The October, 2008 issue of the journal Diabetes published the outcome of a study of middle-aged men and women which found that lower serum vitamin D levels were associated with an increase in the risk of developing insulin resistance and elevated blood sugar over a ten year follow up period.
Researchers at the Institute of Metabolic Science in Cambridge, England followed 524 nondiabetic participants in the Ely Study, a prospective study established in 1990. Upon enrollment, the vitamin D marker serum 25-hydroxyvitamin D, serum parathyroid hormone, insulin-like growth factor-1 (IGF-1) and other factors were measured, and personal health habits such as smoking status and physical activity levels were ascertained. Weight, height, waist circumference, blood pressure, plasma glucose, lipids, and fasting insulin were measured during the initial and ten year follow-up visits.
At the end of the follow-up period, having a higher serum vitamin D level was associated with a lower adjusted ten-year risk of elevated blood sugar, insulin resistance, and high metabolic syndrome score. An association between increased IGF-1 levels and metabolic syndrome risk observed in an earlier study was not noted in the current research.
The authors remark that the study's findings add evidence to previously reported observations concerning vitamin D's effect on metabolic syndrome risk. Possible mechanisms of vitamin D include direct effects on pancreatic beta cell secretory function, and indirect effects involving inflammatory processes. Additionally, insufficient vitamin D can elevate serum parathyroid hormone, which is associated with a reduction in insulin sensitivity in healthy individuals.
In an accompanying editorial, Robert Scragg of the University of Auckland in New Zealand asks the question, "Are we ready for a prevention trial?" In light of the dramatically rising diabetes rates worldwide and the mounting evidence for a role of vitamin D in the prevention of the disease, well-designed clinical trials involving vitamin D supplementation are needed to confirm vitamin D's possible protective benefits. Dr Scragg notes that the dose of vitamin D administered in these trials needs to be at least 2,000 international units per day in order to raise serum 25-hydroxyvitamin D levels above 80 nanomoles per liter, a level at which diabetes risk is lowest. "If well-designed trials are carried out and confirm a protective effect from vitamin D, it could be used by the general population as a simple and cheap solution to help prevent the diabetes epidemic," he concludes.
Related Health Concern: Blood testing
When physicians review a patient's blood test results, their primary concern is any result that falls outside the normal laboratory reference range. The problem is that standard reference ranges usually represent "average" populations rather than the optimal level required to maintain good health. It now appears that most standard reference ranges are too broad to adequately detect health problems or prescribe appropriate therapy on an individual basis. This is especially true when these reference ranges are relied on to treat a patient with a serious medical disorder.
The Life Extension Foundation suggests that a basic battery of tests be performed annually. The recommended male panel consists of a complete blood count (CBC)/chemistry test, homocysteine, free testosterone, estradiol, prostate-specific antigen (PSA), and DHEA. The recommended female panel consists of the CBC/chemistry test, estradiol, progesterone, free testosterone, DHEA, and homocysteine.
In addition to these special male and female panels, the following tests are especially important for men and women over age 40: fasting insulin, fibrinogen, thyroid stimulating hormone (TSH), and free triiodothyroxine (T3). If a serious abnormality is detected--such as elevated blood glucose (sugar), hormone imbalance, or high cholesterol--testing should be repeated more often than annually to determine the benefits of any therapy you are using to correct the potentially life-shortening abnormality.