You probably know that vitamin D is good for your bones—but research increasingly suggests the “sunshine vitamin” may also play an important role in your health in other ways, including reducing the risk of asthma attacks. “Several studies have shown a relationship between vitamin D deficiency and prevalence of asthma in children, and research also finds that low levels of vitamin D can have an effect on the severity and frequency of asthma attacks in both adults and children who have been diagnosed with chronic respiratory disorder,” says Kayleen Eslinger, R.D., a dietitian and nutrition counselor at Medical Offices of Manhattan in New York City.
Meanwhile, higher levels of vitamin D have been associated with decreased airway hyper-responsiveness, Eslinger adds. That means the airways are less likely to be irritated when triggers are present, which can keep inflammation, and asthma attacks, in check.
Curious about the connection? Let’s take a look at the research, along with insights on other nutrients that can play a role in asthma, and how you can work more of these asthma-fighting foods into your diet.
Vitamin D and Asthma
Although the role of vitamin D for asthma is still being investigated, there are some studies that suggest the vitamin could have benefits for those with the respiratory condition:
- Research in the science journal Cureus notes that vitamin D has an effect on immune response, and that, in turn, could reduce inflammation for those with asthma. The researchers note that people with low vitamin D levels are at a higher risk for upper respiratory conditions and progressive lung diseases, and they also tend to be more likely to have uncontrolled asthma.
- A study in Journal of Family & Community Medicine looking at vitamin D deficiency and its potential role in childhood asthma and other allergic diseases found that children with severe D deficiency had significantly higher incidence of wheezing and allergic rhinitis.
- Research in Frontiers in Medicine examining lung function, asthma, and hospitalization rates found that vitamin D deficiency was associated with more asthma symptoms.
Because of findings like these, it’s worth keeping an eye on vitamin D levels overall, and that may involve getting your vitamin levels checked through a blood test, suggests Eslinger.
Symptoms of Vitamin D Deficiency
Vitamin D is a steroid-derived vitamin that is produced by the body after exposure to sunlight and is also found in some foods. While it’s always tricky to try and pinpoint a deficiency of any specific vitamin, there are some indications that low levels of vitamin D may be factor into the following:
- Bone pain
- Mood changes, especially toward depression
- Muscle weakness
According to Cleveland Clinic, vitamin D deficiency is a common global issue, with about 35% of adults in the U.S. considered to be deficient.
“Thankfully, testing vitamin D levels during routine blood work is becoming more common across the board as we’re discovering a higher percentage of our population is below optimal levels,” says Eslinger. “I’m finding it more common for patients in our offices who are diagnosed with asthma to have their vitamin D levels checked in yearly visits.”
Other Nutrients for Asthma
Although vitamin D tends to get the most attention, other key nutrients may also help reduce symptoms of asthma, says Eslinger, including:
- Omega-3 fatty acids
- Vitamin C
- Vitamin E
“These help to reduce inflammation in the body, which is often associated with asthma,” says Eslinger. And it doesn’t take much to get your daily recommended amount—for example, just two or three Brazil nuts every day will meet your requirements for selenium. You’ll find ample omega-3 fatty acids in foods like salmon, avocados, flax seeds, and walnuts, adds Eslinger. Citrus fruits grab the spotlight as a good source of vitamin C, but so are red and green peppers, broccoli and even Brussels sprouts. And you can find plenty of vitamin E in plant-based oils like sunflower or safflower oil and nuts like almonds and hazelnuts.
Research in Nutrition Reviews notes that diets emphasizing the consumption of plant-based foods may protect against asthma development and improve asthma symptoms. For example, researchers noted that regular consumption of fruit was associated with less sensitivity to allergens and lower incidence of wheezing and severe asthma symptoms in children with the condition.
Getting Vitamin D in Your Diet
Although nutritional research—including the kind done on vitamin D and asthma—looks at the specific mechanism of one nutritional component like a vitamin, the fact is that when considering how to get more in your diet, turning to food is often preferable to supplementation, says Deborah Kado, M.D., an associate professor of medicine and family and preventive medicine at UC San Diego School of Medicine in California. That doesn’t mean supplements are worthless, but they should be complementary to a dietary approach, she adds—rather than considered to be replacements for nutrient-dense foods.
These foods have the highest levels of vitamin D per serving, as measured in International Units (IU):
- Salmon (570 IU per 3 ounces)
- Mushrooms grown with UV light (366 IU per 1/2 cup)
- Fortified dairy products like milk (120 IU per 1 cup of milk)
- Fortified plant-based milks (120 IU per 1 cup of soy milk)
- Eggs (44 IU per 1 large egg)
To help your body utilize vitamin D effectively, it’s important to include a range of other healthy choices like fruits and vegetables, says Dr. Kado. In her research, she’s found that healthy eating and regular exercise can lead to better gut health, and better gut health can improve people’s ability to absorb vitamin D, which means they get the most benefits from higher consumption of those vitamin-rich foods.
More specifically, beneficial bacteria in a healthy gut produce more of a substance called butyrate, which increases the body’s ability to absorb the vitamin, according to a study in Nature Communications.
“The easiest way to make sure vitamin D is being absorbed and utilized in the body is ensuring you get plenty of fresh fruits and vegetables of many different colors in your daily diet,” she says. “Not only will this provide important vitamins and minerals but will also promote a nourishing environment for healthy gut bacteria.”
Gut health, a major buzzword right now, may also help asthma symptoms. Research in the International Journal of Molecular Sciences notes that beneficial bacteria play a major part in regulating immune function and in the development of asthma. So keeping your gut happy can be an advantage for your respiratory system as well.
Taking Vitamin D Supplements
Getting vitamin D through food is a good strategy overall, but if you’ve been told you have lower levels of vitamin D, it may not be enough to address the deficiency through diet alone, and your doctor may recommend taking a supplement.
The recommended daily allowance is 600 IU of a D3 supplement, but the Endocrine Society suggests consuming potentially much higher levels of 1,500 to 2,000 IU daily. If you’re concerned you may be deficient, it’s advisable to get your levels checked at your next physical, to ensure you’re not taking doses that are too high, which comes with its own risks.
A meta-analysis of 10 research studies published in Frontiers in Nutrition found that vitamin D supplementation can reduce asthma exacerbations, especially in children, and also improved a measurement of lung function called expiratory volume.
What About Sunshine?
In addition to food and supplements, keep in mind that you can also get a strong dose of vitamin D from sunshine, especially in the summer months when days are longer. Too much sunshine does increase your risk for skin damage, but fortunately you don’t need hours of light to get the right amount of vitamin D, according to Michael Holick, M.D., director of the Heliotherapy, Light, and Skin Research Clinic at Boston University Medical Center in Massachusetts.
“In general, you only need about 10 to 20 minutes of sun exposure per day to get the amount you need,” he says. “Of course, you want to be smart, so you’re not increasing your risk of skin cancer at the same time. With that in mind, there are areas of the body where exposure is better.”
He notes that sunlight on the shoulders, arms, or legs is preferable to the back or face, since sun exposure in those parts can increase chances of developing wrinkles or prompting skin cancer. Dr. Holick also suggests using sunscreen with a minimum SPF of 30after your initial exposure.
“It’s impossible to overstate how beneficial it can be to get enough vitamin D, not just for asthma but for so many other aspects of health like sleep, bone health, and mood,” he says. “Our bodies were made to convert sunlight effectively, so getting that small amount of light can go a long way toward making sure your whole body can respond effectively.”
This article was originally published February 1, 2012 and most recently updated June 28, 2023.