Herbs & Supplements:
Lipoic Acid

Supplement Forms / Alternate Names
  • Alpha-Lipoic Acid, Thioctic Acid
Principal Proposed Uses
  • Diabetic Peripheral Neuropathy, Diabetic Autonomic Neuropathy
Other Proposed Uses
  • Diabetes (in General), Liver Disease, Cancer Prevention, Cataract Prevention, Heart Disease Prevention

Lipoic acid, also known as alpha-lipoic acid, is a sulfur-containing fatty acid. It is found inside every cell of the body, where it helps generate the energy that keeps us alive and functioning. Lipoic acid is a key part of the metabolic machinery that turns glucose (blood sugar) into energy for the body's needs.

Lipoic acid is an antioxidant, which means it neutralizes naturally occurring, but harmful, chemicals known as free radicals. Unlike other antioxidants, which work only in water or fatty tissues, lipoic acid is unusual in that it functions in both water and fat.^1,2By comparison, vitamin E works only in fat and vitamin C works only in water. This gives lipoic acid an unusually broad spectrum of action.

Different antioxidants work together to keep free radicals under control (for more information, see the article on vitamin E). Antioxidants are a bit like kamikaze pilots, sacrificing themselves to knock out free radicals. One of the more interesting findings about lipoic acid is that it may help regenerate other antioxidants that have been used up. Some research also suggests that lipoic acid may be able to do the work of other antioxidants when the body is deficient in them.^3,4

Thanks to its fat solubility, lipoic acid can get inside nerve cells, where it helps prevent free radical damage.

Sources

Because a healthy body makes enough lipoic acid to supply its energy requirements, there is no daily requirement for this supplement. However, several medical conditions appear to be accompanied by low levels of lipoic acid⁵—specifically, diabetes, liver cirrhosis, and heart disease—which suggests (but definitely does not prove) that supplementation would be helpful.

Liver and yeast contain some lipoic acid. Nonetheless, supplements are necessary to obtain therapeutic dosages.

Therapeutic Dosages

The typical dosage of oral lipoic acid for treating complications of diabetes is 300 to 600 mg daily, although much higher doses have been tried in studies. Be patient, as the results take weeks to develop. For use as a general antioxidant, a lower dosage of 20 to 50 mg daily is commonly recommended.

Therapeutic Uses

Lipoic acid has been widely used for decades in Germany to treat diabetic peripheral neuropathy. This is a condition caused by diabetes in which nerves leading to the arms and legs become damaged, leading to numbness, pain, and other symptoms. However, the evidence that it works is largely limited to studies that used the intravenous form of this supplement.^6,7,8

Lipoic acid has shown promise for another type of nerve damage caused by diabetes: autonomic neuropathy. This is a condition in which the nerves that control internal organs become damaged. When this occurs in the heart, the condition is called cardiac autonomic neuropathy, and it leads to irregularities of heart rhythm. There is some evidence that lipoic acid may be helpful for this condition.⁹ When autonomic neuropathy occurs in the intestines, it causes extreme constipation. Based on its other effects, it appears possible that lipoic acid could help this form of autonomic neuropathy as well, although there is no direct evidence to turn to.

Preliminary and sometimes contradictory evidence suggests that lipoic acid may improve other aspects of diabetes, including circulation in small blood vessels, metabolism of sugar and protein, and the body's response to insulin.^10–14 Lipoic acid has been proposed as a treatment for liver conditions as well as for preventing cancer, cataracts, and heart disease. However, there is little to no real evidence that it is effective for these purposes.

One animal study suggests that lipoic acid might help prevent age-related hearing loss.¹⁵

What Is the Scientific Evidence for Lipoic Acid?

Diabetic Peripheral Neuropathy

There is some evidence that intravenous lipoic acid can reduce symptoms of diabetic peripheral neuropathy, at least in the short term. However, oral lipoic acid has not been well evaluated, and the best study of oral lipoic acid failed to find it effective for long-term use. This randomized, double-blind placebo-controlled study enrolled 503 individuals with diabetic neuropathy and found that intravenous lipoic acid helped reduce symptoms over a 3-week period, but long-term oral supplementation did not prove effective.¹⁶

A previous double-blind placebo-controlled study also found short-term benefit with intravenous lipoic acid.^17,18

Warning: You should never attempt to take any drug or supplement intravenously except under the care of a doctor.

The positive evidence for oral lipoic acid is limited to open studies or to trials that were too small upon which to base conclusions.^19–23

There is some preliminary evidence that lipoic acid may be more effective if it is combined with GLA (gamma-linolenic acid), another supplement used for diabetic peripheral neuropathy.^24,25

Diabetic Autonomic Neuropathy

Not only does diabetes damage the nerves in the arms and legs, but it can also affect deep nerves that control organs such as the heart and digestive tract. The DEKAN (Deutsche Kardiale Autonome Neuropathie) study followed 73 people with diabetes who had symptoms caused by nerve damage affecting the heart. Treatment with 800 mg daily of oral lipoic acid showed statistically significant improvement compared to placebo and caused no significant side effects.²⁶

Safety Issues

Lipoic acid appears to have no significant side effects at dosages up to 1,800 mg daily.²⁷

Safety for young children, women who are pregnant or nursing, or those with severe liver or kidney disease has not been established.

Last reviewed March 2002 by Medical Review Board

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