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Cholecalciferol Improves Glycemic Control

Dec 23, 2017

Study reports Vitamin D supplementation may improve HbA1c and lower cholesterol.

Vitamins are necessary for the growth and development of our cells and they play a pivotal role in digestion, immunity, and metabolism. The 13 essential vitamins include: vitamins A, C, D, E, K, thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyroxidine (B6), biotin (B7), folate (B9), and cobalamin (B12). According to the United States National Library of Medicine, the best way to meet the recommended daily intake of vitamins is through a balanced diet containing a variety of foods. Unfortunately, most Americans fall short. These vitamins are naturally occurring and can be found by eating a diet high in fruits, vegetables, beans, nuts, whole grains, fortified dairy products and healthy fats. Patients with type 2 diabetes are more likely to be vitamin deficient, and some studies suggest that vitamin deficiency increases your risk of developing type 2 diabetes. Patients with type 2 diabetes often have carbohydrate-heavy diets and most do not adhere to a healthy, balanced diet. The need to reinforce a healthy lifestyle is more important than ever with the rate of obesity, type 2 diabetes and cardiovascular disease steadily rising.


One of the 13 essential vitamins, vitamin D, has been an area of focus for researchers due to its effects on the parathyroid hormone, glucose homeostasis and immune system. Vitamin D is available in a variety of foods; however, it is hard to reach the recommended daily intake on diet alone. Vitamin D is produced when the skin is exposed to sunshine and just a few minutes outside during peak sun hours (10 am – 3 pm) is often enough for most patients. Most adults require 600 – 800 IU/day of vitamin D with an upper intake level around 4,000 IU/day. Vitamin D plays a role in glucose homeostasis through its effects on insulin secretion and sensitivity. It has been postulated that vitamin D may reduce insulin resistance indirectly through upregulation of the insulin receptor gene and through its effect on calcium and phosphate metabolism. It has also been suggested that vitamin D plays a major role in regulation of the lipid profile. Several observational studies have suggested that high vitamin D levels are associated with a more favorable lipid profile, whereas low vitamin D levels are associated with increased levels of fatty plaque formation in the arteries.

Researchers of this study aimed to determine the effect of vitamin D supplementation on fasting blood glucose, HbA1c, and lipid profile in type 2 diabetes patients with vitamin D deficiency. Researchers recruited 125 patients from a diabetes and endocrinology clinic from March to September 2015. The average age of the participants was 52.7 years old +/- 10.3 years and the average duration of disease was 6.7 years +/- 6.1 years. All participants were taking oral anti-diabetes medications as either monotherapy or combination therapy and had laboratory confirmed vitamin D insufficiency. Vitamin D deficiency was defined as a serum level < 20ng/mL and vitamin D insufficiency was defined as serum levels between 20 – 29 ng/mL. Approximately 85.6% (107 participants) were vitamin D deficient and the remaining 14.4% (18 participants) had clinical vitamin D insufficiency. Of the 125 recruited participants, only 41 were followed until the end of the study. This was due to patients leaving the clinic, switching their diabetes medication regimen, or general lack of follow-up. The 41 patients received cholecalciferol 45,000 units once a week for 8 weeks, then 22,500 units once weekly for 16 weeks. During the first 8 weeks of treatment, patients also received 500 mg calcium carbonate once daily.

The paired t-test and Pearson’s correlation coefficient were used to test for significance and p-values < 0.5 were considered statistically significant. Patients taking vitamin D3 replacement saw significant increases in serum levels. Average baseline vitamin D levels were 14 +/- 4.0 ng/mL, and by the end of the study average vitamin D levels increased to 31 +/- 7.9 (p-value < 0.0001). All 41 patients achieved serum vitamin D levels > 20 ng/mL and 63% achieved serum vitamin D levels > 30 ng/mL. HbA1c levels also saw statistically significant improvement with average HbA1c reductions of 0.54% (p-value: 0.034). In evaluating changes in the lipid panel, the average total cholesterol and LDL-cholesterol saw significant reductions (baseline TC: 4.3 +/- 0.9 vs. final TC: 4.0 +/- 0.9; p-value: 0.036), however there were no changes in triglycerides or HDL values. The results of this trial indicate that vitamin D supplementation can improve glucose homeostasis and the cholesterol profile in patients with type 2 diabetes. The small sample size and short duration of treatment and follow-up contribute to the limitations of this study. Future vitamin D intervention studies are warranted, but for now this study demonstrates the importance of educating patients on maintaining a healthy and varied diet.

Practice Pearls:

  • Vitamin D supplementation was associated with a 45% increase in serum levels following 6 months of treatment.
  • Vitamin D supplementation was associated with an average HbA1c reduction of 0.54%.
  • Vitamin D supplementation can help improve glycemic control and lipid profiles in type 2 patients with diabetes.


“The Importance of Vitamins To Your Body.” Healthy Eating | SF Gate, healthyeating.sfgate.com/importance-vitamins-body-5846.html. Accessed 22 Aug. 2017.

“The Role of Vitamin D & Vitamin D Deficiency.” Cleveland Clinic, The Cleveland Clinic Foundation, 14 June 2017, my.clevelandclinic.org/health/articles/the-role-of-vitamin-d-in-your-health. Accessed 22 Aug. 2017.

Nada, Aml Mohamed, and Dalia A. Shaheen. “Cholecalciferol improves glycemic control in type 2 diabetic patients: a 6-month prospective interventional study.” Therapeutics and Clinical Risk Management 13 (2017): 813.

Jessica Lambert, University of South Florida College of Pharmacy, Doctor of Pharmacy Candidate 2018