Dietary Supplements and Type 2 Diabetes

Some people with diabetes use Complementary and Alternative Medicine (CAM) therapies for their health condition. For example, they may try acupuncture or biofeedback to help with painful symptoms. Some use dietary supplements in efforts to improve their blood glucose control, manage symptoms, and lessen the risk of developing serious complications such as heart problems. In this article you’ll find information about what is known about a few of the many supplements used for diabetes, with a focus on some that have been studied in clinical trials, such as alpha-lipoic acid, chromium, omega-3 fatty acids, and polyphenols.

Alpha-lipoic acid (ALA, also known as lipoic acid or thioctic acid) is an antioxidant—a substance that protects against cell damage. ALA is found in certain foods, such as liver, spinach, broccoli, and potatoes. Some people with type 2 diabetes take ALA supplements in the hope of lowering blood glucose levels by improving the body’s ability to use insulin; others use ALA to prevent or treat diabetic neuropathy (a nerve disorder). Supplements are marketed as tablets or capsules.

• ALA has been researched for its effect on insulin sensitivity, glucose metabolism, and diabetic neuropathy. Some studies have found benefits, but more research is needed. (There are some studies, reported from outside the United States, of ALA delivered intravenously; however, this research is outside the scope of this fact sheet.)
• Because ALA might lower blood sugar too much, people with diabetes who take it must monitor their blood sugar levels very carefully.

Chromium is an essential trace mineral—that is, the body requires small amounts of it to function properly. Some people with diabetes take chromium in an effort to improve their blood glucose control. Chromium is found in many foods, but usually only in small amounts; relatively good sources include meat, whole grain products, and some fruits, vegetables, and spices. In supplement form (capsules and tablets), it is sold as chromium picolinate, chromium chloride, and chromium nicotinate.

• Chromium supplementation has been researched for its effect on glucose control in people with diabetes. Study results have been mixed. Some researchers have found benefits, but many of the studies have not been well designed. Additional, high-quality research is needed.
• At low doses, short-term use of chromium appears to be safe for most adults. However, people with diabetes should be aware that chromium might cause blood sugar levels to go too low. High doses can cause serious side effects, including kidney problems—an issue of special concern to people with diabetes.

Omega-3 fatty acids are polyunsaturated fatty acids that come from foods such as fish, fish oil, vegetable oil (primarily canola and soybean), walnuts, and wheat germ. Omega-3 supplements are available as capsules or oils (such as fish oil). Omega-3s are important in a number of bodily functions, including the movement of calcium and other substances in and out of cells, the relaxation and contraction of muscles, blood clotting, digestion, fertility, cell division, and growth. In addition, omega-3s are thought to protect against heart disease, reduce inflammation, and lower triglyceride levels.

• Omega-3 fatty acids have been researched for their effect on controlling glucose and reducing heart disease risk in people with type 2 diabetes. 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.
• Omega-3s appear to be safe for most adults at low-to-moderate doses. Safety questions have been raised about fish oil supplements, because some species of fish can be contaminated by substances such as mercury, pesticides, or PCBs. In high doses, fish oil can interact with certain medications, including blood thinners and drugs used for high blood pressure.

Polyphenols—antioxidants found in tea and dark chocolate, among other dietary sources—are being studied for possible effects on vascular health (including blood pressure) and on the body’s ability to use insulin.

• Laboratory studies suggest that EGCG, a polyphenol found in green tea, may protect against cardiovascular disease and have a beneficial effect on insulin activity and glucose control. However, a few small clinical trials studying EGCG and green tea in people with diabetes have not shown such effects.
• No adverse effects of EGCG or green tea were discussed in these studies. Green tea is safe for most adults when used in moderate amounts. However, green tea contains caffeine, which can cause, in some people, insomnia, anxiety, or irritability, among other effects. Green tea also has small amounts of vitamin K, which can make anticoagulant drugs, such as warfarin, less effective.

Other supplements are also being studied for diabetes-related effects. For example:

• Preliminary research has explored the use of garlic for lowering blood glucose levels, but findings have not been consistent.
• Studies of the effects of magnesium supplementation on blood glucose control have had mixed results, although researchers have found that eating a diet high in magnesium may lower the risk of diabetes.
• There is not enough evidence to evaluate the effectiveness of coenzyme Q10 supplementation as a CAM therapy for diabetes; studies of its ability to affect glucose control have had conflicting findings.
• Researchers are studying whether the herb ginseng and the trace mineral vanadium might help control glucose levels.
• Some people with diabetes may also try botanicals such as prickly pear cactus, gurmar, Coccinia indica, aloe vera, fenugreek, and bitter melon to control their glucose levels. However, there is limited research on the effectiveness of these botanicals for diabetes.

If You Have Diabetes and Are Thinking About Using a Dietary Supplement

• Tell your health care providers about any complementary and alternative practices you use. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care. For tips about talking with your health care providers about CAM, see NCCAM’s Time to Talk campaign at nccam.nih.gov/timetotalk/. Medicines for diabetes and other health conditions may need to be adjusted if a person is also using a dietary supplement.
• Women who are pregnant or nursing, or people who are thinking of using supplements to treat a child, should consult their health care provider before using any dietary supplement.
• Do not replace scientifically proven treatments for diabetes with CAM treatments that are unproven. The consequences of not following one’s prescribed medical regimen for diabetes can be very serious.
• Be aware that the label on a dietary supplement bottle may not accurately reflect what is inside. For example, some tests of dietary supplements have found that the contents did not match the dose on the label, and some herbal supplements have been found to be contaminated.

Source: NCCAM, National Institutes of Health