Alpha-lipoic acid (thioctic acid, vitamin N)

Also known as thioctic acid, alpha-lipoic acid is a naturally occurring compound that is synthesized by plants and animals, including humans. Lipoic acid is a ''non-vitamin" nutrient that is essential to life. It is not classified as a vitamin because it is produced in the body. It is generally involved in oxidative decarboxylations of keto acids and is presented as a growth factor for some organisms. Alpha-lipoic acid is a disulfide compound that is a cofactor in vital energy-producing reactions in the body. The body appears to be able to manufacture enough alpha-lipoic acid for its metabolic functions, but the excess levels provided by supplements allow alpha-lipoic acid to circulate in a free state.

Although alpha lipoic acid is involved in cellular energy production, its chief role as a dietary supplement may be as a powerful antioxidant. Unlike other antioxidants, lipoic acid is both fat and water-soluble and is easily absorbed and transported across cell membranes. This unique quality offers protection against free radicals both inside and outside the cell while other antioxidants only provide extracellular protection. Lipoic acid has the ability to regenerate other antioxidants like vitamin E, vitamin C and GSH for further use after they have eradicated free radicals.

Lipoic acid is an antioxidant, which means it neutralizes naturally occurring, but harmful, chemicals known as free radicals. Free radicals are high-energy, very unstable chemical substances and are known to damage the cells, DNA, proteins and essential fats in the body. Alpha-lipoic acid boosts glutathione levels in cells, has potent antioxidant action in almost all the tissues of the body, and is a co-factor for some of the key enzymes involved in generating energy from food and oxygen in mitochondria.

Alpha-lipoic acid functions, uses, and health benefits

Alpha-lipoic acid helps to neutralize the effects of free radicals on the body. Free radicals are waste products the body creates when food is turned into energy. The body puts some free radicals to use, but an excess damages cells and contributes to oxidative stress. Alpha-lipoic acid works together with other antioxidants such as vitamins C and E. It is important for growth, helps to prevent cell damage, and helps the body rid itself of harmful substances.

Lipoic acid shows evidence of being effective in the treatment of diabetic neuropathy and may be useful in treating some other aspects of diabetes. In addition to functioning as an antioxidant, this hard-working nutrient assists the B vitamins in producing energy from the proteins, carbohydrates, and fats consumed through foods.

Peripheral neuropathy is a type of nerve damage that may result in decreased sensitivity, numbness, and pain, particularly in the lower extremities. Alpha-lipoic acid may help to block such damage. Because of its effect on glucose metabolism, lipoic acid my improve the glucose-lowering action of insulin. In conjunction with other antioxidants, such as vitamin E, alpha-lipoic acid may be doubly helpful in patients with diabetes. Oxidative stress has been implicated in the pathology of diabetic neuropathy, and alpha-lipoic acid is approved for the treatment of diabetic neuropathy in Germany.

Alpha-lipoic acid may improve long-term memory. Alpha-lipoic acid crosses the blood-brain barrier, and both its oxidised and reduced forms are antioxidants. Alpha-lipoic acid may benefit anyone whose limbs tend to tingle or become numb, or "fall asleep" due to nerve compression.

Alpha-lipoic acid may prove useful in the treatment of chronic hepatitis because it relieves stress on the liver and helps rid the body of toxins. As an antioxidant, alpha-lipoic acid shields the liver from potentially harmful cell changes and assists it in flushing toxins from the body. This makes it useful in treating such liver disorders as chronic hepatitis and cirrhosis.

Alpha-lipoic acid dosage, intake, recommended daily allowance (RDA)

Currently there are no established recommended doses for supplementation. For use as a general antioxidant, a lower dosage of 20 to 50 mg daily is commonly recommended. Recommendations for the use of racemic alpha-lipoic acid as an antioxidant range from 50 mg/day to 400 mg/day. The typical dosage of oral lipoic acid for treating complications of diabetes is 300 to 600 mg daily. Alpha-lipoic acid can be purchased in dosages ranging 30 mg to 100 mg tablets.

Sources of alpha-lipoic acid

Alpha-lipoic acid is mainly derived from dietary sources. Most alpha-lipoic acid in food is derived from lipoamide-containing enzymes and is bound to the amino acid, lysine (lipoyllysine). Good food sources of alpha-lipoic acid include spinach, broccoli, beef, yeast (particularly Brewer's yeast), and certain organ meats (such as the kidney and heart). Animal tissues that are rich in lipoyllysine include kidney, heart, and liver, while plant sources that are rich in lipoyllysine include spinach, broccoli, and tomatoes. Supplemental doses of alpha-lipoic acid are hundreds of times higher than the amounts that can be obtained from food, and should be considered pharmacologic rather than physiologic doses.

Alpha-lipoic acid can be synthesized by plants and animals. The biosynthetic pathway for alpha-lipoic acid is not known, but it appears to be synthesized in the mitochondria from an 8-carbon fatty acid and elemental sulfur. Most alpha-lipoic acid in food is derived from lipoamide-containing enzymes and is bound to the amino acid, lysine (lipoyllysine). Animal tissues that are rich in lipoyllysine include kidney, heart, and liver, while plant sources that are rich in lipoyllysine include spinach, broccoli, and tomatoes. Somewhat lower amounts of lipoyllysine have been measured in peas, brussel sprouts, and rice bran.

Lipoic acid can be found in many common foods such as potatoes, carrots, broccoli, yeasts, beets, yams, and red meat. Dietary sources of ALA include flaxseeds, flaxseed oil, canola (rapeseed) oil, soybeans and soybean oil, pumpkin seeds and pumpkin seed oil, purslane, perilla seed oil, walnuts and walnut oil. The best food sources of lipoic acid are believed to be those foods rich in mitochondria - red meat (skeletal muscle, heart, liver, kidney). Other sources are yeast, spinach, and broccoli.