Low levels of vitamin D may play a key role in inflammatory bowel diseases, according to two studies released this week.
What's more, the findings suggest that supplements of the so-called "sunshine vitamin" may help ease symptoms.
Vitamin D is made naturally in the body when skin is exposed to sunlight. But during winter, when days are cold and the sun is low in the sky, many people experience a drop in their vitamin D stores. This seasonal variation is more pronounced in people who live further north.
In one of the new studies, researchers showed the incidence of Crohn's disease and ulcerative colitis follow a north-south pattern in the United States. Using data from the Nurses' Health Study, which has been following more than 120,000 women for several decades, the researchers charted the geographic distribution of these two gastrointestinal disorders.
"We found that the risk of both ulcerative colitis and Crohn's disease is significantly lower among individuals who lived in southern latitudes compared to northern latitudes," said one of the study authors, Hamed Khalili of Massachusetts General Hospital in Boston.
"So this tells us that the environment plays a key role here," he said, adding that differences in sunlight exposure and vitamin D levels may be responsible.
In the second study, researchers added vitamin D supplements to the treatment of 23 patients suffering from Crohn's disease. About half the patients were given 1,000 international units of vitamin D a day, while the other half took 10,000 IU a day.
After six months, the patients taking the low dose had no change in their symptoms. But the high-dose patients reported a significant improvement, including less abdominal pain and diarrhea.
"You very well may need a higher dose of vitamin D to get an effect," said one of the researchers, Brian Bosworth of New York Presbyterian Hospital/Weill Cornell Medical College. He added the patients tolerated the high dose with no ill effects.
The two separate studies were presented in Washington at the annual meeting of the American College of Gastroenterology.
Both research teams cautioned that more studies are needed to confirm the links between vitamin D and chronic digestive diseases.
Nonetheless, the latest findings add to a growing body of evidence suggesting that low levels of vitamin D may be contributing to a host of health problems including heart disease, certain cancers, autoimmune disorders and depression. If these results hold up under greater scientific scrutiny, vitamin D supplements could become a standard part of disease prevention and medical treatment.
As Dr. Bosworth puts it: "Vitamin D is a relatively safe and easy intervention to make."