Diabetes Forecast

The Pros and Cons of Dietary Supplements

What science says about omega-3s and other "natural" products

By Erika Gebel, PhD , ,

Row upon row of dietary supplements line store shelves, offering better health the "natural" way. It's tempting to stock up on supplements, trying to make up for less than nutritious diets or hoping to find an over-the-counter capsule that can lower blood glucose levels. According to the Council for Responsible Nutrition, more than 150 million Americans use supplements, supporting a $27 billion industry. A February 2002 study in Diabetes Care found that people with diabetes are 1.6 times as likely to use supplements as people without diabetes.

Despite the popularity of supplements, they may do little to boost your health. Many studies have tested supplements against a variety of health conditions, including diabetes, but most experts agree that the science remains inconclusive. Outside the laboratory, some supplement users swear they work, and for many, that's enough. Here is where the science stands, with some tips on how to be supplement smart. After all, spending money on ineffective supplements may not be the best use of your health care dollar.

Tried but Untested

As defined by the Food and Drug Administration (FDA), a dietary supplement is a product taken by mouth that contains a "dietary ingredient," which can be vitamin, mineral, herb, amino acid, enzyme, or metabolite. The supplement needn't be a pill; it could be a bar, liquid, or even a tea, but the FDA does require it to be labeled as a dietary supplement so it is not confused with food or medicine.

Dietary supplement makers can make no health claims; by law, only prescription medications can do that. Supplements often declare benefits anyway, made legal by including the disclaimer "This statement has not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease." The distinction between medication and supplement is important: Prescription medications have passed rigorous tests of safety and effectiveness, while there isn't enough evidence to say whether supplements make an impact on health.

"There is a lot of research on supplements," says Laura Shane-McWhorter, PharmD, BCPS, FASCP, BC-ADM, CDE, author of the American Diabetes Association Guide to Herbs & Nutritional Supplements. "The problem is that the research is less than desirable." One issue is that researchers study only one particular form and dosage of a supplement. "The thing used in a study may not be what's out there in the supplement world," she says. That makes it difficult for doctors to use scientific data to advise their patients because they don't know exactly what's on the shelves at the local store.

Tips for Safe Supplement Use
If you're considering adding a supplement to your health routine, make sure to do so safely and systematically:
1. Avoid drug interactions. Always check with your health care provider first and keep taking conventional medication as prescribed.

2. Treat deficiencies, if so advised. If your blood tests show you are deficient in a vitamin or mineral, ask your provider if treatment is necessary. You may be able to do so with dietary changes, or you may need more help from a supplement or prescription medication.

3. Buy from a trusted source. Ensure that supplements are from a reputable source by looking for a U.S. Pharmacopeial Convention (USP) seal on the packaging or checking here.

4. Take a systematic approach. "For diabetes, we would say, try it for three months," says Laura Shane-McWhorter, PharmD, BCPS, FASCP, BC-ADM, CDE. "By then you'll know if it lowers your A1C." Keep in mind, however, that changes in weight, physical activity levels, and/or prescription medications could affect A1C results—it's difficult to know if the supplement truly helped.

5. Protect your kidney and liver. Ask your doctor about laboratory tests for kidney and liver health to make sure that taking a supplement is helping rather than hurting your health.

Showing Promise
A few supplements may have potential to promote health. They don't lower blood glucose levels, but there's some evidence that omega-3s and alpha-lipoic acid improve common diabetes complications such as heart disease and neuropathy.

Omega-3s: One type of supplement stands above the rest, says Catherine Buettner, MD, instructor in medicine at the Beth Israel Deaconess Medical Center: omega-3 fatty acids, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). There is evidence that the anti-inflammatory and other properties of these fatty acids improve heart health. The American Heart Association (AHA) recommends eating fatty fish (mackerel, salmon, sardines) at least twice a week to get adequate EPA and DHA.

For people who don't eat fish, omega-3s are plentiful in over-the-counter fish oil supplements, but Buettner cautions against buying just any product. "What we want to know is the concentration of EPA and DHA," she says. Not every fish oil product has the same amount of omega-3s; check the label. About 2,200 milligrams weekly of EPA and DHA in the form of supplements should provide a rough equivalent to eating two servings of fish. The AHA also recommends 1,000 mg of EPA/DHA daily in fish or fish oil for people with documented coronary heart disease. Fish oil supplements sometimes are recommended to treat very high triglycerides, but work with your provider to ensure you take the proper amount; prescription medications often are required.

Alpha-lipoic acid: Another supplement Buettner is hopeful about, alpha-lipoic acid, is an antioxidant made by the body. "It may potentially decrease the symptoms of peripheral neuropathy," says Buettner. "The studies that have been done in that particular supplement are in general of high quality." While blood glucose control can help prevent the nerve damage caused by diabetes, there aren't many treatments for the pain and tingling, so a supplement may be one of the best options available.

Mixed Evidence

A few products are commonly labeled as "diabetes supplements," alone or in combination pills, despite often conflicting evidence in the scientific literature. Cinnamon and chromium are perhaps the most discussed. Cinnamon is often touted for its blood glucose–lowering effects, but this hasn't always held up. A September 2007 study published in Diabetes Care found that cinnamon supplements did not lower blood glucose or blood fats in people with type 2. Results on chromium have been mixed. A review of 41 previous studies published in August 2007 in Diabetes Care found evidence that it may lower blood glucose levels in people with diabetes, but a true cause-and-effect relationship could not be established. There are literally dozens of other dietary supplements being tested for effectiveness against diabetes, but none has yet received a nod from science.

At Home

Supplements aren't considered medicine, but your health care providers do need to know about any you take. Some may interact with medications or preexisting conditions in harmful ways. For example, "people think that magnesium supplements need to be taken, but if you have kidney dysfunction, that could be bad," says Shane-McWhorter. If you take blood-thinning medications, be aware that several common supplements, such as Saint-John's-wort, also thin the blood and shouldn't be combined with your prescription.

Supplements aren't under the same regulation as prescription medications, increasing the risk that they contain contaminants. The FDA recently reported finding pesticides in ginseng supplements, for example. Weight-loss supplements are notorious for often containing undisclosed active pharmaceutical ingredients. According to Shane-McWhorter, the best way to protect yourself from tainted supplements is to check product labels for the seal of the U.S. Pharmacopeial Convention (USP). This nonprofit scientific organization tests and ensures the quality and purity of supplements. But keep in mind, Shane-McWhorter says, that this is no evidence that the supplement improves health.

There is promise in the natural world: Many effective prescription drugs have been developed from natural components. A supplement may exist that could help people with diabetes, but science hasn't confirmed it yet. If you do try a dietary supplement, make sure it's from a reputable source and check with your doctor before using it. Be smart about it and be safe, while waiting for science to sort out the evidence about supplements.



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