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Looking at Vitamin D's Role in Asthma

Some evidence suggests that vitamin D may play a role in preventing asthma. Asthma is a common condition in the United States and throughout the world. Seven percent of Americans, about 22 million people, suffer from asthma. A third of them are children. Asthma can be severe but, fortunately, deaths from asthma amount to only about 3,450 per year.

Asthma symptoms and triggers

The major symptom of asthma is difficulty breathing, usually as a result of spasm of the breathing tubes in your lungs, the bronchi. This condition is called bronchospasm. Symptoms can vary from mild to severe.

When bronchospasm occurs, it is called an asthma attack and displays the following symptoms:

  • Chest tightness

  • Cough

  • Shortness of breath

  • Wheezing upon breathing out

As an asthma attack worsens, its severity is determined by having the patient breathe hard into a tube and measuring the flow of air. Air flow continues to lessen if the attack isn’t broken, until the patient is exhausted and may even require help to breathe. The face and fingernails may turn blue from lack of oxygen, and in severe attacks a person can die from hypoxia (oxygen starvation).

Several environmental factors can trigger an asthmatic attack. The most important are listed here:

  • Cigarette smoke

  • Cold air

  • Poor air quality due to pollution, including dust, animal hair, molds/mildews, and perfume

  • Psychological stress

  • Viral respiratory infection

Hereditary factors also are at work, too. Researchers have found variations in more than 30 genes that contribute to asthma.

Asthmatic airway obstruction is reversible. The obstruction results from a combination of spasm and inflammation often associated with infection. An asthma attack may be prevented by using inhaled drugs like steroids or bronchodilators.

If a person avoids triggers such as cigarette smoke and animal hair, they can prevent asthma attacks. They may still carry rapid-acting bronchodilators for an acute asthma attack, but they’ll need them less often.

Half the children with asthma will grow out of it, perhaps because of a change in environment. Those who don’t can control their asthma with inhaled steroids. Many patients often don’t require medication until an infection or other trigger brings on an attack.

Vitamin D levels and asthma

Evidence of an important role for vitamin D in preventing and treating asthma is promising but is based mostly on associations between serum 25-hydroxyvitamin D and various aspects of the disease. Medical researchers know that these types of associations may not hold up under more careful scrutiny. So, although this is interesting, it isn’t yet up to the high standard needed to make public health recommendations.

Cell studies show that calcitriol has beneficial effects on the smooth muscle cells of the airways — if this also happens in the body, then calcitriol might block or slow the type of changes to the lung that develop in advanced asthma.

Looking at studies that associate serum vitamin D levels with asthma, there’s also a lot to be excited about. Some examples are:

  • People with high UV light exposure have low rates of asthma.

  • Among adults, obese African Americans have the highest rate of asthma in the population and the lowest levels of vitamin D.

  • Asthmatic people with low levels of vitamin D perform worse on lung function tests than those with normal levels of vitamin D.

  • Higher vitamin D intake in pregnant women is associated with up to 40 percent lower asthma rates in their offspring.

  • Vitamin D levels in asthmatic children are inversely associated with markers of asthma severity in children. They have fewer visits to the hospital, and they need anti-inflammatory medication less often.

Several studies were started in the last few years that aim to evaluate the effect of vitamin D supplements on the development or severity of asthma. Still, there’s no reason to wait to increase your vitamin D intake if you have serum 25-hydroxyvitamin D levels less than 20 ng/ml or 50 nmol/L. Doing that will at least benefit your bones and may help your lungs as well.

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