Did you ever notice that most people get colds in the winter? Some people even say that’s why its called a “cold” – because you get it in cold weather. As early as the 1960′s, British researcher Dr. R. Edgar Hope-Simpson theorized that a “seasonal factor” was responsible for the annual outbreaks of influenza following the winter solstice and the disappearance of it after the summer solstice. This has been a long standing mystery to the medical community, since it is well documented that the people are exposed to the influenza virus year-round. Why would we be more susceptible to the virus during winter?
Research also shows that vitamin D levels are at their lowest of the year during winter months and highest during the summer months. Is there a connection? New evidence is beginning to link the two.
The name “vitamin D” is actually a bit misleading, because vitamin D is actually a hormone in the same family of hormones as estrogen, progesterone, testosterone and cortisol. These types of hormones play an important role in the function of the nucleolus of our cells. Vitamin D’s role in the body’s absorption of calcium for bone growth, but its only recently that scientists have discovered the link between vitamin D and our cell function. The latest research, published last year, links vitamin D and our body’s immune system.
While many people take vitamin C to help their immune system, there is little evidence to support its effectiveness. Vitamin D however, has a growing base of evidence in its role related to the immune system. Some of the latest research was published in the February 23, 2009 issue of the Archives of Internal Medicine. In that report, researchers studied nearly 19,000 people and found that people with lower levels of vitamin D in their blood were up to 40% more likely to have experienced a cold. The connection was even more dramatic for those who suffered from asthma or other respiratory disease.
When most people think of vitamin D, they think milk. However, cow’s milk contains little to no natural vitamin D. Actually, the U.S. Government began requiring the fortification of cow’s milk with vitamin D as early as the 1930′s in its efforts to combat the bone deforming disease rickets. That’s how the vitamin D gets into milk. While there are other dietary sources that do contain natural vitamin D, the best source is to make it yourself.
Your skin synthesizes vitamin D upon exposure to the Ultra Violet B rays of the sun, which are greatest during the middle part of the day. For people living near the equator, exposing your skin to 15 minutes of sunlight twice a week is enough to generate the vitamin D your body needs to stay healthy. The farther away from the equator you live, the more exposure time you need because of the indirectness of the suns rays. So what happens in wintertime? We stay indoors more, we bundle up in clothing when we do go out and the suns rays are even more direct, limiting our exposure to the UVB rays that produce vitamin D.
The link between wintertime colds and vitamin D is getting stronger isn’t it? While the researchers do want to study vitamin D’s effects on colds in some clinical trials, it seems worth it to me in the meantime to go outside and get some sunshine each day to help your body manufacture some vitamin D. It might be just what you need to get you through this cold and flu season. As for all of the warnings about avoiding the sun, that’s a topic for another blog post that you can read about here.