Low Vitamin D Levels Linked to Prediabetes and Prehypertension

A recently published study showed that adults with low vitamin D levels had more than double the risk of prehypertension and prediabetes than adults with higher vitamin D levels.

Prediabetes and prehypertension have been associated with low vitamin D levels. In a recent issue of the journal Diabetes Care, scientists report a correlation between reduced vitamin D levels and prediabetes and prehypertension in adults. Both prediabetes and prehypertension are estimated to exist in at least one-fourth of disease-free adults. 

Researchers analyzed data from 898 men and 813 women who participated in the National Health and Nutrition Examination Survey (NHANES), 2001-2006. Blood pressure measurements were obtained during examinations conducted upon enrollment, and blood samples were evaluated for glucose, serum 25-hydroxyvitamin D and other factors.


Prediabetes was defined as having a fasting serum glucose of between 100 and 125 milligrams per deciliter, and prehypertension was defined as systolic blood pressure of 120 to 139 mmHg and/or diastolic blood pressure between 80 and 89 mmHg. Prediabetes was 33 percent higher among those with vitamin D levels of 76.3 nmol/l (30.5 ng/ml) or less compared to those with higher levels. Prehypertension was evident in 61 percent of those with the lower vitamin D levels. Participants with undiagnosed diabetes and untreated hypertension had even lower vitamin D levels on average. Serum vitamin D levels tended to decline with increasing age and body mass.

When the risk of having both conditions was considered, those with low vitamin D levels had 2.4 times the risk of that experienced by subjects with higher vitamin D levels.  

It is reasonable that among those with prediabetes or prehypertension, vitamin D supplementation resulting in increased serum vitamin D levels may help reverse subtle changes in fasting serum glucose and resting blood pressure that may lead to more advanced disease states. 

Alok K. Gupta, MD, Meghan M. Brashear, MPH and William D. Johnson, PHD. Prediabetes and Prehypertension in Healthy Adults Are Associated With Low Vitamin D Levels. Diabetes Care March 2011 vol. 34 no. 3 658-660.

Glycemic Load is a Better Predictor of Glycemic Response Than Carbohydrate Content Alone

A new study provides evidence that the glycemic load of a meal is a better predictor of blood glucose and insulin response that simply accounting for total carbohydrates.

The glycemic load (GL) is a ranking system for carbohydrate content in food portions based on their glycemic index (GI) and the portion size. Glycemic load for a single serving of a food can be calculated as the quantity (in grams) of its carbohydrate content, multiplied by its GI, and divided by 100. While GL is increasingly used in nutritional research, its ability to predict postprandial (after meal) blood glucose and insulin response for a wide range of foods or mixed meals has been unclear.   

In a recent issue of the American Journal of Clinical Nutrition, researchers sought to assess the degree of correlation between calculated GL and observed glucose and insulin responses in healthy subjects consuming calorically identical portions of single foods and mixed meals.

In study 1, healthy subjects consumed 240 calorie portions of 121 single foods in 10 food categories. In study 2, healthy subjects consumed 480 calorie servings of 13 mixed meals. Foods and meals varied widely in macronutrient content, fiber, and GL. Blood glucose and insulin responses were measured and compared to a reference food (= 100).

Among the single foods, GL was a more powerful predictor of postprandial glucose and insulin response than was the available carbohydrate content itself. Similarly, for mixed meals, GL was also the strongest predictor of postprandial glucose and insulin responses. Carbohydrate content alone was predictive of the glucose and insulin responses to single foods, but not to mixed meals.

The results of this study are the first to provide large-scale evidence of the superiority of using dietary GL over carbohydrate content alone to estimate postprandial glucose and insulin response in healthy individuals.   

Jiansong Bao et al. Prediction of postprandial glycemia and insulinemia in lean, young, healthy adults: glycemic load compared with carbohydrate content alone. Am J Clin Nutr May 2011 vol. 93 no. 5 984-996.

Increased Magnesium Intake Linked to Lower Risk of Type 2 Diabetes

Type 2 diabetes prevalence is rising in Asian countries. New research indicates that increased magnesium intake may reduce the risk of type 2 diabetes in Japanese adults.

A new study published in the Journal of the American College of Nutrition reports a correlation between higher magnesium intake and a reduced rate of type 2 diabetes. Low magnesium intakes have previously been linked to insulin resistance and impaired glucose utilization.

Researchers evaluated data from 17,592 men and women aged 40 to 79 who took part in the Japan Collaborative Cohort Study for Evaluation of Cancer Risk established between 1988 and 1990. Dietary magnesium was calculated using a validated questionnaire, and incidence of diabetes was defined by self-report of physician diagnosis.

At the five year follow-up, 459 new cases of diabetes were reported. Dietary intake of magnesium was inversely associated with age, body mass index (BMI), and diabetes incidence in both sexes.

After making adjustments for cardiovascular risk factors, participants whose intake of magnesium was among the top 25 percent had a 36 percent lower adjusted risk of developing diabetes.

The incidence of type 2 diabetes is increasing in Asian countries, and this is the first study to examine the association between magnesium intake and the risk of diabetes in adults living in Japan. The results of this study are important for the development of potential health policies to help prevent and control this increasingly common degenerative disease.

Kyoko K, et al. Magnesium Intake and Risk of Self-Reported Type 2 Diabetes among Japanese. 2010. Journal of the American College of Nutrition, Vol. 29, No. 2, 99-106.