Reviewed by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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