Vitamin D research is happening at a fast and furious pace. Global deficiency of the complex vitamin with hormone-like actions, has spawned a flux of research that goes far beyond bone health. A pubmed search for Vitamin D turns up over 57,000 results with ten percent of them being about supplementation. The research is fresh with many studies having been conducted in the last five years. We could talk about it’s role in reducing cardiac deaths, improving outcomes for women with breast cancer, the need for vitamin D to impact depression, MS, rheumatoid arthritis and inflammatory bowel disease. But here’s a quick mention of what most of the population faces every fall and winter: colds and flus.
One of the links between vitamin D and infection fighting comes to us via protein molecule called cathelicidin. Cathelicidin acts like a boxer, punching holes in the outside walls of invading bacteria, viruses and fungi, causing their insides to leak out, thus making them ineffective in their attack. The gene that makes cathelicidin gets more active in the presence of vitamin D.
Vitamin D is generated from exposure to the UV-B rays of the sun. Unfortunately UV-B rays are blocked by cloud cover and pollution, and during lower light months don’t make it to the ground even with clear skies. Such is the state of living anywhere north of San Francisco. In the summer you may get adequate amounts of D if you spend at least 20 minutes outside between 10 and 2 without sunscreen.
During the months of October to May, virtually everyone needs to supplement. Not only are we not getting enough UV-B rays but we also don’t have many food sources. Other than fish, egg yolk, white mushrooms, liver, kidney meat, and fortified sources in milk, cereals and infant formulas, there aren’t many options in our diet.
Supplements are however, easy to find and cheap. Results of the Canadian Measures Survey of 2007 - 2008 showed that most Canadians of all age groups average a lower serum vitamin D level than what is considered to be optimal. Since these results show that almost everyone is deficient, we now have to pay for vitamin D testing.
Toxicity is rare and optimum levels are not clearly established so if you stick within conservative recommendations, you should be taking enough to support your immune system, fight off the microbes and minimize low-light depression. Adults can take between 2000 IU and 4000 IU per day during the winter months and half that in spring and fall. Children doses are 1000 to 2000 IU and infants 500 to 1000 IU.