Can dietary supplements help manage type 2 diabetes?


Patients are going to ask. Pharmacists need to have the answer ready.

With their increasing popularity on the internet and television, the question isn’t whether pharmacists will be asked about dietary supplements and their value in managing or preventing type 2 diabetes. That has already happened. The question becomes how best to respond?

The science on the subject seems clear. There is no evidence that dietary supplements help patients manage or prevent type 2 diabetes.

“A healthy diet, physical activity, and blood glucose testing are the basic tools for managing type 2 diabetes,” says a statement on diabetes and dietary supplements posted at the website of the National Institutes of Health (NIH). “It is very important not to replace proven conventional medical treatment for diabetes with an unproven health product or practice.”

So how should pharmacists respond to the question: “Can dietary supplements help management type 2 diabetes?”

The experts weigh in

 “My preference would be no, do not use them. But, on the other hand, I have to respect my patients,” said Laura Shane-McWhorter, PharmD, BCPS, BC-ADM, CDE, FASCP, FAADE, a clinical professor at the University of Utah’s College of Pharmacy in Salt Lake City.

W. Steven Pray, PhD, DPh, Bernhardt professor of pharmacy in the Department of Pharmaceutical Sciences at Southwestern Oklahoma State University’s College of Pharmacy, is even more blunt. “Is the risk to the patients [from taking dietary supplements] justified by the benefits? With this junk, there are no proven benefits,” Pray said. “Everyone is looking for a magic Band-Aid that lets them continue with bad habits and suffer no consequences. No one wants to hear the bad news that there are no shortcuts.”

Supplement use

While there is no scientific evidence to support their use, pharmacists would be naive to believe that patients are not using dietary supplements as a way to help them manage their diabetes.

A 2006 survey of adult patients with diabetes found that 67% were using either a vitamin or supplement. And a 2011 review of medical histories found that 55% of diabetes patients used a supplement on a daily basis.

Some patients have turned to dietary supplements in reaction to the increased costs of conventional allopathic medications and doctor visits. Others fear the side effects of conventional medications. Still others are discouraged because conventional medications will not cure the condition.


Possible consequences

Despite the lack of scientific studies proving their effectiveness, use of some dietary supplements has been touted as a way to lower blood glucose and to treat hypertension and hyperlipidemia. Among these products are aloe vera, bitter melon, chromium, gymnema sylvestre (Australian cowplant), fenugreek, ginseng, and nopal (Prickly Pear cactus). Other suggested aids include cinnamon, berberine, hibiscus, mulberry, turmeric, and vinegar.

The decision to use dietary supplements comes with plenty of risks. According to a 2013 report in JAMA Internal Medicine, more than half of the Class 1 drug recalls in the United States involve supplements.

In a 2012 report in Consumer Reports, more than 6,300 serious adverse events involving supplements were reported to FDA between 2007 and 2012. Those adverse events included 115 deaths.

Lack of awareness

Pharmacists must realize that many patients believe supplements are “natural,” Shane-McWhorter said; they do not realize that these products contain chemical constituents with pharmacological activity and may cause adverse effects and drug reactions.  

“The reason we have to have an open mind is that we don’t want to alienate our patients,” Shane-McWhorter said.  “The issue is that there is a lot of research done, but I would not say it is good research.”

What to say

What would Shane-McWhorter tell patients who ask about dietary supplements? “Maybe this one might help a little. But it should not be used to replace conventional medication. I don’t think that any of these things alone are going to get you to your target, but they might help a little bit.”

According to Pray, dietary supplements are extremely popular because they can be cash cows for pharmacies. “There is money to be made in this. Some pharmacists are selling all sorts of things. The whole industry is money-driven,” he said. “The money to be made overruns scientific evidence and logic. There is no supplement that has been proven to help type 2 diabetes.”

Pray admits that many of the patients who have asked him about supplement use were not happy with his answers.

“They start to shut down when they don’t like what they’re hearing from you. But I would tell pharmacists to tell their patients exactly what I [tell] them: ‘This stuff is not going to work for you. I’m going to save you some money. The reason I went into pharmacy was to help people. This is not going to help you.’”

Some patients, although not many, eventually return to Pray and thank him for his honest assessment. “We are not used-car salesmen,” Pray said. “A used-car salesman will sell you anything.”


What NIH says about dietary supplements and diabetes

According to the National Institutes of Health (NIH), “There is not enough scientific evidence to suggest that any dietary supplements can help prevent or manage type 2 diabetes.”

NIH officials warn against replacing scientifically proven treatments for diabetes with unproven health products or practices.

“The consequences of not following your prescribed medical regimen for diabetes can be very serious,” notes the statement posted at the NIH website. “Some dietary supplements may have side effects, including interacting with your diabetes treatment or increasing your risk of kidney problems.”

On its diabetes and dietary supplements website page, NIH includes the following information about dietary supplements and diabetes:

Alpha-lipoic acid. A 2011 clinical trial found that supplements of 600 mg of alpha-lipoic acid taken daily did not prevent diabetic macular edema, an eye condition that causes blurred vision. A different 2011 clinical trial found that 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 addition, medical experts warn that high doses of alpha-lipoic acid supplements can cause gastrointestinal problems.

Chromium. Studies have found few or no benefits of chromium supplements connected with controlling diabetes or reducing the risk of developing it. In addition, 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.

Herbal supplements. There is no strong evidence that herbal supplements can help to control diabetes or its complications. A 2012 review of 10 randomized controlled trials did not support use of cinnamon for either type 1 or type 2 diabetes. A trial of 59 people with type 2 diabetes found that a combination of cinnamon, calcium, and zinc did not improve their blood pressure. In addition, some cinnamon contains coumarin, which can cause or worsen liver disease.  

Ginseng may help control glucose levels. However, there is not enough evidence to support its use.  Numerous other herbal supplements have been studied in connection with diabetes, including aloe vera, bitter melon, Chinese herbal medicines, fenugreek, garlic, gymnema sylvestre, milk thistle, nettle, prickly pear cactus, and sweet potato. None has been proven effective.

Magnesium. There is no evidence from clinical trials that magnesium helps manage diabetes. A 2011 review of 13 studies found that people who had lower magnesium intake had a greater risk of developing diabetes. One of the 2011 studies found that people who ate more cereal fiber and magnesium-rich food had a lower risk of developing type 2 diabetes. No serious side effects were reported in studies where people with diabetes were given magnesium supplements for up to 16 weeks. However, 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.

Omega-3s. A 2008 review found that omega-3 supplements do not help people with diabetes control their blood sugar levels. A 2012 study found little evidence that omega-3 supplements affected the risk of developing diabetes. Omega-3 supplements usually do not have negative side effects. 

Vitamins. Neither a 2010 research review nor a 2009 clinical trial found evidence that taking vitamin C supplements is helpful for treatment of diabetes.

The research on diabetes and vitamin D and calcium supplements is not conclusive. A 2007 systematic review and meta-analysis found that taking vitamin D combined with calcium appears to lower the risk of developing type 2 diabetes.

Taking too much calcium, however, may interfere with the body’s ability to absorb iron and zinc, and calcium supplements can interact with certain medications.

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