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Vol 38  No 10
February 23, 2006


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Serum calcium hinders diabetes resistance

Risk factors

By Sharon Gray

Dr. Guang Sun (Photo by HSIMS)

Memorial University medical researcher Dr. Guang Sun has discovered that high serum calcium is a new risk factor for diabetes.

Dr. Sun’s research discovery is featured in the first newsletter of the Institute of Nutrition, Metabolism and Diabetes (INMD), published January 2006. INMD is one of 13 institutes that comprise the Canadian Institutes of Health Research (CIHR).

Dr. Sun’s research discovered that an increase in serum calcium levels causes an increase in insulin resistance and contributes to the development of type 2 diabetes. “This increase in serum calcium is also correlated to a decrease in beta cell function. That study was published late last year in the journal Diabetes.”

Dr. Sun said this is the first paper to explore the relationship between serum calcium with fasting serum glucose, insulin, insulin resistance and beta cell function in a large population. “Higher blood glucose is part of clinical evidence of diabetes.”

The research Dr. Sun did is on blood samples from more than 1,000 human volunteers in Newfoundland. He thoroughly examined factors that might affect serum calcium and insulin sensitivity. The study on serum calcium took into account factors such as vitamin D and levels of parathyroid hormone. The study on insulin sensitivity took into account factors such as age, sex, medication status, menopausal status and trunk fat percentage.

“I used the homeostatis model assessment (HOMA) for the quantification of insulin resistance because this method is highly correlated with other measures of insulin resistance in experimental models. This careful approach was necessary because studies in this area have been controversial, even contradictory.”

Dr. Sun’s data showed a significant positive correlation between serum calcium with glucose levels and insulin resistance in both sexes, but the data generated by female subjects provided the strongest evidence. “Women with the lowest calcium levels had the lowest concentration of glucose and the least insulin resistance.” Those with the highest calcium levels had the highest concentration of glucose and the most insulin resistance.”

Dr. Sun was also able to statistically demonstrate an inverse relationship in women between serum calcium and beta cell function. “The reason for the difference probably related to sample size. The study included approximately four times more women than men, so the larger female sample size probably allowed the statistical correlation to emerge in women but not in men. We did see the trend in men, but it didn’t reach statistical significance.”

The INMD newsletter posed the question “Does this mean we need to be careful how much calcium we take in?” The answer is no. Earlier studies from Dr. Sun’s lab show that dietary calcium, even in the form of a supplement, is not significantly correlated with serum calcium levels.

Dr. Sun is continuing his studies in the areas of obesity from his laboratory in the Faculty of Medicine. Volunteers interested in participating in his study can contact his office at 777-8661 (St. John’s area only).

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