lipoic acid

Foods Richest in lipoic acid

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About lipoic acid

Description

What is this nutrient?

Lipoic acid (also called thioctic acid) is a sulfur-containing compound whose chemical structure was first determined in 1951. It is required for efficient energy production from both carbohydrates and fats, and it functions as an antioxidant that protects cells from oxidative damage. The recycling of several other antioxidants, including vitamins E and C, depends on lipoic acid.

An unusual feature of lipoic acid is its amphiphilicity: it functions in both water-based and lipid-based environments. Vitamin E is associated primarily with cell membranes (lipid phase), while vitamin C operates in the cytoplasm (aqueous phase). Lipoic acid works across both compartments, supporting the activity of both vitamins.

Lipoic acid is not classified as a vitamin because the body can synthesize it endogenously. The biosynthetic pathway is not fully characterized, but the two sulfur atoms appear to derive from the amino acid methionine, while the carbon skeleton comes from octanoic acid, a medium-chain fatty acid.

How it functions

What is the function of this nutrient?

Energy production

Lipoic acid occupies a critical position in energy metabolism. It is a cofactor for the pyruvate dehydrogenase complex, which connects glycolysis (the breakdown of glucose) to the citric acid cycle. The same enzymatic junction also gates entry of fatty acid-derived carbons into the cycle. This positioning at the intersection of carbohydrate and fat metabolism explains the clinical interest in lipoic acid for diabetes (disrupted glucose processing) and skeletal muscle dysfunction (impaired fat oxidation).

Prevention of cell damage

The antioxidant function of lipoic acid has been extensively studied, and its ability to help prevent oxygen-based damage to cells is well established. The antioxidant role of lipoic acid may be the key factor in explaining its success in prevent cataract formation in animal studies. Prevention of oxygen-based damage to nerves is also a key area of clinical research on the possible use of lipoic acid.

Maintaining supplies of other antioxidants

Through its amphiphilic nature, lipoic acid helps recycle both vitamin C and vitamin E, preventing deficiency of each in human and animal studies. It also supports the regeneration of coenzyme Q, glutathione, and NADH (the reduced form of NAD+, a niacin derivative).

Deficiency symptoms

What are deficiency symptoms for this nutrient?

Because lipoic acid works so closely with many other antioxidant nutrients, deficiency symptoms for lipoic acid alone are difficult to pinpoint. Lipoic acid is required for the maintenance of vitamin C supplies, and symptoms of lipoic acid deficiency can imitate symptoms of vitamin C deficiency. These symptoms can include weakened immune function and increased susceptibility to colds and other infections. In research studies on animals, lipoic acid deficiency has been linked to problems with memory, decreased muscle mass, and failure to thrive (in young animals).

Toxicity symptoms

What are toxicity symptoms for this nutrient?

Toxicity symptoms from excessive intake of lipoic acid have not been adequately studied. However, in clinical practice, this nutrient has been given in supplemental form for over 30 years in many European countries as a supportive nutrient for individuals with nervous system damage from diabetes, and no reports of toxicity have been reported in the literature in this regard.

In several animal studies, lipoic acid supplementation has been shown to reduce high blood sugar levels by increasing the activity of insulin and allowing sugar to leave the blood. For this reason, individuals with blood sugar imbalances, particularly hypoglycemia (low blood sugar) may experience toxic effects from excess intake of lipoic acid in the form of insufficient blood sugar. It is important to note that this phenomenon is not well-studied, and that doses of lipoic acid that might cause hypoglycemia are higher than those obtained through diet alone.

One animal study has shown potentially toxic effects of lipoic acid when given simultaneously with thyroid hormone. For this reason, individuals on prescription thyroid hormone medications may want to consult their health practitioner before supplementing with lipoic acid. Once again, the amount of lipoic acid used in this thyroid study was higher than the amount that would be obtained through diet alone.

Although not strictly falling into the category of toxic side effects, individuals with B-complex vitamin deficiencies—especially deficiency of vitamins B1 and B12—should be sure to remedy these deficiencies when supplementing with lipoic acid. Some animal studies have shown a worsening of B-complex vitamin deficiencies when lipoic acid is supplemented in the absence of B-complex vitamins. (Note: All of the above factors involve supplements, not food, and many food sources of lipoic acid—like green leafy vegetables—are also sources of B-complex vitamins.)

Impact of cooking, storage and processing

How do cooking, storage, or processing affect this nutrient?

At present, there are no studies showing the impact of cooking, storage, or processing on levels of lipoic acid in foods.

Factors that affect function

What factors might contribute to a deficiency of this nutrient?

Interestingly, because lipoic acid is found in the mitochondria (energy production units) of animal cells, individuals who eat no animal products may be at higher risk for lipoic acid deficiency than individuals who do. Vegetarians who eat no green leafy vegetables may also be at special risk, since the chloroplasts in these leaves house most of the lipoic acid.

Since lipoic acid protects proteins during aging, older individuals may be at greater risk of deficiency.

Similarly, because lipoic acid is used to help regulate blood sugar, individuals with diabetes may be at special risk of deficiency.

Individuals with poor protein intake, and particularly those with poor intake of the sulfur-containing amino acids (the building blocks of protein that contain sulfur, namely, methionine, cysteine, and taurine) may also be at higher risk of lipoic acid deficiency. The reason for this connection is simple: lipoic acid gets its sulfur atoms from these sulfur-containing amino acids.

Because lipoic acid is asorbed primarily through the stomach, individuals with stomach disorders (for example, hypochlorhydria, or low stomach acid) may also be at increased risk of deficiency.

Nutrient interactions

How do other nutrients interact with this nutrient?

Vitamins C and E, coenzyme Q, glutathione, and NADH all require lipoic acid for their efficient recycling in the body. Deficiency of these antioxidant nutrients will reduce synthesis of lipoic acid in the body.

Lipoic acid gets its two sulfur atoms primarily from the sulfur-containing amino acid methionine. For this reaspon, methionine deficiency can reduce the body’s ability to make lipoic acid. Deficiency of other sulfur-containing amino acids, like cysteine and taurine, can also prevent lipoic acid synthesis in our cells.

Health conditions

What health conditions require special emphasis on this nutrient?

Lipoic acid may play a role in the prevention and/or treatment of the following medical conditions:

Food sources

What foods provide this nutrient?

Food sources of lipoic acid are not well characterized. Two general categories have been identified.

Green plants: Chloroplasts in green leaves require lipoic acid for photosynthetic energy production. Spinach, broccoli, collard greens, and Swiss chard are dietary sources for this reason.

Animal tissues: Mitochondria-dense organs (heart, liver, kidney, skeletal muscle) contain concentrated lipoic acid. Beef steak and organ meats (liver, for example) are animal food sources. Yeast also contains measurable amounts.

Nutrient rating chart

Food Source Analysis not Available for this Nutrient

Public health recommendations

What are current public health recommendations for this nutrient?

There are currently no public health recommendations for lipoic acid.

What events can indicate a need for more high-lipoic foods?

Sources of lipoic include: dark green leafy vegetables, including spinach and collard greens; broccoli; animal foods such as beef steak; and organ meats such as calf’s liver.

For serving size for specific foods, see Nutrient Rating Chart below at the bottom of this page.

Related Articles

References

  1. Barbiroli B, Medori R, Tritschler H-J, et al. Lipoic (thioctic) acid increases brain energy availability and skeletal muscle performance as shown by in vivo 31P-MRS in a patient with mitochondrial cytopathy. J Neurol 1995;242:472-477. 1995. https://doi.org/10.1016/j.jccase.2012.04.002
  2. Groff JL, Gropper SS, Hunt SM. Advanced Nutrition and Human Metabolism. West Publishing Company, New York, 1995. 1995.
  3. Jacob S, Henriksen EJ, Schiemann AL, et al. Enhancement of glucose disposal in patients with type 2 diabetes by alpha-lipoic acid. Arzneimittel-Forschaung 1995;45:872-874. 1995.
  4. Kagan V, Serbinova E, Packer L. Antioxidant effects of ubiquinones in microsomes and mitochondria are mediated by tocopherol recycling. Biochem Biophys Res Comm 1990;169:851-857. 1990. https://doi.org/10.1016/0006-291x(90)91971-t
  5. Maitra I, Serbinova E, Tritschler H-J, et al. Stereospecific effects of R-lipoic acid on buthionine sulfoximine-induced cataract formation in newborn rats. Biochem Biophys Res Commun 1996;221:422-429. 1996. https://doi.org/10.1006/bbrc.1996.0611
  6. Midaoui AE, Elimadi A, Wu L et al. Lipoic acid prevents hypertension, hyperglycemia, and the increase in heart mitochondrial superoxide production. Am J Hypertens 2003 Mar;16(3):173-9. 2003. https://doi.org/10.1016/s0895-7061(02)03253-3
  7. Nichols TW Jr. Alpha-Lipoic acid: biological effects and clinical implications. Alter Med Rew 1997;2(3):177-183. 1997.
  8. Packer L, Witt EH, Tritschler HJ, et al. Antioxidant properties and clinical implications of alpha-lipoic acid. Chapter 22 in: Packer L and Cadenas E. (Eds). Biothiols in health and disease. Marcel Dekker, New York, 1995;479-516. 1995. https://doi.org/10.1186/s12937-016-0186-5
  9. Segermann J, Hotze A, Ulrich H, et al. Effect of alpha-lipoic acid on the peripheral conversion of thyroxine to triiodothyronine and on serum lipid-, protein- and glucose levels. Arzneimittelforschung 1991;41:1294-1298. 1991.
  10. Barbiroli B, Medori R, Tritschler H-J, et al. Lipoic (thioctic) acid increases brain energy availability and skeletal muscle performance as shown by in vivo 31P-MRS in a patient with mitochondrial cytopathy. J Neurol 1995;242:472-477 1995. https://doi.org/10.1016/j.jccase.2012.04.002
  11. Groff JL, Gropper SS, Hunt SM. Advanced Nutrition and Human Metabolism. West Publishing Company, New York, 1995 1995.
  12. Jacob S, Henriksen EJ, Schiemann AL, et al. Enhancement of glucose disposal in patients with type 2 diabetes by alpha-lipoic acid. Arzneimittel-Forschaung 1995;45:872-874 1995.
  13. Kagan V, Serbinova E, Packer L. Antioxidant effects of ubiquinones in microsomes and mitochondria are mediated by tocopherol recycling. Biochem Biophys Res Comm 1990;169:851-857 1990. https://doi.org/10.1016/0006-291x(90)91971-t
  14. Maitra I, Serbinova E, Tritschler H-J, et al. Stereospecific effects of R-lipoic acid on buthionine sulfoximine-induced cataract formation in newborn rats. Biochem Biophys Res Commun 1996;221:422-429 1996. https://doi.org/10.1006/bbrc.1996.0611
  15. Midaoui AE, Elimadi A, Wu L et al. Lipoic acid prevents hypertension, hyperglycemia, and the increase in heart mitochondrial superoxide production. Am J Hypertens 2003 Mar;16(3):173-9 2003. https://doi.org/10.1016/s0895-7061(02)03253-3
  16. Nichols TW Jr. Alpha-Lipoic acid: biological effects and clinical implications. Alter Med Rew 1997;2(3):177-183 1997.
  17. Packer L, Witt EH, Tritschler HJ, et al. Antioxidant properties and clinical implications of alpha-lipoic acid. Chapter 22 in: Packer L and Cadenas E. (Eds). Biothiols in health and disease. Marcel Dekker, New York, 1995;479-516 1995. https://doi.org/10.1186/s12937-016-0186-5
  18. Segermann J, Hotze A, Ulrich H, et al. Effect of alpha-lipoic acid on the peripheral conversion of thyroxine to triiodothyronine and on serum lipid-, protein- and glucose levels. Arzneimittelforschung 1991;41:1294-1298 1991.