Women living in the northeastern United States are more susceptible to developing rheumatoid arthritis (RA), according to a 2010 study published in Environmental Health Perspectives. One of the reasons this may be is that the demographic may be vitamin D deficient, as northern climates see less sunlight.

Unlike many essential vitamins and minerals, vitamin D is found in few foods. You can get your daily recommended vitamin D from a supplement, but vitamin D is unique in that you can also get it from a totally free and natural source—the sun. Basking in the sun will stimulate your body's ability to produce vitamin D, and even just 15 minutes in the sun will help you reach your daily vitamin D needs.

How the Study Was Conducted
The basis for the research came from the Nurses' Health Study, which detailed the health of a sample of female nurses in America. The research team of the vitamin D study analyzed records of 461 women who were diagnosed with RA between the years of 1988 and 2002. The Nurses' Health Study compiled information that included the participants' residential addresses, so the research team found that many of the women diagnosed with rheumatoid arthritis lived in the northeast portion of the US.

Women who live in northeastern states, such as Vermont and Maine, are at an increased risk of becoming vitamin D deficient because there's simply not as much sunlight as in other parts of the country. That, coupled with the fact that women are 2 to 3 times more likely to develop rheumatoid arthritis, may account for why women in the northeast are being diagnosed with the disease more than their counterparts in other parts of the country.

It's important to consider that these findings only suggest that the lack of vitamin D may play a role in rheumatoid arthritis development. The research team noted that though they did not definitively conclude that vitamin D deficiency is a risk factor for rheumatoid arthritis, vitamin D has been connected to other autoimmune diseases, such as multiple sclerosis. The researchers believe further research must be conducted to confirm a direct connection between vitamin D and RA.

If you'd like to read more about this research, click here.