Alpha-lipoic acid is an antioxidant that is made in the body which helps convert glucose into energy in addition to destroying free radicals Evidence also links alpha-lipoic acid to the regeneration of other antioxidants, like vitamin C, after they have attacked free radicals. Alpha-lipoic acid has been shown to improve insulin sensitivity in Type 2 diabetics and promote tumor cell death, suggests Memorial Sloan Kettering Cancer Center.
The Memorial Sloan Kettering Cancer Center reports that alpha-lipoic acid is bound to protein, specifically lysine, in foods. These bound compounds are called lipoyllysine. Alpha-lipoic acid is found in large amounts in body tissue that contain high amounts of mitochondria, the cells' powerhouse. Organ meats contain high amounts of mitochondria and, consequently, high amounts of lipoyllysine. The Linus Pauling Institute notes that kidney, heart and liver are food sources that contain alpha-lipoic acid.
Chloroplasts are the energy production cells in plants. Alpha-lipoic acid is responsible for energy conversion in cells, so foods with high amounts of chloroplasts will have high amounts of alpha-lipoic acid. Plant sources of alpha-lipoic acid include broccoli, spinach, collard greens and chard, explains Linus Pauling Institute. Lipoyllysine has also been found in tomatoes, peas and brussels sprouts.
Alpha-lipoic acid can also be found in yeast, specifically brewer’s yeast, which is made from a single-cell fungus. According to the Linus Pauling Institute, consumption of alpha-lipoic acid from food does not have a significant effect on the free lipoic acid in plasma, while free lipoic acid in supplements results in significant plasma increases. According to the Memorial Sloan Kettering Cancer Center, the bound alpha-lipoic acid in food is difficult to cleave and therefore is less available to enter the blood plasma. The free alpha-lipoic acid found in supplements is not bound and easily enters the plasma, where it is distributed widely throughout the body.