ADA 2010: Herbals helpful for diabetes care, but there's little evidence

Herbals and supplements such as silymarin (milk thistle), fish oil, and red rice yeast can improve some of the conditions associated with diabetes, but the evidence is slim.

"The evidence for herbals in diabetes is quite limited," said Benjamin Kligler, MD, MPH, vice chair of integrative medicine, Beth Israel Medical Center, New York, speaking to a gathering at the 70th Scientific Sessions of the American Diabetes Association in Orlando, Fla. "There may be promising agents, but none have reached the level of large, multicenter trials."

Kligler discussed the pros and cons of herbals and supplements for diabetes during an afternoon presentation, Herbal Remedies for Diabetes - Show Me the Evidence. The reality, he said, is that there may never be randomized, controlled trials.

"These are not patentable substances," Kligler said. "They are all in the public domain. There is very little incentive for manufacturers to research their products. So where is that large trial going to come from? It would have to be funded by NIH or some other organization."

What little evidence there is suggests that herbals have no effect on glycemic control, Kligler continued. But there is evidence that selected herbals can improve lipid profiles, hepatic function, and other forms of metabolic disarray associated with diabetes.

There is a significant body of data showing that silymarin helps hepatic cells regenerate more quickly. That makes it a useful agent for patients with elevated liver enzymes associated with statins, HIV medications, and other agents.

"We all know how often you have to take a patient off a med due to elevated liver enzymes,” Kligler said. "Silymarin can bring those enzymes back to normal, and you can continue your otherwise effective treatment."

Fish oil is another useful supplement, as is fish consumption. Omega-3 fatty acids have no effect on glycemic control, but they do have a positive effect on triglycerides. Red yeast rice, a common ingredient in Chinese medicine, has been shown to reduce low-density lipoproteins by 10% to 20% without affecting hepatic function.

A key problem, Kligler noted, is selecting a product. Herbals and dietary supplements are not required to prove efficacy, and quality control varies dramatically among manufacturers.

Reliable information on herbals also is in short supply. He recommended online information from the Memorial Sloan-Kettering Cancer Center Integrative Medicine Service (www.mskcc.org/mskcc/html/11570.cfm). Useful product analysis and comparisons can be found at ConsumerLab.com, a subscription service.

"It is 'buyer beware' in the herbal marketplace," Kligler cautioned. "There are good products and good brands out there, but you have to be a little suspicious."