By Clipper F. Young, PharmD, MPH, CDCES, BC-ADM, BCGP, APh, and Matthew Wai, DO

Dr. Young is an Associate Professor, Touro University California, College of Osteopathic Medicine, Vallejo, CA.

Dr. Wai is a graduate of Touro University California College of Osteopathic Medicine, Residency Training at Riverside Community Health/University of California Riverside.

Diabetes mellitus (DM), especially type 2 DM, is a major public health concern that affects about 34.1 million people in the United States.1 This chronic health condition, if not properly managed, can cause long-term complications as well as considerable morbidity and mortality in the affected population.2 In 2018, an estimated 1.5 million new cases of diabetes were diagnosed in U.S. adults ≥ age 18 years, with more than half of these new cases in adults age 45-64 years.1

With cases rising, clinicians also are encountering more patients who are turning to complementary and alternative medicine (CAM) to help control their glucose levels. In a 2015 National Consumer Survey on the Medication Experience and Pharmacist Roles, 35% of 26,157 respondents reported using at least one herbal medicine.3 In all, 3,050 respondents had diabetes, and 41.2% reported using a dietary supplement.3 The data revealed respondents with diabetes were associated with higher herbal medicine use vs. respondents without chronic diseases (41% vs. 34%; P < 0.001).3 The results also showed herbal medicine use rose as age increased among the respondents.3

Since the FDA regulates CAM products as dietary supplements, the effectiveness and safety of these products are regulated after they are available in the market, which means the quality and safety of these supplements can be highly variable.4 As more people with diabetes are reporting CAM product use in conjunction with prescription medications, it is important clinicians understand what role these products play in diabetes management with the available evidence. By reviewing the current evidence behind these alternative therapies, medical practitioners will be better equipped to distill information for their patients and address the utility of these proposed diabetes supplements.

The following is a review of the current literature regarding commonly used herbal and dietary supplements among people with diabetes.

We performed an electronic literature search on the American Diabetes Association website based on the recommendation from the American Association of Diabetes Educators (now named Association of Diabetes Care and Education Specialists) to discover what had been written about herbal products relating to diabetes management.5 We cross-referenced these findings with the Natural Medicines Database and Complementary & Alternative Medicine Supplement Use in People with Diabetes: A Clinician’s Guide regarding the identified products’ safety and effectiveness.6

Keywords included dietary supplements, herbal supplements, type 2 diabetes mellitus, Aloe vera, alpha-lipoic acid, chromium, cinnamon, fenugreek, ginseng, ginger, gymnema, magnesium, nopal, and psyllium. The search was limited to studies published in English and from date of inception until 2019. We included systematic reviews; meta-analyses; and randomized, controlled trials. We excluded abstract-only articles, conference presentations, editorials, and studies with fewer than five participants. Articles were screened independently by the authors and included based on relevancy.

The most popular supplements taken by patients are herbal ones derived from natural sources, as opposed to other forms, such as vitamin or mineral mixtures.7 The authors have identified 11 herbal and dietary supplements — Aloe vera, alpha-lipoic acid, chromium, cinnamon, fenugreek, garlic, ginseng, magnesium, psyllium, gymnema, and nopal — that are used commonly among patients with diabetes.

However, because of limited quality control in dietary supplements, it is difficult to make firm recommendations without reviewing the current evidence on efficacy and proposed mechanisms by which these products work in patients with diabetes. In this review, we focus on Aloe vera and alpha-lipoic acid.

ALOE VERA

There are more than 300 species in the Aloe genus, and one is extremely well-known worldwide. Aloe barbadensis, otherwise known as Aloe vera, is a renowned plant of the Liliaceae family, known for its many medicinal properties.8 The spiky succulent plant contains gel and juice, which has become a commercial supplement and cosmetic. It is believed Aloe vera possesses antioxidant, anticancer, anti-inflammatory, laxative, and anti-atherosclerotic properties.9

There are multiple existing hypotheses on why Aloe vera can be a useful diabetes management tool. One hypothesis indicates Aloe vera lowers blood glucose levels through its anti-inflammatory effects. Type 2 DM is an inflammatory disease associated with oxidative stress of the pancreas, which leads to beta-cell dysfunction and insulin resistance.10 Clinical research shows Aloe vera can reduce fasting blood glucose levels by 30 mg/dL to 46.6 mg/dL and hemoglobin A1c (HbA1c) by 0.41% to 1.05% in adults with prediabetes and diabetes.11-13

Another hypothesis suggests a constituent of the Aloe vera plant, glucomannan, is the agent that possesses the hypoglycemic effects.14 Glucomannan is a hydrosoluble agent believed to promote satiety and delaying intestinal absorption because of its increased viscosity.15 There has been a variety of doses and dosage forms, ranging from 100 mg to 1,000 mg of its powder to 15 mL to 150 mL of its juice formulation, suggested to be efficacious in lowering blood glucose.11-13 However, because of the heterogeneity of the available studies, the mixed evidence on Aloe vera’s effectiveness hinders the validity of the reported findings.

ALPHA-LIPOIC ACID

Alpha-lipoic acid (ALA) is an antioxidant that could improve carbohydrate disturbances.15,16 ALA is a naturally occurring antioxidant that promotes the transport of glucose into cells of muscles.16 Additionally, it might alleviate peripheral neuropathy in patients with type 2 diabetes.17 The suggested effective dose to improve insulin sensitivity and fasting blood glucose is 600 mg to 1,800 mg/day orally for four to eight weeks.16 However, conflicting evidence exists, which suggests no effect on insulin sensitivity.12 Dosages of 600 mg to 1,800 mg daily have shown benefits for patients experiencing pain, numbness, and prickling of extremities associated with neuropathy.18

DISCUSSION

Compared to patients without diabetes, patients with diabetes are 1.6 times more likely to include CAM as a component of their diabetes management plans; thus, they are more prone to negative consequences (e.g., side effects and drug interactions) resulting from herbal and dietary supplement usage.19 These products often are purchased over the counter or through the mail. Consumers with DM might be confused about the product contents and labels, adding to the list of safety concerns. For that reason, patients might be at risk of purchasing products that do not match their stated claims if the products have not gone through a third-party verification process.

To ensure safety from the standpoint of clinicians, it is crucial to ask patients at every visit whether any herbal or dietary supplements were added since the last medical appointment to identify potential drug-supplement interactions, side effects, or additive effects when used with antidiabetic medications. Although Aloe vera has been used for skin treatment and incorporated into drugs as laxatives, there is no long-term evidence yet to suggest its effectiveness in diabetes management. ALA — functioning similarly to B-complex vitamin — has been used in peripheral neuropathy treatment, even that secondary to diabetes.20

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