After a summer spent hiding out from Hamas rockets, this might be the time for asthmatics to head for the beach. An Israeli study shows that sun-intensive Vitamin D levels may be linked to frequency of asthma attacks.

Not getting enough Vitamin D appears to put asthmatics at higher risk of flare-ups, the large study found. Much of the Vitamin D in people’s bodies comes from exposure to the sun, though dermatologists recommend getting the vital ingredient from other sources because of the dangers of overexposure to the sun’s rays.

In the study, which included some 21,000 asthma patients in Israel, those with a Vitamin D deficiency were 25 percent more likely than the others to have had at least one flare-up, like an asthma attack, in the recent past.

The researchers behind the large cohort study – published in the journal Allergy in August – suggest that measuring, and considering boosting, Vitamin D levels could help control the worst cases of asthma. vitamin D is produced in the skin in response to sunlight, is found in many foods – including fish, eggs, cod liver oil, and fortified milk – and can be taken as a supplement. In the US, milk has been fortified with vitamin D for decades, and Israel last summer mandated that 3 percent milk be similarly fortified.

A Tel  Aviv beach (photo credit: Tel Aviv beach)

A Tel Aviv beach (photo credit: Tel Aviv beach)

“When patients have asthma, our goal is to control the disease, to have as few exacerbations as possible,” said Dr. Ronit Confino-Cohen an allergist at Meir Medical Center and at Tel Aviv University, who led the study. “Our findings give us another tool to do that without adding on the side effects that go along with medication.”

The study did not imply that normal vitamin D levels could somehow prevent asthma. There was no correlation between the levels and the presence of asthma — only to flare-ups among those who have the disease.

Harder and harder to breath

About 235 million people have asthma worldwide, the World Health Organization estimates. The disease, which inflames and narrows the airways, has become increasingly common in recent decades. While there is no cure, asthma can be managed with medication and by avoiding allergens and other triggers.

Looking for new ways to manage her patients’ asthma, Confino-Cohen analyzed the medical records of the nearly 4 million members of Clalit Health Services, Israel’s largest health care provider. The study included the some 1.8 million Clalit members between the ages of 21 and 50 whose vitamin D levels were measured between 2008 and 2012. A team of Israeli researchers, including Dr. Becca Feldman of the Clalit Research Institute, collaborated on the study.

‘Increasing vitamin D levels is something we can easily do to improve [patients'] quality of life’

Vitamin D is known to play a role in regulating the immune system, but it’s unclear whether it can help protect against various diseases. Previous research suggests vitamin D deficiency may be a risk factor for asthma, but it is far from conclusive. Doctors do not typically take vitamin D into account in their treatment of the disease, and there is no agreement on recommended levels.

Data analysis of the Clalit members’ medical records revealed that among 4,616 asthmatics with a vitamin D deficiency, 702, or 15 percent, had experienced at least one flare-up in the year before their first vitamin D test. In comparison, among 8,265 asthmatics whose vitamin D levels were normal or above, 876, or 11 percent, had a flare-up in that time. Doing the math, that comes out to a 25 percent greater chance of flare-ups among asthmatics with a vitamin D deficiency.

A flare-up was characterized by a patient’s being prescribed at least five inhalers or one emergency asthma medication or visiting the doctor for asthma at least four times in a year.

Across the vitamin D level spectrum – from deficient to high – lower levels were associated with a higher risk of flare-ups. The association stood even after the researchers took into account key predictors of asthma, such as obesity, smoking, and inactivity. The researchers chose the age range they studied to minimize misdiagnoses.

An immunity boost?

The results provide evidence that vitamin D deficiency is a risk factor for asthma flare-ups and suggest that higher levels may be protective, the researchers say.

“Asthma patients can have trouble sleeping, miss work, feel bad, and struggle to exercise,” said Confino-Cohen. “Increasing vitamin D levels is something we can easily do to improve their quality of life.”

The association between asthma and vitamin D makes some sense, given what is known. Among its other effects on the immune system, vitamin D helps limit allergic responses, which are the main trigger for asthma, and strengthens the lining of the lungs.

Most of the handful of previous studies on asthma and vitamin D have supported the association – though some have not. The Israeli study is unusually strong in that it draws on millions of patients, covers several years, and uses physician diagnoses, rather than self-report, to determine who has asthma. It also helps that Israel is a small, sunny country, meaning exposure to sunlight does not vary much geographically or seasonally.

Still, the findings are limited by the fact that the study was not a controlled experiment, and many variables could have influenced the results. More and longer-term studies are needed, the researchers say.

Based on the findings, the researchers recommend that people whose asthma cannot be controlled with existing treatments have their vitamin D levels tested. For those with a vitamin D deficiency, they say supplements may make sense. In Israel, a simpler solution would be to get outside and enjoy what’s left of the summer.