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

Other antioxidants work only in water (such as vitamin C) or fatty tissues (such as vitamin E). But alpha-lipoic acid is both fat and water soluble. That means it can work throughout the body. Antioxidants in the body are used up 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 changed 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. There is confusion between alpha-lipoic acid and alpa linolenic acid because both are sometimes abbreviated ALA. Alpha-lipoic acid is also sometimes called lipoic acid.

Diabetes

Several studies suggest alpha-lipoic acid helps lower blood sugar levels. Its ability to kill free radicals may help people with diabetic peripheral neuropathy, who have pain, burning, itching, tingling, and numbness in arms and legs from nerve damage. Researchers believe Alpha-lipoic acid helps improve insulin sensitivity.

Alpha-lipoic acid has been used for years to treat peripheral neuropathy in Germany. However, most of the studies that have found it helps have used intravenous (IV) alpha-lipoic acid. It's not clear whether taking alpha-lipoic acid by mouth will help. Most studies of oral alpha-lipoic acid have been small and poorly designed. One study did find that taking alpha-lipoic acid for diabetic neuropathy reduced symptoms compared to placebo.

Taking alpha-lipoic acid may help another diabetes-related condition called autonomic neuropathy, which affects the nerves to internal organs. One study of 73 people with cardiac autonomic neuropathy, which affects the heart, found that subjects reported fewer signs of the condition when taking 800 mg of alpha-lipoic acid orally compared to placebo.

Brain Function and Stroke

Because alpha-lipoic acid can pass easily into the brain, it may help protect the brain and nerve tissue. Researchers are investigating it as a potential treatment for stroke and other brain problems involving free radical damage, such as dementia. So far, there's no evidence to say whether or not it works.

Other

Preliminary studies suggest alpha-lipoic acid may help treat glaucoma. But there is not enough evidence to say for sure whether it works. In one study on aging skin, a cream with 5% lipoic acid helped reduce fine lines from sun damage. Studies show ALA binds with toxic metals, such as mercury, arsenic, iron, and other metals that act as free radicals. Preliminary studies also suggest that ALA may play a role in managing other conditions including erectile dysfunction and cancer. And preliminary studies suggest it may reduce complications associated with otitis media (ear infections).

If you are healthy, your 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. Your health care provider can also give it by injection.

Pediatric

Alpha-lipoic acid has not been studied in children, so it is not recommended for pediatric use.

Adult

Check with your doctor regarding dosing recommendations. Studies are mixed about whether or not to take ALA with meals.

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.

Alpha-lipoic acid hasn't been studied in pregnant or breastfeeding women, so researchers don't know if it's safe.

Side effects are generally rare and may include insomnia, fatigue, diarrhea, and skin rash.

Alpha-lipoic acid can lower blood sugar levels, so people with diabetes or low blood sugar should take alpha-lipoic acid only under the supervision of their health care provider.

Animal studies suggest that people who don't get enough thiamine (vitamin B1) should not take alpha-lipoic acid. B1 deficiency is associated with long-term alcohol abuse.

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

Medications for diabetes

Apha-lipoic acid can combine with these drugs to lower blood sugar levels, raising the risk of hypoglycemia or low blood sugar. Ask your provider before taking alpha-lipoic acid, and watch your blood sugar levels closely. Your provider may need to adjust your medication doses.

Chemotherapy medications

Alpha-lipoic acid may interfere with some chemotherapy medications. Always ask your oncologist before taking any herb or supplement, including alpha-lipoic acid.

Thyroid medications, Levothyroxine

Apha-lipoic acid may lower levels of thyroid hormone. Your provider should monitor blood hormone levels and thyroid function tests closely.

Vitamin B1 (Thiamine)

Alpha lipoic acid can lower the level of vitamin B1 (Thiamine) in the body. This can be particularly dangerous in alcoholics where malnutrition is often already present.

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