Blood Glucose

Nutritional Supplements for Glycemic Control

June 14, 2018   /


Anne Danahy, MS, RDN, LDN


According to the American Diabetes Association, approximately 1.5 million Americans are diagnosed with diabetes each year. Patients who are newly diagnosed, or who are in the early stages of the disease are often highly motivated to make diet and lifestyle changes to improve glycemic control and prevent or minimize the use of medications.

In addition to focusing on ways to improve diet quality and achieve moderate weight loss, there is increasing interest among those with diabetes to try complementary and alternative medicine (CAM), especially in the form of herbal supplements and nutraceutical products, to manage their disease. There is some evidence that the following supplements and functional foods may be beneficial for glycemic control, but Registered Dietitian Nutritionists (RDNs) should also be aware of and educate patients about any potential risks and contraindications.


Aloe vera

The succulent plant aloe vera has been used medicinally for thousands of years and for a range of health conditions, including glucose management. Supplements may be taken in the form of gel powder, aloe vera juice, or extract. Studies over the years suggest that taking oral supplements can result in a 30 to 46.6 mg/dL reduction in fasting glucose, and up to a 1% decrease in A1C levels.  

Results of a recent review and meta-analysis on its effects for diabetes and prediabetes support those previous findings, and researchers determined that aloe vera may be beneficial for both prediabetes and diabetes, although more research is needed. Overall, in subjects with diabetes, aloe vera appears to improve both fasting blood sugar as well as A1C levels, while those with prediabetes experience improvements in A1C.1

Because a range of doses and different formulations have been used in research on aloe vera and diabetes, there is no recommended best dosage or formulation. Forms of the gel have been well-tolerated in clinical trials, but patients should be made aware that prolonged high doses (≤1g/day) of aloe latex have resulted in hemorrhagic gastritis, nephritis, and acute renal failure.



Berberine is a yellow, bitter-tasting compound derived from the roots, rhizomes and stem bark of certain plants, which has long been used in Chinese and Aryuvedic medicine. There is evidence that it may be helpful in treating patients with diabetes by a variety of mechanisms, including improving insulin sensitivity, promoting insulin secretion, protecting islet cells, and reducing intestinal absorption of glucose.2

Doses of 500mg 2 to 3 times each day have been used in clinical research, and results indicate that berberine can effectively reduce fasting glucose, postprandial glucose, and A1C. In a study on subjects with poorly controlled diabetes who were treated with berberine for 3 months, researchers determined that berberine was as effective as metformin in reducing fasting glucose and postprandial glucose levels from 1 week until the end of the trial. In addition, by the end of the study, subject’s A1C levels dropped from 8.1% to 7.3%.3

Adverse effects of berberine may include headache, nausea, vomiting, and hypotension, especially at high doses. Patients who take insulin or other anti-diabetes medications should be aware that berberine may have an additive effect. Patients who take cyclosporine should not take berberine.


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