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National Institutes of Health • National Center for Complementary and Alternative Medicine

NCCAM Clinical Digest

Type 2 Diabetes and Dietary Supplements :
What the Science Says

November 2013
Diabetic person checking blood sugar level

Overall, there is not enough scientific evidence to show that any dietary supplement can help manage or prevent type 2 diabetes. It is important to note that there are multiple case reports linking dietary supplement use to kidney disease, which is of particular concern because diabetes is the leading cause of chronic kidney disease and kidney failure in the United States. Supplement use should be monitored closely in patients who have or are at risk for kidney disease.

Minerals

Magnesium

Found in many foods, including whole grains, nuts, and green leafy vegetables, magnesium is essential to the body’s ability to process glucose. Magnesium deficiency has been associated with diabetes.

Strength of Evidence

  • Much research has been done to investigate the effects of magnesium on reducing the risks of developing type 2 diabetes.

Research Results

  • There is no evidence from clinical trials that magnesium is beneficial in managing diabetes in the absence of magnesium deficiency.
  • A 2011 meta-analysis reviewed the results of 13 studies that looked at how much magnesium people got in their diets, either through supplements or food, and their risk of diabetes. The review found that people who had lower magnesium intake had a greater risk of developing diabetes.
  • One of the studies in the 2011 meta-analysis, a large 2007 clinical trial, found an association between a higher intake of cereal fiber and magnesium and a reduced risk of developing type 2 diabetes.
  • A diet rich in magnesium was associated with a 15 percent reduced risk of developing type 2 diabetes, a 2007 meta-analysis found.

Safety

  • No serious side effects were reported in studies where people with diabetes were given magnesium supplements for up to 16 weeks. However, the long-term safety of magnesium supplements for people with diabetes has not been established.
  • Large doses of magnesium in supplements can cause diarrhea and abdominal cramping. Very large doses—more than 5,000 mg/day per day—can be deadly.

Chromium

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.

Strength of Evidence

  • Many studies have been conducted on the effects of chromium for controlling or preventing diabetes. However, many of the studies have been very small or not high quality.

Research Results

  • Studies, including a 2007 systematic review, have found few or no benefits of chromium supplements for controlling diabetes or reducing the risk of developing it.

Safety

  • Chromium supplements may cause stomach pain and bloating.
  • There have been a few reports of kidney damage, muscular problems, and skin reactions following large doses.

Herbs and Other Dietary Supplements

There is no strong evidence that any herbal supplement can help to control diabetes or its complications. 

Cinnamon

Strength of Evidence

  • There has been much research conducted on the effects of cinnamon in people with diabetes.

Research Results

  • Researchers have found no clear benefits and some risks of cinnamon for people with diabetes. For example, a 2012 systematic review of 10 randomized controlled trials did not support using cinnamon for type 1 or type 2 diabetes.

Safety

  • When researchers tested samples of the common spice cassia cinnamon for sale at grocery stores in Europe, they found many samples contained coumarin, a substance that may cause or worsen liver disease in people who are sensitive. Further, eating food containing coumarin may be especially risky for people taking blood-thinning drugs; the interaction of coumarin and blood thinners can increase the likelihood of bleeding.

Alpha-Lipoic Acid

Alpha-lipoic acid is an antioxidant sold as a supplement and is in foods, including liver, spinach, broccoli, and tomatoes.

Strength of Evidence

  • Several studies have examined the effects of alpha-lipoic acid on complications of diabetes.

Research Results

  • A 2011 clinical trial of 467 participants with type 2 diabetes found that 600 milligrams of alpha-lipoic acid daily did not prevent diabetic macular edema, an eye condition that causes blurred vision.
  • Alpha-lipoic acid and vitamin E supplements taken separately or in combination did not improve cholesterol levels or the body’s response to insulin in a 2011 clinical trial of 102 people with type 2 diabetes.

Safety

  • High doses of alpha-lipoic acid can cause nausea, upset stomach, fatigue, and insomnia.

Omega-3s

Strength of Evidence

  • Much research has examined the role of omega-3 fatty acids in reducing the risk of developing type 2 diabetes.

Research Results

  • A 2008 systematic review found that omega-3s supplements don’t help people with diabetes control their blood sugar levels.
  • A 2012 study that combined a meta-analysis and a systematic review looked at the possible link between eating seafood or plants with omega-3s and the risk of developing type 2 diabetes.  The study found little evidence that these dietary sources of omega-3s affected the risk of developing diabetes.

Safety

  • Omega-3 supplements usually do not have negative side effects. When side effects do occur, they typically consist of minor gastrointestinal symptoms, such as belching, indigestion, or diarrhea.
  • Omega-3 supplements may extend bleeding time.

Other Dietary Supplements

Strength of Evidence

  • A few studies have examined the herbs Asian ginseng and American ginseng and their effects on controlling glucose levels.
  • The evidence is still preliminary on the effects on diabetes of polyphenols—antioxidants found in plant-based foods such as fruits, grains, and vegetables.

Research Results

Safety

  • Information on the safety of herbal supplements for people with diabetes is generally inconclusive or unavailable.
  • Interactions between herbs and conventional diabetes drugs have not been well studied and could be a health risk.

NCCAM Clinical Digest is a service of the National Center for Complementary and Alternative Medicine, NIH, DHHS. NCCAM Clinical Digest, a monthly e-newsletter, offers evidence-based information on CAM, including scientific literature searches, summaries of NCCAM-funded research, fact sheets for patients, and more.

The National Center for Complementary and Alternative Medicine is dedicated to exploring complementary and alternative healing practices in the context of rigorous science, training CAM researchers, and disseminating authoritative information to the public and professionals. For additional information, call NCCAM's Clearinghouse toll-free at 1-888-644-6226, or visit the NCCAM Web site at nccam.nih.gov. NCCAM is 1 of 27 institutes and centers at the National Institutes of Health, the Federal focal point for medical research in the United States.

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