Alpha-Lipoic acid

Alpha-Lipoic acid:
Quite Possibly the "Universal" Antioxidant

This article originally appeared in the July 1996 issue of The Nutrition Reporter™ newsletter.


If it's essential role in health is any indication, alpha-lipoic acid may very well join the ranks of vitamins C and E as part of your first-line of defense against free radicals. Discovered in 1951, it serves as a coenzyme in the Krebs cycle and in the production of cellular energy. In the late 1980s, researchers realized that alpha-lipoic acid had been overlooked as a powerful antioxidant.

Over the past few years, the pace of research on lipoic acid has increased dramatically. Last year, Lester Packer, PhD, of the University of California, Berkeley, published a lengthy review article on alpha-lipoic acid in Free Radical Biology & Medicine (1995;19:227-50). In April 1996, he presented a short review of it in the same journal (FRBM;20:625-6).

Several qualities distinguish alpha-lipoic acid from other antioxidants, and Packer has described it at various times as the "universal," "ideal," and "metabolic" antioxidant. It neutralizes free radicals in both the fatty and watery regions of cells, in contrast to vitamin C (which is water soluble) and vitamin E (which is fat soluble).

The body routinely converts some alpha-lipoic acid to dihydrolipoic acid, which appears to be an even more powerful antioxidant. Both forms of lipoic acid quench peroxynitrite radicals, an especially dangerous type consisting of both oxygen and nitrogen, according to a recent paper in FEBS Letters (Whiteman M, et al., FEBS Letters, 1996; 379:74-6). Peroxynitrite radicals play a role in the development of atherosclerosis, lung disease, chronic inflammation, and neurological disorders.

Alpha-lipoic acid also plays an important role in the synergism of antioxidants, what Packer prefers to call the body's "antioxidant network." It directly recycles and extends the metabolic lifespans of vitamin C, glutathione, and coenzyme Q10, and it indirectly renews vitamin E.

In Germany, alpha-lipoic acid is an approved medical treatment for peripheral neuropathy, a common complication of diabetes. It speeds the removal of glucose from the bloodstream, at least partly by enhancing insulin function, and it reduces insulin resistance, an underpinning of many cases of coronary heart disease and obesity. The therapeutic dose for lipoic acid is 600 mg/day. In the United States, it is sold as a dietary supplement, usually as 50 mg tablets. (The richest food source of alpha-lipoic acid is red meat.)

"From a therapeutic viewpoint, few natural antioxidants are ideal," Packer recently explained in Free Radical Biology & Medicine. "An ideal therapeutic antioxidant would fulfill several criteria. These include absorption from the diet, conversion in cells and tissues into usable form, a variety of antioxidant actions (including interactions with other antioxidants) in both membrane and aqueous phases, and low toxicity."

"Alpha-lipoic acid...is unique among natural antioxidants in its ability to fulfill all of these requirements," he continued, "making it a potentially highly effective therapeutic agent in a number of conditions in which oxidative damage has been implicated."

Other research on alpha-lipoic acid has shown that it might:

* help people with genetic defects leading to muscle myopathies (Barbiroli B, et al., Journal of Neurology, 1995;242:472-7);

* reduce ischemia/reperfusion injury to the heart and brain. (Schonheit K, et al., Biochimica et Biophysica Acta, 1995;1271:335-42; and Cao X and Phillis JW, Free Radical Research, 1995;23:365-70); and

* inhibit the activation of "nuclear factor kappa-B," a protein complex involved in cancer and the progression of AIDS. (Suzuki YJ, et al., Biochemical & Biophysical Research Communications, 1992;189:1709-15).

"The therapeutic potential of alpha-lipoic acid is just beginning to be explored," observed Packer, "but this compound holds great promise."