According to a report published on Monday in the Archives of Internal Medicine vitamin D is effective in keeping common colds and flu at bay.

The study was conducted by investigators from the University of Colorado Denver (UC Denver) School of Medicine, Massachusetts General Hospital (MGH) and Children's Hospital Boston. They assessed the vitamin D levels, nutritional habits and respiratory infection rates among nearly 19,000 American men and women and reported that people with the lowest blood vitamin D levels reported having significantly more recent colds or cases of the flu. The risks were even higher for those with chronic respiratory disorders, such as asthma and emphysema.

Adit Ginde, UC Denver Division of Emergency Medicine and lead author of the study said, “We don't want to jump ahead of ourselves. But our study provides support that lower levels of vitamin D are associated with an increased risk for respiratory infections, such as the common cold and the flu. And people who have pre-existing respiratory disease -- like asthma an emphysema -- appear to be at an increased risk for this association."

For years now vitamin C has been touted to be the magic potion for prevention of colds and respiratory diseases and strong bones were in vitamin D’s kitty. In the recent years vitamin D has been associated with playing a key role in the immune system and circumstantial evidence has linked the lack of sunlight in the winter months to a deficiency of vitamin D and the seasonal increase in colds and flu. The report said a few small studies have suggested a link between low blood levels of vitamin D and a higher risk of respiratory infections.

According to the American Dietetic Association (ADA) vitamin D can be found in foods like canned tuna, cereal and fortified milk or juice and the body can also be triggered to naturally produce vitamin D after adequate exposure to sunlight. The ADA said that vitamin D apart from being an established calcium builder and bone fortifier has also been found to play an important role in protection against both colon cancer and multiple sclerosis.

In the study researchers examined data from the Third National Health and Nutrition Examination Survey (NHANES III) conducted by the National Center for Health Statistics collected from 1988 to 1994.

The study participants ages 12 and up and a majority were white were asked to complete a nutrition and health survey as well as undertook a physical examination. Blood samples were taken to measure levels of 25-hydroxyvitamin D (25OHD), considered to be the optimal measure of vitamin D status.

The researchers found that those with the lowest vitamin D blood levels of less than 10 nanograms of vitamin D per milliliter of blood, were nearly 40 % more likely to have had a respiratory infection than those with vitamin D levels of 30 ng or higher. The finding was consistent across all races and ages. People who had a history of asthma or some form of chronic obstructive pulmonary disease (COPD) were even more likely to suffer from vitamin D deficiencies and asthma patients with the lowest vitamin D levels had five times the risk for respiratory infection, and vitamin D-deficient COPD patients had twice the risk.

Carlos Camargo of the MGH Department of Emergency Medicine and senior author of the study said,     "A respiratory infection in someone with otherwise healthy lungs usually causes a few days of relatively mild symptoms.  But respiratory infections in individuals with an underlying lung disease can cause serious attacks of asthma or COPD that may require urgent office visits, emergency department visits or hospitalizations. So the impact of preventing infections in these patients could be very large."

"We still need to do the clinical trials that we already have planned to definitely say whether supplementation with vitamin D would actually reduce the risk we found," Ginde cautioned. "But I think we can say that most Americans probably do need more vitamin D for its effects on bone health, as well as for its general benefits with respect to the immune system." (Harkiran contributed to this report)