By: Ben Eastman
Antioxidants, a main selling point for countless nutritional supplements and multi-vitamins these days, are drawing the attention of health experts.
Some antioxidants, like vitamin E, have been shown to be especially beneficial for common complications of diabetes. Also being touted is lipoic acid, a relatively newly discovered antioxidant. It’s available where vitamins are sold and costs approximately the same as vitamin E and other antioxidants. But because of the lack of large-scale studies to verify its benefits and rule out negative side effects, it may have a hard time getting the full support of health care professionals.
Antioxidants and Diabetes
Free radicals are molecular compounds considered to be the main catalysts for the aging process. Normally electrons are found in pairs within each atomic component of a molecule. Free radicals are missing one electron from this paired system. They attach to any nearby molecule in an attempt to replace the missing electron. This is bad news for the body.
This process, called oxidation, then degenerates the molecules the free radicals attach to – anything from fatty acids to DNA molecules. “When a free radical oxidizes a cell it is like when rust attacks iron. Free radicals turn cells rancid and promote the aging process,” says Jack Challem, editor and publisher of The Nutrition Reporter Newsletter in Beaverton, Ore.
Glucose in the bloodstream auto-oxidizes. It produces free radicals by itself. Therefore, since people with diabetes generally have more glucose in the blood, they have an increased amount of oxidative stress. Several studies have shown that increased oxidative stress is associated with retinopathy, microalbuminuria, neuropathy and cardiovascular disease.
“Diabetes is now defined as a condition that speeds up the aging process,” says Keith Campbell, RPh, CDE. The disease is defined this way because these oxidized compounds damage blood vessels and cause complications, like cardiovascular problems, that are associated with old age.
Treatment with antioxidants helps neutralize these free radicals and helps decrease oxidative stress. Lipoic acid has received special attention because, in addition to its normal antioxidant properties, it has been effective in the treatment of diabetic neuropathy, and it appears that it may lower blood sugar levels as well.
One therapeutic effect of lipoic acid that has been demonstrated in clinical studies done on human subjects is its use to treat diabetic neuropathy. It has been used for this purpose in Germany for some years now.
In his review article published in Free Radical Biology and Medicine Lester Packer, PhD, points out studies that show “dramatic clinical improvements” in the alleviation of pain from peripheral neuropathy after intravenous treatment with lipoic acid. Yet no effect was seen in the neurological and physiological measures of the condition.
Several studies have found that it is effective in treating the pain associated with peripheral neuropathy. A study published in Diabetolgia in 1995 showed that 600 mg of lipoic acid administered daily for three weeks was “associated with a significant reduction of various symptoms of peripheral neuropathy including pain, paraesthesiae [burning, prickling, tingling] and numbness.”
In another study, the same researchers found that lipoic acid can be effective in treating cardiac autonomic neuropathy (CAN) as well. Published in the March 1997 Diabetes Care, the study found that type 2s with CAN had “significant, albeit small” improvement after three weeks on 600 mg of lipoic acid administered orally each day.
In both studies, 600 mg appeared to be the optimal dose, as higher levels occasionally led to stomach upset and showed no greater therapeutic effect.
With the exception of the CAN study, all of the studies on lipoic acid’s effect on diabetic neuropathy show improvement in the symptoms of the complication, but fail to show an improvement in the neurophysiological measures of the complication. While lipoic acid improved the comfort level of the patient, the studies were not long enough to determine if it had any physiological effects.
The fact that lipoic acid eases the discomfort of peripheral neuropathy is enough for doctors like John Morley, MD. According to Morley, the treatment of peripheral neuropathy has been so difficult that anything that shows signs of improving the condition would be welcomed. Still, he is concerned about the lack of studies on humans.
“The reality is there is very little data (on lipoic acid) from human studies,” says Morley. He adds that good pseudo-alternative, or non-pharmaceutical treatments often don’t get studied because they are not patentable.” If the drug industry sees no profit potential, very little, if any, money will be directed towards its study. Without the research funding the treatments “never get proven good or bad,” he says.
Keith Campbell adds, “This [lipoic acid’s positive effects] may be wonderful, but we don’t totally know how it will affect the body until it is studied in depth, and that takes a long time.”
Lowering Blood Sugars
In addition to its effect on neuropathy, several studies have shown that lipoic acid can improve blood glucose utilization. The problem is that most of these studies have been performed on rats, not humans.
In a study published in the August 1996 issue of Diabetes researchers found that 10 days of intravenous administration of lipoic acid “improved insulin sensitivity of whole-body glucose disposal by 30-50 percent” in rat models of diabetes. Several other studies show very similar findings. These findings are promising, but success in rats does not guarantee success in humans.
One of the few studies carried out using human subjects, published in the May 1995 Drug Research, showed that lipoic acid improved insulin sensitivity as well. Unfortunately, it was only performed on 13 subjects and concluded that more studies should be undertaken.
The study found that after as few as 45 minutes an injection of 1000 mg of lipoic acid improved insulin-stimulated glucose disposal. The metabolic clearance of glucose improved by approximately 50 percent. The treatment caused no adverse reactions and no improvement was seen in the subjects who received a placebo.
In addition to the findings mentioned, it is hypothesized that lipoic acid could be helpful for other diabetic complications like retinopathy and cardiovascular disease. Some believe that any diabetic complications that are associated with increased oxidative stress can be mediated with lipoic acid.
So, after all these positive results, why aren’t all doctors recommending lipoic acid for their diabetic patients?
Because the few studies that have been done on humans have been either very small, or over short periods of time.
From the work done so far, lipoic acid appears to exhibit a positive effect on people with diabetes. It has been shown to reduce the pain and numbness associated with peripheral neuropathy and it may improve insulin sensitivity in type 2 diabetes. In addition, it appears to have no negative side effects when given in doses of 600 mg per day. But until some large-scale, long-term studies are done, many doctors will continue to be hesitant to recommend its use.
As with any type of treatment, check with you doctor before supplementing your diet with lipoic acid. If you choose to try lipoic acid, special care must be taken as it may lower blood sugars.