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Diabetes and Dietary Supplements: In Depth


What’s the Bottom Line?

How much do we know about dietary supplements for diabetes?

Many studies have investigated dietary supplements, including vitamins, for preventing or treating type 2 diabetes (the focus of this fact sheet).

What do we know about the effectiveness of dietary supplements for diabetes?

Most of the supplements studied aren’t effective and some may worsen symptoms of diabetes. For example, using omega-3 supplements, such as fish oil, or cinnamon doesn’t appear to help with diabetes. A number of small studies have looked at whether magnesium or chromium supplements help with diabetes, but the results aren’t definitive.

What do we know about the safety of dietary supplements for diabetes?

  • Some dietary supplements have side effects, including interacting with diabetes treatments or increasing the risk of kidney problems.
  • The U.S. Food and Drug Administration (FDA) is warning consumers not to buy illegally marketed, potentially dangerous products claiming to prevent, treat, or cure diabetes.
  • It’s very important not to replace proven conventional medical treatment for diabetes with an unproven health product or practice.

About Diabetes

  • Diabetes is a disease that occurs when your blood glucose, also called blood sugar, is too high. It can lead to serious health problems if it’s not managed well.
  • Between 12 and 14 percent of U.S. adults have diabetes, but more than 25 percent of people with it are undiagnosed.
  • Taking insulin or other diabetes medicine is often key to treating diabetes, along with making healthy food choices and being physically active.
  • Your health care providers can show you how to control your diabetes and track your success.

More About Diabetes

  • There are three types of diabetes—type 1, type 2, and gestational. All three involve problems with how your body responds to the hormone insulin. Food supplies your body with glucose, a sugar and the main fuel for our bodies. To use glucose, your body needs insulin. If you have type 1 diabetes your body is producing little or no insulin. If you have type 2 your body makes insulin but doesn’t respond to it normally. Gestational diabetes affects only pregnant women. It usually goes away after birth, but it increases the mother’s risk of developing diabetes later in life.
  • About 95 percent of people diagnosed with diabetes have type 2. People with type 1, which is usually diagnosed in childhood or early adulthood, must take insulin to survive.
  • For more information about diabetes and related conditions, see the National Institute of Diabetes and Digestive and Kidney Diseases Web site.

Kidney disease has been linked to using some dietary supplements. This is of particular concern for people with diabetes, since diabetes is the leading cause of kidney failure in the United States. If you have or are at risk for kidney disease, a health care provider should closely monitor your use of supplements.

What the Science Says About the Effectiveness and Safety of Dietary Supplements for Diabetes

Alpha-Lipoic Acid

Alpha-lipoic acid is an antioxidant (a substance that may protect against cell damage) being studied for its effect on complications of diabetes, including macular edema, an eye condition that causes blurred vision; unhealthy cholesterol levels; and poor insulin sensitivity. Two 2011 studies of about 570 patients didn’t find that the supplement helped with conditions related to diabetes.


High doses of alpha-lipoic acid supplements can cause stomach problems.


Found in many foods, chromium is an essential trace mineral. If you have too little chromium in your diet, your body can’t use glucose efficiently.

  • Studies have found few or no benefits of chromium supplements for controlling diabetes or reducing the risk of developing it.Taking chromium supplements, along with conventional care, improved blood sugar control in people with diabetes (primarily type 2) who had poor blood sugar control, a 2014 review concluded; however, the improvement was very small. The review included 25 studies with about 1,600 participants.


Chromium supplements may cause stomach pain and bloating, and there have been a few reports of kidney damage, muscular problems, and skin reactions following large doses. The effects of taking chromium long-term haven’t been well investigated.

Herbal Supplements

We don’t have reliable evidence that any herbal supplements can help to control diabetes or its complications.

  • There are no clear benefits of cinnamon for people with diabetes.
  • Other herbal supplements studied for diabetes include bitter melon, Chinese herbal medicines, fenugreek, ginseng, milk thistle, selenium, and sweet potato. Studies haven’t proven that any of these are effective, and some may have side effects.


  • We have little conclusive information on the safety of herbal supplements for people with diabetes.
  • Cassia cinnamon, the most common type of cinnamon sold in the United States and Canada, contains varying amounts of a chemical called coumarin, which might cause or worsen liver disease. In most cases, cassia cinnamon doesn’t have enough coumarin to make you sick. However, for some people, such as those with liver disease, taking a large amount of cassia cinnamon might worsen their condition.
  • Using herbs such as St. John’s wort, prickly pear cactus, aloe, or ginseng with conventional diabetes drugs can cause unwanted side effects.


Found in many foods, including in high amounts in bran cereal, certain seeds and nuts, and spinach, magnesium is essential to the body’s ability to process glucose.

  • Magnesium deficiency may increase the risk of developing diabetes. A number of studies have looked at whether taking magnesium supplements helps people who have diabetes or who are at risk of developing it. However, the studies are generally small and their results aren’t conclusive.


  • Large doses of magnesium in supplements can cause diarrhea and abdominal cramping. Very large doses—more than 5,000 mg per day—can be deadly.

For more information on magnesium, see the Office of Dietary Supplements (ODS) Magnesium: Fact Sheet for Consumers.


  • Taking omega-3 supplements, such as fish oil, hasn’t been shown to help people who have diabetes control their blood sugar levels. Research on whether eating fish lowers your risk of getting diabetes is generally negative. However, the effect of eating fish may depend on what type of fish you eat, among other factors.
  • Studies on the effects of eating fish have had conflicting results, two 2012 research reviews with hundreds of thousands of participants showed. Some research from the United States and Europe found that people who ate more fish had a higher incidence of diabetes. Research from Asia and Australia found the opposite—eating more fish was associated with a lower risk of diabetes. There’s no strong evidence explaining these differences.
  • Taking omega-3 supplements doesn’t help protect against heart disease in people who have or are at risk of having diabetes, an American Heart Association science advisory, based on 5 studies with more than 10,000 participants, stated in 2017. However, it’s unclear whether people who have both diabetes and a high risk of developing heart disease would benefit from taking omega-3 supplements.


  • Omega-3 supplements don’t usually have side effects. When side effects do occur, they typically consist of minor symptoms, such as bad breath, indigestion, or diarrhea.
  • Omega-3 supplements may interact with drugs that affect blood clotting.

For more information on omega-3 supplements, see NCCIH’s Omega-3 Fatty Acids Web page.


  • Studies generally show that taking vitamin C doesn’t improve blood sugar control or other conditions in people with diabetes. However, a 2017 research review of 22 studies with 937 participants found weak evidence that vitamin C helped with blood sugar in people with type 2 diabetes when they took it for longer than 30 days.
  • Having low levels of vitamin D is associated with an increased risk of developing a metabolic disorder, such as type 2 diabetes, metabolic syndrome, or insulin resistance, studies and research reviews from the past 5 years have found. But taking vitamin D doesn’t appear to help prevent diabetes or improve blood sugar levels for adults with normal levels, prediabetes, or type 2 diabetes, a 2014 research review of 35 studies with 43,407 participants showed.


  • Taking too much vitamin D is dangerous and can cause nausea, constipation, weakness, kidney damage, disorientation, and problems with your heart rhythm. You’re unlikely to get too much vitamin D from food or the sun.

For more information on vitamin D, see ODS’s Vitamin D: Fact Sheet for Consumers.

Other Supplements

  • The evidence is still very preliminary on how supplements or foods rich in polyphenols—antioxidants found in tea, coffee, wine, fruits, grains, and vegetables—might affect diabetes.

Healthy Behaviors: Key to Managing Your Diabetes


Develop a meal plan with help from your health care providers. For more information, visit the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Web site.

Physical Activity

Different types and even small amounts of physical activity can help you control diabetes. Physical activity lowers blood sugar, blood pressure, improves blood flow, decreases the risk of falling in older adults, and more. Talk with your health care provider before you start a new physical activity program.

For information on becoming more active, see NIDDK’s Web page Diabetes Diet, Eating, & Physical Activity.

NCCIH-Funded Research

NCCIH is supporting research on the possible effects of:

  • Components of grape skin on blood sugar control
  • Chelation therapy on heart health in people who have diabetes and have had a heart attack
  • Marijuana on the body’s metabolism and risk of developing type 2
  • Acupuncture on painful diabetic neuropathy (nerve damage) in underserved patients.

More to Consider

  • Talk to a health care provider before considering any dietary supplement for yourself, particularly if you’re pregnant or nursing, or for a child. Many supplements have not been tested in pregnant women, nursing mothers, or children.
  • The FDA is warning consumers not to buy illegally marketed, potentially dangerous products claiming to prevent, treat, or cure diabetes. These products make claims like “lowers your blood sugar naturally” or “inexpensive therapy to fight and eliminate type II diabetes.” They may contain harmful ingredients and the label may not tell you what you’re actually taking.
  • Fraudulent diabetes products can be especially dangerous if you use them instead of proven treatments for diabetes. You can develop serious health complications if you don’t follow your doctor’s directions for managing diabetes.
  • Keep in mind that dietary supplements may interact with medications or other dietary supplements. To learn more, visit NCCIH’s Web page on Dietary and Herbal Supplements.
  • Tell all your health care providers about any complementary or integrative health approaches you use. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care.

For More Information

NCCIH Clearinghouse

The NCCIH Clearinghouse provides information on NCCIH and complementary and integrative health approaches, including publications and searches of Federal databases of scientific and medical literature. The Clearinghouse does not provide medical advice, treatment recommendations, or referrals to practitioners.

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A service of the National Library of Medicine, PubMed® contains publication information and (in most cases) brief summaries of articles from scientific and medical journals. For guidance from NCCIH on using PubMed, see How To Find Information About Complementary Health Approaches on PubMed.

NIH Clinical Research Trials and You

The National Institutes of Health (NIH) has created a Web site, NIH Clinical Research Trials and You, to help people learn about clinical trials, why they matter, and how to participate. The site includes questions and answers about clinical trials, guidance on how to find clinical trials through and other resources, and stories about the personal experiences of clinical trial participants. Clinical trials are necessary to find better ways to prevent, diagnose, and treat diseases.

National Diabetes Information Clearinghouse

A service of the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), the clearinghouse responds to inquiries, offers diabetes publications, and makes referrals. For an alphabetical list of publication topics, go to

En español:

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National Diabetes Education Program

The National Diabetes Education Program is sponsored by NIH and the Centers for Disease Control and Prevention, with many Federal, state, and local partners. Its services include information and publications on diabetes.

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To provide resources that help answer health questions, MedlinePlus (a service of the National Library of Medicine) brings together authoritative information from the National Institutes of Health as well as other Government agencies and health-related organizations.

Information on diabetes
Information on magnesium

En español:

Key References

All Other References

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  • Banihani S, Swedan S, Alguraan Z. Pomegranate and type 2 diabetes. Nutrition Research. 2013;33(5):341–348.
  • Barbagallo M, Dominguez LJ. Magnesium and type 2 diabetes. World Journal of Diabetes. 2015;6(10):1152–1157.
  • Breslavsky A, Frand J, Matas Z, et al. Effect of high doses of vitamin D on arterial properties, adiponectin, leptin and glucose homeostasis in type 2 diabetic patients. Clinical Nutrition. 2013;32(6):970–975.
  • Bush TM, Rayburn KS, Holloway SW, et al. Adverse interactions between herbal and dietary substances and prescription medications: a clinical survey. Alternative Therapies in Health and Medicine. 2007;13(2):30–35.
  • Cefalu WT, Rood J, Pinsonat P. et al. Characterization of the metabolic and physiologic response to chromium supplementation in subjects with type 2 diabetes mellitus. Metabolism: Clinical and Experimental. 2010;59(5):755–762.
  • Faghihi T, Radfar M, Barmal M, et al. A randomized, placebo-controlled trial of selenium supplementation in patients with type 2 diabetes: effects on glucose homeostasis, oxidative stress, and lipid profile. American Journal of Therapeutics. 2014;21(6):491–495.
  • Forouhi NG, Ye Z, Rickard AP, et al. Circulating 25-hydroxyvitamin D concentration and the risk of type 2 diabetes: results from the European Prospective Investigation into Cancer (EPIC)-Norfolk cohort and updated meta-analysis of prospective studies. Diabetologia. 2012;55(8):2173–2182.
  • Fuangchan A, Sonthisombat, P, Seubnukarn T, et al. Hypoglycemic effect of bitter melon compared with metformin in newly diagnosed type 2 diabetes patients. Journal of Ethnopharmacology. 2011;134(2):422–428.
  • Gabardi S, Munz K, Ulbricht C. A review of dietary supplement-induced renal dysfunction. Clinical Journal of the American Society of Nephrology. 2007;2(4):757–765.
  • Gutierrez AD, Duran-Valdez E, Robinson I, et al. Does short-term vitamin C reduce cardiovascular risk in type 2 diabetes? Endocrine Practice. 2013;19(5):785–791.
  • Han T, Bai J, Liu W, et al. A systematic review and meta-analysis of α-lipoic acid in the treatment of diabetic peripheral neuropathy. European Journal of Endocrinology. 2012;167(4):465–471.
  • Hanhineva K, Törrönen R, Bondia-Pons I, et al. Impact of dietary polyphenols on carbohydrate metabolism. International Journal of Molecular Sciences. 2010:11(4):1365–1402.
  • Hokayem M, Blond E, Vidal H, et al. Grape polyphenols prevent fructose-induced oxidative stress and insulin resistance in first-degree relatives of type 2 diabetic patients. Diabetes Care. 2013;36(6):1454–1461.
  • Isnard Bagnis C, Deray G, Baumelou A, et al. Herbs and the kidney. American Journal of Kidney Diseases. 2004;44(1):1–11.
  • Kaushik M, Mozaffarian D, Spiegelman D, et al. Long-chain omega-3 fatty acids, fish intake, and the risk of type 2 diabetes mellitus. American Journal of Clinical Nutrition. 2009;90(3):613–620.
  • Lee TC, Ivester P, Hester AG, et al. The impact of polyunsaturated fatty acid-based dietary supplements on disease biomarkers in a metabolic syndrome/diabetes population. Lipids in Health and Disease. 2014;13:196.
  • Mao S, Zhang A, Huang S. Selenium supplementation and the risk of type 2 diabetes mellitus: a meta-analysis of randomized controlled trials. Endocrine. 2014;47(3):758–763.
  • Mooren FC, Krüger K, Völker K, et al. Oral magnesium supplementation reduces insulin resistance in non-diabetic subjects—a double-blind, placebo-controlled, randomized trial. Diabetes, Obesity & Metabolism. 2011;13(3):281–284.
  • Reeds DN, Patterson BW, Okunade A, et al. Ginseng and ginsenoside Re do not improve β-cell function or insulin sensitivity in overweight and obese subjects with impaired glucose tolerance or diabetes. Diabetes Care. 2011;34(5):1071–1076.
  • Rude RK. Magnesium. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. New York, NY: Informa Healthcare; 2010:527–537.
  • Shishtar E, Sievenpiper JL, Djedovic V, et al. The effect of ginseng (the genus panax) on glycemic control: a systematic review and meta-analysis of randomized controlled clinical trials. PLoS One. 2014;9(9):e107391.
  • Song Y, Cook NR, Albert CM, et al. Effects of vitamins C and E and beta-carotene on the risk of type 2 diabetes in women at high risk of cardiovascular disease: a randomized controlled trial. American Journal of Clinical Nutrition. 2009;90(2):429–437.
  • Tovar RT, Petzel RM. Herbal toxicity. Disease-a-Month. 2009;55(10):592–641.
  • Wang Z, Gorski JC, Hamman MA, et al. The effects of St. John’s wort (Hypericum perforatum) on human cytochrome P450 activity. Clinical Pharmacology and Therapeutics. 2001;70(4):317–326.
  • Wu JH, Micha R, Imamura F, et al. Omega-3 fatty acids and incident type 2 diabetes: a systematic review and meta-analysis. British Journal of Nutrition. 2012;107(suppl 2):S214–S227.
  • Xu H, Williams KM, Liauw WS, et al. Effects of St. John’s wort and CYP2C9 genotype on the pharmacokinetics and pharmacodynamics of gliclazide. British Journal of Pharmacology. 2008;153(7):1579–1586.


NCCIH thanks David Shurtleff, Ph.D., NCCIH, for his contributions to the 2017 update of this publication.

This publication is not copyrighted and is in the public domain. Duplication is encouraged.

NCCIH has provided this material for your information. It is not intended to substitute for the medical expertise and advice of your primary health care provider. We encourage you to discuss any decisions about treatment or care with your health care provider. The mention of any product, service, or therapy is not an endorsement by NCCIH.

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Last Updated: 
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This page last modified July 24, 2017