So is all that money going to good use? "There are some indications that some supplements may be helpful, but there's nothing definitive," says Julie T. Chen, MD, an integrative medicine physician in San Jose, Calif. But while you shouldn't use them to replace your diabetes medications, research on some supplements does suggest that they can help with type 2 diabetes management.
Supplements for Type 2 Diabetes: A Closer Look
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If you are taking or considering taking a supplement, telling your doctor is a must because some supplements can interfere with diabetes or other medications.
Here's a look at nine dietary supplements that are commonly used by people with type 2 diabetes:

Chromium. Chromium, a metal and an essential trace mineral, is thought to naturally help reduce blood sugar levels. It is naturally occurring in foods such as meat, fish, fruits, vegetables, spices, and whole-wheat and rye breads. As a supplement, it is sold as chromium picolinate, chromium chloride, and chromium nicotinate.
"People were excited about chromium about 15 years ago," Dr. Tipton says. "But there is no evidence that it does anything to help control blood sugar or diabetes." At low doses, its use appears safe for most people and may be of some help; however, taken over long periods, chromium can cause side effects that include kidney issues, already a problem for some people with diabetes.
Magnesium. Magnesium is essential for healthy bones, muscle function, normal blood pressure, and proper heart rhythm. People with diabetes tend to be low in magnesium, which is linked to lowered insulin production and more insulin insensitivity. "If a blood test shows that magnesium levels are low, a supplement might be helpful," says Susan Weiner, RD, MS, CDE, CDN, a registered dietitian and certified diabetes educator in Merrick, N.Y. Note, however, that taking too much magnesium causes diarrhea. Good food sources of magnesium are pumpkin seeds, sunflower seeds, almonds, cashews, halibut, tuna, spinach, and oat bran.
Omega-3 fatty acids. These come from foods such as fish, some vegetable oils (canola and soybean), walnuts, and wheat germ. Omega-3 supplements are available as capsules or oils. Studies show that omega-3 fatty acids lower triglycerides but do not affect blood glucose control, total cholesterol, or HDL (good) cholesterol in people with diabetes. In some studies, omega-3 fatty acids also raised LDL (bad) cholesterol. Additional research, particularly long-term studies that look specifically at heart disease in people with diabetes, is needed. Fish oil can also interfere with blood-thinning and blood-pressure drugs.
Ginseng. Clinical trials examining the effects of American ginseng on diabetes are limited, Weiner says. However, a small study showed that taking 3 grams of American ginseng 40 minutes before a meal helped to reduce post-meal blood sugar levels. While use of ginseng short-term might be safe, it can cause side effects, including itching, insomnia, and nervousness. People with insomnia or a hormone-sensitive condition should avoid ginseng.

Vanadium. Like chromium, vanadium is also a trace mineral. In the 1980s, research first showed it could lower blood sugars. "Vanadium, along with its heavier cousins, molybedenum and tungsten, can mimic insulin," Weiner says. "In research done with cells, these minerals have been able to replace insulin." However, few studies since support its effectiveness.
Glucosamine. No research shows that glucosamine is helpful for people with diabetes, Tipton says. Evidence in its favor is only anecdotal, meaning that some people report that it helps them, Weiner says. "Glucosamine is important for the repair and maintenance of healthy cartilage in joints, but taking it in an oral form may not get it to where it needs to be in an amount that will do any real good," she says.
Alpha-lipoic acid. ALA, also known as lipoic acid or thioctic acid, is a substance similar to a vitamin. As an antioxidant, it protects against cell damage caused by free radicals. ALA is found in liver, spinach, broccoli, and potatoes. People with type 2 diabetes take ALA supplements to help their body use insulin more efficiently. ALA has also been used to prevent or treat diabetic neuropathy (a nerve disorder).
Some studies have found benefits of ALA, but more research is needed, Weiner says. Among the cautions are that ALA may lower blood levels of iron and may interact with certain cancer drugs. In some cases, ALA might lower blood sugar too much, so blood sugars must be carefully monitored if you use this supplement.
Bitter melon. Despite its name, bitter melon is a vegetable also found in supplement form. There is some evidence that botanicals like bitter melon have glucose-lowering properties. Chen likes bitter melon because it is generally safe for most people. She recommends starting with 900 milligrams of bitter melon and adjusting it if it helps you.
Cinnamon. More research is needed, Chen says, but some studies suggest that cinnamon may improve blood sugar levels in some people. Try adding cinnamon — make sure it's the unsweetened kind — to oatmeal or other foods, or sprinkle it in your coffee.
If you want to use supplements, talk to your doctor to ensure that what you are taking is safe and won't interfere with your conventional diabetes therapy.