Asthma, an inflammatory condition that can lead to shortness of breath, has many different causes. Several environmental and lifestyle factors play a role in its development and affect its severity. Although diet changes can’t treat asthma, they may affect symptoms.

Recently, researchers have become interested in the link between vitamin D and asthma. People with asthma are more likely to have low levels of this nutrient. When people with mild or moderate asthma boost their vitamin D levels, they may be less likely to have asthma attacks, also called asthma exacerbations. However, there are some caveats, and additional studies are needed to help researchers more fully understand vitamin D’s effect on people with asthma.

What Is Vitamin D?

The body uses vitamin D to help the muscles, nerves, and immune system work properly. This nutrient also allows the body to absorb more calcium, which helps keep bones strong.

According to the National Institutes of Health, studies have found that about 94 percent of children and adults don’t consume enough vitamin D. The daily recommendations for vitamin D are as follows:

• Newborns and infants aged 0 to 12 months — 10 micrograms (mcg) or 400 international units (IU)
• Children and adults aged 1 to 70 years — 15 mcg or 600 IU
• Adults over 70 — 20 mcg or 800 IU

Certain people are more likely to have a vitamin D insufficiency (slightly lowered levels) or deficiency (very low levels). You may be at risk if you are over age 65, have dark skin, don’t get much sun exposure, or have a condition that affects the digestive system, kidneys, or liver.

It’s not clear what vitamin D’s role might be when it comes to breathing and the lungs. When the airways are inflamed due to conditions like asthma, vitamin D may be able to help reduce inflammation and fight germs that can trigger asthma attacks.

Vitamin D and Asthma: Is There a Connection?

Researchers are beginning to uncover connections between vitamin D and asthma. There is some evidence to show that maintaining high enough vitamin D levels could help manage asthma symptoms.

However, research is still in the early stages, and not all investigators have come to the same conclusions. Additionally, it’s important to note that vitamin D supplements can’t replace asthma treatments recommended by your doctor.

Vitamin D and Development of Asthma

A couple of studies have found that people with low vitamin D levels are more likely to have asthma or other breathing problems. In one study, researchers measured vitamin D concentrations in children with asthma and related conditions that affect breathing. The results showed that kids with asthma, wheezing, or allergic disease such as seasonal allergies were more likely to have a severe vitamin D deficiency.

Another very large study looked at this connection among children, adolescents, and adults of different races. White non-Hispanic children were 41 percent more likely to have asthma and 40 percent more likely to have wheezing if they had low vitamin D levels, compared with children of the same race. However, Black and Hispanic children did not seem to be more likely to have asthma if they were low on vitamin D. All adults in the study with insufficient vitamin D were also 17 percent more likely to experience wheezing compared with adults who had normal levels.

These studies indicate that vitamin D status (how high or low levels are) may be connected with whether a person has asthma. However, other researchers reported different findings. For example, one large study conducted in Denmark found that adults with low serum vitamin D levels were not diagnosed with asthma or allergies more often than people with normal vitamin D levels. Other research has found similar results.

The link between vitamin D and asthma is not yet entirely clear. More research is needed to better understand if vitamin D deficiency is an asthma risk factor or if there is a link between the two conditions — and if that association exists only in certain groups of people.

Asthma Symptoms and Severity

It’s also possible that low vitamin D levels may affect a person’s asthma symptoms or how severe their condition becomes. Various studies have linked low vitamin D levels with:

• Worse lung function
• Greater airway hyperresponsiveness — when airways react too strongly to allergens or other factors and are more likely to close up
• Increased asthma attacks
• More emergency visits and hospitalizations

Researchers have also found that children with steroid-resistant asthma had the lowest serum vitamin D levels.

It’s important to note that identifying a link doesn’t necessarily mean that vitamin D deficiency is a risk factor or can cause or worsen asthma. More research can help clarify the exact relationship. Having normal vitamin D levels may help reduce the risk or severity of asthma, but it’s possible to experience asthma problems regardless of how much of the nutrient is in the body.

Results of Boosting Vitamin D Levels

When two conditions are linked, treating one doesn’t always fix the other. For example, increasing levels of vitamin D within the body won’t necessarily prevent asthma or reduce symptoms.

Researchers measure the effect of vitamin D supplementation (taking supplements) through studies called clinical trials. Some results showed that when people consume more vitamin D, they have fewer asthma attacks that require corticosteroid treatments, emergency room visits, or hospital stays. On the other hand, taking extra vitamin D doesn’t seem to improve lung function in those with asthma.

Other studies found no difference in asthma symptoms with the use of vitamin D supplements. Some research has even found that boosting vitamin D levels can increase the risk of asthma and upper respiratory tract infections (affecting the nose or throat).

Several questions remain. Most people who took part in clinical studies were adults with mild or moderate asthma, so it’s not clear whether increasing vitamin D in the body plays a role in pediatric asthma or in those with severe disease. Additionally, participants tended to have lower levels of this vitamin. Researchers don’t yet know whether supplementation may help people who already have normal levels.

How To Get More Vitamin D

You can get vitamin D in three ways. First, your skin makes vitamin D when it comes in contact with sunlight. However, sun exposure can lead to premature aging and eye diseases and is the main risk factor for skin cancer. Therefore, many experts suggest getting vitamin D from other sources.

You can also get vitamin D from foods and drinks, including:

• Fatty fish like salmon, tuna, sardines, trout, and mackerel
• Fish liver oil
• Mushrooms
• Eggs
• Beef liver
• Milk, which (unlike many other dairy products, such as cheese) typically contains added vitamin D
• Alternative milk products that are fortified with vitamin D, including certain soy, oat, and almond milks

Additionally, you can take dietary supplements with high amounts of vitamin D. Products containing either vitamin D2 or D3 work well to raise levels of this nutrient in the body, although vitamin D3 may help keep levels elevated longer.

Do You Have a Vitamin D Deficiency?

Talk with your physician if you think you have a vitamin D deficiency. A simple blood test can measure your levels and help indicate any need for supplements. It’s a good idea to get properly evaluated so you know your baseline level and understand whether taking extra vitamin D is necessary.

It’s also a good idea to talk to your doctor anytime you want to try new treatment options, including supplements. Your health care team can help you map out an asthma management plan that works well for you.

Talk With Others Who Understand

MyAsthmaTeam is the social network for people with asthma and their loved ones. On MyAsthmaTeam, more than 9,000 members come together to ask questions, give advice, and share their stories with others who understand life with asthma.

Have you been told you have low vitamin D levels? What steps have you taken to get more vitamin D? Share your experience in the comments below, or start a conversation by posting on your Activities page.