Alpha-lipoic acid is an antioxidant that is made by the body and is found in every cell, where it helps turn glucose into energy. Antioxidants are substances that attack "free radicals," waste products created when the body turns food into energy. Free radicals cause harmful chemical reactions that can damage cells in the body, making it harder for the body to fight off infections. They also damage organs and tissues.

Unlike other antioxidants, which work only in water (such as vitamin C) or fatty tissues (such as vitamin E), alpha-lipoic acid is both fat- and water-soluble. That means it can work throughout the body. In addition, antioxidants are depleted as they attack free radicals, but evidence suggests alpha-lipoic acid may help regenerate these other antioxidants and make them active again.

In the cells of the body, alpha-lipoic acid is converted into dihydrolipoic acid. Alpha-lipoic acid is not the same as alpha linolenic acid, which is an omega-3 fatty acid that may help heart health (See also: Alpha linolenic acid. Confusion can arise because both are sometimes abbreviated ALA.

Diabetes

Alpha-lipoic acid can lower blood sugar levels, and its ability to kill free radicals may help reduce pain, burning, itching, tingling, and numbness in people who have nerve damage caused by diabetes (called peripheral neuropathy). Alpha-lipoic acid has been used for years for this purpose in Europe, and at least one study found that intravenous (IV) doses of alpha-lipoic acid helped reduce symptoms. However, the evidence indicating that taking alpha-lipoic acid orally will help is weaker. Most studies have been small and poorly designed. One 2006 study did show benefit from taking alpha-lipoic acid for diabetic neuropathy compared to placebo.

Taking alpha-lipoic acid does appear to help another diabetes-related condition called autonomic neuropathy, which affects the nerves supplying the heart. One study found that 73 people with autonomic neuropathy improved when taking 800 mg of alpha-lipoic acid orally compared to placebo.

Liver Disease

Alpha-lipoic acid has been proposed as a treatment for alcohol-related liver disease, but so far there is no evidence that it works. Alpha-lipoic acid has been administered by IV along with silymarin to treat people who have eaten the poisonous mushroom Amanita, which causes liver damage.

Brain Function and Stroke

Because alpha-lipoic acid can pass easily into the brain, it has protective effects on brain and nerve tissue. Scientists are investigating it as a potential treatment for stroke and other brain disorders involving free radical damage. Animals treated with alpha-lipoic acid, for example, suffered less brain damage and had a four times greater survival rate after a stroke than animals who did not receive this supplement. More research is needed to understand whether this benefit applies to people as well.

Other

Some preliminary studies suggest alpha-lipoic acid may be helpful in treating glaucoma, but there is not enough evidence to say for sure whether it is beneficial. In test tubes, alpha-lipoic acid appears to inhibit growth of the HIV virus, but it isn't known whether the supplement would have the same effect in people.

A healthy body makes enough alpha-lipoic acid. It is also found in red meat, organ meats (such as liver), and yeast (particularly Brewer's yeast).

Alpha-lipoic acid supplements are available as capsules. It may also be given by injection under the supervision of a health care provider.

Pediatric

Because alpha-lipoic acid has not been studied for pediatric use, do not give it to children.

Adult

Alpha-lipoic acid can be purchased in doses of 30 - 100 mg tablets. There are no established recommended doses.

• General antioxidant support: 20 - 50 mg per day
• Diabetes and diabetic neuropathy: 800 mg per day in divided doses

Because of the potential for side effects and interactions with medications, you should take dietary supplements only under the supervision of a health care provider.

No evidence suggests whether or not alpha-lipoic acid is safe for women who are pregnant or breastfeeding, so such women should not take alpha-lipoic acid.

Side effects are generally rare and may include skin rash.

Alpha-lipoic acid can lower blood sugar levels, so people with diabetes or hypoglycemia should take alpha-lipoic acid only under the supervision of their doctor. (See "Interactions" section.)

Results of animal studies suggest that people who are deficient in thiamine (vitamin B1), a condition often associated with alcoholism, should not take alpha-lipoic acid.

If you are currently being treated with any of the following medications, you should not use alpha-lipoic acid without first talking to your health care provider.

Insulin and drugs that lower blood sugar -- Apha-lipoic acid can combine with these drugs to further reduce blood sugar levels, resulting in hypoglycemia (low blood sugar). Tell your doctor before taking alpha-lipoic acid and monitor your blood sugar levels closely; your doctor may need to adjust your medication doses.

Thyroid-regulating medications, Levothyroxine -- Apha-lipoic acid may lower levels of thyroid hormone. Blood hormone levels and thyroid function tests should be monitored closely in people taking thyroid hormones who are also taking alpha-lipoic acid.

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