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Guidance needed for dietary supplement use in diabetes
In this issue, Susan Weiner, MS, RDN, CDE, CDN, FAADE, talks with pharmacy professor Laura Shane-McWhorter, PharmD, BCPS, BC-ADM, CDE, FASCP, FAADE, about guiding people with diabetes in dietary supplement use. The 2012 National Health Interview Survey found that 26.2% of adults with diabetes reported using some type of complementary and alternative medicine in the previous year.
Why do people use supplements for diabetes?
Shane-McWhorter: More than half of U.S. residents who use complementary and alternative medicine (CAM) cite wellness or treatment as a reason. Regardless of rationale, 56.9% of CAM use reported in the National Health Interview Survey was herbal therapies. Patients often say they trust supplements more than prescribed medications because they believe supplements are “natural” and are attracted to the mystique of using something they hope would manage hyperglycemia without side effects or drug interactions. Often patients feel that taking prescribed medications “brands” their diabetes control as less than optimal but taking supplements makes them feel more in control.
What are some supplements that might be particularly beneficial or harmful for people with diabetes?
Shane-McWhorter: Although not definitive, beneficial supplements may include alpha-lipoic acid for neuropathy, coenzyme Q10 for cardiovascular health, and milk thistle for hepatoprotection and glucose lowering.
Products that may be particularly harmful include weight-loss supplements and those marketed for body building or men’s health. Someone with hepatic disease should avoid potentially hepatotoxic agents such as cinnamon, and someone with difficult-to-manage blood pressure should avoid ginseng.
Health care providers should be aware of the popular supplements listed below and their possible effects on diabetes.
Aloe vera may lower blood glucose. The mechanism of action in humans is unknown, but animal studies have shown increased pancreatic insulin production and hepatic gluconeogenesis and decreased insulin resistance with its use. Aloe’s fiber content may delay or prevent glucose absorption and promote probiotic effects. Aloe gel, called sábila in Spanish, is often used in smoothies.
Bitter melon is used as a supplement and consumed as a vegetable in Asia and India. It may increase tissue glucose uptake, glycogen synthesis and AMP-activated protein kinase (AMPK) activity; enhance glucose oxidation of the glucose-6-phosphate dehydrogenase (G6PDH) pathway; and inhibit alpha-glucosidase. A 2012 meta-analysis of low-quality trials found no difference in effects between bitter melon and placebo, or between bitter melon and oral diabetes medications, including glyburide and metformin. Bitter melon use is not recommended as a diabetes therapy because it is not effective.
Cinnamon used for diabetes and hyperlipidemia has been shown to increase insulin sensitivity, enhance insulin-receptor phosphorylation and improve insulin signaling. It may enhance glucose uptake and delay gastric emptying. Although a 2012 Cochrane Review found insufficient evidence to support cinnamon’s use for diabetes, a 2013 systematic review found that cinnamon showed statistically significant lowering of fasting glucose and triglycerides, but not HbA1c.
Flaxseed is a soluble fiber containing alpha-linolenic acid, a plant-based omega-3 fatty acid and lignans, a phytoestrogen. People with and without diabetes frequently use flaxseed whole, ground or as an oil for cardiovascular disease protection, weight loss and relief of constipation. The soluble fiber delays glucose absorption and gastric emptying, and the lignan content may reduce glucose concentration and delay postprandial glucose absorption. The omega-3 may improve insulin sensitivity and has antioxidant properties. However, research does not consistently demonstrate benefit.
Milk thistle is used for hepatoprotection, nonalcoholic steatohepatitis and diabetes. Some evidence shows benefit for nephropathy. It has anti-inflammatory and antioxidant effects and decreases insulin resistance and oxidative stress in pancreatic beta cells. Studies have shown benefit in hepatic disorders as well as improved glucose control.
What advice would you give health care providers about discussing supplement use with people who have diabetes?
Clinicians must educate themselves about the supplements their patients may be taking and approach discussions about supplement use without judgment. They should provide evidence-based information and participate in shared decision-making with patients regarding realistic goals, possible side effects and drug interactions. Patients must also understand that supplements are not FDA approved and are regulated as foods, not drugs. A useful source of information provided by the NIH is HerbList, a mobile app on herbal products.
- References:
- NIH. Use of complementary health approaches in the U.S., National Health Interview Survey. 2017. Available at: nccih.nih.gov/research/statistics/NHIS/2012. Accessed Jan. 7, 2019.
- Rios JL, et al. Planta Med. 2015;doi;10.1055/s-0035-1546131.
- Shane-McWhorter L. Diabetes Spectr. 2009;doi:10.2337/diaspect.22.4.206.
- For more information:
- Laura Shane-McWhorter, PharmD, BCPS, BC-ADM, CDE, FASCP, FAADE, is emerita clinical professor at the University of Utah College of Pharmacy and a clinical pharmacist at a federally qualified community health center. She is author of Complementary and Alternative Medicine (CAM) Supplement Use in People with Diabetes: A Clinician’s Guide and Guide to Herbs and Nutritional Supplements, both published by the American Diabetes Association. She can be reached at lmcwhorter@pharm.utah.edu.
- Susan Weiner, MS, RDN, CDE, CDN, FAADE, is author of The Complete Diabetes Organizer and Diabetes: 365 Tips for Living Well. She is the owner of Susan Weiner Nutrition PLLC and is the Endocrine Today Diabetes in Real Life column editor. She can be reached at susan@ susanweinernutrition.com.
Disclosures: Shane-McWhorter reports no relevant financial disclosures. Weiner reports she is a clinical adviser to Livongo Health.