Could Chicagoans be more vulnerable to swine flu and similar illness because of where our city is situated?

Our northern locale and dreary winters means less sunlight hits our skin, resulting in a lack of the immune system-boosting vitamin D. And some experts say the key to warding off illnesses like swine flu, is a strong immune system.

"You live at a higher latitude, so you're at a higher risk," says Boston University professor of medicine, physiology and biophysics Michael Holick.

Holick co-authored an article in the medical journal Epidemiology and Infection that concluded that low vitamin D levels during the winter, where there is less sunlight, had a direct connection to rising flu cases.

He says Chicagoans, who suffer through long, gloomy winters, are naturally likely to produce less vitamin D than people in sunnier, more temperate parts of the country.

Dr. John Cannell, executive director of the Vitamin D Council and lead author of the 2006 article, agrees.

"You just don't get sick when you're in the sun a lot," he says.

Does that mean Chicagoans should break out the vitamin D supplements because of the swine flu outbreak? Some health experts say not yet.

Because the virus is new, no research has been done to determine whether vitamin D would prevent infection, says Sue Penckofer, a professor at the Loyola University Chicago School of Nursing.
 
"We haven't been able to study (swine flu and vitamin D). I think now is the time," Penckofer says.

Still, Chicago-based physician Dr. Mayer Eisenstein, who recommends vitamin D to his patients in lieu of some antibiotics, says vitamin D could help stave off something like swine flu.

"Will it be effective against this flu? I would guess yes, but we don't know a lot about it," he says. "But vitamin D is protective."

Holick says any extra doses of vitamin will be beneficial in warding off sickness.

"Vitamin D is critically important for your innate immunity," he says. "There's no downside to increasing your vitamin D intake."

Cannell notes that there's little risk to taking vitamin D supplements.

In the case of swine flu, "There's always the case that people say there's not enough research," Cannell says. "The question is always the same: Do we wait - vitamin D deficient - while we're waiting for more research, or do we wait - vitamin D sufficient - while we're waiting for research?"

Holick recommends using vitamin D supplements to boost sagging levels. But both Penckofer and Eisenstein say getting vitamin D levels checked by a physician should be part of a regular check up.

Cannell says people should spend more time in the sun as the weather turns.

"When your shadow is shorter than you and you sunbathe for 15 minutes, you make as much vitamin D as is in 200 glasses of milk."

The benefits of vitamin D, Holick says, shouldn't outshine those of regular healthy habits. While using vitamin D is helpful, it's not a panacea.

"Vitamin D is not a miracle drug," he says. "But if you sustain healthy levels, it's likely to provide you with many health benefits, and reducing the risk of infectious disease."