Living in the Chicago area it’s really not possible to ignore winter. Unless you’re a winter sports enthusiast, and I’m not, there’s not a lot to do outdoors in winter time. And there is an important health-related issue associated with avoiding the outdoors too! During the winter months, we are unable to produce enough vitamin D.
In the strictest sense, vitamin D – the “sunshine vitamin” – isn’t really a vitamin because it is possible for us to synthesize the compound in sufficient quantities (technically, vitamins are certain kinds of compounds we cannot make enough of ourselves). Direct exposure of our skin to sunlight converts a form of cholesterol into the precursor of vitamin D, and sun exposure can make loads of vitamin D. But, there are a number of complications with that system. First, exposure to sunlight increases our risk for skin cancers, and is strongly discouraged these days. Second, seasonal variations as we get farther away from the equator limit the intensity of sunlight, like during Chicago winters (it’s not only the cold weather). Third, the darker your skin, the less vitamin D you can make. And, fourth, vitamin D gets “captured” by excess body fat, keeping some vitamin D unavailable to participate in critical functions.
How important is vitamin D? It is positively important for bone health, being necessary for the proper absorption and use of bone-building calcium and phosphorous. But, some evidence hints at a much broader range of benefits to health, and to diabetes in particular. Adequate levels of vitamin D seem to help regulate your immune system, reducing inflammation and the buildup of dangerous plaques in arteries (atherosclerosis). An inadequate level of vitamin D suppresses insulin production too.
The recommended minimum blood level of 25-hydroxyvitamin D is 20 nanograms per milliliter, and learning your level is a lab test I recommend you request. Vitamin D (as vitamin D3) is also one of the few nutritional supplements I suggest to my patients. That’s because sun exposure is too limited for many people, adequate vitamin D is difficult to get from food, excess body fat (common in type 2 patients) captures vitamin D (meaning extra amounts are required), and I’m convinced vitamin D is very important to diabetes health. Talk with your doctor about a test to determine and treat your serum levels of vitamin D.