Since the 1960s, asthma has increased so dramatically as to be declared an epidemic. This increase has hit heaviest in developed countries, leading us to question what lifestyle changes might be to blame.
Many hereditary and environmental factors contribute to asthma, so it’s impossible to target a single cause, but one of the more intriguing possibilities is that asthma is more common when people have vitamin D deficiency. The parallels between lifestyle, asthma and vitamin D deficiency in developed countries are many and include decreased sun exposure with increased time spent indoors (especially among dark-skinned races) and poor nutrition.
Vitamin D is an essential nutrient, meaning the human body cannot make enough to prevent deficiency so diet is important. Our skin helps make some vitamin D during sun exposure, just not enough to prevent deficiency. Because very few foods naturally contain vitamin D, we fortify milk, orange juice and other items. Without a healthy diet, the risk of vitamin D deficiency increases.
Vitamin D seems to be the new vitamin C. In the ’60s, Linus Pauling made vitamin C all the rage as a cure for colds, cancer and other diseases, although with very little evidence. Now, studies of vitamin D and health are everywhere in medical literature. It is common knowledge that vitamin D is important for bone health, helping us absorb calcium to prevent rickets and osteoporosis. But many of us aren’t aware that vitamin D deficiency might contribute to a wide variety of disorders, from depression to heart disease and from infections to allergies.
So what’s the evidence that vitamin D deficiency could lead to asthma?
First, vitamin D appears to be important for normal lung development. Children born to mothers with vitamin D deficiency have smaller, less well-developed lungs and are at increased risk of asthma. Recent studies in children with severe asthma have shown a direct relationship between severity of vitamin D deficiency and airway narrowing, a major defect in asthma. Second, vitamin D is important for immunity to infection. Children and adults with vitamin D deficiency have more viral infections that can cause lung and airway damage, making them more prone to asthma. Third, people with vitamin D deficiency are at greater risk of allergies and sensitivity to inhaled irritants, making asthma more severe. Finally, there is excellent evidence that vitamin D deficiency makes adult lung diseases such as chronic obstructive pulmonary disease worse.
But a word of caution. Although vitamin D deficiency might lead to disease, there is no evidence that more than normal amounts are helpful. Unlike with vitamin C, in which “megadoses” were very trendy and usually harmless, large doses of vitamin D can be dangerous. So good nutrition and vitamin D supplementation is important for good bone and lung health, especially in mothers and children, but don’t overdo it. Ask your health care provider how much is right for you or your child.
In the meantime, play outside and eat healthy.
Paul G. Smith is the director of Pediatric Critical Care and Pulmonary Services at Community Medical Center.