Nutritional Supplements for Glycemic Control

Author

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

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.

Bitter gourd (Momordica charantia)

This small green-white, warty fruit is also known as bitter melon, because of its bitter flavor when ripe. It is used in Traditional Chinese Medicine, and the entire plant, including fruit, seeds and leaves is believed to have antidiabetic properties. Bitter gourd appears to improve glycemic control by enhancing insulin signaling pathways, glucose uptake, glycogen storage, and stimulating insulin secretion. Extracts of the gourd are structurally similar to animal insulin. 

In clinical studies, however, the effectiveness of bitter gourd is mixed, with some studies showing an improvement in fasting glucose and 2-hour post prandial glucose, and other studies showing no effect. Researchers question whether the dose, preparation or formulation of the bitter gourd used in the study impacted the results, as these have ranged from juice, to dried fruit, to commercially prepared extract in capsules. The most positive results were seen in 2 different studies using freshly prepared juice. Researchers noted a significant reduction in post prandial glucose and fasting glucose in subjects with type 2 diabetes in both studies.⁴

Bitter melon has been well-tolerated in clinical studies, but there are reports of gastrointestinal upset. In addition, there are 2 cases reported in the literature of hypoglycemic coma and seizure in children after drinking bitter melon tea.

Chromium

Chromium in the form of picolinate has been long-examined for potential glycemic benefits, but over the years, study results on the benefits of this mineral have been mixed. In a 2016 review of 20 randomized controlled trials on various types of chromium, but most frequently chromium picolinate, researchers did not find enough evidence to recommend the use of the supplement for diabetes management.⁵

Cinnamon

Although study results are mixed, there is some evidence that this aromatic spice can improve glycemic control by facilitating the entry of glucose into cells, increasing glycogen synthesis, and inhibiting gluconeogenesis. Cinnamon also exhibits antioxidant and anti-inflammatory properties, and it appears to be safe for most people to take.

Results of a randomized controlled trial which tested the effect of the commercially available freeze-dried cinnamon extract, CinSulin® against a placebo, subjects who received 250 mg capsules twice per day for 2 months had reduced fasting glucose, 2-hour oral glucose tolerance test, and fasting insulin levels compared to the control group. In addition, insulin resistance markers were improved, and total and LDL-cholesterol were reduced.⁶

Fenugreek

Fenugreek is an aromatic herb native to the Mediterranean region and western Asia, with a flavor similar to maple syrup. It is used to treat diabetes in many parts of the world. Many smaller studies have shown that taking between 5 and 50 g of powdered fenugreek seed with 1 or 2 meals per day can improve fasting and postprandial glucose, as well as oral glucose tolerance tests.

Fenugreek appears to be safe to use for most people, but its effectiveness may be dependent on the dose, as studies using smaller doses of fenugreek, similar that used for culinary purposes, have not shown any significant benefit.⁷

Flaxseed

Ground flaxseeds are a source of alpha-linolenic-acid (ALA), a plant-based source of omega-3 fatty acid. In addition, they provide dietary fiber, much of which is soluble fiber, which has been shown to delay gastric emptying, improve cholesterol levels, and improve glycemic control. A 2 tbsp. serving of ground flaxseed, or flax meal provides 4 g of fiber.

In a research study on subjects with diabetes, supplementing with 10 g of flaxseed powder for 1 month resulted in a 19.7% reduction in fasting glucose, and a 15.6% reduction in A1C. Additionally, subjects saw a reduction in total cholesterol, LDL-cholesterol, and triglycerides, along with an increase in HDL-cholesterol.⁸

In terms of its ability to improve glucose levels, flaxseed appears to be most beneficial for those with diabetes. Studies on those with prediabetes show that it may improve other metabolic markers, including lipids and blood pressure, but not necessarily fasting or postprandial glucose.⁹

Flaxseed is generally well-tolerated, with no adverse effects. In higher doses, it may cause gastrointestinal side effects associated with high fiber intake, including gas and bloating.

Summary

Nutritional supplements and functional foods are among the most widely used form of CAM, and their use has been increasing in the United States and worldwide. It is estimated that people with diabetes are 1.6 times more likely than those without the disease to use a CAM as part of their treatment.

As RDNs, we are aware that even though many of these nutritional supplements are natural foods or herbs, they may still come with side effects, especially if taken at inappropriate doses. Our patients should be made aware of any risks, as well as proper dosing, and potential interactions with other supplements or medications especially where hypoglycemia may be a risk. In addition, it is essential to stress to patients who use herbal, vitamin or nutraceutical supplements to share this information with all members of their medical team.

Nutritional Supplements for Glycemic Control in Type 2 Diabetes

Natural Medicines Database. Available by subscription. https://naturalmedicines.therapeuticresearch.com/. Accessed May 31, 2018.

References and recommended reading

1. Suksomboon N, Poolsup N, Punthanitisarn S. Effect of Aloe vera on glycaemic control in prediabetes and type 2 diabetes: a systematic review and meta-analysis. J Clin Pharm Ther. 2016;41(2):180-188.
2. Pang B, Zhao LH, Zhou Q, et al. Application of berberine on treating type 2 diabetes mellitus. Int J Endocrinol. 2015;2015.
3. Yin J, Xing H, Ye J. Efficacy of berberine in patients with type 2 diabetes mellitus. Metabolism. 2008;57(5):712-717.
4. Medagama AB, Bandara R. The use of Complementary and Alternative Medicines (CAMs) in the treatment of diabetes mellitus: is continued use safe and effective. Nutri J. 2014;13(1):102.
5. Costello RB, Dwyer JT, Bailey RL. Chromium supplements for glycemic control in type 2 diabetes: limited evidence of effectiveness. Nutri Rev. 2016;74(7):455-468.
6. Anderson RA, Zhan Z, Luo R, et al. Cinnamon extract lowers glucose, insulin and cholesterol in people with elevated serum glucose. J Tradit Complement Med. 2016;6(4):332-336.
7. Neelakantan N, Narayanan M, de Souza RJ, van Dam RM. Effect of fenugreek (Trigonella foenum-graecum L.) intake on glycemia: a meta-analysis of clinical trials. Nutri J. 2014;13(1):7.
8. Mani UV, Mani I, Biswas M, Kumar SN. An open-label study on the effect of flax seed powder (Linum usitatissimum) supplementation in the management of diabetes mellitus. J Diet Suppl. 2011;8(3):257-265.
9. Javidi A, Mozaffari-Khosravi H, Nadjarzadeh A, Dehghani A, Eftekhari MH. The effect of flaxseed powder on insulin resistance indices and blood pressure in prediabetic individuals: A randomized controlled clinical trial. J Res Med Sci. 2016;21:70.
10. Natural Medicines Database. Available by subscription. https://naturalmedicines.therapeuticresearch.com/. Accessed May 8, 2018.
11. Statistics about diabetes. American Diabetes Association website. http://www.diabetes.org/diabetes-basics/statistics/. Accessed May 8, 2018.
12. Vogler BK, Ernst E. Aloe vera: a systematic review of its clinical effectiveness. Br J Gen Pract. 1999;49(447):823-828.

Review date: 6/14/18