Although vitamins play a role in blood-glucose control, minerals dominate the category, with significant volumes of research on zinc, vanadium and chromium, to name a few. In 2010, researchers have focused on a few other nutritional ingredients' role in managing hyperglycemia and related cell damage.
Vitamin D deficiency has been associated with numerous nonskeletal diseases, including type 2 diabetes. In April, researchers from Tufts University in Boston released the results of a seven-year study examining the relationship between vitamin D status and the incidence of type 2 diabetes. Using a subsample from the 1972 Framingham Offspring Study, researchers discovered that those with the highest 25-hydroxyvitamin D (25(OH)D) status—an indicator of serum vitamin D levels—had a 40 percent lower incidence of type 2 diabetes than those with the lowest levels. Researchers made adjustments for various risk factors.
These findings suggest that maintaining optimal 25(OH)D levels may help prevent type 2 diabetes. Increasing evidence also shows vitamin D could have therapeutic benefits for those with prediabetes. Thus, the role of vitamin D continues to expand beyond its traditional function as a bone-health ingredient.
In 2009, results from the National Health and Nutrition Examination Survey suggested a detrimental health link between high plasma-selenium levels and diabetes. However, some limitations may have biased researchers' conclusions.
A 2010 study from the Université Montpellier in France examined the risk of developing type 2 diabetes based on selenium levels in an elderly French population over a nine-year period. The study found that men with higher plasma-selenium levels had a significantly lower risk of elevated blood glucose—a relationship that was not observed in women. This study suggests a gender-specific protective effect of higher selenium status at baseline on later occurrence of diabetes.
The benefits of higher selenium intake are controversial given the recent cohort of negative selenium trials. One of the primary differences in the Montpellier trial is that selenium intakes in France, and more generally in Europe, are considerably lower than in the United States. Additionally, differences in supplemental intake of selenium may also have been a factor leading to a much greater intake of selenium over time (as in the NHANES trial) compared to the study in France.
In examining both studies, it's important to assess the dose and time response, while controlling dietary intake, before making any consumer recommendations for selenium.
Salba (Salvia hispanica)
Salba, a branded strain of chia seeds, is known as an excellent source of omega-3 fatty acids, fiber, protein and antioxidants, and because of this profile, it has been researched for its therapeutic role in diabetes care. A Canadian trial considered whether Salba whole grain reduces healthy subjects' postprandial (after a meal) blood-glucose levels as a possible explanation for its cardioprotective effects observed in individuals with diabetes.
In the randomized, double-blind trial, 11 healthy men and women consumed zero, 7, 15 or 24 grams of Salba baked into white bread. Blood samples were collected over a two-hour period after consumption. A significant dose-response reduction in blood glucose was observed with all three doses of Salba.
The decrease in postprandial blood glucose observed in this trial provides a potential explanation for improvements in blood pressure, coagulation and inflammatory markers previously observed after 12-week Salba supplementation in type 2 diabetics.